Aims. Osteoarthritis (OA) is a common degenerative joint disease worldwide, which is characterized by articular cartilage lesions. With more understanding of the disease, OA is considered to be a disorder of the whole joint. However, molecular communication within and between tissues during the disease process is still unclear. In this study, we used transcriptome data to reveal crosstalk between different tissues in OA. Methods. We used four groups of transcription profiles acquired from the Gene Expression Omnibus database, including articular cartilage, meniscus, synovium, and subchondral bone, to screen differentially expressed genes during OA. Potential crosstalk between tissues was depicted by ligand-receptor pairs. Results. During OA, there were 626, 97, 1,060, and 2,330 differentially expressed genes in articular cartilage, meniscus, synovium, and subchondral bone, respectively. Gene Ontology enrichment revealed that these genes were enriched in extracellular matrix and structure organization, ossification, neutrophil degranulation, and activation at different degrees. Through ligand-receptor pairing and proteome of OA synovial fluid, we predicted ligand-receptor interactions and constructed a crosstalk atlas of the whole joint. Several interactions were reproduced by transwell experiment in chondrocytes and synovial cells, including TNC-NT5E, TNC-SDC4, FN1-ITGA5, and FN1-NT5E. After lipopolysaccharide (LPS) or interleukin (IL)-1β stimulation, the ligand expression of chondrocytes and synovial cells was upregulated, and corresponding receptors of co-culture cells were also upregulated. Conclusion. Each tissue displayed a different expression pattern in transcriptome, demonstrating their specific roles in OA. We highlighted tissue molecular crosstalk through ligand-receptor pairs in OA pathophysiology, and generated a crosstalk atlas. Strategies to interfere with these candidate ligands and receptors may help to discover molecular targets for future OA therapy. Cite this article: Bone Joint Res 2022;11(12):862–872

Aims. Cartilage injuries rarely heal spontaneously and often require surgical intervention, leading to the formation of biomechanically inferior fibrous tissue. This study aimed to evaluate the possible effect of amelogenin on the healing process of a large osteochondral injury (OCI) in a rat model. Methods. A reproducible large OCI was created in the right leg femoral trochlea of 93 rats. The OCIs were treated with 0.1, 0.5, 1.0, 2.5, or 5.0 μg/μl recombinant human amelogenin protein (rHAM. +. ) dissolved in propylene glycol alginate (PGA) carrier, or with PGA carrier alone. The degree of healing was evaluated 12 weeks after treatment by morphometric analysis and histological evaluation. Cell recruitment to the site of injury as well as the origin of the migrating cells were assessed four days after treatment with 0.5 μg/μl rHAM. +. using immunohistochemistry and immunofluorescence. Results. A total of 12 weeks after treatment, 0.5 μg/μl rHAM. +. brought about significant repair of the subchondral bone and cartilage. Increased expression of proteoglycan and type II collagen and decreased expression of type I collagen were revealed at the surface of the defect, and an elevated level of type X collagen at the newly developed tide mark region. Conversely, the control group showed osteoarthritic alterations. Recruitment of cells expressing the mesenchymal stem cell (MSC) markers CD105 and STRO-1, from adjacent bone marrow toward the OCI, was noted four days after treatment. Conclusion. We found that 0.5 μg/μl rHAM. +. induced in vivo healing of injured articular cartilage and subchondral bone in a rat model, preventing the destructive post-traumatic osteoarthritic changes seen in control OCIs, through paracrine recruitment of cells a few days after treatment. Cite this article: Bone Joint Res 2023;12(10):615–623

Aims. Rotational acetabular osteotomy (RAO) has been reported to be effective in improving symptoms and preventing osteoarthritis (OA) progression in patients with mild to severe develomental dysplasia of the hip (DDH). However, some patients develop secondary OA even when the preoperative joint space is normal; determining who will progress to OA is difficult. We evaluated whether the preoperative cartilage condition may predict OA progression following surgery using T2 mapping MRI. Methods. We reviewed 61 hips with early-stage OA in 61 patients who underwent RAO for DDH. They underwent preoperative and five-year postoperative radiological analysis of the hip. Those with a joint space narrowing of more than 1 mm were considered to have 'OA progression'. Preoperative assessment of articular cartilage was also performed using 3T MRI with the T2 mapping technique. The region of interest was defined as the weightbearing portion of the acetabulum and femoral head. Results. There were 16 patients with postoperative OA progression. The T2 values of the centre to the anterolateral region of the acetabulum and femoral head in the OA progression cases were significantly higher than those in patients without OA progression. The preoperative T2 values in those regions were positively correlated with the narrowed joint space width. The receiver operating characteristic analysis revealed that the T2 value of the central portion in the acetabulum provided excellent discrimination, with OA progression patients having an area under the curve of 0.858. Furthermore, logistic regression analysis showed T2 values of the centre to the acetabulum’s anterolateral portion as independent predictors of subsequent OA progression (p < 0.001). Conclusion. This was the first study to evaluate the relationship between intra-articular degeneration using T2 mapping MRI and postoperative OA progression. Our findings suggest that preoperative T2 values of the hip can be better prognostic factors for OA progression than radiological measures following RAO. Cite this article: Bone Joint J 2021;103-B(9):1472–1478

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by progressive cartilage degradation, synovial membrane inflammation, osteophyte formation, and subchondral bone sclerosis. Pathological changes in cartilage and subchondral bone are the main processes in OA. In recent decades, many studies have demonstrated that activin-like kinase 3 (ALK3), a bone morphogenetic protein receptor, is essential for cartilage formation, osteogenesis, and postnatal skeletal development. Although the role of bone morphogenetic protein (BMP) signalling in articular cartilage and bone has been extensively studied, many new discoveries have been made in recent years around ALK3 targets in articular cartilage, subchondral bone, and the interaction between the two, broadening the original knowledge of the relationship between ALK3 and OA. In this review, we focus on the roles of ALK3 in OA, including cartilage and subchondral bone and related cells. It may be helpful to seek more efficient drugs or treatments for OA based on ALK3 signalling in future

Aims. Osteoarthritis (OA) is a prevalent joint disorder with inflammatory response and cartilage deterioration as its main features. Dihydrocaffeic acid (DHCA), a bioactive component extracted from natural plant (gynura bicolor), has demonstrated anti-inflammatory properties in various diseases. We aimed to explore the chondroprotective effect of DHCA on OA and its potential mechanism. Methods. In vitro, interleukin-1 beta (IL-1β) was used to establish the mice OA chondrocytes. Cell counting kit-8 evaluated chondrocyte viability. Western blotting analyzed the expression levels of collagen II, aggrecan, SOX9, inducible nitric oxide synthase (iNOS), IL-6, matrix metalloproteinases (MMPs: MMP1, MMP3, and MMP13), and signalling molecules associated with nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) pathways. Immunofluorescence analysis assessed the expression of aggrecan, collagen II, MMP13, and p-P65. In vivo, a destabilized medial meniscus (DMM) surgery was used to induce mice OA knee joints. After injection of DHCA or a vehicle into the injured joints, histological staining gauged the severity of cartilage damage. Results. DHCA prevented iNOS and IL-6 from being upregulated by IL-1β. Moreover, the IL-1β-induced upregulation of MMPs could be inhibited by DHCA. Additionally, the administration of DHCA counteracted IL-1β-induced downregulation of aggrecan, collagen II, and SOX9. DHCA protected articular cartilage by blocking the NF-κB and MAPK pathways. Furthermore, DHCA mitigated the destruction of articular cartilage in vivo. Conclusion. We present evidence that DHCA alleviates inflammation and cartilage degradation in OA chondrocytes via suppressing the NF-κB and MAPK pathways, indicating that DHCA may be a potential agent for OA treatment. Cite this article: Bone Joint Res 2023;12(4):259–273

3D printing and Bioprinting technologies are becoming increasingly popular in surgery to provide a solution for the regeneration of healthy tissues. The aim of our project is the regeneration of articular cartilage via bioprinting means, to manage isolated chondral defects. Chrondrogenic hydrogel (chondrogel: GelMa + TGF-b3 and BMP6) was prepared and sterilised in our lab following our standard protocols. Human adipose-derived mesenchymal stem cells were harvested from the infrapatellar fat pad of patients undergoing total knee joint replacements and incorporated in the hydrogel according to our published protocols. The chondrogenic properties of the chondrogel have been tested (histology, immunohistochemistry, PCR, immunofluorescence, gene analysis and 2. nd. harmonic generation microscopy) in vitro and in an ex-vivo model of human articular defect and compared with standard culture systems where the growth factors are added to the media at repeated intervals. The in-vitro analysis showed that the formation of hyaline cartilage pellet was comparable between the two strategies, with a similar metabolic activity of the cells. These results have been confirmed in the ex-vivo model: hyaline-like cartilage was observed within the chondral defect in both the chondrogel group and the control group after 28 days in culture. The use of bioprinting techniques in vivo requires the ability of stem cells to access growth factors directly in the environment they are in, as opposed to in vitro techniques where these factors are provided externally at recurrent intervals. This study showed the successful strategy of incorporating chondrogenic growth factors for the formation of hyaline-like cartilage in vitro and in an ex-vivo model of chondral loss. The incorporation of chondrogenic growth factors in a hydrogel is a possible strategy for articular cartilage regeneration

This study aims to assess the changes in mechanical behaviour over time in ‘haemarthritic’ articular cartilage compared to ‘healthy’ articular cartilage. Pin-on-plate and indentation tests were used to determine the coefficient of friction (COF) and deformation of ‘healthy’ and ‘haemarthritic articular cartilage. Osteochondral pins (8 mm) were extracted from porcine tali and immersed in exposure fluid for two hours prior to test. Pins were articulated against a larger bovine femoral plate for 3600 seconds under a load of 50 N. Osteochondral pins (8 mm) were loaded during indentation testing for 3600 seconds under a load of 0.25 N. To mimic the effect of a joint bleed in vitro; serum, whole blood and 50% v/v were used as exposure and lubricant fluids. COF and deformation were expressed as mean (n=3) and statistically analysed using a one-way ANOVA and post-hoc Tukey test (p>0.05). The serum condition yielded a COF of 0.0428 ± 0.02 with 0.08mm ± 0.04 deformation. The 50% v/v condition produced a higher COF of 0.0485 ± 0.02 and 0.21mm ± 0.04 deformation. The lowest COF and deformation were produced by the whole blood condition (0.0292 ± 0.02 and 0.06mm ± 0.006 respectively). Statistical analysis indicated no significant difference across the friction test conditions but a significant difference across all indentation test conditions (ANOVA, p>0.05). Combination of creep deformation and wear was observed on the articular surface up to 24 hours post-test in 50% v/v and whole blood conditions. The average haemophilia patient can experience multiple joint bleeds per year of which this study demonstrates the effect of just one joint bleed. This study has provided evidence of potential reversible and irreversible mechanical changes to articular cartilage surface during a joint bleed

Osteoarthritis (OA) is mainly caused by ageing, strain, trauma, and congenital joint abnormalities, resulting in articular cartilage degeneration. During the pathogenesis of OA, the changes in subchondral bone (SB) are not only secondary manifestations of OA, but also an active part of the disease, and are closely associated with the severity of OA. In different stages of OA, there were microstructural changes in SB. Osteocytes, osteoblasts, and osteoclasts in SB are important in the pathogenesis of OA. The signal transduction mechanism in SB is necessary to maintain the balance of a stable phenotype, extracellular matrix (ECM) synthesis, and bone remodelling between articular cartilage and SB. An imbalance in signal transduction can lead to reduced cartilage quality and SB thickening, which leads to the progression of OA. By understanding changes in SB in OA, researchers are exploring drugs that can regulate these changes, which will help to provide new ideas for the treatment of OA. Cite this article: Bone Joint Res 2023;12(9):536–545

Aims. After a few passages of in vitro culture, primary human articular chondrocytes undergo senescence and loss of their phenotype. Most of the available chondrocyte cell lines have been obtained from cartilage tissues different from diarthrodial joints, and their utility for osteoarthritis (OA) research is reduced. Thus, the goal of this research was the development of immortalized chondrocyte cell lines proceeded from the articular cartilage of patients with and without OA. Methods. Using telomerase reverse transcriptase (hTERT) and SV40 large T antigen (SV40LT), we transduced primary OA articular chondrocytes. Proliferative capacity, degree of senescence, and chondrocyte surface antigen expression in transduced chondrocytes were evaluated. In addition, the capacity of transduced chondrocytes to synthesize a tissue similar to cartilage and to respond to interleukin (IL)-1β was assessed. Results. Coexpression of both transgenes (SV40 and hTERT) were observed in the nuclei of transduced chondrocytes. Generated chondrocyte cell lines showed a high proliferation capacity and less than 2% of senescent cells. These cell lines were able to form 3D aggregates analogous to those generated by primary articular chondrocytes, but were unsuccessful in synthesizing cartilage-like tissue when seeded on type I collagen sponges. However, generated chondrocyte cell lines maintained the potential to respond to IL-1β stimulation. Conclusion. Through SV40LT and hTERT transduction, we successfully immortalized chondrocytes. These immortalized chondrocytes were able to overcome senescence in vitro, but were incapable of synthesizing cartilage-like tissue under the experimental conditions. Nonetheless, these chondrocyte cell lines could be advantageous for OA investigation since, similarly to primary articular chondrocytes, they showed capacity to upregulate inflammatory mediators in response to the IL-1β cytokine. Cite this article: Bone Joint Res 2023;12(1):46–57

Abstract. OBJECTIVES. An unresolved challenge in osteoarthritis research is characterising the localised intra-tissue mechanical response of articular cartilage. The aim of this study was to explore whether laboratory micro-computed tomography (micro-CT) and digital volume correlation (DVC) permit non-destructive visualisation of three-dimensional (3D) strain fields in human articular cartilage. METHODS. Human articular cartilage specimens were harvested from the knee (n=4 specimens from 2 doners), mounted into a loading device and imaged in the loaded and unloaded state using a micro-CT scanner. Strain was calculated throughout the volume of the cartilage using the CT image data. RESULTS. Strain was calculated in the 3D volume with a spatial resolution of 75 µm, and the volumetric DVC calculated strain was within 5% of the known applied stain. Variation in strain distribution between the superficial, middle and deep zones was observed, consistent with the different architecture of the material in these locations. CONCLUSIONS. The DVC method is suitable for calculating strain in human articular cartilage. This method will be useful to generate chondral repair scaffolds that that seek to replicate the strain gradient in cartilage. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Electrospinning is an advantageous technique for cartilage tissue engineering (CTE) applications due to its ability to produce nanofibers recapitulating the size and alignment of the collagen fibers present within the articular cartilage superficial zone. Moreover, coaxial electrospinning allows the fabrication of core-shell fibers able to encapsulate and release bioactive molecules in a sustained manner. Kartogenin (KTG) is a small heterocyclic molecule, which was demonstrated to promote the chondrogenic differentiation of human bone marrow-derived mesenchymal stem/stromal cells(hBMSCs)[1]. In this work, we developed and evaluated the biological performance of core-shell poly(glycerol sebacate)(PGS)/poly(caprolactone)(PCL) aligned nanofibers (core:PGS/shell:PCL) mimicking the native articular cartilage extracellular matrix(ECM) and able to promote the sustained release of the chondroinductive drug KTG[2]. The produced coaxial aligned PGS/PCL scaffolds were characterized in terms of their structure and fiber diameter, chemical composition, thermal properties, mechanical performance under tensile testing and in vitro degradation kinetics, in comparison to monoaxial PCL aligned fibers and respective non-aligned controls. KTG was incorporated into the core PGS solution to generate core-shell PGS-KTG/PCL nanofibers and its release kinetics was studied by HPLC analysis. KTG-loaded electrospun aligned scaffolds capacity to promote hBMSCs chondrogenic differentiation was evaluated by assessing cell proliferation, typical cartilage-ECM production (sulfated glycosaminiglycans(sGAG)) and chondrogenic marker genes expression in comparison to non-loaded controls. All the scaffolds fabricated showed average fiber diameters within the nanometer-scale and the core-shell structure of the fibers was clearly confirmed by TEM. The coaxial PGS-KTG/PCL nanofibers evidenced a more sustained drug release over 21 days. Remarkably, in the absence of the chondrogenic cytokine TGF-β3, KTG-loaded nanofibers promoted significantly the proliferation and chondrogenic differentiation of hBMSCs, as suggested by the increased cell numbers, higher sGAG amounts and up-regulation of the chondrogenic genes COL2A1, Sox9, ACAN and PRG4 expression. Overall, our results highlight the potential of core-shell PGS-KTG/PCL aligned nanofibers for the development of novel MSC-based CTE strategies. Acknowledgements: The authors thank FCT for funding through the project InSilico4OCReg (PTDC/EME-SIS/0838/2021) and to institutions iBB (UID/BIO/04565/2020) and Associate Laboratory I4HB (LA/P/0140/2020)

The superficial zone (SFZ) of articular cartilage has unique structural and biomechanical features, and is important for joint long-term function. Previous studies have shown that TGF-β/Alk5 signaling upregulating PRG4 expression maintains articular cartilage homeostasis. However, the exact role and molecular mechanism of TGF-β signaling in SFZ of articular cartilage homeostasis are still lacking. In this study, a combination of in vitro and in vivo approaches were used to elucidate the role of Alk5 signaling in maintaining the SFZ of articular cartilage and preventing osteoarthritis initiation. Mice with inducible cartilage SFZ-specific deletion of Alk5 were generated to assess the role of Alk5 in OA development. Alterations in cartilage structure were evaluated histologically. The chondrocyte apoptosis and cell cycle were detected by TUNEL and Edu staining, respectively. Isolation, culture and treatment of SFZ cells, the expressions of genes associated with articular cartilage homeostasis and TGF-β signaling were analyzed by qRT-PCR. The effects of TGF-β/Alk5 signaling on proliferation and differentiation of SFZ cells were explored by cells count and alcian blue staining. In addition, SFZ cells isolated from C57 mice were cultured in presence of TGF-β1 or SB505124 for 7 days and transplanted subcutaneously in athymic mice. Postnatal cartilage SFZ-specific deletion of Alk5 induced an OA-like phenotype with degradation of articular cartilage, synovial hyperplasia as well as enhanced chondrocyte apoptosis, overproduction of catabolic factors, and decreased expressions of anabolic factors in chondrocytes. qRT-PCR and IHC results confirmed that Alk5 gene was effectively deleted in articular cartilage SFZ cells. Next, the PRG4-positive cells in articular cartilage SFZ were significantly decreased in Alk5 cKO mice compared with those in Cre-negative control mice. The mRNA expression of Aggrecan and Col2 were decreased, meanwhile, expression of Mmp13 and Adamts5 were significantly increased in articular cartilage SFZ cells of Alk5 cKO mice. In addition, Edu and TUNEL staining results revealed that slow-cell cycle cell number and increase the apoptosis positive cell in articular cartilage SFZ of Alk5 cKO mice compared with Cre-negative mice, respectively. Furthermore, all groups of SFZ cells formed ectopic solid tissue masses 1 week after transplantation. Histological examination revealed that the TGF-β1-pretreated tissues was composed of small and round cells and was positive for alcian blue staining, while the SB505124-pretreated tissue contained more hypertrophic cells though it did stain with alcian blue. TGF-β/alk5 signaling is an essential regulator of the superficial layer of articular cartilage by maintaining chondrocyte number, its differentiation properties, and lubrication function. Furthermore, it plays a critical role in protecting cartilage from OA initiation

