In a healthy joint, mechanical loading increases matrix synthesis and maintains cell phenotype, while reducing catabolic activities. It activates several pathways, most of them yet largely unknown, with integrins, TGF-β, canonical (Erk 1/2) and stress-activated (JNK) MAPK playing a key role. Degenerative joint diseases are characterized by Wnt upregulation and by the presence of proteolytic fibronectin fragments (FB-fs). Despite they are known to impair some of the aforementioned pathways, little is known on their modulatory effect on cartilage mechanoresponsiveness. This study aims at investigating the effect of mechanical loading in healthy and in vitro diseased cartilage models using pro-hypertrophic Wnt agonist CHIR99021 and the pro-catabolic FB-fs 30 kDa. Human primary chondrocytes from OA patients have been grown in alginate hydrogels for one week, prior to be incubated for 4 days with 3μM CHIR99021 or 1 μM FB-fs. Human cartilage explants isolated from OA patients have incubated 4 days with 3 μM CHIR99021 or 1 μM FB-fs. Both groups have then been mechanically stimulated (unconfined compression, 10% displacement, 1.5 hours, 1 Hz), using a BioDynamic bioreactor 5270 from TA Instruments. Expression of collagen type I, II and X, aggrecan, ALK-1, ALK-5, αV, α5 and β1 integrins, TGF-β1 have been assessed by Real Time-PCR and normalized with the expression of S29. Percentage of phosphorylated Smad2, Smad1 and JNK were determined through western blot. TGF-β1 content was quantified by sandwich ELISA; MMP-13 and GAG by western blot and DMMB assay, respectively. At least three biological replicates were used. ANOVA test was used for parametric analysis; Kruskal-Wallis and Mann-Whitney post hoc test for non-parametric. Preliminary data show that compression increased collagen II expression in control, but not in CHIR99021 and FB-fs pre-treated group (Fig. 1A-B). This was associated with downregulation of β1-integrin expression, which is the main collagen receptor and further regulates collagen II expression, suggesting inhibition of Erk1/2 pathway. A trend of increase expression of collagen type X after mechanical loading was observed in CHIR and FB-fs group. ALK-1 and ALK-5 showed a trend toward stronger upregulation in CHIR99021 group after compression, suggesting the activation of both Smad1/5/8 and Smad 2/3 pathways. To further investigate pathways leading to these different mechano-responses, the phosphorylation levels of Smad1 and Smad2, Erk1/2 and JNK proteins are currently being studied. Preliminary results show that Smad2, Smad1 and JNK protein levels increased in all groups after mechanical loading, independently of an increase in TGF-β1 expression or content. Compression further increased phosphorylation of Smad2, but not of Smad1, in all groups

Senescent chondrocyte and subchondral osteoclast overburden aggravate inflammatory cytokine and pro-catabolic proteinase overproduction, accelerating extracellular matrix degradation and pain during osteoarthritis (OA). Fibronectin type III domain containing 5 (FNDC5) is found to promote tissue homeostasis and alleviate inflammation. This study aimed to characterize what role Fndc5 may play in chondrocyte aging and OA development. Serum and macroscopically healthy and osteoarthritic cartilage were biopsied from patients with knee OA who received total knee replacement. Murine chondrocytes were transfected with Fndc5 RNAi or cDNA. Mice overexpressing Fndc5 (Fndc5Tg) were operated to have destabilized medial meniscus mediated (DMM) joint injury as an experimental OA model. Cellular senescence was characterized using RT-PCR analysis of p16INK4A, p21CIP1, and p53 expression together with ß-galactosidase activity staining. Articular cartilage damage and synovitis were graded using OARSI scores. Osteophyte formation and mechanical allodynia were quantified using microCT imaging and von Frey filament, respectively. Osteoclast formation was examined using tartrate-resistant acid phosphatase staining. Senescent chondrocyte and subchondral osteoclast overburden together with decreased serum FNDC5 levels were present in human osteoarthritic cartilage. Fndc5 knockdown upregulated senescence program together with increased IL-6, MMP9 and Adamts5 expression, whereas Alcian blue-stained glycosaminoglycan production were inhibited. Forced Fndc5 expression repressed senescence, apoptosis and IL-6 expression, reversing proliferation and extracellular matrix production in inflamed chondrocytes. Fndc5Tg mice showed few OA signs, including articular cartilage erosion, synovitis, osteophyte formation, subchondral plate sclerosis and mechanical allodynia together with decreased IL-6 production and few senescent chondrocytes and subchondral osteoclast formation during DMM-induced joint injury. Mechanistically, Fndc5 reversed histone H3K27me3-mediated IL-6 transcription repression to reduce reactive oxygen species production. Fndc5 loss correlated with OA development. It was indispensable in chondrocyte growth and anabolism. This study sheds light onto the anti-ageing and anti-inflammatory actions of Fndc5 to chondrocytes; and highlights the chondroprotective function of Fndc5 to compromise OA

