Industries such as agriculture, construction and military have stringent rules about hearing protection due to the risk of noise induced hearing loss (NIHL). Due to the use of power tools, orthopaedic staff may be at risk of the same condition. The UK Health and Safety Executive (HSE) have clear standards as to what is deemed acceptable occupational noise levels on an A-weighted and C weighted scale. This review is aimed to assess evidence on noise exposure testing within Orthopaedic theatres to see if it exceeds the HSE regulations. A targeted search of online databases PUBMED and EMBASE was conducted using Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) principles. This review was registered prospectively in PROSPERO. An eligibility criterion identifying clinical studies which assessed noise exposure for Orthopaedic staff in theatres were included. Noise exposure data was extracted from these studies and a comparison was made with A weighted and C weighted acceptable exposure levels as quoted in the HSE regulations. Fourteen papers were deemed eligible, which reviewed 133 Orthopaedic operations and 64 Orthopaedic instruments. In total, 61% (81 of 132) of Orthopaedic operations and 70% (45 of 64) of instruments exceeded the noise regulations on an A weighted scale. 22% (10 of 46) of operations exceeded the maximum C weighted peak acceptable noise level. Orthopaedic instruments and operations can exceed safe occupational noise levels. NHS Trusts have clear policies about noise exposure in the workplace but have yet to identify Orthopaedic theatres as a potential at risk area. Orthopaedic staff need education, monitoring and protection whereas Employers and Occupational Health should consider assessments to identify at risk staff in Orthopaedic theatres and offer preventative methods from NIHL

Aims. Circular RNA (circRNA) is involved in the regulation of articular cartilage degeneration induced by inflammatory factors or oxidative stress. In a previous study, we found that the expression of circStrn3 was significantly reduced in chondrocytes of osteoarthritis (OA) patients and OA mice. Therefore, the aim of this paper was to explore the role and mechanism of circStrn3 in osteoarthritis. Methods. Minus RNA sequencing, fluorescence in situ hybridization, and quantitative real-time polymerase chain reaction (qRT-PCR) were used to detect the expression of circStrn3 in human and mouse OA cartilage tissues and chondrocytes. Chondrocytes were then stimulated to secrete exosomal miR-9-5p by cyclic tensile strain. Intra-articular injection of exosomal miR-9-5p into the model induced by destabilized medial meniscus (DMM) surgery was conducted to alleviate OA progression. Results. Tensile strain could decrease the expression of circStrn3 in chondrocytes. CircStrn3 expression was significantly decreased in human and mouse OA cartilage tissues and chondrocytes. CircStrn3 could inhibit matrix metabolism of chondrocytes through competitively ‘sponging’ miRNA-9-5p targeting Kruppel-like factor 5 (KLF5), indicating that the decrease in circStrn3 might be a protective factor in mechanical instability-induced OA. The tensile strain stimulated chondrocytes to secrete exosomal miR-9-5p. Exosomes with high miR-9-5p expression from chondrocytes could inhibit osteoblast differentiation by targeting KLF5. Intra-articular injection of exosomal miR-9-5p alleviated the progression of OA induced by destabilized medial meniscus surgery in mice. Conclusion. Taken together, these results demonstrate that reduction of circStrn3 causes an increase in miR-9-5p, which acts as a protective factor in mechanical instability-induced OA, and provides a novel mechanism of communication among joint components and a potential application for the treatment of OA. Cite this article: Bone Joint Res 2023;12(1):33–45

Extracellular matrix (ECM) mechanical cues guide healing in tendons. Yet, the molecular mechanisms orchestrating the healing processes remain elusive. Appropriate tissue tension is essential for tendon homeostasis and tissue health. By mapping the attainment of tensional homeostasis, we aim to understand how ECM tension regulates healing. We hypothesize that diseased tendon returns to homeostasis only after the cells reach a mechanically gated exit from wound healing. We engineered a 3D mechano-culture system to create tendon-like constructs by embedding patient-derived tendon cells into a collagen I hydrogel. Casting the hydrogel between posts anchored in silicone allowed adjusting the post stiffness. Under this static mechanical stimulation, cells remodel the (unorganized) collagen representing wound healing mechanisms. We quantified tissue-level forces using post deflection measurements. Secreted ECM was visualized by metabolic labelling with non-canonical amino acids, click chemistry and confocal microscopy. We blocked cell-mediated actin-myosin contractility using a ROCK inhibitor (Y27632) to explore the involvement of the Rho/ROCK pathway in tension regulation. Tissue tension forces reached the same homeostatic level at day 21 independent of post compliance (p = 0.9456). While minimal matrix was synthesized in early phases of tissue formation (d3-d5), cell-deposited ECM was present in later stages (d7-d9). More ECM was deposited by tendon constructs cultured on compliant (1Nm) compared to rigid posts (p = 0.0017). Matrix synthesized by constructs cultured on compliant posts was less aligned (greater fiber dispersion, p = 0.0021). ROCK inhibition significantly decreased tissue-level tensional forces (p < 0.0001). Our results indicate that tendon cells balance matrix remodeling and synthesis during tissue repair to reach an intrinsically defined “mechanostat setpoint” guiding tension-mediated exit from wound healing towards homeostasis. We are identifying specific molecular mechanosensors governing tension-regulated healing in tendon and investigate the Rho/ROCK system as their possible downstream pathway