Lesions in the joint surface are commonly treated with osteoarticular autograft transfer system (OATS), autologous cell implantation (ACI/MACI), or microfracture. Tissue formed buy the latter commonly results in mechanically inferior fibrocartilage that fails to integrate with the surrounding native cartilage, rather than durable hyaline cartilage. Fractional laser treatment to make sub-millimeter (<500 µm) channels has been employed for tissue regeneration in the skin to facilitate rejuvenation without typical scarring. Additionally, we have pioneered a means to generate articular cartilage matrix from chondrocytes—dynamic Self-Regenerating Cartilage (dSRC). Combining these two approaches by performing fractional laser treatment of the joint cartilage and treating with dSRC is a new paradigm for joint surface restoration. This approach was refined in a series of in vitro experiments and tested in swine knee defects during a 6-month study in 12 swine. dSRC are generated by placing 10. 7. swine knee chondrocytes into sealed 15-mL polypropylene tubes and cultured on a rocker at 40 cycles per minute for 14 days at 37°C. The chondrocytes aggregate and generate new extracellular matrix to form a pellet of dSRC. Channels of approximately 300-500 µm diameter were created by infrared laser ablation in swine cartilage (in vitro) and swine knees (in vivo). The diameter and depth of the ablated channel in the cartilage was controlled by the light delivery parameters (power, spot size, pulse duration) from a fractional 2.94 µm Erbium laser. The specimens were evaluated with histology (H&E, safranin O, toluidine blue) and polarized-sensitive optical coherence tomography for collagen orientation. We can consistently create laser-ablated channels in the swine knee and successfully implant new cartilage from dSRC to generate typical hyaline cartilage in terms of morphology and biochemical properties. The neocartilage integrates with host cartilage in vivo. These findings demonstrate our novel combinatorial approach for articular cartilage rejuvenation

The avascular nature of articular cartilage relies on diffusion pathways to obtain essential nutrients and molecules for cellular activity. Understanding these transport pathways is essential to maintaining and improving the health of articular cartilage and ultimately synovial joints. Several studies have shown that joint articulation is associated with fluid and solute uptake although it remains unclear what role sliding motion independently plays. This study investigates the role of sliding with a non-stationary contact area on the uptake of small molecular weight tracers into articular cartilage. Ten-millimeter diameter cartilage-bone plugs were obtained from porcine knee joints and sealed into purpose made diffusion chambers. The chambers were designed to eliminate diffusion from the radial edge and only allow diffusion through the articular surface. The bone side of the chamber was filled with PBS to maintain tissue hydration while the cartilage side was filled with 0.01mg/ml fluorescein sodium salt (FNa) prepared using PBS. Sliding loads with a non-stationary contact area were applied across the articular surface by a custom apparatus using a 4.5 mm diameter spherical indenter. A moving contact area was chosen to represent physiological joint motions. Reciprocal sliding was maintained at a rate of 5 mm/s for 2 and 4 hours. Control samples were subject to passive diffusion for 0, 4, and 88 hours. After diffusion tests, samples were snap frozen and 20 µm cross-sectional cuts were taken perpendicular to the sliding direction. Samples were imaged using a Zeiss AxioImager M2 epifluorescent microscope under 5× magnification with a filter for FNa. Intensity profiles were mapped from the articular surface to the subchondral bone. Unloaded control samples demonstrated minimal solute uptake at 4 hours penetrating less than 5% of the total cartilage depth. By 88 hours solute penetration had reached the subchondral bone although there was minimal accumulation within the cartilage matrix indicated by the relatively low intensity profile values. Samples that had been subjected to reciprocal sliding demonstrated accelerated penetration and solute accumulation compared to unloaded samples. After 1 hour of reciprocal sliding, the solute had reached 40% of the cartilage depth, this increased to approximately 80% at 4 hours, with much higher intensities compared to unloaded controls. Sliding motion plays an important role in the uptake of solutes into the cartilage matrix. Maintaining joint motion both post injury and in the arthritic process is a critical component of cartilage nutrition. Samples that had been subject to reciprocal sliding demonstrated accelerated solute penetration and accumulation in the cartilage matrix, exceeding steady state concentrations achieved by passive diffusion

Mincing cartilage with commercially available shavers is increasingly used for treating focal cartilage defects. This study aimed to compare the impact of mincing bovine articular cartilage using different shaver blades on chondrocyte viability. Bovine articular cartilage was harvested using a scalpel or three different shaver blades (2.5 mm, 3.5 mm, or 4.2 mm) from a commercially available shaver. The cartilage obtained with a scalpel was minced into fragments smaller than 1 mm. 3. All four conditions were cultivated in a culture medium for seven days. After Day 1 and Day 7, metabolic activity, RNA isolation, and gene expression of anabolic (COL2A1, ACAN) and catabolic genes (MMP1, MMP13), Live/Dead staining and visualization using confocal microscopy, and flow cytometric characterization of minced cartilage chondrocytes were measured. The study found that mincing cartilage with shavers significantly reduced metabolic activity after one and seven days compared to scalpel mincing (p<0.001). Gene expression of anabolic genes was reduced, while catabolic genes were increased after day 7 in all shaver conditions. The MMP13/COL2A1 ratio was also increased in all shaver conditions. Confocal microscopy revealed a thin line of dead cells at the lesion site with viable cells below for the scalpel mincing and a higher number of dead cells diffusely distributed in the shaver conditions. After seven days, there was a significant decrease in viable cells in the shaver conditions compared to scalpel mincing (p<0.05). Flow cytometric characterization revealed fewer intact cells and proportionally more dead cells in all shaver conditions compared to the scalpel mincing. Mincing bovine articular cartilage with commercially available shavers reduces the viability of chondrocytes compared to scalpel mincing. This indicates that mincing cartilage with a shaver should be considered a matrix rather than a cell therapy. Further experimental and clinical studies are required to standardize the mincing process with a shaver. Acknowledgements: This study received unrestricted funding from KARL STORZ SE & Co. KG

Articular cartilage has poor repair potential and the tissue formed is mechanically incompetent. Mesenchymal stromal cells (MSCs) show chondrogenic properties and the ability to re-grow cartilage, however a viable human model for testing cartilage regeneration and repair is lacking. Here, we describe an ex vivo pre-clinical femoral head model for studying human cartilage repair using MSCs. Human femoral heads (FHs) were obtained following femoral neck fracture with ethical permission/patient consent and full-depth cartilage wells made using a 3mm biopsy punch. Pancreas-derived mesenchymal stromal cells (P-MSC) were prepared in culture media at ~5000 cells/20µl and added to each well and leakage prevented with fibrin sealant. After 24hrs, the sealant was removed and medium replaced with StemPro. TM. chondrogenesis differentiation medium. The FHs were incubated (37. o. C;5% CO. 2. ) for 3wks, followed by a further 3wks in standard medium with 10% human serum with regular medium changes throughout. Compared to wells with medium only, A-MSCs produced a thin film across the wells which was excised en-block, fixed with 4% paraformaldehyde and frozen for cryo-sectioning. The cell/tissue films varied in thickness ranging over 20-440µm (82±21µm; mean±SEM; N=3 FHs). The thickness of MSC films abutting the cartilage wells was variable but generally greater (15-1880µm) than across the wells, suggesting an attachment to native articular cartilage. Staining of the films using safranin O (for glycosaminoglycans; quantified using ImageJ) was variable (3±8%; mean±SEM; N=3) but in one experiment reached 20% of the adjacent cartilage. A preliminary assessment of the repair tissue gave an O'Driscoll score of 10/24 (24 is best). These preliminary results suggest the ex vivo femoral head model has promise for studying the capacity of MSCs to repair cartilage directly in human tissue, although optimising MSCs to produce hyaline-like tissue is essential. Supported by the CSO (TCS/17/32)

Aims. To determine the relationship between articular cartilage status and clinical outcomes after medial opening-wedge high tibial osteotomy (MOHTO) for medial compartmental knee osteoarthritis at intermediate follow-up. Methods. We reviewed 155 patients (155 knees) who underwent MOHTO from January 2008 to December 2016 followed by second-look arthroscopy with a mean 5.3-year follow-up (2.0 to 11.7). Arthroscopic findings were assessed according to the International Cartilage Repair Society (ICRS) Cartilage Repair Assessment (CRA) grading system. Patients were divided into two groups based on the presence of normal or nearly normal quality cartilage in the medial femoral condyle: good (second-look arthroscopic) status (ICRS grade I or II; n = 70), and poor (second-look arthroscopic) status (ICRS grade III or IV; n = 85) groups at the time of second-look arthroscopy. Clinical outcomes were assessed using the International Knee Documentation Committee (IKDC) score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and 36-Item Short Form survey. Results. Significant improvements in all clinical outcome categories were found between the preoperative and second-look arthroscopic assessments in both groups (p < 0.001). At the latest follow-up, the mean IKDC and WOMAC scores in the good status group further improved compared with those at the time of second-look arthroscopic surgery (p < 0.001), which was not shown in the poor status group. The mean IKDC (good status, 72.8 (SD 12.5); poor status, 64.7 (SD 12.1); p = 0.002) and mean WOMAC scores (good status, 15.7 (SD 10.8); poor status, 21.8 (SD 13.6); p = 0.004) significantly differed between both groups at the latest follow-up. Moreover, significant correlations were observed between ICRS CRA grades and IKDC scores (negative correlation; p < 0.001) and WOMAC scores (positive correlation; p < 0.001) at the latest follow-up. Good cartilage status was found more frequently in knees with the desired range of 2° to 6° valgus correction than in those with corrections outside this range (p = 0.019). Conclusion. Second-look arthroscopic cartilage status correlated with clinical outcomes after MOHTO at intermediate-term follow-up, despite the relatively small clinical differences between groups. Cite this article: Bone Joint J 2021;103-B(11):1686–1694

Even minor lesions in articular cartilage (AC) can cause underlying bone damage creating an osteochondral (OC) defect. OC defects can cause pain, impaired mobility and can develop to osteoarthritis (OA). OA is a disease that affects nearly 10% of the population worldwide. [1]. , and represents a significant economic burden to patients and society. [2]. While significant progress has been made in this field, realising an efficacious therapeutic option for unresolved OA remains elusive and is considered one of the greatest challenges in the field of orthopaedic regenerative medicine. [3]. Therefore, there is a societal need to develop new strategies for AC regeneration. In recent years there has been increased interest in the use of tissue-specific aligned porous freeze-dried extracellular matrix (ECM) scaffolds as an off-the-shelf approach for AC repair, as they allow for cell infiltration, provide biological cues to direct target-tissue repair and permit aligned tissue deposition, desired in AC repair. [4]. However, most ECM-scaffolds lack the appropriate mechanical properties to withstand the loads passing through the joint. [5]. One solution to this problem is to reinforce the ECM with a stiffer framework made of synthetic materials, such as polylactic acid (PLA). [6]. Such framework can be 3D printed to produce anatomically accurate implants. [7]. , attractive in personalized medicine. However, typical 3D prints are static, their design is not optimized for soft-hard interfaces (OC interface), and they may not adapt to the cyclic loading passing through our joints, thus risking implant failure. To tackle this limitation, more compliant or dynamic designs can be printed, such as coil-shaped structures. [8]. Thus, in this study we use finite element modelling to create different designs that mimic the mechanical properties of AC and prototype them in PLA, using polyvinyl alcohol as support. The optimal design will be combined with an ECM scaffold containing a tailored microarchitecture mimicking aspects of native AC. Acknowledgments: This project has received funding from the European Union's Horizon Europe research and innovation MSCA PF programme under grant agreement No. 101110000

Aims. The intra-articular administration of tranexamic acid (TXA) has been shown to be effective in reducing blood loss in unicompartmental knee arthroplasty and anterior cruciate reconstruction. The effects on human articular cartilage, however, remains unknown. Our aim, in this study, was to investigate any detrimental effect of TXA on chondrocytes, and to establish if there was a safe dose for its use in clinical practice. The hypothesis was that TXA would cause a dose-dependent damage to human articular cartilage. . Materials and Methods. The cellular morphology, adhesion, metabolic activity, and viability of human chondrocytes when increasing the concentration (0 mg/ml to 40 mg/ml) and length of exposure to TXA (0 to 12 hours) were analyzed in a 2D model. This was then repeated, excluding cellular adhesion, in a 3D model and confirmed in viable samples of articular cartilage. Results. Increasing concentrations above 20 mg/ml resulted in atypical morphology, reduced cellular adhesion and metabolic activity associated with increased chondrocyte death. However, the cell matrix was not affected by the concentration of TXA or the length of exposure, and offered cellular protection for concentrations below 20 mg/ml. Conclusion. These results show that when in vitro chondrocytes are exposed to higher concentrations of TXA, such as that expected following recommended intra-articular administration, cytotoxicity is observed. This effect is dose-dependent, such that a tissue concentration of 10 mg/ml to 20 mg/ml could be expected to be safe. Cite this article: Bone Joint J 2018;100-B:404–12

Abstract. Introduction. This study aimed to assess the effect of PRP on knee articular cartilage content (thickness and/or volume) and establish if there is a correlation between changes in cartilage and clinical outcomes in patients with knee osteoarthritis. Methodology. A systematic review was performed following the Cochrane methodology. Studies were included if they reported on cartilage content with MRI or Ultrasound before and after the injection. A random-effects model meta-analysis was performed. Results. 11 studies (n=786) from 1,453 records met the inclusion criteria, with five (n=444) being RCTs. The PRP treatment protocol varied widely. Follow-up ranged from 6–12 months. Eight studies reported increase in cartilage content in the PRP group as compared to control (four showing significant difference). In meta-analysis: PRP treatment was not associated with a significant increase in cartilage thickness in medial and lateral femoral condyle, or in the overall cartilage content (4 studies, n=187, Hedges’ g: 0.079; 95%CI: 0.358-0.516; p=0.723). Meta-analysis of 3 RCTs (n=112) showed no significant difference in increasing cartilage content overall with PRP injections compared with no PRP (Hedges’ g: 0.217; 95%CI: -0.177 – 0.611; P=0.281). There was no correlation between changes in cartilage and clinical outcomes following PRP treatment. Conclusion. Treatment of knee osteoarthritis with PRP is not associated with a significant increase in articular cartilage content and any effect on cartilage is not associated with better clinical outcomes. A multi-centre, adequately powered RCT, with a standardized preparation / administration protocol assessing long-term effect of PRP in knee osteoarthritis is needed to guide clinical care

This systematic review examines the current literature regarding surgical techniques for restoring articular cartilage in the hip, from the older microfracture techniques involving perforation to the subchondral bone, to adaptations of this technique using nanofractures and scaffolds. This review discusses the autologous and allograft transfer systems and the autologous matrix-induced chondrogenesis (AMIC) technique, as well as a summary of the previously discussed techniques, which could become common practice for restoring articular cartilage, thus reducing the need for total hip arthroplasty. Using the British Medical Journal Grading of Recommendations, Assessment, Development and Evaluation (BMJ GRADE) system and Grade system. Comparison of the studies discussed shows that microfracture has the greatest quantity and quality of research, whereas the newer AMIC technique requires more research, but shows promise. Cite this article: W. E. Hotham, A. Malviya. A systematic review of surgical methods to restore articular cartilage in the hip. Bone Joint Res 2018;7:336–342. DOI: 10.1302/2046-3758.75.BJR-2017-0331

The aim of this study was to determine whether subchondral bone influences in situ chondrocyte survival. Bovine explants were cultured in serum-free media over seven days with subchondral bone excised from articular cartilage (group A), subchondral bone left attached to articular cartilage (group B), and subchondral bone excised but co-cultured with articular cartilage (group C). Using confocal laser scanning microscopy, fluorescent probes and biochemical assays, in situ chondrocyte viability and relevant biophysical parameters (cartilage thickness, cell density, culture medium composition) were quantified over time (2.5 hours vs seven days). There was a significant increase in chondrocyte death over seven days, primarily within the superficial zone, for group A, but not for groups B or C (p < 0.05). There was no significant difference in cartilage thickness or cell density between groups A, B and C (p > 0.05). Increases in the protein content of the culture media for groups B and C, but not for group A, suggested that the release of soluble factors from subchondral bone may have influenced chondrocyte survival. In conclusion, subchondral bone significantly influenced chondrocyte survival in articular cartilage during explant culture. The extrapolation of bone-cartilage interactions in vitro to the clinical situation must be made with caution, but the findings from these experiments suggest that future investigation into in vivo mechanisms of articular cartilage survival and degradation must consider the interactions of cartilage with subchondral bone

Cells with stem/progenitor characteristics can be isolated from articular cartilage and may have utility in cartilage repair and regeneration therapies. Unlike other adult cell types with differentiation capabilities, clonal chondroprogenitors differentiate into cartilage that resembles stable cartilage rather than endochondral cartilage. We have isolated a large series of chondroprogenitor clones from normal human articular cartilage from individuals of one to forty-five years of age and characterized them with known and novel markers. The clones were isolated separately from different zones of the articular cartilage. As first reported by others, the cloneable cells were mainly found in the upper zones. However, there are clones with chondroprogenitor status in the deeper zones, albeit at far lower frequency. These deep zone clones have different characteristics to those from the upper zones. We have used selected clones to re-engineer stable cartilage with use of the right environmental conditions (growth factors, oxygen level etc)

Matrix metalloproteinase enzymes (MMPs) play a crucial role in the remodeling of articular cartilage, contributing also to osteoarthritis (OA) progression. The pericellular matrix (PCM) is a specialized space surrounding each chondrocyte, containing collagen type VI and perlecan. It acts as a transducer of biomechanical and biochemical signals for the chondrocyte. This study investigates the impact of MMP-2, -3, and -7 on the integrity and biomechanical characteristics of the PCM. Human articular cartilage explants (n=10 patients, ethical-nr.:674/2016BO2) were incubated with activated MMP-2, -3, or -7 as well as combinations of these enzymes. The structural degradative effect on the PCM was assessed by immunolabelling of the PCM's main components: collagen type VI and perlecan. Biomechanical properties of the PCM in form of the elastic moduli (EM) were determined by means of atomic force microscopy (AFM), using a spherical cantilever tip (2.5µm). MMPs disrupted the PCM-integrity, resulting in altered collagen type VI and perlecan structure and dispersed pericellular arrangement. A total of 3600 AFM-measurements revealed that incubation with single MMPs resulted in decreased PCM stiffness (p<0.001) when compared to the untreated group. The overall EM were reduced by ∼36% for all the 3 individual enzymes. The enzyme combinations altered the biomechanical properties at a comparable level (∼36%, p<0.001), except for MMP-2/-7 (p=0.202). MMP-induced changes in the PCM composition have a significant impact on the biomechanical properties of the PCM, similar to those observed in early OA. Each individual MMP was shown to be highly capable of selectively degrading the PCM microenvironment. The combination of MMP-2 and -7 showed a lower potency in reducing the PCM stiffness, suggesting a possible interplay between the two enzymes. Our study showed that MMP-2, -3, and -7 play a direct role in the functional and structural remodeling of the PCM. Acknowledgements: This work was supported by the Faculty of Medicine of the University of Tübingen (grant number.: 2650-0-0)