Material-based strategies seek to engineer synthetic microenvironments that mimic the characteristics of physiological extracellular matrices for applications in regenerative therapies, including bone repair and regeneration. In our group, we identified a specific chemistry, poly(ethyl acrylate) (PEA), able to induce the organization of fibronectin (FN), upon adsorption of the protein, into fibrillar networks similar to the physiological ones, leading to enhanced cellular response, in terms of cell adhesion and differentiation. In this work, we exploit these FN networks to capture and present growth factors (GF) in combination with the integrin binding domain of FN during bone tissue healing. Fibrillar conformation of FN adsorbed on PEA favors the simultaneous availability of the GF binding domain (FNIII12–14) next to the integrin binding region (FNIII9–10), compared to poly(methyl acrylate) (PMA), a material with similar chemistry, where FN adopts a globular conformation. The combined exposure of specific adhesive sequences recognized by integrins and GF binding domains was found to improve the osteogenic differentiation of mesenchymal stem cells. A higher expression of bone proteins was found when BMP2 is bound or sequestered on the material surface versus its administration in the culture media in vitro. The potential of this system as recruiter of GFs was also investigated in a critical-size bone segmental defect in mouse. The synergistic integrin-GF signalling, induced by fibrillar FN, promoted bone formation in vivo with lower BMP2 doses than current technologies. Furthermore, we optimized the system for its potential use in translational research, seeking to address the clinical need of using biocompatible and biodegradable material implants. Polycaprolactone scaffolds were synthesized and coated with a thin layer of plasma- polymerized PEA that recruits and efficiently presents GF during healing of critical size defects. The material-driven FN fibrillogenesis provides a new strategy to efficiently reduce the GF doses administrated in bone regenerative therapies

The success of long-term transcutaneous implants depends on dermal attachment to prevent downgrowth of the epithelium and infection. Hydroxyapatite (HA) coatings and fibronectin (Fn) have independently been shown to regulate fibroblast activity and improve attachment. In an attempt to enhance this phenomenon we adsorbed Fn onto HA-coated substrates. Our study was designed to test the hypothesis that adsorption of Fn onto HA produces a surface that will increase the attachment of dermal fibroblasts better than HA alone or titanium alloy controls. . Iodinated Fn was used to investigate the durability of the protein coating and a bioassay using human dermal fibroblasts was performed to assess the effects of the coating on cell attachment. Cell attachment data were compared with those for HA alone and titanium alloy controls at one, four and 24 hours. Protein attachment peaked within one hour of incubation and the maximum binding efficiency was achieved with an initial droplet of 1000 ng. We showed that after 24 hours one-fifth of the initial Fn coating remained on the substrates, and this resulted in a significant, three-, four-, and sevenfold increase in dermal fibroblast attachment strength compared to uncoated controls at one, four and 24 hours, respectively

Regeneration of bone defects in elderly patients is limited due to the decreased function of bone forming cells and compromised tissue physiology. Previous studies suggested that the regenerative activity of stem cells from aged tissues can be enhanced by exposure to young systemic and tissue microenvironments. The aim of our project was to investigate whether extracellular matrix (ECM) engineered from human induced pluripotent stem cells (hiPSCs) can enhance the bone regeneration potential of aged human bone marrow stromal cells (hBMSCs). ECM was engineered from hiPSC-derived mesenchymal-like progenitors (hiPSC-MPs), as well as young (<30 years) and aged (>70 years) hBMSCs. ECM structure and composition were characterized before and after decellularization using immunofluorescence and biochemical assays. Three hBMSCs of different ages were cultured on engineered ECMs. Growth and differentiation responses were compared to tissue culture plastic, as well as to collagen and fibronectin coated plates. Decellularized ECMs contained collagens type I and IV, fibronectin, laminin and < 5% residual DNA, suggesting efficient cell elimination. Cultivation of young and aged hBMSCs on the hiPSC-ECM in osteogenic medium significantly increased hBMSC growth and markers of osteogenesis, including collagen deposition, alkaline phosphatase activity, bone sialoprotein expression and matrix mineralization compared to plastic controls and single protein substrates. In aged BMSCs, matrix mineralization was only detected in ECM cultures in osteogenic medium. Comparison of ECMs engineered from hiPSC-MPs and hBMSCs of different ages suggested similar structure, composition and potential to enhance osteogenic responses in aged BMSCs. Engineered ECM induced a higher osteogenic response compared to specific matrix components. Our studies suggest that aged BMSCs osteogenic activity can be enhanced by culture on engineered ECM. hiPSCs represent a scalable cell source, and tissue engineering strategies employing engineered ECM materials could potentially enhance bone regeneration in elderly patients