Cell therapies hold significant promise for the treatment of injured or diseased musculoskeletal tissues. However, despite advances in research, there is growing concern about the increasing number of clinical centres around the world that are making unwarranted claims or are performing risky biological procedures. Such providers have been known to recommend, prescribe, or deliver so called ‘stem cell’ preparations without sufficient data to support their true content and efficacy. In this annotation, we outline the current environment of stem cell-based treatments and the strategies of marketing directly to consumers. We also outline the difficulties in the regulation of these clinics and make recommendations for best practice and the identification and reporting of illegitimate providers. Cite this article: Bone Joint J 2020;102-B(2):148–154

The inflammatory cascade associated with prosthetic implant wear debris, in addition to diseases such as rheumatoid arthritis and periodontitis, it is shown to drastically influence bone turnover in the local environment. Ultimately, this leads to enhanced osteoclastic resorption and the suppression of bone formation by osteoblasts causing implant failure, joint failure, and tooth loosening in the respective conditions if untreated. Regulation of this pathogenic bone metabolism can enhance bone integrity and the treatment bone loss. The current study used novel compounds that target a group of enzymes involved with the epigenetic regulation of gene expression and protein function, histone deacetylases (HDAC), to reduce the catabolism and improve the anabolism of bone material in vitro. Human osteoclasts were differentiated from peripheral blood monocytes and cultured over a 17 day period. In separate experiments, human osteoblasts were differentiated from human mesenchymal stem cells isolated from bone chips collected during bone marrow donations, and cultured over 21 days. In these assays, cells were exposed to the key inflammatory cytokine involved with the cascade of the abovementioned conditions, tumour necrosis factor-α (TNFα), to represent an inflammatory environment in vitro. Cells were then treated with HDAC inhibitors (HDACi) that target the individual isoforms previously shown to be altered in pathological bone loss conditions, HDAC-1, −2, −5 and −7. Analysis of bone turnover through dentine resorptive measurements and bone mineral deposition analyses were used to quantify the activity of bone cells. Immunohistochemistry of tartrate resistant acid phosphatase (TRAP), WST-assay and automated cell counting was used to assess cell formation, viability and proliferation rates. Real-time quantitative PCR was conducted to identify alterations in the expression of anti- and pro-inflammatory chemokines and cytokines, osteoclastic and osteoblastic factors, in addition to multiplex assays for the quantification of cytokine/chemokine release in cell supernatant in response to HDACi treatments in the presence or absence of TNFα. TNFα stimulated robust production of pro-inflammatory cytokines and chemokines by PBMCs (IL-1β, TNFα, MCP1 and MIP-1α) both at the mRNA and protein level (p < 0 .05). HDACi that target the isoforms HDAC-1 and −2 in combination significantly suppressed the expression or production of these inflammatory factors with greater efficacy than targeting these HDAC isoforms individually. Suppression of HDAC-5 and −7 had no effect on the inflammatory cascade induced by TNFα in monocytes. During osteoclastic differentiation, TNFα stimulated the size and number of active cells, increasing the bone destruction observed on dentine slices (p < 0 .05). Targeting HDAC-1 and −2 significantly reduced bone resorption through modulation of the expression of RANKL signalling factors (NFATc1, TRAF6, CatK, TRAP, and CTR) and fusion factors (DC-STAMP and β3-integerin). Conversely, the anabolic activity of osteoblasts was preserved with HDACi targeting HDAC-5 and −7, significantly increasing their mineralising capacity in the presence of TNFαthrough enhanced RUNX2, OCN and Coll-1a expression. These results identify the therapeutic potential of HDACi through epigenetic regulation of cell activity, critical to the processes of inflammatory bone destruction