The zonal organization of articular cartilage is crucial in providing the tissue with mechanical properties to withstand compression and shearing force. Current treatments available for articular cartilage injury are not able to restore the hierarchically organized architecture of the tissue. Implantation of zonal chondrocyte as a multilayer tissue construct could overcome the limitation of current treatments. However, it is impeded by the lack of efficient zonal chondrocyte isolation protocol and dedifferentiation of chondrocytes during expansion on tissue culture plate (TCP). This study aims to develop a protocol to produce an adequate number of high-quality zonal chondrocytes for clinical application via size-based zonal chondrocyte separation using inertial spiral microchannel device and expansion under dynamic microcarrier culture. Full thickness (FT) chondrocytes isolated from porcine femoral condyle cartilage were subjected to two serial of size-based sorting into three subpopulations of different cell sizes, namely small (S1), medium (S2), and large (S3) chondrocytes. Zonal phenotype of the three subpopulations was characterised. To verify the benefit of stratified zonal chondrocyte implantation in the articular cartilage regeneration, a bilayer hydrogel construct composed of S1 chondrocytes overlaying a mixture of S2 and S3 (S2S3) chondrocytes was delivered to the rat osteochondral defect model. For chondrocyte expansion, two dynamic microcarrier cultures, sort-before-expansion and sort-after-expansion, which involved expansion after or before zonal cells sorting, were studied to identify the best sort-expansion strategy. Size-sorted zonal chondrocytes showed zone-specific characteristics in qRT-PCR with a high level of PRG4 expression in S1 and high level of aggrecan, Type II and IX collagen expression in S2 and S3. Cartilage reformation capability of sorted zonal chondrocytes in three-dimensional fibrin hydrogel showed a similar trend in qRT-PCR, histology, extracellular matrix protein quantification and mechanical compression test, indicating the zonal characteristics of S1, S2 and S3 as superficial (SZ), middle (MZ) and deep (DZ) zone chondrocytes, respectively. Implantation of bilayered zonal chondrocytes resulted in better cartilage tissue regeneration in a rat osteochondral defect model than FT control group, with predominantly Type II hyaline cartilage tissue and significantly lower Type I collagen. Dynamic microcarrier expansion of sorted zonal chondrocytes was able to retain the zonal cell size difference that correlate to zonal phenotype, while maintaining the rounded chondrocyte morphology and F-actin distribution similar to that in mature articular cartilage. With the better retention of zonal cell size and zonal phenotype relation on microcarrier, zonal cells separation was achievable in the sort-after-expansion strategy with cells expanded on microcarrier, in comparison to cells expanded on TCP. Inertial spiral microchannel device provides a label-free and high throughput method to separate zonal chondrocytes based on cell size. Stratified implantation of zonal chondrocytes has the potential to improve articular cartilage regeneration. Dynamic microcarrier culture allows for size-based zonal chondrocyte separation to be performed on expanded chondrocytes, thus overcoming the challenge of limited tissue availability from the patients. Our novel zonal chondrocyte isolation and expansion protocol provide a translatable strategy for stratified zonal chondrocyte implantation that could improve articular cartilage regeneration of critical size defects

This review briefly summarises some of the definitive studies of articular cartilage by microscopic MRI (µMRI) that were conducted with the highest spatial resolutions. The article has four major sections. The first section introduces the cartilage tissue, MRI and µMRI, and the concept of image contrast in MRI. The second section describes the characteristic profiles of three relaxation times (T. 1. , T. 2. and T. 1ρ. ) and self-diffusion in healthy articular cartilage. The third section discusses several factors that can influence the visualisation of articular cartilage and the detection of cartilage lesion by MRI and µMRI. These factors include image resolution, image analysis strategies, visualisation of the total tissue, topographical variations of the tissue properties, surface fibril ambiguity, deformation of the articular cartilage, and cartilage lesion. The final section justifies the values of multidisciplinary imaging that correlates MRI with other technical modalities, such as optical imaging. Rather than an exhaustive review to capture all activities in the literature, the studies cited in this review are merely illustrative

Objectives. Patient-specific (PS) implantation surgical technology has been introduced in recent years and a gradual increase in the associated number of surgical cases has been observed. PS technology uses a patient’s own geometry in designing a medical device to provide minimal bone resection with improvement in the prosthetic bone coverage. However, whether PS unicompartmental knee arthroplasty (UKA) provides a better biomechanical effect than standard off-the-shelf prostheses for UKA has not yet been determined, and still remains controversial in both biomechanical and clinical fields. Therefore, the aim of this study was to compare the biomechanical effect between PS and standard off-the-shelf prostheses for UKA. Methods. The contact stresses on the polyethylene (PE) insert, articular cartilage and lateral meniscus were evaluated in PS and standard off-the-shelf prostheses for UKA using a validated finite element model. Gait cycle loading was applied to evaluate the biomechanical effect in the PS and standard UKAs. Results. The contact stresses on the PE insert were similar for both the PS and standard UKAs. Compared with the standard UKA, the PS UKA did not show any biomechanical effect on the medial PE insert. However, the contact stresses on the articular cartilage and the meniscus in the lateral compartment following the PS UKA exhibited closer values to the healthy knee joint compared with the standard UKA. Conclusion. The PS UKA provided mechanics closer to those of the normal knee joint. The decreased contact stress on the opposite compartment may reduce the overall risk of progressive osteoarthritis. Cite this article: K-T. Kang, J. Son, D-S. Suh, S. K. Kwon, O-R. Kwon, Y-G. Koh. Patient-specific medial unicompartmental knee arthroplasty has a greater protective effect on articular cartilage in the lateral compartment: A Finite Element Analysis. Bone Joint Res 2018;7:20–27. DOI: 10.1302/2046-3758.71.BJR-2017-0115.R2

Objectives. Recent studies have shown that systemic injection of rapamycin can prevent the development of osteoarthritis (OA)-like changes in human chondrocytes and reduce the severity of experimental OA. However, the systemic injection of rapamycin leads to many side effects. The purpose of this study was to determine the effects of intra-articular injection of Torin 1, which as a specific inhibitor of mTOR which can cause induction of autophagy, is similar to rapamycin, on articular cartilage degeneration in a rabbit osteoarthritis model and to investigate the mechanism of Torin 1’s effects on experimental OA. Methods. Collagenase (type II) was injected twice into both knees of three-month-old rabbits to induce OA, combined with two intra–articular injections of Torin 1 (400 nM). Degeneration of articular cartilage was evaluated by histology using the Mankin scoring system at eight weeks after injection. Chondrocyte degeneration and autophagosomes were observed by transmission electron microscopy. Matrix metallopeptidase-13 (MMP-13) and vascular endothelial growth factor (VEGF) expression were analysed by quantitative RT-PCR (qPCR).Beclin-1 and light chain 3 (LC3) expression were examined by Western blotting. Results. Intra-articular injection of Torin 1 significantly reduced degeneration of the articular cartilage after induction of OA. Autophagosomes andBeclin-1 and LC3 expression were increased in the chondrocytes from Torin 1-treated rabbits. Torin 1 treatment also reduced MMP-13 and VEGF expression at eight weeks after collagenase injection. Conclusion. Our results demonstrate that intra-articular injection of Torin 1 reduces degeneration of articular cartilage in collagenase-induced OA, at least partially by autophagy activation, suggesting a novel therapeutic approach for preventing cartilage degeneration and treating OA. Cite this article: N-T. Cheng, A. Guo, Y-P. Cui. Intra-articular injection of Torin 1 reduces degeneration of articular cartilage in a rabbit osteoarthritis model. Bone Joint Res 2016;5:218–224. DOI: 10.1302/2046-3758.56.BJR-2015-0001

Aims. Extracellular matrix (ECM) and its architecture have a vital role in articular cartilage (AC) structure and function. We hypothesized that a multi-layered chitosan-gelatin (CG) scaffold that resembles ECM, as well as native collagen architecture of AC, will achieve superior chondrogenesis and AC regeneration. We also compared its in vitro and in vivo outcomes with randomly aligned CG scaffold. Methods. Rabbit bone marrow mesenchymal stem cells (MSCs) were differentiated into the chondrogenic lineage on scaffolds. Quality of in vitro regenerated cartilage was assessed by cell viability, growth, matrix synthesis, and differentiation. Bilateral osteochondral defects were created in 15 four-month-old male New Zealand white rabbits and segregated into three treatment groups with five in each. The groups were: 1) untreated and allogeneic chondrocytes; 2) multi-layered scaffold with and without cells; and 3) randomly aligned scaffold with and without cells. After four months of follow-up, the outcome was assessed using histology and immunostaining. Results. In vitro testing showed that the secreted ECM oriented itself along the fibre in multi-layered scaffolds. Both types of CG scaffolds supported cell viability, growth, and matrix synthesis. In vitro chondrogenesis on scaffold showed an around 400-fold increase in collagen type 2 (COL2A1) expression in both CG scaffolds, but the total glycosaminoglycan (GAG)/DNA deposition was 1.39-fold higher in the multi-layered scaffold than the randomly aligned scaffold. In vivo cartilage formation occurred in both multi-layered and randomly aligned scaffolds treated with and without cells, and was shown to be of hyaline phenotype on immunostaining. The defects treated with multi-layered + cells, however, showed significantly thicker cartilage formation than the randomly aligned scaffold. Conclusion. We demonstrated that MSCs loaded CG scaffold with multi-layered zonal architecture promoted superior hyaline AC regeneration. Cite this article: Bone Joint Res 2020;9(9):601–612

Abstract. Objectives. In the human knee, the cells of the articular cartilage (AC) and subchondral bone (SB) communicate via the secretion of biochemical factors. Chondrocyte-based AC repair strategies, such as articular chondrocyte implantation, are widely used but there has been little investigation into the communication between the native SB cells and the transplanted chondrocytes. We hypothesise that this communication depends on the health state of the SB and could influence the composition and quality of the repair cartilage. Methods. An indirect co-culture model was developed using transwell inserts, representing a chondrocyte/scaffold-construct for repair of AC defects adjoining SB with varying degrees of degeneration. Donor-matched populations of human bone-marrow derived mesenchymal stromal cells (BM-MSCs) were isolated from the macroscopically and histologically best and worst osteochondral tissue, representing “healthy” and “unhealthy” SB. The BM-MSCs were co-cultured with normal chondrocytes suspended in agarose, with the two cell types separated by a porous membrane. After 0, 7, 14 and 21 days, chondrocyte-agarose scaffolds were assessed by gene expression and biochemical analyses. Results. Matched healthy and unhealthy BM-MSCs from five patients undergoing knee arthroplasty (2 male, 3 female; 72.8±2.2. SD. years-old) were used, together with normal chondrocytes from a healthy patient (male; 24 years-old). At day 21, there was significantly more glycosaminoglycan per chondrocyte in the scaffolds co-cultured with healthy BM-MSCs (4.37×10. −4. μg/cell±2.69×10. −5. SEM. ) than in those cultured with unhealthy BM-MSCs (3.52×10. −4. μg/cell±2.19×10. −5. SEM. ; p<0.001). Co-culture with unhealthy BM-MSCs caused a difference in expression of COL2A1 (day 0–21 fold change; unhealthy:-32.8±12.9. SEM. ; healthy:-7.82±4.46. SEM. ; p<0.001) and ACAN (unhealthy:+1.51±0.51. SEM. ; healthy:+4.05±0.49. SEM. ; p=0.002). Conclusions. Co-culture with unhealthy BM-MSCs caused a reduction in GAG deposition and expression of genes encoding matrix-specific proteins, compared to culturing with healthy BM-MSCs. There are clinical implications for cell-based cartilage repair, where the health of the SB may influence the outcome of chondrocyte-based therapies

The weight-bearing status of articular cartilage has been shown to affect its biochemical composition. We have investigated the topographical variation of sulphated glycosaminoglycan (GAG) relative to the DNA content of the chondrocyte in human distal femoral articular cartilage. Paired specimens of distal femoral articular cartilage, from weight-bearing and non-weight-bearing regions, were obtained from 13 patients undergoing above-knee amputation. After papain enzyme digestion, spectrophotometric GAG and fluorometric DNA assays assessed the biochemical composition of the samples. The results were analysed using a paired t-test. Although there were no significant differences in cell density between the regions, the weight-bearing areas showed a significantly higher concentration of GAG relative to DNA when compared with non-weight-bearing areas (p = 0.02). We conclude that chondrocytes are sensitive to their mechanical environment, and that local loading conditions influence the metabolism of the cells and hence the biochemical structure of the tissue

Objectives. Mesenchymal stem cells have the ability to differentiate into various cell types, and thus have emerged as promising alternatives to chondrocytes in cell-based cartilage repair methods. The aim of this experimental study was to investigate the effect of bone marrow derived mesenchymal stem cells combined with platelet rich fibrin on osteochondral defect repair and articular cartilage regeneration in a canine model. Methods. Osteochondral defects were created on the medial femoral condyles of 12 adult male mixed breed dogs. They were either treated with stem cells seeded on platelet rich fibrin or left empty. Macroscopic and histological evaluation of the repair tissue was conducted after four, 16 and 24 weeks using the International Cartilage Repair Society macroscopic and the O’Driscoll histological grading systems. Results were reported as mean and standard deviation (. sd. ) and compared at different time points between the two groups using the Mann-Whitney U test, with a value < 0.05 considered statistically significant. Results. Higher cumulative macroscopic and histological scores were observed in stem cell treated defects throughout the study period with significant differences noted at four and 24 weeks (9.25, . sd. 0.5 vs 7.25, . sd. 0.95, and 10, . sd. 0.81 vs 7.5, . sd. 0.57; p < 0.05) and 16 weeks (16.5, . sd. 4.04 vs 11, . sd. 1.15; p < 0.05), respectively. Superior gross and histological characteristics were also observed in stem cell treated defects. Conclusion. The use of autologous culture expanded bone marrow derived mesenchymal stem cells on platelet rich fibrin is a novel method for articular cartilage regeneration. It is postulated that platelet rich fibrin creates a suitable environment for proliferation and differentiation of stem cells by releasing endogenous growth factors resulting in creation of a hyaline-like reparative tissue. Cite this article: D. Kazemi, K. Shams Asenjan, N. Dehdilani, H. Parsa. Canine articular cartilage regeneration using mesenchymal stem cells seeded on platelet rich fibrin: Macroscopic and histological assessments. Bone Joint Res 2017;6:98–107. DOI: 10.1302/2046-3758.62.BJR-2016-0188.R1

Adult articular cartilage mechanical functionality is dependent on the unique zonal organization of its tissue. Current mesenchymal stem cell (MSC)-based treatment has resulted in sub-optimal cartilage repair, with inferior quality of cartilage generated from MSCs in terms of the biochemical content, zonal architecture and mechanical strength when compared to normal cartilage. The phenotype of cartilage derived from MSCs has been reported to be influenced by the microenvironmental biophysical cues, such as the surface topography and substrate stiffness. In this study, the effect of nano-topographic surfaces to direct MSC chondrogenic differentiation to chondrocytes of different phenotypes was investigated, and the application of these pre-differentiated cells for cartilage repair was explored. Specific nano-topographic patterns on the polymeric substrate were generated by nano-thermal imprinting on the PCL, PGA and PLA surfaces respectively. Human bone marrow MSCs seeded on these surfaces were subjected to chondrogenic differentiation and the phenotypic outcome of the differentiated cells was analyzed by real time PCR, matrix quantification and immunohistological staining. The influence of substrate stiffness of the nano-topographic patterns on MSC chondrogenesis was further evaluated. The ability of these pre-differentiated MSCs on different nano-topographic surfaces to form zonal cartilage was verified in in vitro 3D hydrogel culture. These pre-differentiated cells were then implanted as bilayered hydrogel constructs composed of superficial zone-like chondro-progenitors overlaying the middle/deep zone-like chondro-progenitors, was compared to undifferentiated MSCs and non-specifically pre-differentiated MSCs in a osteochondral defect rabbit model. Nano-topographical patterns triggered MSC morphology and cytoskeletal structure changes, and cellular aggregation resulting in specific chondrogenic differentiation outcomes. MSC chondrogenesis on nano-pillar topography facilitated robust hyaline-like cartilage formation, while MSCs on nano-grill topography were induced to form fibro/superficial zone cartilage-like tissue. These phenotypic outcomes were further diversified and controlled by manipulation of the material stiffness. Hyaline cartilage with middle/deep zone cartilage characteristics was derived on softer nano-pillar surfaces, and superficial zone-like cartilage resulted on softer nano-grill surfaces. MSCs on stiffer nano-pillar and stiffer nano-grill resulted in mixed fibro/hyaline/hypertrophic cartilage and non-cartilage tissue, respectively. Further, the nano-topography pre-differentiated cells possessed phenotypic memory, forming phenotypically distinct cartilage in subsequent 3D hydrogel culture. Lastly, implantation of the bilayered hydrogel construct of superficial zone-like chondro-progenitors and middle/deep zone-like chondro-progenitors resulted in regeneration of phenotypically better cartilage tissue with higher mechanical function. Our results demonstrate the potential of nano-topographic cues, coupled with substrate stiffness, in guiding the differentiation of MSCs to chondrocytes of a specific phenotype. Implantation of these chondrocytes in a bilayered hydrogel construct yielded cartilage with more normal architecture and mechanical function. Our approach provides a potential translatable strategy for improved articular cartilage regeneration using MSCs

Objectives. Adult mice lacking the transcription factor NFAT1 exhibit osteoarthritis (OA). The precise molecular mechanism for NFAT1 deficiency-induced osteoarthritic cartilage degradation remains to be clarified. This study aimed to investigate if NFAT1 protects articular cartilage (AC) against OA by directly regulating the transcription of specific catabolic and anabolic genes in articular chondrocytes. Methods. Through a combined approach of gene expression analysis and web-based searching of NFAT1 binding sequences, 25 candidate target genes that displayed aberrant expression in Nfat1. -/-. AC at the initiation stage of OA, and possessed at least four NFAT1 binding sites in the promoter of each gene, were selected and tested for NFAT1 transcriptional activities by chromatin immunoprecipitation (ChIP) and promoter luciferase reporter assays using chondrocytes isolated from the AC of three- to four-month-old wild-type mice or Nfat1. -/-. mice with early OA phenotype. Results. Chromatin immunoprecipitation assays revealed that NFAT1 bound directly to the promoter of 21 of the 25 tested genes encoding cartilage-matrix proteins, growth factors, inflammatory cytokines, matrix-degrading proteinases, and specific transcription factors. Promoter luciferase reporter assays of representative anabolic and catabolic genes demonstrated that NFAT1-DNA binding functionally regulated the luciferase activity of specific target genes in wild-type chondrocytes, but not in Nfat1. -/-. chondrocytes or in wild-type chondrocytes transfected with plasmids containing mutated NFAT1 binding sequences. Conclusion. NFAT1 protects AC against degradation by directly regulating the transcription of target genes in articular chondrocytes. NFAT1 deficiency causes defective transcription of specific anabolic and catabolic genes in articular chondrocytes, leading to increased matrix catabolism and osteoarthritic cartilage degradation. Cite this article: M. Zhang, Q. Lu, T. Budden, J. Wang. NFAT1 protects articular cartilage against osteoarthritic degradation by directly regulating transcription of specific anabolic and catabolic genes. Bone Joint Res 2019;8:90–100. DOI: 10.1302/2046-3758.82.BJR-2018-0114.R1