The anterior cruciate ligament (ACL) is the connective tissue located at the end of long bones providing stability to the knee joint. After tear or rupture clinical reconstruction of the tissue remains a challenge due to the particular mechanical properties required for proper functioning of the tissue. The outstanding mechanical properties of the ACL are characterized by a viscoelastic behavior responsible of the dissipation of the loads that are transmitted to the bone. These mechanical properties are the result of a very specialized graded extracellular matrix that transitions smoothly between the heterotypic cells, stiffness and composition of the ACL and the adjacent bone. Thus, mimicking the zonal biochemical composition, cellular phenotype and organization are key to reset the proper functioning of the ACL. We have previously shown how the biochemical composition presented to cells in electrospun scaffolds results in haptokinesis, reverting contact-guidance effects. [1]. Here, we demonstrate that contact guidance can also be disrupted by structural parameters in aligned wavy scaffolds. The presentation of a wavy fiber arrangement affected the cell organization and the deposition of a specific ECM characteristic of fibrocartilage. Cells cultured in wavy scaffolds grew in aggregates, deposited an abundant ECM rich in fibronectin and collagen II, and expressed higher amounts of collagen II, X and tenomodulin as compared to aligned scaffolds. In-vivo implantation in rabbits of triphasic scaffolds accounting for aligned-wavy-aligned zones showed a high cellular infiltration and the formation of an oriented ECM, as compared to traditional aligned scaffolds. [2]

Chondrocytic activity is downregulated by compromised autophagy and mitochondrial dysfunction to accelerate the development of osteoarthritis (OA). Irisin is a cleaved form of fibronectin type III domain containing 5 (FNDC5) and known to regulate bone turnover and muscle homeostasis. However, little is known about the role of irisin in chondrocytes and the development of OA. This talk will shed light on FNDC5 expression by human articular chondrocytes and compare normal and osteoarthritic cells with respect to autophagosome marker LC3-II and oxidative DNA damage marker 8-hydroxydeoxyguanosine (8-OHdG). In chondrocytes in vitro, irisin improves IL-1β-mediated growth inhibition, loss of specific cartilage markers and glycosaminoglycan production. Irisin further suppressed Sirt3 and UCP- 1 to improve mitochondrial membrane potential, ATP production, and catalase. This attenuated IL-1β-mediated production of reactive oxygen species, mitochondrial fusion, mitophagy, and autophagosome formation. In a surgical murine model of destabilization of the medial meniscus (DMM) intra-articular administration of irisin alleviates symptoms like cartilage erosion and synovitis. Furthermore, gait profiles of the treated limbs improved. In chondrocytes, irisin treatment upregulates autophagy, 8-OHdG and apoptosis in cartilage of DMM limbs. Loss of FNDC5 in chondrocytes correlates with human knee OA and irisin repressed inflammation-mediated oxidative stress and deficient extracellular matrix synthesis through retaining mitochondrial biogenesis and autophagy. The talk sheds new light on the chondroprotective actions of this myokine and highlights the remedial effects of irisin during progression of OA

Low back pain resulting from Interertebral disc (IVD) degeneration is a serious worldwide problem, with poor treatment options available. Notochordal (NC) cells, are a promising therapeutic cell source with anti-catabolic and regenerative effect. However, their behaviour in the harsh degenerate environment is unknown. Porcine NC cells (pNCs), and Human NP cells from degenerate IVDs were cultured in alginate beads to maintain phenotype. Cells were cultured alone or in combination, or co-stimulated with notochordal cell condition media (NCCM), in media to mimic the healthy and degenerate disc environment, together with controls for up to 1 week. Following culture viability, qPCR and proteomic analysis using Digiwest was performed. A small increase in pNC cell death was observed in degenerated media compared to standard and healthy media, with a further decrease seen when cultured with IL-1β. Whilst no significant differences were seen in phenotypic marker expression in pNCs cultured in any media at gene level (ACAN, KRT8, KRT18, FOXA2, COL1A1 and Brachyury). Preliminary Digiwest analysis showed increased protein production for Cytokeratin 18, src and phosphorylated PKC but a decrease in fibronectin in degenerated media compared to standard media. Human NP cells cultured with NCCM, showed a decrease in IL-8 production compared to human NP cells alone when cultured in healthy media. However, gene expression analysis (ACAN, VEGF, MMP3 and IL-1β) demonstrated no significant difference between NP only and NP+NCCM groups. Studying the behaviour of the NCs in in vitro conditions that mimic the in vivo healthy or degenerate niche will help us to better understand their potential for therapeutic approaches. The potential use of NC cell sources for regenerative therapies can then be translated to investigate the potential use of iPSCs differentiated into NC cells as a regenerative cell source