Aims. Proliferation, migration, and differentiation of anterior cruciate ligament (ACL) remnant and surrounding cells are fundamental processes for ACL reconstruction; however, the interaction between ACL remnant and surrounding cells is unclear. We hypothesized that ACL remnant cells preserve the capability to regulate the surrounding cells’ activity, collagen gene expression, and tenogenic differentiation. Moreover, extracorporeal shock wave (ESW) would not only promote activity of ACL remnant cells, but also enhance their paracrine regulation of surrounding cells. Methods. Cell viability, proliferation, migration, and expression levels of Collagen-I (COL-I) A1, transforming growth factor beta (TGF-β), and vascular endothelial growth factor (VEGF) were compared between ACL remnant cells untreated and treated with ESW (0.15 mJ/mm. 2. , 1,000 impulses, 4 Hz). To evaluate the subsequent effects on the surrounding cells, bone marrow stromal cells (BMSCs)’ viability, proliferation, migration, and levels of Type I Collagen, Type III Collagen, and tenogenic gene (Scx, TNC) expression were investigated using coculture system. Results. ESW-treated ACL remnant cells presented higher cell viability, proliferation, migration, and increased expression of COL-I A1, TGF-β, and VEGF. BMSC proliferation and migration rate significantly increased after coculture with ACL remnant cells with and without ESW stimulation compared to the BMSCs alone group. Furthermore, ESW significantly enhanced ACL remnant cells’ capability to upregulate the collagen gene expression and tenogenic differentiation of BMSCs, without affecting cell viability, TGF-β, and VEGF expression. Conclusion. ACL remnant cells modulated activity and differentiation of surrounding cells. The results indicated that ESW enhanced ACL remnant cells viability, proliferation, migration, and expression of collagen, TGF-β, VEGF, and paracrine regulation of BMSC proliferation, migration, collagen expression, and tenogenesis. Cite this article: Bone Joint Res 2020;9(8):457–467

Summary Statement. We have shown that integrin mRNA expression is regulated by the application of mechanical load. This indicates that mechanical loading may modify cell sensitivity to perceive further load through increased interaction with the ECM. Introduction. Tendinopathies are a range of diseases characterised by pain and insidious degeneration. Although poorly understood, onset is often associated with physical activity. We have previously investigated the regulation by mechanical strain of metalloproteinase gene expression in human tenocyte in a 3D collagen matrix. Integrins are important in cellular interaction with the ECM and are reported to mediate mechanotransduction in various non-tendon tissues. We have reported that TGFbeta activation is a key player in the regulation of metalloproteinases in response to mechanical load, which may be mediated by integrins. This project aims to investigate the effect of cyclic loading and TGFbeta stimulation on integrin expression by human tenocytes, in collagen and fibrin matrices. Methods. Human tenocytes were seeded at 1.5×106 cells/ml into collagen (rat tail type I, 1mg/ml) or fibrin (fibrinogen 6mg/ml, Thrombin 0.2u/ml) gels and stretched using a sinusoidal waveform of 0–5% at 1Hz using the Flexcell FX4000T(trade mark) system. Cultures were treated with or without 1ng/ml TGFbeta1 and load for 0–48 hours. Taqman Low density Array was used to asses a range of integrin, including ITGA1-6, ITGA10 and ITGA11 as well as ITGB1-5 (n=3). Results. In collagen cultures all integrins assayed were detectable (Ct < 35). ITGB1 was increased 2 fold with 48 hours of cyclic strain (p=0.006). ITGA6 and ITGA10 were decreased 1.4 and 2 fold with TGFbeta treatment after 24 hours (p=0.019, p=0.006). ITGA3 and ITGB3 were significantly decreased 7.6 and 8.3 fold with TGFbeta treatment after 48 hours (p=0.012, p=0.023). ITGA5 and ITGB1 showed similar responses with strain and TGFbeta, i.e. an increased trend. However, the other integrins showed a dissimilar response to strain and TGFbeta. Here we compare these responses to those in fibrin under the same conditions. Discussion. We have shown that integrin mRNA expression is regulated by the application of mechanical load. This indicates that mechanical loading may modify cell sensitivity to perceive further load through increased interaction with the ECM. Any differences in the cellular response to load in collagen and fibrin cultures, indicates that cellular interaction with the ECM is an important factor in the detection of load. Due to the differential regulation of some of the integrins with strain and TGFbeta, it appears that TGFbeta may not be responsible for the regulation of all integrins with strain. However this remains unconfirmed and may be explained by a temporal difference. Further analysis of how integrins are regulated in response to mechanical load and how this expression is translated to the protein level is required