Objectives. The purpose of this study was to create a novel ex vivo organ culture model for evaluating the effects of static and dynamic load on cartilage. Methods. The metatarsophalangeal joints of 12 fresh cadaveric bovine feet were skinned and dissected aseptically, and cultured for up to four weeks. Dynamic movement was applied using a custom-made machine on six joints, with the others cultured under static conditions. Chondrocyte viability and matrix glycosaminoglycan (GAG) content were evaluated by the cell viability probes, 5-chloromethylfluorescein diacetate (CMFDA) and propidium iodide (PI), and dimethylmethylene blue (DMMB) assay, respectively. Results. Chondrocyte viability in the static model decreased significantly from 89.9% (. sd. 2.5%) (Day 0) to 66.5% (. sd. 13.1%) (Day 28), 94.7% (. sd. 1.1%) to 80. 9% (. sd. 5.8%) and 80.1% (. sd. 3.0%) to 46.9% (. sd. 8.5%) in the superficial quarter, central half and deep quarter of cartilage, respectively (p < 0.001 in each zone; one-way analysis of variance). The GAG content decreased significantly from 6.01 μg/mg (. sd. 0.06) (Day 0) to 4.71 μg/mg (. sd. 0.06) (Day 28) (p < 0.001; one-way analysis of variance). However, with dynamic movement, chondrocyte viability and GAG content were maintained at the Day 0 level over the four-week period without a significant change (chondrocyte viability: 92.0% (. sd. 4.0%) (Day 0) to 89.9% (. sd. 0.2%) (Day 28), 93.1% (. sd. 1.5%) to 93.8% (. sd. 0.9%) and 85.6% (. sd. 0.8%) to 84.0% (. sd. 2.9%) in the three corresponding zones; GAG content: 6.18 μg/mg (. sd. 0.15) (Day 0) to 6.06 μg/mg (. sd. 0.09) (Day 28)). Conclusion. Dynamic joint movement maintained chondrocyte viability and cartilage GAG content. This long-term whole joint culture model could be of value in providing a more natural and controlled platform for investigating the influence of joint movement on articular cartilage, and for evaluating novel therapies for cartilage repair. Cite this article: Y-C. Lin, A. C. Hall, A. H. R. W. Simpson. A novel organ culture model of a joint for the evaluation of static and dynamic load on articular cartilage. Bone Joint Res 2018;7:205–212. DOI: 10.1302/2046-3758.73.BJR-2017-0320

Articular cartilage is attached to subchondral bone but it is not clear whether the tissues interact and influence in situ (within the matrix) chondrocyte survival. The aim of this study was to determine whether subchondral bone influences in situ chondrocyte survival. Articular cartilage explants harvested from the meta-carpophalangeal joints (N=6) of three-year old cows were placed into three groups:. subchondral bone excised from articular cartilage (Group A). subchondral bone left attached to articular cartilage (Group B). subchondral bone excised, but co-cultured with articular cartilage (Group C). Explants were cultured in serum-free media over 7 days. Using confocal laser scanning microscopy, fluorescent probes and biochemical assays, in situ chondrocyte viability and biophysical parameters (cartilage thickness, cell density, culture medium composition) were quantified over time (2.5 hours vs. 7 days) for Groups A, B and C. With excision of subchondral bone from articular cartilage (Group A), there was a marked increase in chondrocyte death over 7 days primarily within the superficial zone (p< 0.05). There was no significant increase in chondrocyte death within the superficial zone over the same time period for Groups B and C (p> 0.05). There was no significant difference in cartilage thickness or cell density between Groups A, B and C (p> 0.05). Corresponding increases in the protein content of the culture media for Groups B and C but not for Group A, suggested that the release of soluble factors from subchondral bone may have influenced chondrocyte survival. Subchondral bone significantly influences chondrocyte survival in articular cartilage in vitro. These data support the concept of a functional bone-cartilage system in vivo

One reason why NICE (National Institute for Clinical Excellence) does not support operations by the NHS to heal hyaline cartilage lesions using a patients own cells is because there is no clear evidence to show that these operations are beneficial and cost-effective in the long term. Specifically, NICE identified a deficiency of high quality cartilage being produced in repaired joints. The presence of high quality cartilage is linked to long-lasting and functional repair of cartilage. The benchmark for quality, NICE stipulate, is repair cartilage that is stiff and strong and looks similar to the normal tissue surrounding it, i.e. mature hyaline articular cartilage. Biopsy material from autologous cartilage implantation surgical procedures has the appearance of immature articular cartilage and is frequently a mixture of hyaline and fibrocartilage. Osteoarthritic cartilage, in its early stages, also exhibits characteristics of immature articular cartilage in that it expresses proteins found in embryonic and foetal developmental stages, and is highly cellular as evidenced through the presence of chondrocyte clusters. Therefore, an ability to modulate the phenotype and the structure of the extracellular matrix of articular cartilage could positively affect the course of repair and regeneration of articular cartilage lesions. In order to do this, the biochemical stimuli that induce the transition of an essentially unstructured amorphous cartilage mass (immature articular cartilage) to one that is highly structured and ordered, and biomechanically adapted to its particular function (mature articular cartilage) has to be identified. We show for the first time, that fibroblast growth factor-2 and transforming growth factor beta-1 induce precocious maturation of immature articular cartilage. Our data demonstrates that it is possible to significantly enhance maturation of cartilage tissue using growth factor stimulation; consequently this may have applications in transplantation therapy, or through phenotypic modulation of osteoarthritic chondrocytes in diseased cartilage in order to stimulate growth and maturation of repair tissue

Abstract. Objective. Clinical treatments to repair articular cartilage (AC) defects such as autologous cartilage implantation (mosaicplasty) often suffer from poor integration with host tissue, limiting their long-term efficacy. Thus to ensure the longevity of AC repair, understanding natural repair mechanisms that allow for successful integration between cartilaginous surfaces, as has been reported in juvenile tissue, may be key. Here, we evaluated cartilage integration over time in a pig explant model of natural tissue repair by assessing expression and localisation of major ECM proteins, enzymatic cross-linkers including the five isoforms of lysyl oxidase (LOX), small leucine-rich repeat proteoglycans (SLRP's), and proteases (e.g. ADAMTS4). Methods. AC was retrieved from the femoral condyles of 8-week-old pigs. Full thickness 6mmØ AC discs were prepared, defects were induced, and explants cultured for up to 28 days. After fixation, sections were stained using Safranin-O and antibodies against Collagen types I & II, LOX, and ADAMTS4. Gene expression analyses were performed using qPCR. We also cultured devitalized samples, either with or without enzymatic treatment to deplete proteoglycans, for 28 days and similarly assessed repair. Results. Safranin-O staining demonstrated successful integration of cartilage defects over a 28-day period. No significant regulation in the expression of Col1a1, Col2a1, LOX or SLPR genes was observed at any time point. Immunofluorescence staining revealed that only ADAMTS4 localized at the injury surface in integrated samples. Interestingly, we also observed successful spontaneous integration of proteoglycan-depleted devitalized tissue. Conclusion. Cartilage integration in our pig cartilage explant model did not appear to be mediated by upregulation of major cartilage ECM components, enzymatic cross-linkers, or SLRPs. However, spontaneous integration of devitalized, proteoglycan-depleted AC, and localised upregulation of ADAMTS4 at the injured surface in successfully integrated samples, suggest that ADAMTS4 may enhances normal repair in injured AC through local aggrecan depletion, therefore enabling spontaneous cross-linking of collagen fibrils. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Introduction: Articular cartilage has compressive stiffness determined primarily by the matrix and it is quite characteristic and distinct from that of degenerative articular cartilage or regenerative fibrocartilage.Alterations that are evident when articular cartilage begins to degenerate include a decrease in proteoglycan content and water content and resultant reduction in stiffness. Regenerative fibrocartilage has greatly reduced stiffness with functional implications. Identification of cartilaginous stiffness for various sites of normal articular cartilage in the knee is important to enable comparison measures of suspected degenerative cartilage and regenerative articular cartilage either hyaline, fibrocartilage or mixed. Aim: To map the biomechanical properties of normal human articular cartilage in vivo using the Artscan 1000 arthroscopic cartilage stiffness tester (Artscan Oy, Finland). Method: Over a period of 12 months, 94 patients (aged 15 to 69 years) undergoing a knee arthroscopy consented to having their normal articular surfaces evaluated biomechanically for stiffness. Cartilage stiffness (N) was defined by the mean indenter force at each site where the applied force on the measurement rod equalled 10 ±1.5N. `Results: Medial femoral condyle stiffness (mean ± SD; 3.71 ± 1.28N) was greater than all other sites and was significantly greater than mean values obtained for proximal, distal and lateral trochlea (1.87 ± 0.91, 2.44 ±1.02 and 2.69 ±1.52N, respectively); medial (1.71 ± 0.70N) and lateral patella (2.18 ± 1.03N); and medial and lateral tibial plateaux for all subjects (2.33 ± 1.26 and 2.27 ± 1.19N, respectively; p < 0.05). There were no significant differences between sexes for each site. There was no trend for cartilage stiffness to be lower in patients over forty compared with younger patients for both sexes, for all sites. There was however, statistically significant less stiffness of the distal trochlea for females under 40 when compared with that of females older than 40 years. The clinical significance of this is under review. Conclusion: Further research involving the characterisation of cartilage stiffness in pathological situations and evaluation of stiffness following articular cartilage repair is now possible

Articular cartilage repair remains a challenge to surgeons and basic scientists. The field of tissue engineering allows the simultaneous use of material scaffolds, cells and signalling molecules to attempt to modulate the regenerative tissue. This review summarises the research that has been undertaken to date using this approach, with a particular emphasis on those techniques that have been introduced into clinical practice, via in vitro and preclinical studies

Healthy cartilage is essential for optimal joint function. Although, articular cartilage defects are highly prevalent in the active population and might hamper joint function, the effect of articular cartilage defects on knee contact forces and pressures is not yet documented. Therefore, the present study compared knee contact forces and pressures between patients with a tibiofemoral cartilage defect and healthy controls. This might provide additional insights in movement adaptations and the role of altered loading in the progression from defect to OA. Experimental gait data was collected in 15 patients with isolated articular cartilage defects (8 medial-affected, 7 lateral-affected) and 19 healthy asymptomatic controls and was processed using a musculoskeletal model to calculate contact forces and pressures. Differences between medial-affected, lateral-affected and controls were evaluated using Kruskal-Wallis tests and individually compared using Mann-Whitney-U tests (alpha <0.05). The lateral-affected group walked significantly slower compared to the healthy controls. No adaptations in the movement pattern that resulted in decreased loading on the injured condyle were observed. Additionally, the location of loading was not significantly affected. The current results suggest that isolated cartilage defects do not induce changes in the knee joint loading pattern. Consequently, the involved condyle will be equally loaded, indicating that a similar amount of force should be distributed over the remaining cartilage surrounding the articular cartilage defect and may cause local degenerative changes in the cartilage. This in combination with inflammatory responses might play a key role in the progression from articular cartilage defect to a more severe OA phenotype

Introduction: The load bearing status of articular cartilage has been shown to affect its biochemical composition. This study investigates the topographical variation of glycosaminoglycan (GAG) relative to DNA content in human distal femoral articular cartilage. Methods: 26-paired specimens of distal femoral articular cartilage, from weight bearing and non-weight regions, were obtained from thirteen patients undergoing amputation. Following papain enzyme digestion, spectropho-tometric (GAG) and fluorometric (DNA) assays assessed the biochemical composition of the explants. Data was analysed using a paired T test. Results: Despite no significant differences in absolute DNA concentrations, weight-bearing regions of articular cartilage showed a significantly higher concentration of GAG relative to DNA compared with non-weight bearing areas (p=0.021). Discussion: This study suggests that chondrocytes in weight bearing regions of human articular cartilage produce a greater quantity of GAG than those located in non-weight bearing areas. We conclude that mechanical loading is essential in maintaining the biochemical composition of human articular cartilage

Articular cartilage is attached to subchondral bone but little is known regarding bone-cartilage interactions important for chondrocyte survival. In this study, bovine articular cartilage has been evaluated in vitro to determine if the presence of subchondral bone influences chondrocyte survival. We hypothesised that. Excision of subchondral bone from articular cartilage would increase in situ chondrocyte death in explant culture and,. Chondrocyte death could be abrogated by co-culturing articular cartilage with the excised subchondral bone. Articular cartilage explants (n=132) harvested from the metacarpophalangeal joints of three-year old cows (N=12) were placed into three groups:. subchondral bone excised from articular cartilage (Group A). sub-chondral bone left attached to articular cartilage (Group B). subchondral bone excised, but co-cultured with articular cartilage (Group C). Explants were cultured in serum-free media over 7 days with or without media changes to assess the effect of potential soluble mediators. Using confocal laser scanning microscopy to image in situ chondrocytes, fluorescent probes to determine cell viability and biochemical assays to detect alterations in the culture media, differences in the chondrocyte responses (cell density, spatial distribution, percentage cell death) and culture medium composition between Groups A, B and C were quantified over time (2.5 hours versus 7 days). There was no significant change in cell density for Groups A, B and C over 7 days (t-test, p> 0.05). With excision of subchondral bone from articular cartilage (Group A), there was a marked increase in chondrocyte death over 7 days primarily within the superficial zone involving an extensive area of the articular surface (p< 0.05). There was no significant increase in chondrocyte death over the same time period for Groups B and C (p> 0.05). Corresponding increases in the protein content of the culture media for Groups B and C but not for Group A, suggested that the release of soluble factors from subchondral bone may have influenced chondrocyte survival in the superficial zone. Subchondral bone interacts with articular cartilage in vitro and promotes chondrocyte survival in the superficial zone. These data support the concept of a functional bone-cartilage system in vivo

Articular cartilage injury has a high prevalence in elite and recreational athletes. Articular cartilage repair remains a challenge due to cost effectiveness and clinical effectiveness issues. There are now several effective technologies and it is possible to return to competitive sports following many of the procedures available. The durability of repair tissue is variable and there remains extensive growth in the Scientific world. Evolving cartilage restoration technologies focus on increasing cartilage quality and quantity, while optimising surgery and rehabilitation. In UK ACI has undergone extensive cost effectiveness analysis and the in-depth review has shown that ACI is cost effective compared to microfracture. ACI is indicated for lesions >2cm sq but NICE has considered that it is not indicated for problems after microfracture. This presentation details the various options available to surgeons and examines the cost effectiveness

1. Isografts of articular cartilage of young rats, with mucoproteins labelled with . 35. S, extracellular fibrous proteins labelled with . 3. H-glycine, and nuclei labelled with . 3. H-thymidine, were transplanted into the anterior chamber of the eye. 2. Thin split-thickness transplants of the cells of the gliding surface of immature articular cartilage induced the formation of fibrous tissue. 3. Thick transplants and subsurface slices of immature articular cartilage, containing germinal cells of the epiphysial cartilage, induced the formation of new bone consistently within 4 weeks. 4. Full-thickness transplants in articular cartilage from senile rats induced only the formation of fibrous tissue. 5. Slices of growing cartilage, devitalised by cryolysis, or extraction of acid-soluble proteins, produced scanty deposits of bone or cartilage, or both, but only infrequently and generally after a lag phase extending from six to twelve weeks. 6. Reduction in the amount of mucoprotein in the cartilage matrix by papain, and suppression of the resynthesis of tissue proteins by cortisone, retarded but did not prevent bone induction. 7. Bone induction is the product of a series of interactions between inducing cells and responding cells by intracellular and intercellular reactions too complex to characterise in physico-chemical terms at this time

Articular cartilage has compressive stiffness determined primarily by the matrix which is quite characteristic and distinct from that of degenerative articular cartilage or regenerative fibrocartilage. Alterations evident when articular cartilage begins to degenerate include a decrease in proteoglycan content and water content and resultant reduction in stiffness. Regenerative fibro-cartilage has greatly reduced stiffness with functional implications. Identification of cartilaginous stiffness for various sites of normal articular cartilage in the knee is important to enable comparison measures of suspected degenerative cartilage and regenerative articular cartilage either hyaline, fibrocartilage or mixed. The aim of this study was to map the in vivo biomechanical properties of normal human articular knee cartilage using the Artscan 1000 arthroscopic cartilage stiffness tester (Artscan Oy, Finland). It has been shown that the Artscan 1000 is reliable when measuring the stiffness of thin articular cartilage (Lyra et al., 1999). Over a period of 12 months, 94 patients (age 15–69 yr) undergoing a knee arthroscopy consented to having their normal articular surfaces biomechanically evaluated for stiffness. Cartilage stiffness (N) was defined by the mean indenter force at each site where the applied force on the measurement rod equalled 10 ±1.5 N. Medial femoral condyle stiffness (M ±SD; 3.71 ±1.28 N) was greater than all other sites and was significantly greater than mean values obtained for proximal, distal and lateral trochlea (1.87 ±0.91, 2.44 ±1.02 and 2.69 ±1.52 N, respectively); medial (1.71 ±0.70 N) and lateral patella (2.18 ±1.03 N); and medial and lateral tibial plateau for all subjects (2.33 ±.1.26 and 2.27 ±1.19 N, respectively; p < 0.05). There were no significant differences between sexes for each site. There was no trend for cartilage stiffness to be lower in patients over forty compared to younger patients for both sexes for all sites. There was, however, statistically significant less stiffness of the distal trochlea for females under 40 years when compared to that of females older than 40 years. The clinical significance of this is under review. Further research involving the characterisation of cartilage stiffness in pathological situations and evaluation of stiffness following articular cartilage repair is now possible

The aim of this study was to determine whether exposure of human articular cartilage to hyperosmotic saline (0.9%, 600 mOsm) reduces in situ chondrocyte death following a standardised mechanical injury produced by a scalpel cut compared with the same assault and exposure to normal saline (0.9%, 285 mOsm). Human cartilage explants were exposed to normal (control) and hyperosmotic 0.9% saline solutions for five minutes before the mechanical injury to allow in situ chondrocytes to respond to the altered osmotic environment, and incubated for a further 2.5 hours in the same solutions following the mechanical injury. Using confocal laser scanning microscopy, we identified a sixfold (p = 0.04) decrease in chondrocyte death following mechanical injury in the superficial zone of human articular cartilage exposed to hyperosmotic saline compared with normal saline. These data suggest that increasing the osmolarity of joint irrigation solutions used during open and arthroscopic articular surgery may reduce chondrocyte death from surgical injury and could promote integrative cartilage repair

Aims

To identify unanswered questions about the prevention, diagnosis, treatment, and rehabilitation and delivery of care of first-time soft-tissue knee injuries (ligament injuries, patella dislocations, meniscal injuries, and articular cartilage) in children (aged 12 years and older) and adults.