Neoangiogenesis drives the replacement of mineralised cartilage by trabecular bone during bone growth regulated by molecules like e.g. VEGF, OPG and RANKL. The Heparan sulfate proteoglycan Syndecan-1 (Sdc1) plays a role in the interaction of osteoclasts and osteoblasts and the development of blood vessels. We expected Sdc1 to have an influence on bone structure and vessel development. Therefore, bone structure and angiogenesis at the growth plate in mice was compared and the influence of Syndecan-1 deficiency was characterised. Animals: Femura of male and female C57BL/6 WT (5♀, 6♂) and Sdc1-/- (9♀, 5♂) mice were used for native bone analysis at 4 month age. Histology: Bone structure was analysed using microCT scans with a resolution of 9µm. Vascularisation was visualised using an anti-Endomucin antibody in 80µm thick cryosections. In vitro angiogenesis: Bone marrow isolates were used to generate endothelial progenitor cells by sequential cultivation on fibronectin. Microvessel development was analysed 4h after plating on matrigel. Bone structure in male Sdc1 deficient mice was significantly reduced compare to male WT, whereas female mice of both genotypes did not differ. Sdc1 deficient mice at the age of 4 month showed a high decrease in the number of vessel bulbs at the chondro-osseous border (growth plate) compared to WT mice. However, no sex related differences were shown. Quantification of microvessel outgrowth of endothelial cells revealed a decreased amount of sprouting, but increased length of microvessels of Sdc1-/- cells compared to WT. Syndecan-1 has a significant impact on neoangiogenesis at the chondro-osseous border of the native bone, but the impact of Syndecan-1 deficiency on the loss of bone structure was significantly higher in male mice. This emphasises the importance to further characterise the function of Syndecan-1 regulated processes during enchondral ossification in a sex dependent manner

Introduction. Osteoporosis accounts for a major risk factor of fracture-associated disability or premature death in the elderly. Enhancement of bone anabolism for slowing osteoporosis is highly demanding. Exerkine fibronectin type III domain containing 5 (FNDC5) regulates energy metabolism, inflammation, and aging. This study was aimed to investigate whether Fndc5 signaling in osteoblasts changed estrogen deficiency-mediated bone loss or microarchitecture deterioration. Method. Female osteoblast-specific Fndc5 transgenic mice (Fndc5Tg), which overexpressed Fndc5 under the control of key osteoblast marker osteocalcin promoter, were given bilateral ovariectomy to induce estrogen deficiency-mediated osteoporosis. Bone mass, microstructures, and biomechanical properties were quantified using μCT imaging and material testing. Dynamic bone formation was traced using fluorescence calcein. Osteogenic differentiation and adipocyte formation of bone-marrow mesenchymal cells were investigated using von Kossa staining and Nile red staining, respectively. Serum osteocalcin, CTX-1 and TRAP5b levels were quantified using designated ELISA kits. Mitochondrial respiration was investigated using Seahorse Extracellular Flux Analyzer. Result. Fndc5Tg mice developed relatively higher bone mass and microarchitecture than wild-type mice. Fndc5 overexpression attenuated the losses of bone mineral density and trabecular network, including trabecular volume, thickness, and trabecular number, and improved cortical thickness and porosity in ovariectomized mice. Gain of Fndc5 function preserved biomechanical characteristics (maximum load, breaking force, and energy), serum bone formation marker osteocalcin levels, and bone formation rate, whereas it reduced serum bone resorption makers CTX-1 and TRAP5b levels, osteoclast overburden, and marrow adiposis. In vitro, Fndc5 reversed the estrogen deficiency-mediated mineralized matrix underproduction and adipocyte formation of bone-marrow mesenchymal cells, and inhibited osteoclast formation in osteoporotic bone. Mechanistically, Fndc5 activated AMPK signaling, promoting mitochondrial respiration and ATP production to enhance osteoblastic activity. Conclusion. Fndc5 signaling exerted bone-protective actions delaying estrogen deficiency-mediated osteoporosis. This study highlighted a new molecular remedial option for osteoporosis development by manipulating Fndc5 functions