Onset and progression of osteoarthritis (OA) is affected by a plethora of factors, including joint injury, obesity, aging, and heredity. This multi-factorial etiology obstructs our understanding of driving molecular mechanisms, which likely comprise an interplay between systemic and local factors. Next to biomechanical factors and cytokines, the course of OA appears to be altered by microenvironmental oxidative stress: cumulative evidence now suggests a prominent participation of cell signalling mediated by nuclear factor (erythroid-derived 2)-like 2 (Nrf2), a master regulator of cellular protective processes, in this process. Nrf2 activation through phosphorylation of mitogen-activated protein kinases (MAPKs) regulates Nrf2 target genes, like hemeoxygenase-1 (HO-1), superoxide dismutase 2 (SOD2), or NAD(P)H Quinone Dehydrogenase 1 (NQO1) in OA chondrocytes. Maintaining high levels of HO-1 appears to be beneficial against OA development. Experimental manipulation of putative antioxidant response element (ARE) binding sites alters the in vitro expression of key transcription factors of chondrocyte markers in promoter-reporter assays. Potentially, Nrf2 is involved in autophagy, intermediary metabolism and unfolded protein response. RNAi-mediated depletion of Nrf2 further significantly abrogated anti-inflammatory and chondroprotective effects and epigenetics link transcriptional pathways of ‘N-factors’, Nrf2 and NFATs, to micro-RNA signalling. Current findings thus reveal novel mechanisms regulating extracellular matrix synthesis by chondrocytes. A further understanding of these pathways and their regulation will lead to important novel targets to slow OA progression

Infected wounds are a major problem for patients and health care systems. The inflammation triggers expression of high levels of extracellular protease activities which degrade newly formed granulation tissue. The expression of host-derived proteases had been studied in wound healing extensively. In contrast, the contribution of bacterial proteases in impaired healing acute and chronic wounds is poorly understood as is how bacterial proteases can be blocked.

In this study the expression of P. aeruginosa proteases was studied. P. aeruginosa is associated with poor healing and sufficiently common in wound infections to merit closer study. We used in vitro biofilm and planktonic culture models to analyze the culture-dependent expression of different P. aeruginosa proteases and how protease modulating polymers can inhibit activities.

P. aeruginosa (PAO1, DSM 22644) was grown in LB_o medium (aerated planktonic cultures) or in a biofilm culture model (dialysis tubing on LB_o plates). The supernatant of planktonic or wash fluids from biofilm cultures were analyzed for protease activity.

Global extracellular protease activities increased in a time- and culture condition-dependent manner (for planktonic cultures 180 ng/ml trypsin equivalent 8h, 330 ng/ml 24h, 490 ng/ml 48h; biofilm cultures 190 ng/ml trypsin equivalent 8h, 420 ng/ml 24h, 170 ng/ml 48h). Enzyme zymography revealed in biofilm cultures predominant bands at 50 kD (8h, 24h, 48h), 90 kD (24h) and > 200 kD (8h, 24h, 48h). In planktonic cultures the pattern was different 50 kD (8h), 90 kD (8h, 24h, 48h), 130 kD (24h, 48h) and > 200 kD (8h, 24h). Two different polyacrylate superabsorbers could inhibit P. aeruginosa protease activities. Favor PAC 300 blocked protease activity by 60% and SXM 9170 by 35%.

These data demonstrate complex, culture-dependent expression of extracellular proteases in P. aeruginosa, a microorganism associated with poor wound healing outcomes. From a therapeutic perspective polyacrylate superabsorbers strongly inhibited global protease activities. In the next steps the protease expression pattern needs to be analyzed in P. aeruginosa wounds and correlated with healing progression.