It is well known that articular cartilage in adults has a limited capacity for self-repair. Numerous methods have been devised to augument its natural healing response, but these methods generally lead to filling of the defect with fibrous tissue or fibrocartilage, which lacks the mechanical characteristics of articular cartilage and fails with time. Tissue engineering combines aspects of cell biology, engineering, material science and surgery to generate new functional tissue and provides an important approach to the repair of articular cartilage lesions and, ultimately, functional success. The purpose of our study was to perform experimental resurfacing of articular cartilage in 18 sheep using different techniques: before implantation in all sheep a full-thickness chondral lesion of medial femoral condyle was created; subsequently, autologous chondrocytes seeded into the matrix were implantd into five sheep; a periosteum flap was implanted in five sheep; and, as source of growth factors, adipocytes by vascular peduncle of Hoffa tissue were implanted in five sheep. The reparative tissue of the chondral lesion was compared with uninjured contralateral knee. The results present the bonding between implantation tissue and host tissue, preservation of phenotypic stability of chondrocytes culture, standard dosage of growth factor secreted by adipocytes and characterisation of the histological properties of reparative tissue, comparing different surgical techniques

The medial meniscus was resected from the right knees of twelve young grivet monkeys that were killed at intervals of twenty-one to 252 days after operation. The knees operated upon and the control knees were investigated radiologically and histologically. Degenerative changes occurred in the medial femoral and tibial condyles. At first there was loss of cells from the superficial layer of the articular cartilage, with a marked decrease in the acid mucopolysaccharide content of the matrix. The chondrocytes in the deeper layer of the non-calcified zone proliferated to form clones before finally degenerating. The acellular cartilage showed splitting, and with progress of the degenerative process there was thinning and erosion of the cartilage. Eventually there was complete loss of articular cartilage with thickening and exposure of the subchondral bone. These degenerative changes were confined to a small area of the articular cartilage and had occurred despite regeneration of the meniscus. The rest of the cartilage looked normal. It is concluded that articular cartilage deprived of the protection of a meniscus may undergo arthritic changes

Background: Animal studies have shown that 0.9% NaCl causes inhibition of proteoglycan metabolism in articular cartilage yet it continues to be the most commonly used irrigation fluid for arthroscopic surgery. Ringer’s solution and non ionic fluids have been shown to cause less damage. There is currently no such comparison in human articular cartilage. The aim of this study was to assess the effect of different irrigation fluids on arthritic and non arthritic human articular cartilage. Materials and Methods: Non arthritic cartilage specimens were obtained from femoral heads of hip fracture patients undergoing hemiarthroplasty where there were no radiological or macroscopic signs of osteoarthritis. Arthritic articular cartilage was obtained from tibial plateau of total knee arthroplasty patients or femoral heads with macroscopic signs of osteoarthritis. Cartilage explants were exposed to either 0.9% normal saline or Ringer’s solution, 1.5% Glycine, 10% Mannitol or a control solution of M199 culture medium. 0.5% bupivacaine, which has been shown to be toxic to chondrocytes, was used as a second control solution. The specimens were then incubated in culture medium containing radiolabelled 35-SO4 for 16 hours and uptake was measured as counts per gram per minute. Results: In non arthritic cartilage, the inhibition of proteoglycan synthesis was 0% with Ringer’s solution (p> 0.05), 3% with Glycine and Mannitol (p> 0.05), 12% with 0.9% NaCl (p> 0.05) and 75% with 0.5% bupivacaine (p< 0.001). In arthritic cartilage, the inhibition was 15% with Ringer’s solution (p> 0.05), 20% with Mannitol (p> 0.05), 30% with 0.9% NaCl and Glycine (p=0.04) and 85% with 0.5% bupivacaine (p< 0.001). Conclusion: Normal saline was most harmful to human articular cartilage. Ringer’s solution was the best solution for joint irrigation. We have provided yet more evidence to suggest that 0.5% bupivacaine is severely toxic to articular cartilage

Summary Statement. In articular cartilage defects, chemokines are upregulated and potentially induce the migration of bone marrow cells to accelerate the healing processes. Introduction. The treatment of damaged articular cartilages is one of the most challenging issues in sports medicine and in aging societies. In the microfracture technique for the treatment of articular cartilage defects, bone marrow cells are assumed to migrate from the bone marrow. Bone marrow cells are well-known for playing crucial roles in the healing processes, but how they can migrate from underlying bone marrow remains to be investigated. We have previously shown that SDF-1, one of chemokines, play crucial roles in the recruitment of mesenchymal stem cells in bone healing processes, and the induction of SDF-1 can induce a successful bone repair. If the migration can be stimulated by any means in the cartilage defects, a better result can be expected. The aim of this study was to elucidate the mechanisms of the migration of bone marrow cells and which factors contribute to the processes. Materials & Methods. Articular cartilage defects of 2 mm of diameter were created by drilling the cartilage with a wire to just the subchondral bone in 5-week-old SD rats. The width and depth of the created defects were confirmed by HE staining in histology. The healing tissues were harvested at days 2, 6, and 14 after the operation, and total RNAs were entracted. PCR array was conducted according to the manufacturer's instruction. Quantitative PCR (qPCR) was performed using cDNA of the healing tissues. Bone marrow cells were harvested from 5-week-old SD rat, and a standard migration assay was performed using chemokines. Results. CCL2, CCL3, CCL7 and CCL12 were upregulated in the healing tissues of cartilage defects shown by PCR array. The expression pattterns were confirmed by an expression analysis by qPCR. Both CCL2 and CCL3 induced the migration of bone marrow cells in the in vitro migration assay. Discussion/Conclusion. This study showed for the first time that CCL chemokines are upregulated in the articular cartilage defects and induce the migration of bone marrow cells. These results lead to an innovative measures along with an appropriate delivery method in induction the migration of bone marrow cells from the underlying bone marrow to stimulate articular cartilage healing processes

Surgical reconstruction of articular surfaces by transplantation of osteochondral autografts has shown considerable promise in the treatment of focal articular lesions. During mosaicplasty, each cylindrical osteochondral graft is centred over the recipient hole and delivered by impacting the articular surface. Impact loading of articular cartilage has been associated with structural damage, loss of the viability of chondrocytes and subsequent degeneration of the articular cartilage. We have examined the relationship between single-impact loading and chondrocyte death for the specific confined-compression boundary conditions of mosaicplasty and the effect of repetitive impact loading which occurs during implantation of the graft on the resulting viability of the chondrocytes. Fresh bovine and porcine femoral condyles were used in this experiment. The percentage of chondrocyte death was found to vary logarithmically with single-impact energy and was predicted more strongly by the mean force of the impact rather than by the number of impacts required during placement of the graft. The significance of these results in regard to the surgical technique and design features of instruments for osteochondral transplantation is discussed

We have previously shown that joint distraction and movement with a hinged external fixation device for 12 weeks was useful for repairing a large articular cartilage defect in a rabbit model. We have now investigated the results after six months and one year. The device was applied to 16 rabbits who underwent resection of the articular cartilage and subchondral bone from the entire tibial plateau. In group A (nine rabbits) the device was applied for six months. In group B (seven rabbits) it was in place for six months, after which it was removed and the animals were allowed to move freely for an additional six months. The cartilage remained sound in all rabbits. The areas of type II collagen-positive staining and repaired soft tissue were larger in group B than in group A. These findings provide evidence of long-term persistence of repaired cartilage with this technique and that weight-bearing has a positive effect on the quality of the cartilage

Summary Statement. Re-biopsies of five patients after spheroid-based, scaffold-free autologous chondrocyte transplantation revealed regeneration of cartilage with immunohistochemical characteristics of articular cartilage. Introduction. Traumatic lesions of articular cartilage represent a crucial risk-factor for cartilage degradation and osteoarthritis, because the regenerative capacity of articular cartilage is highly limited. Even if there exist several strategies to treat traumatic cartilage damages such as the classical autologous chondrocyte transplantation (ACT) or matrix assisted ACT, the optimal solution is not yet been found since transplantation errors are known. A relatively new strategy represents the scaffold-free spheroid based autologous chondrocyte transplantation. After harvesting articular cartilage in this strategy spheroids of chondrocytes will be synthesised after chondrocyte isolation and expansion. The spheroids will be implanted and rest at the transplantation site by adhesion. Patients & Methods. During the last two years 5 patients, which underwent spheroid-based ACT, gave reason for a second look arthroscopy due to clinical problems independent from the initial damage (e.g. meniscus lesion). In these patients a biopsy after informed consent was taken by help of a Jamshidi-needle (1,5 mm) which underwent histological analyses after haematoxilin-eosin and alcian blue staining as well as immunohistological analyses for Coll-II, Coll-X, Aggrecan, SOX-9 and lubricin via standardised automated staining methods. Furthermore, from one patient a surplus spheroid was analyzed by scanning and transmission electron microscopical methods after standard processing of the specimen. Results. The re-biopsies were taken after different time-points after ACT according to the clinical indication for arthroscopy. The histological analyses revealed in all patients the typical feature of hyaline chondroid tissue with high alcian-blue staining. The apical zone of the regenerated tissue demonstrated flattened chondrocytes, immunohistochemically positive for lubricine, a typical feature for normal articular chondrocytes. The middle and the deep zone revealed round shaped chondrocytes, which were positive for Coll-II, Sox-9 and aggrecan, the typical pattern for articular cartilage, but negative for Coll-X, which is typical for hypertrophic chondrocytes. In the surplus spheroid of one patient we could demonstrate collagen fibers between the round-shaped chondrocytes, which indicates collagen syntheses by the cells in the spheroid. Discussion/Conclusion. The present date represents the first histomorphological data after spheroid-based ACT. The findings indicate a proper regeneration of cartilage with immunohistological characteristics typical for articular cartilage. One explanation for these positive results even after 6 months of ACT could be a smooth phenotypic re-differentiation of the chondrocytes within the spheroid, which is given by the round shaped phenotype of the cells within the spheroid and the ultrastructural detection of collagen fibers. Finally, our findings demonstrate the need for further re-biopsy based analyses. To reach this goal a registry of ACT-Patients with an integrated alert-system by further Arthroscopy could give a chance to get more biopsies for histological and immunohistological data

High resolution imaging techniques such as atomic force microscopy, provide a platform to study the fibrillary architecture of biological tissues, but are not capable of imaging the internal microstructure of tissues in 3D. Conversely, multiphoton microscopes facilitate 3D imaging to study the spatial relationship of micro-components within tissues, but without the resolution of atomic force microscopy. The lamina splendens is the most superficial layer of articular cartilage. It is believed to play a crucial role in the health of the tissue. However, the precise form of this layer is uncertain as it has never been independently studied. Here, we use multiphoton microscopy and atomic force microscopy to demonstrate the anatomic form of the lamina splendens. The lamina splendens were peeled from the femoral condyles of healthy, adult sheep (n=20). Using atomic force microscopy, we show that the collagen and elastin form an interweaving fibrillary network at the surface of the lamina splendens and at the interface of the lamina splendens with the underlying cartilage. Moreover, using fluorescent stains; sulforhodamine B and acridine orange, multiphoton microscopy shows the heterogeneous distribution of collagen, elastin and chondrocytes throughout the depth of the lamina splendens. Our results demonstrate the fibrillary and component level architecture of the lamina splendens. We believe our findings provide the backbone of knowledge to advance tissue engineering techniques that will lead to more promising strategies to treat cartilage pathologies, including osteoarthritis. Furthermore, our results provide a starting point to determine the role of the lamina splendens in cartilage pathology

1. Articular cartilage from immature rabbits was placed in and near the rabbit knee joints for periods up to ten weeks. 2. Autografts of articular cartilage when placed free in the joint soon became adherent to its synovial lining; the cartilage with its subchondral bone remained viable. 3. Homografts remained viable in the presence of joint fluid, but when in contact with synovium antigenic cellular reaction was produced early. The presence of subchondral bone intensified this reaction and led to graft invasion and destruction. 4. Partial thickness homografts of articular cartilage were also antigenic and were absorbed. When full thickness cartilage was used, this cellular invasion was resisted by the zone of provisional calcification which appeared to function as a physical barrier against antigenic cells of the host. 5. When placed in muscle, both autogenous and homogenous grafts failed to survive through lack of nutrition, although the autogenous subchondral bone remained viable. It is inferred that subchondral circulation is not sufficient for cartilage survival and synovial fluid is essential for its proper nutrition. 6. Surviving immature articular cartilage transplants underwent "ageing" changes

Cryoprotectant toxicity has become more relevant because of increased use of high concentrations of cryoprotectants for vitrification of biologic tissues. A single toxicity model that integrates cryoprotectant concentration, time and temperature is essential to optimize the cryopreservation of tissues. The Weibull probabilistic distribution has been used in environmental toxicology research. This objective of this study was to fit the Weibull model to experimental data for chondrocyte recovery from articular cartilage exposed to various concentrations of dimethyl sulfoxide at different temperatures as a function of time. This study indicated that the Weibull model is an appropriate model to describe cryoprotectant toxicity to chondrocytes in articular cartilage. This study was designed to examine the toxicity of dimethyl sulfoxide (DMSO) on chondrocytes in porcine articular cartilage (AC) as a function of time, temperature and concentration. The Weibull model is suitable for modeling cryoprotectant toxicity in cartilage and can be further extended to other cellular and tissue systems. The model provides a simple method to predict toxicity and to assess the feasibility of cryopreservation protocols. The model proved to be a good fit for the entire data set of concentration, temperature and time, yielding an R2 value of 0.87 and a maximum discrepancy of 20% between the experimental data and the model. Estimates of the model’s parameters within a confidence interval of 95% were found to be: _=30±2, _=0.67±0.05, _C=0.38±0.03, _T=−2300±300 and _CT=700±100. Sliced porcine AC was exposed to DMSO (1, 3, 5, 6M) at different temperatures (0, 22, 37°C) for various durations. Cellular viability was determined by membrane integrity stains. Experimental data for chondrocyte recovery was fit to the global Weibull probabilistic distribution model using SPSS SigmaPlot 2000 to estimate the five parameters. A model integrating concentration, time, and temperature of exposure is required to optimize addition and removal protocols of high concentrations of cryoprotectant for cryopreservation. The Weibull distribution is a simple and flexible model used to describe similar processes. In the current study, chondrocyte viability decreased with increased concentration, temperature and time of exposure. The model indicated a significant interaction between the toxic effects of concentration and temperature

Acetabular reconstruction with impaction bone grafting and a cemented polyethylene aims to reconstitute the bone stock in hip revision. This is an effective but expensive, resource intensive and time consuming technique. Most surgeons remove the articular cartilage from the femoral head allograft. The aim of this study is to reproduce the results using the whole femoral head with the articular cartilage for acetabular impaction grafting. 38 acetabular revisions using impacted morselised bone graft retaining the articular cartilage and a cemented cup were studied retrospectively. The operations were performed by the senior author in Wrightington Hospital, UK with a posterior hip approach. The mean follow up was 4.1 years (range, 1–10 years). Clinical and radiological assessment was made using the Oxford hip score, Hodgkinson's criteria (1988) for socket loosening and the Gie classification (1993) for evaluation of allograft incorporation. Thirty-six (94.7%) sockets were considered radiologically stable (type 0, 1, 2 demarcations) and two (5.3%) sockets were radiologically loose (type 3 demarcations) but there was no socket migration. Twenty-one (55.3%) cases showed good trabecular remodeling (grade 3). Fourteen (36.8 %) cases showed trabecular remodeling (grade 2). Only three (7.9%) cases showed poor allograft incorporation (grade 1). Mean pre-operative hip score was 41 and post-operative hip score was 21. There was one (2.6%) wound infection treated with oral antibiotics and one (2.6%) periprosthetic femoral fracture treated with cables. Furthermore, there was one (2.6%) case of pulmonary embolism and three (7.89%) cases of asymptomatic heterotopic ossification. One year mortality rate was 2.6% (one case) from heart failure but not associated with the surgery. There have been no socket re-revisions (100% survival) at an average of 4 years. At a mean follow up of 4 years, results with the aforementioned technique are comparable to other major studies. Compared to the 40% of minimal loss in obtaining pure cancellous graft less than 10% of initial graft mass is lost without removing the articular cartilage. Particularly when the supply of allograft and operative time are limited retaining the articular cartilage of the femoral head is a safe and effective alternative to be considered

The purpose of the present study is to determine a correlation between articular cartilage changes and underlying bone contusions in ACL-deficient knees. Analysis of surgical and MRI findings in thirty-seven knees shows that medial femoral condyle and medial tibial plateau bone contusions, present in 30% of ACL injuries, correlate strongly with articular cartilage damage, irrespective of meniscal status. Although lateral compartment bone contusions are more commonly seen following injury, we have not found this to be associated with the status of the overlying cartilage. Degenerative changes in the ACL-deficient knee are multifactorial, but medial compartment bone contusions may be an important contributor that warrants further investigation. Despite successful reconstruction of the anterior cruciate ligament, many patients eventually develop osteoarthritis, suggesting that something in addition to mechanical instability may contribute. The purpose of the present study is to determine a correlation between articular cartilage changes and underlying bone contusions in ACL-deficient knees. Between January 2002 and March 2003, sixty-eight knees consecutively underwent ACL reconstruction at our institution. Presence and location of bone contusions on MRI were noted, and correlated to presence of articular cartilage changes and meniscal pathology witnessed during surgery. Of the sixty-eight knees operated, thirty-one were excluded because of either: pre-existing arthritis, previous surgery, presence of multiple ligament injury, or absence of bone contusions on MRI. In the analysis of the thirty-seven remaining knees, bone contusions were present on the medial tibial plateau and medial femoral condyle in 30%, on the lateral tibial plateau in 84%, and on the lateral femoral condyle in 73%. Articular cartilage damage is most commonly seen on the medial femoral condyle, irrespective of meniscal status. Analysis using Fisher’s Exact test shows that medial femoral condyle (p=0.026) and medial tibial plateau articular cartilage damage (p= 0.011) is strongly correlated with presence of underlying bone contusions. No association was found between lateral compartment articular cartilage status and presence of bone contusions. Although lateral compartment bone contusions are common following ACL injuries, we have not found an association with cartilage damage. Degenerative changes in the ACL-deficient knee are multifactorial, but medial compartment bone contusions may be an important contributor