Dupuytren’s disease is a chronic inflammatory process which produces contractures of the fingers. The nodules present in Dupuytren’s tissue contain inflammatory cells, mainly lymphocytes and macrophages. These express a common integrin known as VLA4. The corresponding binding ligands to VLA4 are vascular cell adhesion molecule-1 (VCAM-1) present on the endothelial cells and the CS1 sequence of the fibronectin present in the extracellular matrix. Transforming growth factor-beta (TGF-ß) is a peptide hormone which has a crucial role in the process of fibrosis. We studied tissue from 20 patients with Dupuytren’s disease, four samples of normal palmar fascia from patients undergoing carpal tunnel decompression and tissue from ten patients who had received perinodular injections of depomedrone into the palm five days before operation. The distribution of VLA4, VCAM-1, CS1 fibronectin and TGF-ß was shown by immunohistochemistry using an alkaline phosphorylase method for light microscopy. In untreated Dupuytren’s tissue CS1 fibronectin stained positively around the endothelial cells of blood vessels and also around the surrounding myofibroblasts, principally at the periphery of many of the active areas of the Dupuytren’s nodule. VCAM-1 stained very positively for the endothelial cells of blood vessels surrounding and penetrating the areas of high nodular activity. VCAM-1 was more rarely expressed outside the blood vessels. VLA4 was expressed by inflammatory cells principally in and around the blood vessels expressing VCAM-1 and CS1 but also on some cells spreading into the nodule. TGF-ß stained positively around the inflammatory cells principally at the perivascular periphery of nodules. These cells often showed VLA4 expression and co-localised with areas of strong production of CS1 fibronectin. Normal palmar fascia contained only scanty amounts of CS1 fibronectin, almost no VCAM-1 and only an occasional cell staining positively for VLA4 or TGF-ß. In the steroid-treated group, VCAM-1 expression was downregulated in the endothelium of perinodular blood vessels and only occasional inflammatory cell expression remained. Expression of CS1 fibronectin was also much reduced but still occurred in the blood vessels and around the myofibroblast stroma. VLA4-expressing cells were also reduced in numbers. A similar but reduced distribution of production of TGF-ß was also noted. Our findings show that adherence of inflammatory cells to the endothelial wall and the extravasation into the periphery of the nodule may be affected by steroids, which reduce expression of VCAM-1 in vivo. This indicates that therapeutic intervention to prevent the recommencement of the chronic inflammatory process and subsequent fibrosis necessitating further surgery may be possible

Mesenchymal stem cells (MSC) have a well recognised potential for tissue repair. This potential is two pronged: they can differentiate into the functional cell types of the damaged tissues and they can support tissue recovery by secreting trophic factors, depositing an extracellular matrix (ECM) and dampening inflammation. Three-dimensional microscopy recently shown that MSCs in the bone marrow create an intricate proteo-cellular scaffold with the ECM forming an interconnected cellular continuum whose structure is guided by the deposited ECM. This proteo-cellular scaffold controls bone marrow functions from hematopoiesis to osteogenesis. In the current study we aimed to optimise ECM production under in vitro conditions by immortalised MSCs with the view that the generated ECM can be utilised for tissue repair. With immunocytochemistry we determined the deposition of bone marrow-characteristic ECM proteins: collagen I, III, IV, V, VI, laminin and fibronectin. While primary MSCs produced slightly higher amount ECM proteins than immortalised MSCs, the relative abundancy of the ECM proteins was very similar. In order to isolate the ECM, we optimised a decellularisation method based on gentle lysis with sodium-deoxycholate and DNase digestion. Immunostaining for collagen I, III, VI and fibronectin and labelling the nuclei with Hoechst-33342 confirmed removal of all cells while retaining the ECM in its original architecture. Ideally, the decellularised ECM retains associated cytokines and chemokines, such as CXCL12, important for attracting MSCs. To test this, we seeded Molm-13 leukemia cells on decellularised ECM as MSC-produced CXCL12- and other cytokines protect leukemia cells against chemotherapeutics. We found that the decellularisation process however removed these factors and thus for therapeutic purposes, the decellularised ECM would need to be re-loaded with the essential chemo/cytokines. Overall, we developed a system for decellularised ECM production by immortalised MSCs and the results warrant further exploration of this avenue