To overcome the severely limited regenerative capacity of cartilage, bone marrow mesenchymal stromal cells (MSCs) are an attractive cell source that is accessible less invasively and in higher quantity than articular chondrocytes (ACs). However, current in vitro chondrogenic protocols induce MSCs to form transient cartilage reminiscent of growth plate cartilage that becomes hypertrophic and is remodeled into bone. In contrast, under the same conditions, ACs form stable articular-like cartilage. Developmental studies in mice have revealed that TGF-beta/BMP, Wnt, and Hedghog/PTHrP signaling are the major regulators of both, articular cartilage and endochondral bone formation. While the differential regulation of TGF-beta/BMP and Hedgehog/PTHrP in endochondral MSC versus AC chondral differentiation is established knowledge, little is known about Wnt in these cells. Aim of this study was therefore to compare in vitro levels of Wnt network components in MSC-derived endochondral versus AC-derived articular cartilage. Whole genome expression data comparing human MSCs and ACs at days 0 and 28 of in vitro chondrogenesis were screened for differential expression of Wnt ligands, receptors, co-receptors, activators/inhibitors and signaling molecules. Expression of the most strongly differentially regulated Wnt network genes was studied in detail during in vitro chondrogenesis of MSCs vs ACs via qPCR at days 0, 7, 14, 21, 35, and 42. During early chondrogenesis, most Wnt components were expressed at low levels in both MSCs and ACs, with two exceptions. MSCs started into chondrogenesis with significantly higher levels of the non-canonical ligand WNT5A. ACs on the other hand expressed significantly higher levels of the canonical antagonist FRZB on day 0. During advancing and late chondrogenesis, MSCs downregulated WNT5A but still expressed it at significantly higher levels at day 42 than ACs. Strong regulation was also evident for WNT11 and the receptor PTK7 which were both strongly upregulated in MSCs. Unlike MSCs, ACs barely regulated these non-canonical Wnt genes. With regard to canonical signaling, only the transcription factor LEF1 showed strong upregulation in MSCs, while FZD9 and FRZB were only slightly upregulated in late MSC chondrogenesis. Again, these genes remained unregulated in ACs. Our data suggest that a dynamic Wnt network regulation may be a unique characteristic of endochondral MSC differentiation while during AC chondral differentiation Wnt expression remained rather low and stable. Overall, mRNA of the non-canonical Wnt network components were stronger regulated than canonical factors which may indicate that primarily non-canonical signaling is dynamic in endochondral differentiation. Next step is to assess levels of active and total beta-catenin, the canonical Wnt mediator, and to use Wnt antagonists to establish a causal relationship between Wnt signaling and endochondral differentiation

Introduction. Cell-based therapy is needed to overcome the lacking intrinsic ability of cartilage to heal. Generating cartilage tissue from human bone marrow-derived stromal cells (MSC) is limited by up-regulation of COL10, ALP and other hypertrophy markers in vitro and calcifying cartilage at heterotopic sites in vivo. MSC hypertrophic differentiation reflects endochondral ossification, unable to maintain a stable hyaline stage, as observed by redifferentiation of articular chondrocytes (AC). Several transcription factors (TF), are held responsible for hypertrophic development. SOX9, the master regulator of chondrogenesis is also, alongside MEF2C, regulating hypertrophic chondrocyte maturation and COL10 expression. RUNX2/3 are terminal markers driving chondrocyte hypertrophy, and skeletogenesis. However, so far regulation of these key fate determining TFs has not been studied thoroughly on mRNA and protein level through chondrogenesis of human MSC. To fill this gap in knowledge, we aim to uncover regulation of SOX9, RUNX2/3, MEF2C and other TFs related to hypertrophy during MSC chondrogenesis in vitro and in comparison to the gold standard AC redifferentiation. Methods. Expression of SOX9, RUNX2/3 and MEF2C was compared before and during 6-week chondrogenic re-/differentiation of human MSC and AC on mRNA level via qRT-PCR and protein level via Western-Blotting. Chondrogenesis was evaluated by histology at d42 and expression of chondrogenic markers like COL2. Hypertrophic development was characterized by ALP activity and expression of hypertrophic markers like COL10. Results. Hypertrophic development, characterized by upregulation of COL10, high COL10/COL2 ratios and ALP activity, was confirmed in MSC and absent in AC. MSC started into differentiation with less SOX9 before induction, while higher RUNX2/3 was observed compared to AC. During MSC chondrogenesis SOX9 and MEF2C steadily increased on mRNA and protein level. Surprisingly, although RUNX2 mRNA level increased in MSC over 42 days, RUNX2 protein remained undetectable. During AC redifferentiation, SOX9 levels remained high on mRNA and protein level while RUNX2/3 and MEF2C remained low. Conclusion. After expansion and before applying chondrogenic stimuli, a chondrogenic priming with more SOX9 and lower RUNX2/3 was found in AC. In contrast osteochondral priming with higher RUNX2/3 and lower SOX9 levels was observed in MSC which could set the stage for endochondral development, leading to hypertrophy. Dynamic regulation of RUNX2/3 and MEF2C at lower SOX9 background levels separated MSC from AC differentiation over 42 days. Adjusting transcription factor levels in MSC could be essential for creating a protocol leading to diminished hypertrophy of MSC during chondrogenesis

