Objectives. Osteoarthritis (OA) is characterised by articular cartilage degradation. MicroRNAs (miRNAs) have been identified in the development of OA. The purpose of our study was to explore the functional role and underlying mechanism of miR-138-5p in interleukin-1 beta (IL-1β)-induced extracellular matrix (ECM) degradation of OA cartilage. Materials and Methods. Human articular cartilage was obtained from patients with and without OA, and chondrocytes were isolated and stimulated by IL-1β. The expression levels of miR-138-5p in cartilage and chondrocytes were both determined. After transfection with miR-138-5p mimics, allele-specific oligonucleotide (ASO)-miR-138-5p, or their negative controls, the messenger RNA (mRNA) levels of aggrecan (ACAN), collagen type II and alpha 1 (COL2A1), the protein levels of glycosaminoglycans (GAGs), and both the mRNA and protein levels of matrix metalloproteinase (MMP)-13 were evaluated. Luciferase reporter assay, quantitative real-time polymerase chain reaction (qRT-PCR), and Western blot were performed to explore whether Forkhead Box C1 (FOCX1) was a target of miR-138-5p. Further, we co-transfected OA chondrocytes with miR-138-5p mimics and pcDNA3.1 (+)-FOXC1 and then stimulated with IL-1β to determine whether miR-138-5p-mediated IL-1β-induced cartilage matrix degradation resulted from targeting FOXC1. Results. MiR-138-5p was significantly increased in OA cartilage and in chondrocytes in response to IL-1β-stimulation. Overexpression of miR-138-5p significantly increased the IL-1β-induced downregulation of COL2A1, ACAN, and GAGs, and increased the IL-1β-induced over expression of MMP-13.We found that FOXC1 is directly regulated by miR-138-5p. Additionally, co-transfection with miR-138-5p mimics and pcDNA3.1 (+)-FOXC1 resulted in higher levels of COL2A1, ACAN, and GAGs, but lower levels of MMP-13. Conclusion. miR-138-5p promotes IL-1β-induced cartilage degradation in human chondrocytes, possibly by targeting FOXC1. Cite this article: Y. Yuan, G. Q. Zhang, W. Chai,M. Ni, C. Xu, J. Y. Chen. Silencing of microRNA-138-5p promotes IL-1β-induced cartilage degradation in human chondrocytes by targeting FOXC1: miR-138 promotes cartilage degradation. Bone Joint Res 2016;5:523–530. DOI: 10.1302/2046-3758.510.BJR-2016-0074.R2

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

Aims. This study aimed to investigate whether human umbilical cord mesenchymal stem cells (UC-MSCs) can prevent articular cartilage degradation and explore the underlying mechanisms in a rat osteoarthritis (OA) model induced by monosodium iodoacetate (MIA). Methods. Human UC-MSCs were characterized by their phenotype and multilineage differentiation potential. Two weeks after MIA induction in rats, human UC-MSCs were intra-articularly injected once a week for three weeks. The therapeutic effect of human UC-MSCs was evaluated by haematoxylin and eosin, toluidine blue, Safranin-O/Fast green staining, and Mankin scores. Markers of joint cartilage injury and pro- and anti-inflammatory markers were detected by immunohistochemistry. Results. Histopathological analysis showed that intra-articular injection of human UC-MSCs significantly inhibited the progression of OA, as demonstrated by reduced cartilage degradation, increased Safranin-O staining, and lower Mankin scores. Immunohistochemistry showed that human UC-MSC treatment down-regulated the expression of matrix metalloproteinase-13 (MMP13) and a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS-5), and enhanced the expression of type II collagen and ki67 in the articular cartilage. Furthermore, human UC-MSCs significantly decreased the expression of interleukin (IL)-1β and tumour necrosis factor-α (TNF-α), while increasing TNF-α-induced protein 6 and IL-1 receptor antagonist. Conclusion. Our results demonstrated that human UC-MSCs ameliorate MIA-induced OA by preventing cartilage degradation, restoring the proliferation of chondrocytes, and inhibiting the inflammatory response, which implies that human UC-MSCs may be a promising strategy for the treatment of OA. Cite this article: Bone Joint Res 2021;10(3):226–236