Introduction and Objective. Chronic tendinopathy is a multifactorial disease and a common problem in both, athletes and the general population. Mechanical overload and in addition old age, adiposity, and metabolic disorders are among the risk factors for chronic tendinopathy but their role in the pathogenesis is not yet unequivocally clarified. Materials and Methods. Achilles tendons of young (10 weeks) and old (100 weeks) female rats bred for high (HCR) and low (LCR) intrinsic aerobic exercise capacity were investigated. Both Achilles tendons of 28 rats were included and groups were young HCR, young LCR, old HCR, and old LCR (n = 7 tendons per group/method). In this rat model, genetically determined aerobic exercise capacity is associated with a certain phenotype as LCR show higher body weight and metabolic dysfunctions in comparison to HCR. Quantitative real-time PCR (qPCR) was used to evaluate alterations in gene expression. For histological analysis, semi-automated image analysis and histological scoring were performed. Results. Age-related downregulation of tenocyte marker genes (Tenomodulin), genes related to matrix modelling and remodeling (Collagen type 1, Collagen type 3, Elastin, Biglycan, Fibronectin, Tenascin C), and Transforming growth factor beta 3 (Tgfb3) were detected in tendons from HCR and LCR. Furthermore, inflammatory marker Cyclooxygenase 2 (Cox2) was downregulated, while Microsomal prostaglandin E synthase 2 (Ptges2) was upregulated in tendons from old HCR and old LCR. No significant alteration was seen in Interleukin 6 (Il6), Interleukin 1 beta (Il1b), and Tumor necrosis factor alpha (Tnfa). Histological analysis revealed that Achilles tendons of old rats had fewer and more elongated tenocyte nuclei compared to young rats, indicating a reduced metabolic activity. Even though higher content of glycosaminoglycans as a sign of degeneration was found in tendons of old HCR and LCR, no further signs of tendinopathy were detectable in histological evaluation. Conclusions. Overall, aging seems to play a prominent role in molecular and structural alterations of Achilles tendon tissue, while low intrinsic exercise capacity did not cause any changes. Even though tendinopathy was not present in any of the groups, some of the shown age-related changes correspond to single characteristics of chronic tendon disease. This study gives an insight into tendon aging and its contribution to molecular and cellular changes in Achilles tendon tissue

Regeneration of bone defects in elderly patients is limited due to the decreased function of bone forming cells and compromised tissue physiology. Previous studies suggested that the regenerative activity of stem cells from aged tissues can be enhanced by exposure to young systemic and tissue microenvironments. The aim of our project was to investigate whether extracellular matrix (ECM) engineered from human induced pluripotent stem cells (hiPSCs) can enhance the bone regeneration potential of aged human bone marrow stromal cells (hBMSCs). ECM was engineered from hiPSC-derived mesenchymal-like progenitors (hiPSC-MPs), as well as young (70 years) hBMSCs. ECM structure and composition were characterized before and after decellularization using immunofluorescence and biochemical assays. Three hBMSCs of different ages were cultured on engineered ECMs. Growth and differentiation responses were compared to tissue culture plastic controls. Decellularized ECMs contained collagens type I and IV, fibronectin, laminin and < 5% residual DNA. Cultivation of young and aged hBMSCs on the hiPSC-ECM in osteogenic medium significantly increased hBMSC growth and markers of osteogenesis, including collagen deposition, alkaline phosphatase activity, bone sialoprotein expression and matrix mineralization compared to plastic controls. In aged BMSCs, matrix mineralization was only detected in ECM cultures in osteogenic medium. Comparison of ECMs engineered from hiPSC-MPs and hBMSCs of different ages suggested similar structure, composition and potential to enhance osteogenic responses in aged BMSCs. Our studies suggest that aged BMSCs regenerative activity can be enhanced by culture on hiPSC-engineered ECM

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

While new biomaterials for regenerative therapies are being reported in the literature, clinical translation is slow. Existing regenerative approaches rely on high doses of growth factors, such as BMP-2 in bone regeneration, which can cause serious side effects. We describe an ultra-low-dose growth factor technology yielding high bioactivity based on a simple polymer, poly (ethyl acrylate) (PEA), and report its translation to a clinical veterinary setting. This polymer-based technology triggers spontaneous fibronectin organization and stimulates growth factor signaling, enabling synergistic integrin and BMP-2 receptor activation in mesenchymal stem cells. To translate this technology, we use plasma-polymerized PEA on 2D and 3D substrates to enhance cell signaling in vitro, showing the complete healing of a critical-size bone injury in mice in vivo. We demonstrate its safety and efficacy in a Münsterländer dog with a non-healing humerus fracture, establishing the clinical translation of advanced ultra-low-dose growth factor treatment