Objectives. Osteoporosis is a systemic bone metabolic disease, which often occurs among the elderly. Angelica polysaccharide (AP) is the main component of angelica sinensis, and is widely used for treating various diseases. However, the effects of AP on osteoporosis have not been investigated. This study aimed to uncover the functions of AP in mesenchymal stem cell (MSC) proliferation and osteoblast differentiation. Methods. MSCs were treated with different concentrations of AP, and then cell viability, Cyclin D1 protein level, and the osteogenic markers of runt-related transcription factor 2 (RUNX2), osteocalcin (OCN), alkaline phosphatase (ALP), bone morphogenetic protein 2 (BMP-2) were examined by Cell Counting Kit-8 (CCK-8) and western blot assays, respectively. The effect of AP on the main signalling pathways of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) and Wnt/β-catenin was determined by western blot. Following this, si-H19#1 and si-H19#2 were transfected into MSCs, and the effects of H19 on cell proliferation and osteoblast differentiation in MSCs were studied. Finally, in vivo experimentation explored bone mineral density, bone mineral content, and the ash weight and dry weight of femoral bone. Results. The results revealed that AP significantly promoted cell viability, upregulated cyclin D1 and increased RUNX2, OCN, ALP, and BMP-2 protein levels in MSCs. Moreover, we found that AP notably activated PI3K/AKT and Wnt/β-catenin signalling pathways in MSCs. Additionally, the relative expression level of H19 was upregulated by AP in a dose-dependent manner. The promoting effects of AP on cell proliferation and osteoblast differentiation were reversed by H19 knockdown. Moreover, in vivo experimentation further confirmed the promoting effect of AP on bone formation. Conclusion. These data indicate that AP could promote MSC proliferation and osteoblast differentiation by regulating H19. Cite this article: X. Xie, M. Liu, Q. Meng. Angelica polysaccharide promotes proliferation and osteoblast differentiation of mesenchymal stem cells by regulation of long non-coding RNA H19: An animal study. Bone Joint Res 2019;8:323–332. DOI: 10.1302/2046-3758.87.BJR-2018-0223.R2

Problems of vertebral growth plate metabolism regulation at different stages of ontogenesis are insufficiently covered in the literature. However, the study of function mechanism of provisional cartilage of vertebral growth plate is a practical and theoretical basis of pathogenesis model of idiopathic scoliosis and Scheuermann’s disease both associated with growth disorders. Objective: To investigate the function mechanism of vertebral growth plate structural components during formation and growth. Materials and methods: Fifty vertebral body specimens of children at the age from 1 to 14 years obtained from the forensic medicine department were studied by methods of morphohistochemistry, biochemistry, and ultra-structural analysis. The expression of five proteoglycan genes and their albuminous products was investigated by RT-PCR method. Results: The process of growth represents a sequence of morphogenetic movements ongoing up to the achievement of sexual maturity. But morphofunctional organization and regulation of growth are different in different periods of ontogenesis. Early postnatal growth of vertebral bodies is governed by a radially located zone of growth. The cell population in a just-formed cartilage growth plate is non-uniform: from poorly differentiated chondroblast through the form of highly differentiated ones to degrading chondrocyte. This period of the spine development is characterised by the presence of vessels in provisional cartilage tissue. The concept of “chondro/hematic barrier” suggested and validated by A.M Zaidman explains a conservation of homeostasis at a stage of vertebral bodies differentiation. The process of chondrogenic differentiation of prechondroblasts in the early postnatal period is inducted by the chorda influence. In the late postnatal period (12–14 years) the laws of structural and functional organization of cartilage growth plate of vertebral body remain the same: phenotypic heterogeneity, polarity, and zonality of cells. A metabolic centre of complex architectonics of cartilage tissue is chondroblast. Chondroblast is functioning at the level of chondron which is a functional unit of vertebral growth plate. Chondroblast (chondrocyte) is located in the centre of chondron and surrounded by pericellular matrix presented by diffuse aggrecan molecules, or growth plate aggregates. Due a peculiar architectonics, growth plate molecules have inner spaces comparable in size with Golgi’s vesicles. Metabolites, small molecules, and water freely penetrate through these molecules. Diffuse molecules together with type II thin collagenic fibres, minor collagenes, and structure-forming growth plates perform barrier function. Besides barrier function, diffuse molecules perform information function inside a chondron, forming a kind of information field. Signals of this field are perceived by chondroblast receptors, and the cell gene apparatus expression is carried out through second messengers. Thus, either stimulation of proliferative activity with subsequent differentiation during intensive growth, or interruption of these processes (period of growth delay) occurs. Single chondrons unite into chains in proliferation zones. Cell interaction inside chondron occurs due transmembrane structures, as a contact coordination of functions of cells with inherent high specificity. Concentration of diffuse molecules of growth plate (aggrecan) in proliferation zones is the highest on evidence of histochemical and ultrastructural assays. Besides, diffuse molecules are the short-distance regulators of DNA synthesis the mechanism of action of which is realised through the system of receptors on a cellular membrane. Hence, contact intercellular interactions are one of the mechanisms controlling cell division. These are so-called extracellular factors of chondroblast proliferation regulation. Thus, the process of growth represents a complex two-stage mechanism of proliferation and differentiation of chondroblasts, and adequate osteogenesis. All three processes provide harmonious spine formation, and disturbance of one of them results in pathology development