Aims. The study aimed to determine whether the microRNA miR21-5p (MiR21) mediates temporomandibular joint osteoarthritis (TMJ-OA) by targeting growth differentiation factor 5 (Gdf5). Methods. TMJ-OA was induced in MiR21 knockout (KO) mice and wild-type (WT) mice by a unilateral anterior crossbite (UAC) procedure. Mouse tissues exhibited histopathological changes, as assessed by: Safranin O, toluidine blue, and immunohistochemistry staining; western blotting (WB); and quantitative real-time polymerase chain reaction (RT-qPCR). Mouse condylar chondrocytes were transfected with a series of MiR21 mimic, MiR21 inhibitor, Gdf5 siRNA (si-GDF5), and flag-GDF5 constructs. The effects of MiR-21 and Gdf5 on the expression of OA related molecules were evaluated by immunofluorescence, alcian blue staining, WB, and RT-qPCR. Results. UAC altered the histological structure and extracellular matrix content of cartilage in the temporomandibular joint (TMJ), and KO of MiR21 alleviated this effect (p < 0.05). Upregulation of MiR21 influenced the expression of TMJ-OA related molecules in mandibular condylar chondrocytes via targeting Gdf5 (p < 0.05). Gdf5 overexpression significantly decreased matrix metalloproteinase 13 (MMP13) expression (p < 0.05) and reversed the effects of MiR21 (p < 0.05). Conclusion. MiR21, which acts as a critical regulator of Gdf5 in chondrocytes, regulates TMJ-OA related molecules and is involved in cartilage matrix degradation, contributing to the progression of TMJ-OA. Cite this article: Bone Joint Res 2020;9(10):689–700

Cite this article: Bone Joint Res 2023;12(10):654–656.

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

Introduction. Osteoarthritis (OA) causes pain, stiffness, and loss of function due to degenerative changes in joint cartilage and bone. In some forms of OA, exercise can alleviate symptoms by improving joint mobility and stability. However, excessive training after joint injury may have negative consequences for OA development. Sensory nerve fibers in joints release neuropeptides like alpha-calcitonin gene-related peptide (alpha-CGRP), potentially affecting OA progression. This study investigates the role of alpha-CGRP in OA pathogenesis under different exercise regimen in mice. Method. OA was induced in C57Bl/6J WT mice and alpha-CGRP KO mice via surgical destabilization of the medial meniscus (DMM) at 12 weeks of age (N=6). Treadmill exercise began 2 weeks post-surgery and was performed for 30 minutes, 5 days a week, for 2 or 6 weeks at intense (16 m/min, 15° incline) or moderate (10 m/min, 5° incline) levels. Histomorphometric assessment of cartilage degradation (OARSI scoring), serum cytokine analysis, immunohistochemistry, and nanoCT analysis were conducted. Result. OARSI scoring confirmed OA induction 4 weeks post-DMM surgery, with forced exercise exacerbating cartilage degradation regardless of intensity. No significant genotype-dependent differences were observed. Serum analysis revealed elevated cytokine levels associated with OA and inflammation in KO mice compared to WT mice 4 and 8 weeks post-surgery (VEGF-A, MCP-1, CXCL10, RANTES, MIP1-alpha, MIP1-beta, and RANKL). The observed effects were often exacerbated by intense exercise but rarely by DMM surgery. NanoCT analysis demonstrated increased sclerotic bone changes after 6 weeks of forced exercise in KO mice compared to WT mice. Conclusion. Our results suggest an OA promoting effect of exercise in early disease stages of posttraumatic OA. Intense exercise induced inflammatory processes correlated to increased cytokine levels in the serum that might exacerbate OA pathogenesis in later stages. The neuropeptide alpha-CGRP might play a role in protecting against these adverse effects