Background. There are several case reports of chondrolysis following joint arthroscopy. Continuous post-operative infusion of local anaesthetic solutions, especially 0.5% Bupivacaine, has been implicated as the causative factor in many of these cases. Recent in vitro studies have shown that even a single exposure of articular cartilage to different local anaesthetic solutions can cause apoptosis and mitochondrial dysfunction in chondrocytes leading to cell death. There is currently no study looking at methods to prevent this toxicity of local anaesthetic solutions to articular cartilage. Glucosamine has a protective and reparative effect on articular cartilage and a Cochrane review in 2007 found that it provides mild benefit in pain and function in patients with arthritis. Aims. Oncologic: To compare the effect of a single exposure, in vitro, of different local anaesthetic solutions on human articular cartilage. To investigate the protective and reparative effects of Glucosamine on articular cartilage exposed to 0.5% Bupivacaine. Methods. Chondral explants (n = 354) were obtained from femoral heads of 14 fracture neck of patients undergoing hemiarthroplasty. To compare the effect of local anaesthetics, each specimen was exposed to one of 8 test solutions for one hour. After this exposure, the specimens were washed and incubated in culture medium containing radio-labelled 35-sulphur for 16 hours. The unbound radioactivity was then washed off and the chondral specimens were digested with proteinase for 24 hours. The uptake of 35-S by each specimen was measured and this gave an estimate of proteoglycan metabolism. Test solutions: 1. 1% Lidocaine; 2. 2% Lidocaine; 3. 0.25% Bupivacaine; 4. 0.5% Bupivacaine,. 5. 0.5% Levo-Bupivacaine; 6. Control solution of M199 culture medium. 7. To investigate its protective effect, 100 micrograms of Glucosamine was added along with 0.5% Bupivacaine; 8. To investigate the reparative effect of Glucosamine, the specimen was exposed to 0.5% Bupivacaine for one hour. After washing, 100 mcg of Glucosamine was added to the culture medium in which the chondral specimen was incubated. Results. Compared to the control culture medium, the inhibition of proteoglycan metabolism was 54% with 1% Lidocaine (p<0.001), 75% with 2% Lidocaine (p<0.01), 50% with 0.25% Bupivacaine (p = 0.04), 78% with 0.5% Bupivacaine (p<0.001) and 73% with 0.5% Levo-Bupivacaine (p<0.001). Adding Glucosamine for protection reduced the toxicity of 0.5% Bupivacaine to 43%, compared to 78% without. However, Glucosamine was not able to repair the damage caused by 0.5% Bupivacaine, with inhibition of proteoglycan metabolism at 70% even after 16 hours of incubation. Conclusion. All local anaesthetic solutions tested were toxic to articular cartilage, 0.5% Bupivacaine being the worst offender. Higher concentrations were more harmful. The addition of Glucosamine to 0.5% Bupivacaine protected against its toxicity to articular cartilage but was not able to repair the damage caused

Bone tendon junction (BTJ) healing after injury is often slow, without restoration of fibrocartilage transition zone. Fibrocartilage formation has been observed near articular cartilage. It was hypothesised that articular cartilage interposition could stimulate fibrocartilage transition zone regeneration and improve BTJ healing. Partial patellectomy repair was performed in goat. Articular cartilage harvested from excised patella segment was interposed between the patella and patellar tendon during repair. No cartilage interposition was used in control group. Samples were harvested at six, 12, and 24 weeks for histological examination (n=6 each). The histological images were digitised and analyzed using an image analysis system. Healing progress was assessed by the amount of new bone formation and fibrocartilage transition zone regeneration. Quantitative data were analyzed using SPSS version 14.0. Statistic al significance level was set at p < 0.05. There was progressive increase in maximum new bone length and area of new bone formed with time (p< 0.05, Kruskal-Wallis test). No difference was observed between treatment groups. Articular cartilage interposition resulted in more fibrocartilage regeneration and higher proteoglycan uptake at all time points. At 24 weeks, length of fibrocartilage formed measured 7760 ± 629 μm with articular cartilage interposition, compared with 787± 274 μm in control (p = 0.002, Mann-Whitney test). Safranin O length measured 3301 ± 1236 μm with articular cartilage interposition, compared with 277 ± 187 μm in control (p = 0.03, Mann-Whitney test). Autologous articular cartilage interposition stimulates fibrocartilage transition zone regeneration in BTJ repair without affecting bone formation

In least 12% of patients with symptomatic OA, the cause is joint injury that progressed over time to post-traumatic OA. Human adult articular cartilage has a limited innate ability to regenerate. Available treatment options are unable to restore native structure and function of hyaline cartilage. Agili-C (CartiHeal, Israel) is a first-in-class acellular scaffold consisted of two layers corresponding to cartilage and bone that is capable of attracting stem cells and guide a regenerative process in both tissues. Agili-C has been extensively tested in vitro in our laboratory using human normal cartilage and in vivo in preclinical and currently clinical studies. This scaffold consists of a natural crystalline aragonite, derived from corals, to which hyaluronic acid is added. It showed a great ability to induce regeneration of chondral and osteochondral lesions and attract chondrocytes and stems cells to fill the defect area. Cells remained viable over the course of the study (up to 2 months). Signs of the extracellular matrix formation were evident inside 3D structure of the scaffold. PG synthesis and gene expression of collagen type II and aggrecan were elevated by more than 2.5-fold in cartilage with the scaffold vs corresponding controls. Agili-C scaffold displays a potential in the treatment of focal chondral and osteochondral defects

1. The utilisation of labelled proline in normal and injured mature rabbit articular cartilage has been studied and compared simultaneously in one phase of the study with radiosulphate utilisation. The morphologic features of lacerative injury paralleled those reported previously. 2. Labelled proline is actively utilised by mature articular cartilage and can be recovered in time from the matrix as labelled hydroxyproline. This is taken as evidence of collagen synthesis. 3. Evidence is presented to suggest that the rate of formation of labelled hydroxyproline may be augmented after lacerative trauma. 4. Parallel utilisation of radiosulphate and labelled proline suggests that the synthesis of chondromucoprotein and collagen are closely related and that the continual synthesis of both moieties is necessary for the maintenance of normal matrix. 5. Despite evidence of increased chondromucoprotein and collagen synthesis no significant contribution is made to the healing of lacerative defects in mature rabbit articular cartilage

The hip joints are commonly affected in Juvenile Idiopathic Arthritis (JIA) in childhood. Common features are pain, subluxation, femoral anteversion, coxa valga, significant fixed flexion deformity and a true arthritis, with loss of articular cartilage principally from the femoral head but also the acetabulum. In children with JIA, it is accepted that a medial soft tissue release of the hips, dividing adductor longus, adductor brevis and the ilio-psoas, is a useful tool in the management of significant hip joint involvement. The principal indication for surgery is the relief of pain, but other benefits are correction of fixed flexion deformity, restoration of articular cartilage, increased abduction of the hips and, in those children who are unable to walk, frequently a transition to the potential to walk. The procedure is nearly always performed bilaterally. Our study aimed to document the restoration of articular cartilage at the hips following soft tissue release. It has been noted in the literature that there is regrowth of articular cartilage in the hip but there has been no true documentation of this and x-ray studies are unreliable as the elimination of fixed flexion deformity can prejudice accurate analysis of femoral head geometry on 2 –dimensional views. We therefore carried out MRI scanning of the hips, immediately prior to the soft tissue release and 12–18 months post-operatively. In 10 consecutive patients analysed, scans demonstrated true articular cartilage regrowth in 8 cases. We thus conclude that soft tissue release of the hips in JIA is a useful management tool, and may to some extent reverse the severe articular cartilage loss seen in these children. The next stage of our study is to analyse the articular cartilage at the time of subsequent hip arthroplasty to determine whether true hyaline cartilage is reformed or whether the reconstitute represents fibrocartilage

Summary Statement. Extended expansion of cells derived from equine articular cartilage reveal maintenance of chondrogenic potency and no evidence of senescence up to 100 population doublings. The data suggests the reclassification of these cells from progenitor cells to stem cells. Introduction. One sign of ‘in vitro aging’ is the diminishing capacity for cell division. In contrast to embryonic stem cells that show no loss of proliferative potency, the maximal population doublings (PD) for mesenchymal stem cells (MSCs) in vitro is reported to be between 30 and 40 replications 1,2,3. We have isolated a population of chondroprogenitor cells from articular cartilage of several species, including equine4. These cells have demonstrated functional equivalence in their differentiation capacity when compared with MSCs but have the advantage of retaining the highly desirable stable (permanent) chondrocyte phenotype. In this study, we examined the age-related capacity of these cells for extended division and retention of potency. Methods. Chondroprogenitors were isolated from equine articular cartilage by adhesion onto fibronectin5. Cells were isolated from both skeletally immature (1 year-old) and mature animals (8 year-old). Clonal and polyclonal cell lines (at least 5 of each for each age) were cultured in the presence of 10% FCS, 1ng/ml TGFb-1 & 2.5 ng/ml FGF-2. Cells were seeded at low density and passaged weekly. Results. Chondroprogenitors from both animals reached over 40 (mean) PD in 50 days with growth remaining linear. Little difference in growth rates was observed between clonal and polyclonal cell lines. For the mature animal, 96% of cells were BrDU positive at 22 PD whilst none of cells were (senescence associated) β-gal positive. At 44 PD, 88% of cells were BrDU positive and just 15% of cells were β-gal positive. Three clonal and three polyclonal cell lines from the mature animal were cultured beyond the 50-day time point. At 120 days, cells reached up to 90 PD with the same pattern of linear growth observed. When tested at 70 PD, 79% of these cells were still BrDU positive (range 55–97%) and just 11% of cells were β-gal positive (range 2–22%). Furthermore, little difference in cell morphology was observed throughout this extended expansion. At 70 PD, we found that both clonal and polyclonal cell lines in monolayer culture were still expressing the chondrogenic transcription factor; Sox-9. Expression of genes for aggrecan and collagen type II was also detected in cells that were chondrogenically induced for 72 hours. Discussion & Conclusions. We have demonstrated for the first time the extended expansion of cells derived from articular cartilage that retain chondrogenic potency. These equine cells have since been cultured to over 100 PD without evidence of senescence. One hundred PD is equivalent to 1 × 1030 cells originating from a single cell. We have previously reported that the human equivalents of these cells surpass MSCs in doubling capacity but senesce at approximately 60 PD6. The properties of these equine chondroprogenitor cells make them ideal candidates for allogeneic cell therapy for articular cartilage repair. In addition, the data suggest the reclassification of these cells from progenitor cells to stem cells

Use of scaffolds for articular cartilage repair (ACR) has increased over the last years with many biomaterials options suggested for this purpose. It is known that scaffolds for ACR have to be optimally biodegradable with simultaneous promotion of chondrogenesis, favouring hyaline cartilage formation under rather complex biomechanical and physiological conditions. Whereas improvement of the scaffolds by their conditioning with stem cells or adult chondrocytes can be employed in bioreactors, “ideal” scaffolds should be capable of performing such functions directly after implantation. It was previously considered that scaffold structure and composition would be the best if it mimics the structure of native cartilage. However, in this case no clear reparative stimuli are being imposed on the scaffold area, which would drive chondrocytes activity in a desired way. In this work, we studied new xeno-free, recombinant human type III collagen-laden polylactide (PLA) mesh scaffolds, which have been designed, produced, and biomechanically optimized in vitro and in vivo validated in a porcine and equine model. The scaffolds were additionally assessed for relative performance simulated synovial fluids for both human conditions and veterinary cases. It was experimentally shown that success of the scaffolds in ACR eventually require lower stiffness than surrounding cartilage yet matching the strain compliance, different in static and dynamic conditions. This ensures an optimal combination of load transfer and oscillatory nutrients supply to the cells, which otherwise is difficult to rely on just with a passive diffusion in avascular cartilage conditions. The results encourage further development of such scaffold structures targeted on their best clinical performance rather than trying to imitate the respective original tissue. The authors would like to thank Finnish Agency for Innovation (Tekes) for providing financial support to this project. A.Z. also acknowledges Teknos Foundation (Finland) for the scholarship

The collagen framework of articular cartilage is disposed, as in other connective tissues, to resist tension forces within the material. In this paper the fine structure of articular cartilage, as demonstrated by polarised light microscopy and electron microscopy, is related to the gross anatomy and to the naked eye changes of chondromalacia and fibrillation

Purpose: Hormone replacement therapy for the menopause seems to be associated with a decrease in the prevalence of symptoms and radiological alterations related to hip and knee osteoarthritis. However, little is known on the effects of estrogen in articular cartilage and intervertebral disc (IVD). The aim of this study was to evaluate the developmental changes in mouse articular cartilage and intervertebral discs under estrogen deficiency. Method: Experimental studies used 6- to 7-month-old adult female wild-type or bilaterally ovariectomized (OVX) C57Bl/6 mice. All animals were sacrificed at the same age interval (8- to 9-months) and stored at −20°C. Prior to dissection, posterior-anterior and lateral x-rays of whole mice were done. Right knee joint and cervical to lumbar spine were stained with hematoxylineosin (H& E), Safranin-O/Fast green, and Weigert’s hematoxylin/alcian blue/picrosirius red for histological analysis. Bone mineral density (BMD) was measured using a PIXImus Bone Densitometer System. Micro computed tomography (CT) data were acquired on a SkyScan T1072 X-ray Microscope-Microtomograph. Results: Degeneration, including the loss of notochordal cells, was observed in the nucleus pulposus (NP) of the IVD of OVX mice. The annulus fibrosus (AF) showed marked thinning as compared to the wild type. Furthermore, the OVX group showed decreased IVD heights and trend of endplate ossification. Knee joints of OVX mice showed a trend towards having more gross degenerative changes, like areas of cartilage erosion. A decrease in articular cartilage thickness was also observed. Certain layers of cartilage were more affected than others, suggesting a specific role of estrogens in the developing cartilage. Also, the BMD was reduced in both the femur and lumbar vertebrae of the OVX group. Finally, MicroCT results showed a decrease in percent bone volume, trabecular thickness, trabecular number, and an increase in trabecular separation. Conclusion: The present study showed AF thinning, decreased IVD height, NP degeneration, and loss of cellular components in the NP in ovariectomized mice. Likewise, the articular cartilage revealed more degenerative changes, including a decrease in articular thickness. Results suggest that estrogens play a role in maintaining healthy cartilage and IVD

1. The routes by which adult human articular cartilage can receive its nutrition is still a subject of controversy. 2. Microscopic examination of normal adult human femoral heads has revealed vascular channels which penetrate the subchondral plate and calcified cartilage. These channels bring the medullary soft tissue into contact with the articular cartilage. 3. A fluorescent dye migration technique was used to show that the observed vascular channels are pathways for dye from the medullary cavity to the articular cartilage. It is suggested that these pathways could also be routes by which articular cartilage receives part of its nutrition. 4. The nutritional mechanism in the mature rabbit and adult human femoral heads cannot be compared because histological studies revealed differences in their subchondral structures

1. Twelve trephine specimens of articular cartilage and subchondral bone taken from six fresh osteoarthritic femoral heads were incubated in a medium containing tritiated thymidine, and autoradiographs were prepared from serial sections five microns thick. 2. Scattered labelling of chondrocytes in sections from four of the six femoral heads was demonstrated. No more than four labelled cells were seen in any one section. About half were found in typical chondrocyte clusters. 3. The implications of this evidence of chondrocyte multiplication with regard to the repair of damaged articular cartilage are discussed

Background. Osteoarthritis (OA), a common degenerative disorder of synovial joints, is characterized by disruption of the extracellular matrix (ECM) homeostasis with an overall misbalance towards cartilage catabolism. Integrins are alpha/beta heterodimeric transmembrane proteins transmitting chemical and biomechanical signals into the cells. There is a growing consensus that changes of ECM composition by proteolytic degradation of matrix constituents, or alteration of the biomechanical microenvironment of chondrocytes caused by chronic stress or injury significantly increase the risk of OA through the perturbation of integrin signaling. In order to further investigate the role of the b1 integrin subfamily in OA, we have challenged hip cartilage explants dissected for mice lacking beta1 integrins in chondrocytes by cytokines, ECM degradation products or mechanical stimulation. Methods. Femoral articular cartilages were avulsed from hip joints of 6 weeks old wild type (WT) and b1fl/fl-PrxCre mutant (MT) mice. For the chemically-induced OA-like stimulation, femoral caps were cultured for 3 days in serum-free DMEM/F12 with or without the supplementation of interleukin-1a (IL1a), 120kDa cell-binding fibronectin fragments (120FNf), or tumor necrosis factor-alpha (TNFa) + oncostatin M (OM). Sulphated glycosaminoglycan (sGAG) release of the explants were measured in the supernatants by the 1,9-dimethylmethlene blue (DMMB) assay. Proteoglycan loss was monitored by Safranin-O (SO) staining on cryo-sections of the explants. For the cartilage injury model, avulsed femoral caps were either directly snap-frozen or kept in serum-free DMEM/F12 for 4 hours before snap-freezing. Gene expression changes were analyzed by quantitative RT-PCR using a pre-determined set of genes regulated by injury. Results. Articular cartilages of MT mice were found to have consistently higher release of GAGs when exposed to cytokines or 120FNf. IL-1a exerted the highest catabolic stimulation. The ex vivo biochemical analysis was further verified by SO staining demonstrating more pronounced proteoglycan loss on MT sections compared to WT. Assessing the mRNA of articular cartilages subjected to the injury model, revealed expression changes in genes which have been previously implicated in OA: Il1a (interleukin 1, alpha) and Ptgs2 (prostaglandin-endoperoxide synthase 2) were upregulated in MT mice; whereas Il1rl1 (interleukin 1 receptor-like 1) and Nos2 (nitric oxide synthase 2) expression levels were significantly reduced in MT compared to WT. Conclusion. The data imply that b1 integrins play a protective role against cytokine- and fibronectin fragment-induced cartilage degradation. Our findings also suggest that b1 integrins modulate the expression of catabolic factors upon mechanical insults

Purpose: Damage to articular cartilage leads to an incomplete healing response. This has elicited interest in improving the understanding of chondrocyte biology and finding ways to stimulate a more effective repair response. Neuropeptides play a role in the proliferative and reparative processes of many tissue types, but little is known about their effects on articular cartilage. This research aimed to investigate the effect of four neuropeptides on articular chondrocytes. Method: Bovine chondrocytes were cultivated in monolayer culture in media alone or media containing one of four neuropeptides: NPY, CGRP, SP, and VIP. Enzymatically digested chondrocytes from the articular surface of the femoral trochlea, femoral condyles, and patella of freshly slaughtered veal (n=8) were plated at 1×10^5 cells/mL in DMEM complete media with 5% FCS. Proliferation and proteoglycan assays were conducted at days 2,4,6, and 8. Results: Substance P showed a statistically significant stimulatory effect on chondrocyte proliferation and proteoglycan production that was greatest at a concentration of 5 μg/ml. NPY and VIP showed a dose dependent suppressive effect on chondrocyte proliferation that was greatest at their highest concentrations and was significant at all time points, with the exception of VIP at day 2. CGRP showed no significant effect on proliferation or proteoglycan production. Conclusion: Substance P showed a reliable stimulation of chondrocyte proliferation and proteoglycan production while NPY and VIP showed dose-dependent depressive effects. These findings support the idea that the peripheral nervous system, through neuropeptides, exerts direct influence on articular chondrocytes. This may provide some insight into the pathophysiology of inflammatory and degenerative arthritis and provide targets for modifying the repair response of articular cartilage

We have investigated in vitro the release kinetics and bioactivity of fibroblast growth factor-2 (FGF-2) released from a carrier of fibrin sealant. In order to evaluate the effects of the FGF-2 delivery mechanism on the repair of articular cartilage, full-thickness cylindrical defects, 5 mm in diameter and 4 mm in depth, which were too large to undergo spontaneous repair, were created in the femoral trochlea of rabbit knees. These defects were then filled with the sealant. Approximately 50% of the FGF-2 was released from the sealant within 24 hours while its original bioactivity was maintained. The implantation of the fibrin sealant incorporating FGF-2 successfully induced healing of the surface with hyaline cartilage and concomitant repair of the subchondral bone at eight weeks after the creation of the defect. Our findings suggest that this delivery method for FGF-2 may be useful for promoting regenerative repair of full-thickness defects of articular cartilage in humans