Osteoarthritis (OA) is the most common form of joint disease leading to disability and dependence. In severe cases of knee OA, the joint is deemed irrecoverable and total knee replacements are indicated. Tissue engineering is a possible solution for this pathology and previous work from our laboratory has demonstrated that it is possible to isolate and expand chondroprogenitor cells in vitro from healthy knee-joint articular cartilage. Work presented here describes the detection and isolation of chondroprogenitor cells derived from osteoarthritic cartilage following total knee replacement in patients with severe OA, suggesting a pool of viable cells from this degenerate region which has been previously deemed non-recoverable. Human articular cartilage was excised from tibial plateaux (TP's) obtained from total knee replacements following the diagnoses of severe OA. Cells were isolated by a sequential pronase and collagenase digestion and subject to a fibronectin adhesion assay. Cells were expanded in monolayer in supplemented growth medium. Clonal 3D pellet cultures were established in chondrogenic and osteogenic differentiation media. Adipogenic cultures were also established in monolayer cultures. Histological procedures, immunohistochemistry and molecular biology were undertaken in order to determine the extent of differentiation. In addition, osteochondral plugs were excised from the TP's and wax embedded for further histological and immunohistochemical analysis. Clonal cell lines obtained from osteoarthritic knee-joint cartilage using the fibronectin adhesion assay were isolated and successfully cultured to a maximum of 60 population doublings whilst still demonstrating a chondrogenic capacity. Three-D pellet cultures after 21 days of chondrogenic induction produced smooth and iridescent pellets which stained positively for toluidine blue and safranin O. Positive labelling for collagen type II and aggrecan were also observed. Following osteogenic induction; evidence of mineralisation was indicated by the von Kossa stain. Adipogenic induction revealed a positive result. Osteochondral plugs demonstrated sporadic positive labelling in the surface region for putative stem cell marker Stro-1. Chondroprogenitor cells isolated from osteoarthritic display a strong chondrogenic phenotype, and have the ability to be induced into different lineages. These findings suggest the presence of a pool of viable chondroprogenitors from osteoarthritic tissue which was otherwise deemed irrecoverable

Summary. Attachment, proliferation and osteogenic maturation of hMSCs are enhanced on a sub-micron grooved Ti6Al4V alloy, while osteoblasts are less sensitive. These effects are attributed to their different maturation stage and may be mediated through differential activation of the RhoA/ROCK pathway. Introduction. Ti6Al4V alloy is the most widely used titanium-based biomaterial for manufacturing bone-anchoring devices. We report on the interactions of human bone-forming cells, mesenchymal stem cells from bone marrow (hMSCs) and primary osteoblasts (hOBs), with an anisotropic Ti6Al4V alloy that displays submicron grooves. Materials. Submicrometric Ti6Al4V surfaces (GV) with parallel grooves and mean average roughness values around 200 nm were generated by mechanical abrasion. A polished Ti6Al4V surface (PL) was used for comparative purposes. hMSCs were phenotypically characterised as progenitors and hOBs as committed osteogenic cells at a late stage of maturation. Cell attachment, proliferation, cytoskeleton organisation, adhesion sites and fibronectin matrix distribution, RhoA and ROCK distributions and activities, and osteogenic maturation, were analysed in cells cultured on the investigated alloys by means of scanning electron and confocal microscopy and biochemical assays. Results. hMSCs adhered and proliferated at a higher rate on GV alloy than on PL, while no differences were found in hOBs behavior. Patterned Ti6Al4V alloy promoted the orientation of hOBs and hMSCs in the direction of the anisotropy. Filopodia were involved in the alignment of both cell types along the grinding direction while cells exhibited a lamellipodia-dominated state on PL samples. In both cell types, focal adhesions, actin and tubulin networks and fibronectin extracellular matrix aligned with the direction of the grooves. RhoA/ROCK signaling contributed to hMSCs alignment on the patterned alloy, while osteoblastic orientation does not rely on the activation of this pathway. RhoA activity increased in both cell types cultured on GV alloy and interference on RhoA functioning by treatment with C3 transferase led to loss of organisation of actin and tubulin cytoskeletons. ROCK activity of hMSCs was up-regulated on GV samples, but not affected in hOBs. Treatment with hydroxyfasudil, an inhibitor of ROCK activity, disrupted the alignment of adhesion sites in hMSCs but not in hOBs. RhoA/ROCK signaling is not involved in the orientation of microtubule bundles of hOBs neither hMSCs on any surface, suggesting that such process is controlled by the RhoA effector mDia. When cultured on media that support osteogenic maturation, hMSCs and hOBs behaved differently on the anisotropic surfaces. OPN secretion increased in hMSCs cultured on GV alloy while it remained unaffected in hOBs. Cell mineralisation proceeded to a same extent in hMSCs cultured on the two metallic surfaces but decreased in hOBs cultured on the patterned samples. Discussion/Conclusion. Collected results indicate that hOBs are less sensitive to the patterned topography of Ti6Al4V alloy than hMSCs. These effects could be attributed to their different stages of maturation and can be mediated, at least in part, through ROCK since its activity increased on hMSCs cultured on the patterned alloy, while hOBs failed to up-regulate it. Collectively, these findings indicate that topography of Ti6Al4V can be manipulated to control cell functions via contact guidance responses. Altogether with the available data in the literature, results herein may also provide guidance to the implant technology for the design of Ti-based alloys with bioinspired surfaces topographies able to enhance specific bone cell activities