Aims. Knee osteoarthritis (OA) involves a variety of tissues in the joint. Gene expression profiles in different tissues are of great importance in order to understand OA. Methods. First, we obtained gene expression profiles of cartilage, synovium, subchondral bone, and meniscus from the Gene Expression Omnibus (GEO). Several datasets were standardized by merging and removing batch effects. Then, we used unsupervised clustering to divide OA into three subtypes. The gene ontology and pathway enrichment of three subtypes were analyzed. CIBERSORT was used to evaluate the infiltration of immune cells in different subtypes. Finally, OA-related genes were obtained from the Molecular Signatures Database for validation, and diagnostic markers were screened according to clinical characteristics. Quantitative reverse transcription polymerase chain reaction (qRT‐PCR) was used to verify the effectiveness of markers. Results. C1 subtype is mainly concentrated in the development of skeletal muscle organs, C2 lies in metabolic process and immune response, and C3 in pyroptosis and cell death process. Therefore, we divided OA into three subtypes: bone remodelling subtype (C1), immune metabolism subtype (C2), and cartilage degradation subtype (C3). The number of macrophage M0 and activated mast cells of C2 subtype was significantly higher than those of the other two subtypes. COL2A1 has significant differences in different subtypes. The expression of COL2A1 is related to age, and trafficking protein particle complex subunit 2 is related to the sex of OA patients. Conclusion. This study linked different tissues with gene expression profiles, revealing different molecular subtypes of patients with knee OA. The relationship between clinical characteristics and OA-related genes was also studied, which provides a new concept for the diagnosis and treatment of OA. Cite this article: Bone Joint Res 2023;12(12):702–711

Aims. This study aimed to define the histopathology of degenerated humeral head cartilage and synovial inflammation of the glenohumeral joint in patients with omarthrosis (OmA) and cuff tear arthropathy (CTA). Additionally, the potential of immunohistochemical tissue biomarkers in reflecting the degeneration status of humeral head cartilage was evaluated. Methods. Specimens of the humeral head and synovial tissue from 12 patients with OmA, seven patients with CTA, and four body donors were processed histologically for examination using different histopathological scores. Osteochondral sections were immunohistochemically stained for collagen type I, collagen type II, collagen neoepitope C1,2C, collagen type X, and osteocalcin, prior to semiquantitative analysis. Matrix metalloproteinase (MMP)-1, MMP-3, and MMP-13 levels were analyzed in synovial fluid using enzyme-linked immunosorbent assay (ELISA). Results. Cartilage degeneration of the humeral head was associated with the histological presentation of: 1) pannus overgrowing the cartilage surface; 2) pores in the subchondral bone plate; and 3) chondrocyte clusters in OmA patients. In contrast, hyperplasia of the synovial lining layer was revealed as a significant indicator of inflammatory processes predominantly in CTA. The abundancy of collagen I, collagen II, and the C1,2C neoepitope correlated significantly with the histopathological degeneration of humeral head cartilage. No evidence for differences in MMP levels between OmA and CTA patients was found. Conclusion. This study provides a comprehensive histological characterization of humeral cartilage and synovial tissue within the glenohumeral joint, both in normal and diseased states. It highlights synovitis and pannus formation as histopathological hallmarks of OmA and CTA, indicating their roles as drivers of joint inflammation and cartilage degradation, and as targets for therapeutic strategies such as rotator cuff reconstruction and synovectomy. Cite this article: Bone Joint Res 2024;13(10):596–610