Introduction. Within the intervertebral disc (IVD), nucleus pulposus (NP) cells reside within a unique microenvironment. Factors such as hypoxia, osmolality, pH and the presence of cytokines all dictate the function of NP cells and as such the cells must adapt to their environment to survive. Previously we have identified the expression of aquaporins (AQP) within human IVD tissue. AQPs allow the movement of water across the cell membrane and are important in cellular homeostasis. Here we investigated how AQP gene expression was regulated by the microenvironment of the IVD. Methods. Human NP cells were cultured in alginate beads prior to cytokine, osmolality, pH and hypoxia treatments and subsequent RT-qPCR to assess regulation of AQP gene expression. Results. Physiological conditions observed within the native IVD regulated AQP gene expression in human NP cells. Hyperosmotic treatment up-regulated the expression of AQP1 and 5 during hypoxic conditions, whereas AQP4 expression was down-regulated. During hypoxia and physiological pH treatments AQP5 expression was increased. Pro-inflammatory cytokines, increased during IVD degeneration, also altered AQP gene expression. Interleukin-1β (IL-1β) decreased expression of AQP1 and 3 yet up-regulated AQP9, interleukin-6 (IL-6) increased expression of AQP1, 3, and 9 and tumour necrosis factor α (TNFα) upregulated the gene expression of both AQP2 and 9. Conclusion. The microenvironment in which NP cells reside in vivo directly contributes to their correct function and survival. AQP gene expression was differentially regulated under healthy compared to degenerate conditions; this potentially highlights that during IVD degeneration NP cells differentially express AQPs. No conflicts of interest. Funded by BMRC, Sheffield Hallam University

Abstract

Introduction: In the growth plate, chondrocyte swelling (hypertrophy) is a crucial event during endochondral ossification and bone lengthening, accounting for ~80% of the increase in bone length (. 1. ,. 3. ). The swelling is dramatic (~10x) and closely regulated. Failure of chondrocyte hypertrophy may underlie the chondrodysplasias of the vertebrate skeleton (. 1. ). However, the mechanisms which control cell swelling are poorly understood although there must be a key role for chondrocyte osmolyte transporters which are sensitive to an increase in cell volume. We have used confocal scanning laser microscopy (CLSM) to study volume regulation by living in situ growth plate chondrocytes at varying degrees of hypertrophy. Methods: Bovine growth plates were taken from the ends of young (~12d) bovine ribs. In situ growth plate chondrocytes at the proliferative through to hypertrophic stages were fluorescently-labelled (calcein-AM; 5μM), imaged (Zeiss CLSM510) and volumes determined quantitatively as described (. 2. ). An acute osmotic challenge (280-140mOsm) was delivered by perfusion to determine volume-regulatory capacity by cells in the various zones. Results: The resting volumes of proliferative and hypertrophic cells were 550±63μm. 3. and 5227±1974μm. 3. respectively. Reducing osmolarity resulted in a rapid (within ~1min) cell swelling, proliferative and hypertrophic chondrocytes increasing in volume by 126±2% and 146±5% (n=5) respectively. Chondrocytes within the proliferative zone then recovered in volume by ~60% over the following 20mins (p=0.04), whereas no volume recovery was detected in hypertrophic cells (p=0.94). Conclusions: For the increase in growth plate chondrocyte volume to produce hypertrophy it is essential that the membrane transporters which normally prevent cell swelling are suppressed, otherwise the increase in volume will be compromised. These results suggest that chondrocyte hypertrophy is associated with reduced activity of the swelling-stimulated osmolyte transporter whereas the pathway is active in proliferating chondrocytes. Changes in the activity of this pathway are likely to be an important component in the control of chondrocyte hypertrophy. It is clear that the contributions of other membrane transporters in mediating chondrocyte swelling must be identified in order to understand the overall hypertrophic process