Summary. Nasal Chondrocytes are safe and feasible for tissue engineering approaches in articular cartilage repair. Introduction. As compared to articular chondrocytes (AC), nasal septum chondrocytes (NC) proliferate faster and have a higher and more reproducible capacity to generate hyaline-like cartilaginous tissues. Moreover, the use of NC would allow reducing the morbidity associated with the harvesting of cartilage biopsy from the patient. The objective of the present study was to demonstrate safety and feasibility in the use of tissue engineered cartilage graft based on autologous nasal chondrocytes for the repair of articular defect in goats. Methods. Isolated autologous NC and AC from 6 goats were expanded and GFP-labelled before seeding 4×10. 4. cells/cm. 2. on a type I/III collagen membrane (Chondro-Gide®, Geistlich). After 2 weeks of chondrogenic differentiation 2 NC- and 2 AC-based grafts were implanted into chondral defects (6mm diameter) of the same posterior stifle joint. Repair tissue was harvested after 3 or 6 months and the decalcified samples evaluated according to O'Driscoll. Furthermore, samples from the surrounding fat pad, ligament, synovium, tendon and patellar cartilage were harvested and isolated cells tested for GFP-positivity after expansion using FACS. Results. No surgical complication or signs of inflammation occurred in any of the animals. GFP-positive cells were detectable in the repair tissue, indicating the contribution of the implanted cells to the newly formed cartilage. The O'Driscoll score of the repair tissue increased from 8.6 and 7.6 after 3 months to 14.1 and 12.4 after 6 months for nasal and articular grafts, respectively. Surrounding tissues showed no or very low (fat pad 0–0.36%) migration of the grafted cells. Conclusion. Our results demonstrate the use of NC as safe and feasible for tissue engineering approaches in articular cartilage repair. The repair tissue-quality generated by NC-grafts was demonstrated to be at least comparable to that of AC-grafts, thus opening the way for clinical test of a novel therapeutic strategy

Osteoarthritis is one of the most common musculoskeletal diseases. It involves degeneration and loss of articular cartilage, leading to a painful bone on bone articulation during movement. Numerical FEA models exist to predict the mechanical behaviour of degenerated cartilage. One of the limitations of these models arises from the poor validation that can be attained with traditional experimental data. This typically relies on comparison with global mechanical quantities such as total tissue strain, which mask the individual contributions originating from the different layers. In order to improve on this, an experimental method was developed to visualise the through-thickness behaviour of articular cartilage. Four experiments were performed on hemi-cylindrical cartilage plugs, harvested from a porcine femoral head, and immersed in a fluid solution. An Indian ink speckle pattern was applied to the flat surface of each hemi-cylinder. The specimens were equilibrated in 2.5M NaCl solution, transferred to a custom designed testing rig, and a reference image of the tissue cross-section was taken. The solution concentration was then decreased to 0.15M and, predictably, the tissue thickness changed. Images of the tissue cross section were taken every 60s for the duration of the experiment (3600s). All images were analysed using a DIC algorithm (Ncorr open-source 2D digital image correlation matlab program), and documented the strain changes through the tissue thickness as a function of time. The measured total strain in the tissue was consistent with that reported by Lai et al. (1991). However the present technique allows to quantify the strain contribution from any of the tissue layers or sublayer. This poses a significant advantage over traditional methods as resulting information can further the understanding of the factors contributing to the mechanical behaviour of the tissue and provides an ideal platform for validating more and more refined models of tissue behaviour

1. Six cases of necrosis of articular cartilage complicating slipping of the upper femoral epiphysis are reviewed: histological examination in one case showed death of the superficial two-thirds of the articular cartilage, with survival of a layer of basal chondrocytes. In all six cases, after severe initial reduction of joint space as seen radiographically, there was gradual return of joint space, suggesting some regeneration of articular cartilage. The prognosis after cartilage necrosis is therefore not always so bad as has been supposed. 2. Various hypotheses concerning the cause of cartilage necrosis complicating slipped epiphysis are reviewed. The precise cause remains unknown, but there is substantial evidence against its being a consequence of ischaemia of the femoral head

Aims. The aim of this study was to evaluate antegrade autologous bone grafting with the preservation of articular cartilage in the treatment of symptomatic osteochondral lesions of the talus with subchondral cysts. Patients and Methods. The study involved seven men and five women; their mean age was 35.9 years (14 to 70). All lesions included full-thickness articular cartilage extending through subchondral bone and were associated with subchondral cysts. Medial lesions were exposed through an oblique medial malleolar osteotomy, and one lateral lesion was exposed by expanding an anterolateral arthroscopic portal. After refreshing the subchondral cyst, it was grafted with autologous cancellous bone from the distal tibial metaphysis. The fragments of cartilage were fixed with 5-0 nylon sutures to the surrounding cartilage. Function was assessed at a mean follow-up of 25.3 months (15 to 50), using the American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot outcome score. The radiological outcome was assessed using MRI and CT scans. Results. The mean AOFAS score improved from 65.7 (47 to 81) preoperatively to 92 (90 to 100) at final follow-up, with 100% patient satisfaction. The radiolucent area of the cysts almost disappeared on plain radiographs in all patients immediately after surgery, and there were no recurrences at the most recent follow-up. The medial malleolar screws were removed in seven patients, although none had symptoms. At this time, further arthroscopy was undertaken, when it was found that the mean International Cartilage Repair Society (ICRS) arthroscopic score represented near-normal cartilage. Conclusion. Autologous bone grafting with fixation of chondral fragments preserves the original cartilage in the short term, and could be considered in the treatment for adult patients with symptomatic osteochondral defect and subchondral cysts. Cite this article: Bone Joint J 2018;100-B:590–5

Experimental and clinical studies have documented that meniscal allografts show capsular ingrowth in meniscectomized knees. However it remains to be established whether meniscal allograft transplantation can prevent degenerative changes after total meniscectomy. In this study, functional changes in articular cartilage after meniscus transplantation in rabbits were evaluated quantitatively. Thirty rabbits were divided into five groups. Group A and Group C were subjected to meniscectomy. Group B and Group D underwent meniscal transplantation immediately after meniscectomy. Group E had delayed transplantation 6 weeks after meniscectomy. Six nonoperated knees served as controls. Using image analysis with QwinPro software ffunctional changes of articular cartilage were examined 6 weeks (Groups A, B) and 1 year (Groups C, D, E, controls) after surgery by measuring the lactate dehydrogenase (LDH) activity in chondrocytes as a measure of their vitality and the proteoglycan content of the extracellular matrix as a measure of its quality. All experimental groups demonstrated a significant decrease in proteoglycan content of the cartilage as compared with the control group. At 6 weeks and 1 year follow-up, no significant differences were found between the postmeniscectomy group and immediate transplant group. The delayed transplant group showed a significantly decreased proteoglycan content as compared with the postmeniscectomy group. Compared to the control group, no significant differences in cellular LDH activity were found in the postmeniscectomy group and immediate transplant group at 6 weeks and 1 year. However, delayed transplantation caused diminished vitality of chondrocytes. No significant differences were found between the postmeniscectomy group and immediate transplant group at 6 weeks and 1 year. The delayed transplant group showed a significant decrease in LDH activity as compared with the postmeniscectomy group. It can be concluded that immediate meniscal transplantation in rabbits did not significantly reduce degenerative changes of articular cartilage whereas delayed transplantation leads to even more degenerative changes than meniscectomy

We produced large full-thickness articular cartilage defects in 33 rabbits in order to evaluate the effect of joint distraction and autologous culture-expanded bone-marrow-derived mesenchymal cell transplantation (ACBMT) at 12 weeks. After fixing the knee on a hinged external fixator, we resected the entire surface of the tibial plateau. We studied three groups: 1) with and without joint distraction; 2) with joint distraction and collagen gel, and 3) with joint distraction and ACBMT and collagen gel. The histological scores were significantly higher in the groups with ACBMT collagen gel (p < 0.05). The area of regenerated soft tissue was smaller in the group allowed to bear weight (p < 0.05). These findings suggest that the repair of large defects of cartilage can be enhanced by joint distraction, collagen gel and ACBMT

Background. Continuous post-operative infusion of local anaesthetic solutions has been implicated as the causative factor in many cases of chondrolysis. Recent in-vitro studies have shown that even a single exposure to local anaesthetic can cause apoptosis and mitochondrial dysfunction leading to chondrocyte death. Glucosamine has been shown to have a protective and reparative effect on articular cartilage. Aims. To compare the effect of a single exposure of different local anaesthetic solutions on human articular cartilage and to investigate the protective and reparative effects of Glucosamine on articular cartilage exposed to 0.5% Bupivacaine. Methods. Chondral explants (n=354) were obtained from femoral heads of hip fracture patients undergoing hemiarthroplasty. Each specimen was exposed to one of 8 test solutions for one hour. The specimens were then incubated in culture medium containing radio-labelled 35-sulphur for 16 hours. The uptake of 35-S by each specimen was measured to give an estimate of proteoglycan metabolism. Test solutions. 1. 1% Lidocaine 2. 2% Lidocaine 3. 0.25% Bupivacaine, 4. 0.5% Bupivacaine, 5. 0.5% Levo-Bupivacaine 6. Control solution of M199 culture medium. 7. To investigate its protective effect, 100 micrograms of Glucosamine was added along with 0.5% Bupivacaine 8. To investigate its reparative effect, Glucosamine was added after exposure to Bupivacaine for an hour. Results. Compared to the control solution, the inhibition of proteoglycan metabolism was 64% with 1% Lidocaine(p< 0.001), 79% with 2% Lidocaine(p< 0.001), 61% with 0.25% Bupivacaine(p< 0.001), 85% with 0.5% Bupivacaine(p< 0.001) and 77% with 0.5% Levo-Bupivacaine(p< 0.001). Adding Glucosamine reduced Bupivacaine toxicity to 43%(p< 0.001). Glucosamine marginally repaired the damage caused by Bupivacaine, with inhibition of proteoglycan metabolism at 70%(p=0.004). Conclusion. All local anaesthetic solutions were toxic to articular cartilage. The addition of Glucosamine to 0.5% Bupivacaine protected against its toxicity to articular cartilage

Due to recent advances in diagnostic technology and an increased awareness among clinicians, osteochondral damage is being detected more frequently. Thus, there is a need to preserve and store articular cartilage for the repair of joint surfaces. Chondrocytes, embedded within extracellular matrix must remain viable during storage for successful tissue transplantation. We have been able to store osteochondral tissue for over a month and maintain high chondrocyte viability. Apoptosis can be minimized in articular cartilage during hypothermic storage if biopreservation media (XVIVO-10) is used. Cadaveric osteochondral dowels are a potential source of tissue for banking and allogeneic transplantation. The purpose of this study was to:. Establish a timeline and optimal conditions for storing human articular cartilage (AC). Determine a suitable source of AC for banking and transplantation. Distinguish apoptosis from necrosis in human AC following hypothermic storage. Forty fresh human AC samples from femoral condyle notchplasties were used to determine a storage timeline. Each sample was divided into three portions:. initial chondrocyte viability,. stored in phosphate buffered saline,. stored in Biowhitaker XVIVO-10. All samples were randomly allocated to one of five time intervals (2–10 weeks). Following each time period final viability assays were conducted. Secondly, osteochondral dowels were drilled from eight cadaveric femoral condyles. Five dowels were obtained from each joint: one for initial viability/annexin V assays, the others were stored in PBS or XVIVO-10 for four and six weeks. Following storage, final viability, annexin V, and TUNEL assays were preformed. Notchplasty samples stored in XVIVO-10 for four weeks had an average final viability of 68%, but an average loss in viability of only 6%. By one month the viability of samples stored in PBS had dropped to 5%. Osteochondral dowels stored in XVIVO-10 not only had greater chondrocyte viability, but less apoptosis. Cadaveric dowels are a suitable source of osteochon-dral tissue for hypothermic storage and in turn allogeneic transplantation. An osteochondral tissue bank would provide a reliable source of articular cartilage for repairing joint surfaces for patients who are not suitable candidates for total joint replacements

Background. Mechanical trauma to articular cartilage is a known risk factor for Osteoarthritis (OA). The application of single impact load (SIL) to equine articular cartilage is described as a model of early OA changes and shown to induce a damage/repair response. Recombinant Human Fibroblast Growth Factor-18 (rhFGF-18) has been previously shown to have anabolic effects on chondrocytes in vitro. The aim of this in vitro study was to ascertain the effect of rhFGF-18 on the repair response of mechanically damaged articular cartilage. Methods. Articular cartilage discs were harvested from healthy mature horses (n=4) and subjected to single impact load using a drop tower device. The impacted explants, together with unimpacted controls were cultured in modified DMEM +/− 200ng/ml rhFGF-18 for up to 30 days. Glycosaminoglycan (GAG) release into the media was measured using the dimethylmethylene blue (DMMB) assay, aggrecan neopepitope CS846 and Collagen Propeptide II (CPII) were measured by ELISA. Histological analysis, immunohistochemistry and TUNEL staining were used to assess proteoglycan content, type II and type VI collagen localisation, cell morphology, repair cell number and cell death. Results. Impacted explants treated with rhFGF-18 showed significantly more GAG release and CS846 release into the media compared to other experimental groups (p<0.05), but no significant increase in CPII levels. Loaded sections treated with rhFGF-18 had increased type II and VI collagen immunohistochemistry scores, more repair cells on the tissue surface and significantly less cell death (p<0.001) compared to other experimental groups at day 30 in culture. Conclusion. In an in vitro damage/repair model, rhFGF-18 increases the proteoglycan synthesis, collagen type II and VI protein within sections and the repair cell number and prevents apoptosis at Day 30. This suggests that rhFGF18 may be a good candidate for enhancement of cartilage repair following mechanical damage

The three-dimensional architecture of bovine articular cartilage collagen and its relationship to split lines has been studied with scanning electron microscopy. In the middle and superficial zones, collagen was organised in a layered or leaf-like manner. The orientation was vertical in the intermediate zone, curving to become horizontal and parallel to the articular surface in the superficial zone. Each leaf consisted of a fine network of collagen fibrils. Adjacent leaves merged or were closely linked by bridging fibrils and were arranged according to the split-line pattern. The surface layer (lamina splendens) was morphologically distinct. Although ordered, the overall collagen structure was different in each plane (anisotropic) a property described in previous morphological and biophysical studies. As all components of the articular cartilage matrix interact closely, the three-dimensional organisation of collagen is important when considering cartilage function and the processes of cartilage growth, injury and repair

We have studied whether the state of the articular cartilage at the time of rotational acetabular osteotomy for dysplasia of the hip affects the outcome 2 to 5.5 years after surgery. Arthroscopy in 57 patients (59 joints) at the time of the operation showed grade-0 changes in seven, grade-1 in nine, grade-2 in 17, grade-3 in 14 and grade-4 in 12 joints, according to the classification of Outerbridge. There was radiological evidence of the progression of arthritis in four joints which were classified at arthroscopy as grade 4. Stepwise regression analysis showed that damage to acetabular or femoral articular cartilage significantly affected the progression of arthritis. We conclude that the short-term results of successful rotational acetabular osteotomy for dysplasia are affected by the state of the articular cartilage

We describe 119 meniscal allograft transplantations performed concurrently with articular cartilage repair in 115 patients with severe articular cartilage damage. In all, 53 (46.1%) of the patients were over the age of 50 at the time of surgery. The mean follow-up was for 5.8 years (2 months to 12.3 years), with 25 procedures (20.1%) failing at a mean of 4.6 years (2 months to 10.4 years). Of these, 18 progressed to knee replacement at a mean of 5.1 years (1.3 to 10.4). The Kaplan-Meier estimated mean survival time for the whole series was 9.9 years (. sd. 0.4). Cox’s proportional hazards model was used to assess the effect of covariates on survival, with age at the time of surgery (p = 0.026) and number of previous operations (p = 0.006) found to be significant. The survival of the transplant was not affected by gender, the severity of cartilage damage, axial alignment, the degree of narrowing of the joint space or medial versus lateral allograft transplantation. Patients experienced significant improvements at all periods of follow-up in subjective outcome measures of pain, activity and function (all p-values < 0.05), with the exception of the seven-year Tegner index score (p = 0.076)

1. The changes resulting from superficial scarification of articular cartilage have been observed in the knee joint of adult rabbits. A reduction in the amount of stainable matrix ground substance occurred at the sites of damage. Particular attention was therefore paid to sulphated mucopolysaccharide synthesis by cartilage cells in or near the traumatised areas. 2. The femoral groove cartilage one week after scarification showed evidence of increased mucopolysaccharide synthesis, especially by the more superficial chondrocytes near the cuts, but three or four weeks later the enhanced chondrocyte activity tended to diminish, and after six weeks the superficial cells near the cuts were found to be inactive. From six to thirty-four weeks the loss of stainable ground substance extended more deeply, but cell degeneration in these deeper areas of matrix depletion was preceded by a period in which many of the deeper chondrocytes still showed evidence of active mucopolysaccharide synthesis. Cellular activity in tags of depleted cartilage was usually lost before the tags finally disintegrated. Chondrocyte clusters were often seen in the scarified areas, especially in the deeper zones. They seemed to be a reactive rather than degenerative phenomenon. 3. In the scarified cartilages of the patella examined after one week a reactive response by superficial chondrocytes was less evident than in the femoral cartilage from the same joint, and after six weeks areas of deeply extending matrix loss were exceptional. 4. The structural and functional changes in the rabbits' femoral articular cartilage after its scarification resembled those which have been observed in the developing cartilage lesion of human osteoarthritis–namely, loss of interstitial matrix and superficial fibrillation, a stimulated synthesis of chondroitin sulphate by the chondrocytes, and the appearance of cell clusters in the deeper zones. Within the period of the experiment, up to thirty-four weeks, the joint lesions remained strictly localised to the traumatised areas ofcartilage, and exposure of bone and joint remodelling, which are features of advanced osteoarthritis in man, were not seen

Cryopreserving agents (CPAs) can cryopreserve articular cartilage (AC) but their use is limited due to cellular toxicity. This study examined the time-dependent penetration of multiple CPAs into intact porcine AC. Porcine AC was immersed in CPAs for various amounts of time at three temperatures (4°C, 22°C, and 37°C). The results demonstrated an initial sharp rise in CPA concentration within the matrix for dimethyl sulfoxide and propylene glycol with maximum concentration after three to six hours. The trehalose and glucose concentration increased minimally even after twenty-four hours of exposure. The information from this study provides insight into the penetration kinetics of cryoprotectant agents into AC. This study examined the time-dependent penetration of cryoprotectant agents (CPAs) [dimethyl sulfoxide (DMSO), propylene glycol (PG), trehalose and glucose] into intact porcine articular cartilage (AC). Penetration of DMSO and PG into AC was rapid but time and temperature dependent while trehalose and glucose had poor penetration. The information gathered from this study can determine concentrations of CPAs within the cartilage matrix to create cryopreservation/vitrification solutions while minimizing toxicity. The results demonstrated there was a sharp rise in the CPA concentration within 15–30min exposure to DMSO and PG and the concentration peaked after three to six hours exposure at a concentration approximately 90% of the original concentration (6.5 molar). This was temperature dependent with slower penetration at lower temperatures. The trehalose and glucose had very poor penetration into the matrix at all temperatures, with a maximum penetration of 2% of the original concentration. Dowels of porcine AC (10mm diameter) were immersed in high concentration of each CPA for various amounts of time (0min, 15min, 30min, 60min, 3hr, 6hr, and 24hr) at three temperatures (4°C, 22°C, and 37°C). The cartilage was excised and the amount of cryoprotectant within the matrix determined. Successful cryopreservation of AC could improve clinical results of osteochondral allografting and provide a useful treatment alternative for large cartilage defects. However, successful cartilage cryopreservation is limited by chondrocyte death and matrix disruption due to inadequate CPA penetration