Aims. Exosomes (exo) are involved in the progression of osteoarthritis (OA). This study aimed to investigate the function of dysfunctional chondrocyte-derived exo (DC-exo) on OA in rats and rat macrophages. Methods. Rat-derived chondrocytes were isolated, and DCs induced with interleukin (IL)-1β were used for exo isolation. Rats with OA (n = 36) or macrophages were treated with DC-exo or phosphate-buffered saline (PBS). Macrophage polarization and autophagy, and degradation and chondrocyte activity of cartilage tissues, were examined. RNA sequencing was used to detect genes differentially expressed in DC-exo, followed by RNA pull-down and ribonucleoprotein immunoprecipitation (RIP). Long non-coding RNA osteoarthritis non-coding transcript (OANCT) and phosphoinositide-3-kinase regulatory subunit 5 (PIK3R5) were depleted in DC-exo-treated macrophages and OA rats, in order to observe macrophage polarization and cartilage degradation. The PI3K/AKT/mammalian target of rapamycin (mTOR) pathway activity in cells and tissues was measured using western blot. Results. DC-exo inhibited macrophage autophagy (p = 0.002) and promoted M1 macrophage polarization (p = 0.002). DC-exo at 20 μg/ml induced collagen degradation (p < 0.001) and inflammatory cell infiltration (p = 0.023) in rats. OANCT was elevated in DC (p < 0.001) and in cartilage tissues of OA patients (p < 0.001), and positively correlated with patients’ Kellgren-Lawrence grade (p < 0.001). PIK3R5 was increased in DC-exo-treated cartilage tissues (p < 0.001), and OANCT bound to fat mass and obesity-associated protein (FTO) (p < 0.001). FTO bound to PIK3R5 (p < 0.001) to inhibit the stability of PIK3R5 messenger RNA (mRNA) (p < 0.001) and disrupt the PI3K/AKT/mTOR pathway (p < 0.001). Conclusion. Exosomal OANCT from DC could bind to FTO protein, thereby maintaining the mRNA stability of PIK3R5, further activating the PI3K/AKT/mTOR pathway to exacerbate OA. Cite this article: Bone Joint Res 2022;11(9):652–668

Osteoarthritis (OA) is a multifactorial debilitating disease that affects over four million Canadians. Although the mechanism(s) of OA onset is unclear, the biological outcome is cartilage degradation. Cartilage degradation is typified by the progressive loss of extracellular matrix components - aggrecan and type II collagen (Col II) – partly due to the up-regulation of catabolic enzymes - aggrecanases a disintegrin and metalloprotease with thrombospondin motifs (ADAMTS-) 4 and 5 and matrix metalloproteinases (MMPs). There is currently no treatment that will prevent or repair joint damage, and current medications are aimed mostly at pain management. When pain becomes unmanageable arthroplastic surgery is often performed. Interest has developed over the presence of calcium crystals in the synovial fluid of OA patients, as they have been shown to activate synovial fibroblasts inducing the expression of catabolic agents. We recently discovered elevated levels of free calcium in the synovial fluid of OA patients and raised the question on its role in cartilage degeneration. Articular cartilage was isolated from 5 donors undergoing total hip replacement. Chondrocytes were recovered from the cartilage of each femoral head or knee by sequential digestion with Pronase followed by Collagenase and expanded in DMEM supplemented with 10% heat-inactivated FBS. OA and normal human articular chondrocytes (PromoCell, Heidelberg, Germany) were transferred to 6-well plates in culture medium containing various concentrations of calcium (0.5, 1, 2.5, and 5 mM CaCl2), and IL-1β. Cartilage explants were prepared from the same donors and included cartilage with the cortical bone approximately 1 cm2 in dimension. Bovine articular cartilage explants (10 months) were used as a control. Explants were cultured in the above mentioned media, however, the incubation period was extended to 21 days. Immunohistochemistry was performed on cartilage explants to measure expression of Col X, MMP-13, and alkaline phosphatase. The sulfated glycosaminoglycan (GAG, predominantly aggrecan) content of cartilage was analyzed using the 1,9-dimethylmethylene blue (DMMB) dye-binding assay, and aggregan fragmentation was determined by Western blotting using antibody targeted to its G1 domain. Western blotting was also performed on cell lysate from both OA and normal chondrocytes to measure aggrecan, Col II, MMP-3 and −13, ADAMTS-4 and −5. Ca2+ significantly decreased the proteoglycan content of the cartilage explants as determined by the DMMB assay. The presence of aggrecan and Col II also decreased as a function of calcium, in both the human OA and bovine cartilage explants. When normal and OA chondrocytes were cultured in medium supplemented with increasing concentrations of calcium (0.5–5 mM Ca2+), aggrecan and Col II expression decreased dose-dependently. Surprisingly, increasing Ca2+ did not induce the release of MMP-3, and −13, or ADAMTS-4 and-5 in conditioned media from OA and normal chondrocytes. Interestingly, inhibition of the extracellular calcium-sensing receptor CaSR) reversed the effects of calcium on matrix protein synthesis. We provide evidence that Ca2+ may play a direct role in cartilage degradation by regulating the expression of aggrecan and Col II through activation of CaSR