Fragility fractures are skeletal complications associated with type 2 diabetes (T2D) causing disability, hospitalization, impaired quality of life, and increased mortality. Increased circulating sclerostin and accumulation of advanced glycation end-products (AGEs) are two potential mechanisms underlying low bone turnover and increased fracture risk. We have recently shown that T2D affects the expression of genes controlling bone formation (SOST and RUNX2) and that accumulation of AGEs is associated with impaired bone formation in T2D. We hypothesized that Wnt/B- catenin target genes are down-regulated in bone of T2D subjects as a consequence of decreased SOST and AGEs accumulation. To this end, we studied gene expression in extracts of bone samples obtained from femoral heads of 14 subjects with relatively well-controlled T2D (HbA1c 6.5±1.7%) and 21 control, non-diabetic postmenopausal women (age >65 years) undergoing hip replacement. There were no differences in age (73.2± .8 vs. 75.2±8.5 years) or BMI (27.7±5.6 vs. 29.9±5.4 kg/m2) between control and T2D groups, respectively. Expression of LEF1 mRNA was significantly lower in T2D compared to non-diabetic subjects (p=0.002), while DKK1 was not different between groups (p=0.108). Correlation analysis showed that DKK1 (r2=0.038; p=0.043) and HbA1c (r2=0.503; p=0.048) increased with age in T2D. COL1A1 mRNA trended lower in T2D compared to controls (p=0.056). Bone volume (9,333 ± 1,443 vs. 15,53 ± 2,442 mm2; p=0.048), mineralized volume (9,278 ± 1,418 vs. 15,45 ± 2,444 mm²; p=0.048) and BV/TV (0,2125 ± 0,03114 vs. 0,3719 ± 0,03196 %; p=0.002) measured by bone histomorphometry were lower in T2D compared to controls. Our data show that even in patients with relatively good glycemic control, T2D decreases expression of Wnt/B-catenin target genes andCOL1A1, associated with decreased bone density. These results may help understand the mechanisms underlying bone fragility in T2D.

TGF-β/Smad2 signaling is considered to be one of the important pathways involved in osteoarthritis (OA) and protein phosphatase magnesium-dependent 1A (PPM1A) functions as an exclusive phosphatase of Smad2 and regulates TGF-β signaling, here, we investigated the functional role of PPM1A in OA pathogenesis.

PPM1A expressions in both human OA cartilage and experimental OA mice chondrocytes were analyzed immunohistochemically. Besides, the mRNA and protein expression of PPM1A induced by IL-1β treatment were also detected by q-PCR and immunofluorescence in vitro. OA was induced in PPM1A knockout (KO) mice by destabilization of the medial meniscus (DMM), and histopathological examination was performed. OA was also induced in wild-type (WT) mice, which were then treated with an intra-articular injection of a selective PPM1A inhibitor for 8 weeks.

PPM1A protein expressions were increased in both human OA cartilage and experimental OA mice chondrocytes. We also found that treatment with IL-1β in mouse primary chondrocytes significantly increased both mRNA and protein expression of PPM1A in vitro. Importantly, our data showed that PPM1A deletion could substantially protect against surgically induced OA. Concretely, the average OARSI score and quantification of BV/TV of subchondral bone in KO mice were significantly lower than that in WT mice 8 weeks after DMM surgery. Besides, TUNEL staining revealed a significant decrease in apoptotic chondrocytes in PPM1A-KO mice with DMM operation. With OA induction, the rates of chondrocytes positive for Mmp-13 and Adamts-5 in KO mice were also significantly lower than those in WT mice. Moreover, compared with WT mice, the phosphorylation of Smad2 in chondrocytes was increased in KO mice underwent DMM surgery. However, articular-injection with SD-208, a selective inhibitor of TGF-β/Smad2 signaling could significantly abolish the chondroprotective phenotypes in PPM1A-KO mice. Additionally, both cartilage degeneration and subchondral bone subchondral bone sclerosis in DMM model were blunted following intra-articular injection with BC-21, a small-molecule inhibitor for PPM1A.

Our study demonstrated that PPM1A inhibition attenuates OA by regulating TGF-β/Smad2 signaling. Furthermore, PPM1A is a potential target for OA treatment and BC-21 may be employed as alternative therapeutic agents for the management of OA.

Rheumatoid arthritis (RA) is an autoimmune disease characterized by symmetrical and chronic polyarthritis. Fibroblast-like synoviocytes are mainly involved in joint inflammation and cartilage and bone destruction by inflammatory cytokines and matrix-degrading enzymes in RA. Approaches that induce various cellular growth alterations of synoviocytes are considered as potential strategies for treating RA. However, since synoviocytes play a critical role in RA, the mechanism and hyperplastic modulation of synoviocytes and their motility need to be addressed. In this review, we focus on the alteration of synoviocyte signalling and cell fate provided by signalling proteins, various antioxidant molecules, enzymes, compounds, clinical candidates, to understand the pathology of the synoviocytes, and finally to achieve developed therapeutic strategies of RA.

Cite this article: Bone Joint Res 2021;10(4):285–297.