Anterior knee pain is one of the most frequently reported musculoskeletal complaints in all age groups. However, patient's complaints are often nonspecific, leading to difficulty in properly diagnosing the condition. One of the causes of pain is the degeneration of the articular cartilage. As the cartilage deteriorates, its ability to distribute the joint reaction forces decreases and the stresses may exceed the pain threshold. Unfortunately, the assessment of the cartilage condition is often limited to a detailed interview with the patient, careful physical examination and x-ray imaging. The X-ray screening may reveal bone degeneration, but does not carry sufficient information of the soft tissues' conditions. More advanced imaging tools such as MRI or CT are available, but these are expensive, time consuming and are only suitable for detection of advanced arthritis. Arthroscopic surgery is often the only reliable option, however due to its semi-invasive nature, it cannot be considered as a practical diagnostic tool. However, as the articular cartilage degenerates, the surfaces become rougher, they produce higher vibrations than smooth surfaces due to higher friction during the interaction. Therefore, it was proposed to detect vibrations non-invasively using accelerometers, and evaluate the signals for their potential diagnostic applications. Vibration data was collected for 75 subjects; 23 healthy and 52 subjects suffering from knee arthritis. The study was approved by the IRB and an Informed Consent was obtained prior to data collection. Five accelerometers were attached to skin around the knee joint (at the patella, medial and lateral femoral condyles, tibial tuberosity and medial tibial plateau). Each subject performed 5 activities; (1) flexion-extension, (2) deep knee bend, (3) chair rising, (4) stair climbing and (5) stair descent. The vibration and motion components of the signals were separated by a high pass filter. Next, 33 parameters of the signals were calculated and evaluated for their discrimination effectiveness (Figure 1). Finally the pattern recognition method based on Baysian classification theorem was used for classify each signal to either healthy or arthritic group, assuming equal prior probabilities. The variance and mean of the vibration signals were significantly higher in the arthritic group (p=2.8e-7 and p=3.7e-14, respectively), which confirms the general hypothesis that the vibration magnitudes increase as the cartilage degenerates. Other signal features providing good discrimination included the 99. th. quantile, the integral of the vibration signal envelope, and the product of the signal envelope and the activity duration. The pattern classification yielded excellent results with the success rate of up to 92.2% using only 2 features, up to 94.8% using 3 (Figure 2), and 96.1% using 4 features. The current study proved that the vibrations can be studied non-invasively using a low-cost technology. The results confirmed the hypothesis that the degeneration of the cartilage increases the vibration of the articulating bones. The classification rate obtained in the study is very encouraging, providing over 96% accuracy. The presented technology has certainly a potential of being used as an additional screening methodology enhancing the assessment of the articular cartilage condition

A case of calcification of articular cartilage in association with a parathyroid tumour is described. Previously reported cases of articular calcification are briefly discussed, and it is recommended that patients with articular calcification of undetermined cause should be investigated for hyperparathyroidism

Lesions to articular cartilage have a poor capability of regeneration and by mechanical wear and enzymatic digestion they may progress to osteoarthritis. In Sweden more than 900 patients with chondral or osteochondral lesions have been treated with autologous chondrocyte transplantation (ACT) since 1987. Cartilage is harvested arthroscopically and the chondrocytes are isolated. After two weeks of culturing the chondrocytes are deposited in the cartilage lesion in a cell suspension. The chondrocytes start to produce matrix and gradually form new hyaline cartilage able to withstand the forces of the knee. Lesions to the femoral condyles have shown the most promising results when treated with ACT (90% Good/Excellent, n=57), osteochonditis dissecans showed 84% Good/Excellent results (n=32), multiple knee joint lesions 75% Good/Excellent (n=53) and femoral condyle lesions with anterior cruciate ligament reconstruction 74% Good/Excellent (n=−27) at a long term follow up (2–11 years). The outcome after patella lesions treated with ACT were initially not as good (2 of 7 patients were graded Good or Excellent at a mean follow-up of 36 months) but better understanding of the nature of patellar lesions and development of the surgical technique have improved the result (65% Good or Excellent, n=32). Patients treated with ACT for cartilage lesion to the femoral trochlea showed Good/Excellent results in 58% (n=12). At a second look arthroscopy biopsies were taken in 37 patients. In 80% of the biopsies the repair tissue was classified as hyaline like cartilage. Immunohistochemical analysis of collagen II, aggrecan and comp showed ++ to +++ for the hyaline like repair tissue compared to +++ for normal cartilage. There were also a strong correlation (0.73) between hyaline like repair and Good/ Excellent results. Other areas have been transplanted as well such as the tibial plateau, the talus and the head of the humerus, but due to the small numbers of patients and short follow-up ACT to these areas is not yet recommended. The clinical outcome after treating chondral and osteochondral lesions in the knee is good at a long term follow-up and the repair tissue is histological similar to normal articular cartilage

Introduction. Kashin-Beck disease (KBD) is an endemic degenerative osteoarthropathy affecting approximately 3 million people in China (Stone R, 2009). The precise aetiology of KBD is not clear, but the lack of selenium and the pollution of mycotoxins in food are a suspected cause of KBD. In this pilot study, we use a rat model to investigate the effect of low selenium and T-2 toxin on articular cartilage metabolism. Methods. 140 male Sprague-Dawley rats were fed with selenium-deficient or normal diet for 4 weeks to produce a low selenium or normal nutrition status. The rats were then fed for a further 4 weeks with low selenium or normal diets with or without T-2 toxin (100ng per gram body weight per day). The rat knee joints were fixed and paraffin embedded and histological and immunohistochemical staining was performed to analyse the metabolism of articular cartilage. Results. There was increased cell cluster formation in the middle and/or deep zones in rats fed with both diets. However, an apparent cell loss was observed in the low selenium + T-2 toxin group with an apparent increase in caspase-3 staining, indicating the increased cell apoptosis. Moreover, toluidine blue staining was reduced in the low selenium + T-2 toxin group, suggesting a loss of sulphated glycosaminoglycans. Similarly, there was reduced 2B6 and 6C3 staining in the territorial matrix of chondrocytes, indicating a reduced synthesis in 4-sulhated and native CS motifs. In contrast, increased 1B5 staining was observed in the articular cartilage from the low selenium + T-2 toxin group, suggesting a lack of CS sulphatransferase activity. Interestingly, there was increased 7D4 staining in the superficial zone of articular cartilage from low selenium + T-2 toxin group, suggesting an initiation of an osteoarthritis-like lesion. Discussion. These results indicated that low selenium nutrition and T-2 toxin could promote cell apoptosis and disrupt CS-GAG metabolism in ECM of rat articular cartilage in this animal model, which is similar to that observed in KBD patients. Collectively, our results support the hypothesis that low selenium and T-2 toxin are the cause of KBD

1. Idiopathic calcification of articular cartilages is described in a Jamaican woman of thirty-one years who had intermittent joint pains for ten years and who had evidence of past gonococcal infection. She was otherwise normal. 2. The etiology of the condition is unknown. 3. Previous literature is reviewed

Aims: The aim of this study was to evaluate the application of collagen scaffold in the reconstruction of articular cartilage. Methods: 28 rabbits was used in the study. A defect penetrating into the subchondral bone was made. The animals were divided into 2 groups according to the procedure: group I consisted of rabbits with defects þlled with collagen scaffold, in group II the defects remained empty. The results were observed after 4 and 12 weeks macroscopically and microscopically (modif. OñDriscoll scale). Results: Total þlloing of the defect with regenerated tissue was revealed, with smooth surface and good integration with the surrounding cartilage in 1st group. In 2nd group the surface of the newly formed tissue was irregular, defect was partially þlled and incompletely integrated with cartilage. Hyaline-like cartilage dominated on microscopic examination of the 1st group the (2±0.8). In the 2nd group regenerating tissue was mostly þbrous (1.5±0.8). Signs of degeneration were more signiþcant in 2nd group (0.7±0.7) when compared to 1st group (1.6±0.8). However they deteriorated over time in both groups with loss of structural integrity and integration with sourounding cartilage. The main adventage of scaffold application was better þlling of cartilage defect (1.6±0.8 vs. 1±0.6). Possibly incorporation of chondrogenic cells into defect would improve cellular integrity and properties of regenerating tissue. Conclusion: This study showed better results of reconstruction of articular cartilage by means of biodegradable scaffold

Purpose: Intraarticular use of anaesthetic agents is common for postoperative pain relief after arthroscopic knee surgery. In this study, we have evaluated and compared the effects of Bupivacaine, Levobupivacaine and Tramadol both invivo and invitro experimental rat models on articular cartilage and chondrocytes. Materials and Methods: Invivo Experiment: 1. Injections: Thirty mature Sprague-Dawley rats weighing 230 – 300 g were randomized into 3 groups. Bupivacaine (Group 1), Levobupivacaine (Group 2) and Tramadol (Group 3) were injected into the right knee joints and physiological 0.9% saline into the left. 2. Histopathologic Analysis: The specimens were fixed, decalcified and stained with Hematoxylen and Eosin (H& E) and Toluidin Blue. All slides were examined by the same pathologist, who was blinded to the injectate used in each joint. All samples were evaluated histopathologically according to the recommendation of International Cartilage Repair Society’s osteoarthritis and cartilage histopathology grading and staging system. Invitro Experiment: Articular cartilage cells of the rats were cultured and seeded. Cartilage cell seeded samples (104 cells/mL) were incubated in three different anesthetic agents (0,5%); Bupivacaine, Levobupivacaine, and Tramadol respectively. Cell Titer 96TM Nonradioactivity Cell Proliferation (MTS) assay was used to determine the cell density on the samples. Results:. Invivo: There were pathologic changes like cartilage hypertrophy, active chronic inflammation with abscess formation, cellular proliferation, focal vertical fissures and focal discontunity on cartilage matrix at superficial zone in all three groups on the drug injected sides. Although those histopathologic findings were not found statistically significant when compared the OARSI grade, OA stage and OA score with the control groups (p> 0.05), statistically significant higher OARSI grade, OA stage and OA scores were detected when compared the Levobupivacaine injected group after 10 days with the Levobupivacaine injected group after 48 hours (p< 0.01 [ p=0.008]). Invitro: MTS results show that 0.5% Tramadol is cytotoxic to rat chondrocyte in vitro after 30 min of exposure. Also the cell number in both Bupivacaine and Levobupivacaine treated wells showed decrease throughout 15, 30 and 60 min exposures. Conclusion: No report has been appointed comparing the effects of the mentioned three drugs both invivo and invitro. Although chondrotoxicity of Bupivacaine was less harmful than Levobupivacaine and Tramadol, these findings suggest that local anesthetics negatively affect articular cartilage and chondrocytes. Given that chondrocyte loss has been implicated in the development of chondrosis and osteoarthritis, orthopaedic surgeons should be careful in their preference for pain control with intraarticular drug injections after arthroscopic procedures

Intra-articular screw fixation is indicated for internal fixation of large osteochondral fragments secondary to trauma or osteochondritis dissecans. During surgery, orthopaedic drills are used to prepare a hole through which the screw can pass. Previous work has shown that mechanical injury to articular cartilage results in a zone of cell death adjacent to the traumatised articular cartilage (1). Here, we characterise and quantify the margin of in situ chondrocyte death surrounding drill holes and screws (standard cortical and headless compression designs) placed in mature bovine articular cartilage to model the orthopaedic procedure. Drill holes (1mm) were made through the articular cartilage and bone of intact bovine metacarpophalangeal joints obtained from 3-yr old cows within 12hrs of slaughter. Osteochondral explants (∼1cm square and 2-3mm thick) encompassing the drilled holes in articular cartilage and subchondral bone were harvested using a chisel. Explants were then incubated in Dulbecco's modified Eagle's medium for 45mins with CMFDA (5-chloromethylfluorescein diacetate) and PI (propidium iodide; both at 10micromolar) to identify/quantify living and dead in situ chondrocytes respectively in a consecutive series of axial optical sections using confocal scanning laser microscopy (CLSM). The drill holes through cartilage appeared to have clearly defined edges with no macroscopic evidence of cartilage splitting. However visualisation of fluorescently-labelled in situ chondrocytes by CLSM demonstrated clear cell death around the periphery of the drilled hole which was 166±19 micrometers in width. This increased with a larger diameter (1.5mm) drill to 450±151 micrometers (all data are means±s.e.m.; n=3). Preliminary experiments indicated that the margin of chondrocyte death around a 1.5mm hole was dramatically increased further by the insertion of screws into pre-drilled holes. These results suggest that the mechanical trauma associated with cartilage drilling and the insertion of intra-articular screws occurs with marked death of in situ chondrocytes extending into normal cartilage beyond the area occupied by the screw. As chondrocytes are not replaced in mature cartilage, their loss around the hole/screw will mean that the extracellular matrix is not maintained, inevitably leading to cartilage failure

Purpose: The objective of this project is to determine the suitability of modified fibrin hydrogels as scaffolds for articular cartilage tissue engineering. The attractive feature of the fibrin system is that the gel precursors are available in autologous form. We have previously demonstrated that genipin, a naturally occurring cross-linking agent, stabilizes the fibrin gel. Methods: Human articular chondrocytes were isolated from articular cartilage harvested from consenting patients undergoing total knee arthroplasty. The human cells were encapsulated into fibrin gels where gelation was induced by combining fibrinogen, thrombin, and genipin. The resulting gels were evaluated for extracellular matrix (ECM) production, mechanical properties, cell viability, and biodegradation. Results: No breakdown of the gels was detected during 5 weeks of cell culture. After several weeks in culture, histology indicates significant proteoglycan production by encapsulated cells, and collagen II and aggrecan were detected in this ECM by immunostaining. There was a greater accumulation of cartilage-like ECM in the gels cross-linked with genipin. Dynamic compression tests performed at 0.1 Hz for 10 cycles using an MTS machine indicate that accumulation of ECM was associated with increased stiffness of the material. Cell viability was assessed using live/dead staining, and was found to be > 50% after 24 hours and at 1 week in culture. The presence of genipin cross-linking did not significantly affect cell viability. Real-Time RT-PCR indicated that encapsulated chondrocytes show an increase in Sox9, collagen II and aggrecan expression over 5 weeks and that this is further increased in the presence of genipin. The gene expression results agreed with the enhanced ECM seen under these conditions by histology and immunostaining. The fibrin material was also implanted subcutaneously into rats and after 30 days the material was removed, sectioned and evaluated. Immunostaining indicated that while there was evidence of biodegradation, the material did not appear to cause an inflammatory response. Conclusions: Modified fibrin hydrogels show potential as cellular scaffolds for articular cartilage tissue engineering. An in vivo orthopaedic model must now be developed to fully evaluate the potential of the fibrin gel. Funding: Other Education Grant

To clarify the normal range of articular cartilage volumes of the patella and femur in the human knee joints of healthy adults using three-dimensional magnetic resonance imaging and to analyze the correlation of the articular volumes with the background characteristics. Fifty seven knees of 57 healthy volunteers aged from twenties to forties (30 males and 27 females), who had no past history of joint disease or trauma in the legs, were imaged by a fat-suppressed three-dimensional sequence (SPGR; 1.5T GE; Horizon LX 8.2.5) The obtained data were analyzed by 4 examiners independently with a computer workstation, and a average of the four was adopted as the articular volume. Analyzed characteristics factors of the volunteers were: age, body weight, height, leg length, foot size, circumference of the thigh and lower leg, quadriceps angle, foot angle, body-mass index, and general laxity. The mean articular cartilage volume was 7.2 +- 1.6 ml. It was significantly larger in males than in females. Concerning the relationship between the volume and the characteristic factors, there was a significant correlation of the cartilage volume with the foot size in males (r=0.47), and with height, leg length and foot size in females (r=0.53, 0.60, 0.60, respectively), but no significant correlation with the other factors. Conclusion. The articular cartilage volumes of the patella and femur was 7.2+- 1.6 ml. The size of skeletal structure, especially the skeletal size of the lower extremity, were assumed to be important factors in estimating cartilage volume

Subtotal synovectomy was performed in the knee joints of New Zealand white rabbits. The changes noted in the articular cartilage as manifest by decreased metachromatic staining of the matrix were considered to indicate matrix degradation caused by the altered joint environment. The documentation of the enzyme changes suggests that the histological alteration in the articular cartilage noted after synovectomy may be mediated through the activation of endogenous chondrocyte lysozomal enzymes, particularly cathepsin and acid hydrolases

Once damaged, articular cartilage has limited capacity for self-repair due to their avascular and acellular nature. Tissue engineering approaches using cultured chondrocytes and biomaterials as scaffoldings hold promises for repairing cartilage defects. However, the source of articular chondrocytes is limited and the chon-drocytes may de-differentiate when cultured for a prolonged period. Bone marrow derived mesenchymal stem cells (BMSCs) have multi-differentiation potentials and autologous BMSCs are easy to obtain and culture with no/little immunological reaction when re-implanted. 24 NZW rabbits were used. Rabbit autologous BMSCs were obtained through marrow aspirations and expanded in culture under the chondrogenic induction media (DMEM, 10% FCS, plus 10ng/ml TGF-β1) for 3 weeks. A full-thickness articular cartilage defect (3 mm in diameter and 3 mm in depth) was created on both medial condyles in the rabbit. For experimental group (16 joints), the defects were filled immediately with alginate capsules containing autologous chondrogenic cells (8.5 x 104); for the control groups, the defects were filled with either alginate capsules alone (16 joints) or left untreated (16 joints). All the animals were terminated at 6 and 12 weeks after surgery and the cartilage samples were harvested for histology, immunochemistry and in situ hybridization examinations. For histology, in the experimental group the defects were filled with immature hyaline-like cartilaginous tissues at 6 weeks; by 12 weeks the newly formed cartilage showing signs of remodeling and integrating into the surrounding articular cartilage. The expression of type II collagen in the newly formed cartilaginous tissues was confirmed by immunohistochemistry and by in situ hybridization methods. In the control groups, the defects were mainly filled with fibrous tissues in all the animals at the two time points examined. We have used Wakitani cartilage grading system for semi-quantitative histological evaluation. Significant lower scores (with superior histology) were found in the experimental group comparing to the two control groups. Our results confirmed that full-thickness articular cartilage defects can be repaired by chondrogenically differentiated autologous BMSCs seeded into alginate capsules. Further studies are ongoing to explore the long term outcome of this treatment approach as well as using new scaffolds for cartilage tissue engineering