Cellular therapies play an important role in tendon tissue engineering with tenocytes being described as the most prominent cell population if available in large numbers. In vitro expansion of tenocytes in standard culture leads to phenotypic drift and cellular senescence. Maintenance of tenogenic phenotype in vitro can be achieved by recapitulating different aspects of the tendon microenvironment. One approach used to modulate in vitro microenvironment and enhance extracellular matrix (ECM) deposition is macromolecular crowding (MMC). In addition, as tendon has been described to be a relatively avascular and hypoxic tissue and low oxygen tension can stimulate collagen synthesis and cross-linking through the activation of hypoxia-inducible factor 1-alpha (HIF1-α), we venture to assess the synergistic effect of MMC and low oxygen tension on human tenocyte phenotype maintenance. SDS-PAGE and immunocytochemistry analysis demonstrated that human tenocytes treated with MMC at 2 % oxygen tension showed increased synthesis and deposition of collagen type I. Moreover, immunocytochemistry for the tendon-specific ECM proteins collagen type III, V, VI and fibronectin illustrated enhanced deposition when cells were treated with MMC at 2 % oxygen tension. In addition, western blot analysis revealed increased expression of tendon-specific protein Scleraxis, while a detailed gene analysis illustrated upregulation of tendon-specific genes and downregulation of trans-differentiation genes again when cells cultured with MMC under hypoxic conditions. Collectively, results suggest that the synergistic effect of MMC and low oxygen tension can accelerate the formation of ECM-rich substitutes, which stimulates tenogenic phenotype maintenance

Introduction. Despite the high regenerative capacity of bone, large bone defects often require treatment involving bone grafts. Conventional autografting and allografting treatments have disadvantages, such as donor site morbidity, immunogenicity and lack of donor material. Bone tissue engineering offers the potential to achieve major advances in the development of alternative bone grafts by exploiting the bone-forming capacity of osteoblastic cells. However, viable cell culture models are essential to investigate osteoblast behavior. Three-dimensional (3D) cell culture systems have become increasingly popular because biological relevance of 3D cultures may exceed that of cell monolayers (2D) grown in standard tissue culture. However, only few direct comparisons between 2D and 3D models have been published. Therefore, we performed a pilot study comparing 2D and 3D culture models of primary human osteoblasts with regard to expression of transcription factors RUNX2 and osterix as well as osteogenic differentiation. Patients and Methods. Primary human osteoblasts were extracted from femoral neck spongy bone obtained during surgery procedures. Primary human osteoblasts of three donor patients were cultured in monolayers and in three different 3D culture models: 1) scaffold-free cultures, also referred to as histoids, which form autonomously after multilayer release of an osteoblast culture; 2) short-term (10-day) collagen scaffolds seeded with primary human osteoblasts (HOB); 3) long-term (29-day) collagen scaffolds seeded with HOB. Expression levels of transcription factors RUNX2 and osterix, both involved in osteoblast differentiation, were investigated using quantitative PCR and immunohistochemical staining. Furthermore, markers of osteogenic differentiation were evaluated, such as alkaline phosphatase activity, osteocalcin expression, and mineral deposition, as well as the expression of collagen type I and fibronectin extracellular matrix proteins. Results. Cells of the same origin, which were cultivated in different culture models, showed varying expression levels with regard to transcription factors RUNX2 and osterix as well as osteogenic markers. Increased levels of transcription factor RUNX2 and the extracellular matrix protein fibronectin were observed in all 3D cell culture models compared to monolayers. Furthermore, long-term cultivated histoids showed increased levels of osteogenic late-stage marker osteocalcin and transcription factor osterix. Additionally, long-term collagen scaffolds seeded with HOB showed elevated levels of osteocalcin compared to monolayers and short-term scaffolds. Moreover, alkaline phosphatase activity and mineralization capacity were increased in histoids. Conclusion. Considering the complex biochemical interactions of cells with surrounding cells and the extracellular matrix in vivo, important biological properties are disregarded when cells are only studied in 2D study models. Hence, we compared different 3D HOB cell culture models to 2D HOB monolayers with regard to expression of transcription factors RUNX2 and osterix as well as osteogenic differentiation in vitro. Our pilot study indicated that three-dimensional study models may promote osteogenic differentiation in vitro. Additionally, a beneficial effect of longer culture duration on osteogenic differentiation was observed. Hence, our findings emphasise the importance of dimension and culture duration when studying osteoblast function. Subsequent studies with higher sample sized may lead to the development of viable primary human osteoblast cell culture models for bone tissue engineering. Summary. Three-dimensional cell culture models of primary human osteoblasts (HOB), including collagen scaffolds and scaffold-free cultures, were compared to HOB monolayers with regard to osteogenic differentiation. Our study indicated that three-dimensional study models may promote osteogenic differentiation of HOB in vitro