Osteoarthritis (OA) is a disease that affects both bone and cartilage. Typically, this disease leads to cartilage degradation and subchondral bone sclerosis but the link between the two is unknown. Also, while OA was traditionally thought of as non-inflammatory condition, it now seems that low levels of inflammation may be involved in the link between these responses. This is particularly relevant in the case of Post-Traumatic OA (PTOA), where an initial phase of synovial inflammation occurs after injury. The inflammatory mediator interleukin 1 beta (IL-1B) is central to this response and contributes to cartilage degradation. However, whether there is a secondary effect of this mediator on subchondral bone, via bone-cartilage crosstalk, is not known. To address this question, we developed a novel patellar explant model, to study bone cartilage crosstalk which may be more suitable than commonly used femoral head explants. The specific aim of this study was to validate this novel patellar explant model by using IL-1B to stimulate the inflammatory response after joint injury and the subsequent development of PTOA. Female Sprague Dawley rats (n=48) were used to obtain patellar explants, under an institutional ethical approval license. Patellae were maintained in high glucose media, under sterile culture conditions, with or without IL-1B (10ng/ml), for 7 days. Contralateral patellae served as controls. One group (n= 12) of patellae were assessed for active metabolism, using two both Live and Dead (L/D) staining and an Alamar Blue assay (AB). A second group (n=12) was used for tissue specific biochemical assays for both bone (Alkaline Phosphatase) and cartilage (sulfated proteoglycan and glycosaminoglycan (sGaG)). Finally, a third group (n=28) of explants were used for histologically analysis. Samples were decalcified, embedded in paraffin and sectioned to 7µm thickness, and then stained using H&E; and Safranin O with fast green. Additionally, toluidine blue and alkaline phosphatase staining were also performed. Our results demonstrate that our system can maintain good explant viability for at least 7 days, but that IL-1B reduces cell viability in patellar cartilage, as measured by both L/D and AB assays after 0, 2, 4 and 7 days in culture. In contrast, sGaG content in cartilage were increased by this treatment. Additionally, ALP, a marker of osteoblastic activity, was increased in IL-1B treated group 4 and 7 days, but was also showed some increase in control groups. Histological analyses showed that IL-1B treatment resulted in reduced proteoglycan staining, demonstrating the powerful effect of this factor in injury response over time. Thus, we conclude that IL-1B affects both bone and cartilage tissues independently in this system, which may have relevance in understanding bone-cartilage crosstalk after injury and how this is involved in PTOA development

Development of osteoarthritis (OA) correlates with epigenetic alteration in chondrocytes. H3K27me3 demethylase UTX is known to regulate tissue homeostasis, but its role in the homeostasis of articulating joint tissue is poorly understood. Forced UTX expression upregulated H3K27me3 enrichment at the Sox9 promoter region to inhibit key extracellular matrix (ECM) molecules, like e.g. type II collagen, aggrecan, and glycosaminoglycans in articular chondrocytes. Utx loss in vitro altered the H3K27me3-binding epigenomic landscape, which contributes to mitochondrial activity, cellular senescence, and cartilage development. Functional target genes of Utx comprise insulin-like growth factor 2 (Igf2) and polycomb repressive complex 2 (PRC2) core components Eed and Suz12. Specifically, Utx deletion promoted Tfam transcription, mitochondrial respiration, ATP production and Igf2 transcription, but inhibited Eed and Suz12 expression. Igf2 inhibition or forced Eed or Suz12 expression increased H3K27 trimethylation and H3K27me3 enrichment at the Sox9 promoter, compromising Utx loss-induced ECM overproduction. Overexpression of Utx in murine knee joints aggravated OA development, including articular cartilage damage, synovitis, osteophyte formation, and subchondral bone loss. Transgenic mice with a chondrocytespecific Utx knockout develop thicker articular cartilage as compared to wild-type controls and show fewer gonarthrotic symptoms during destabilized medial meniscus- and collagenase-induced joint injury. In summary, UTX represses chondrocytic activity and accelerates cartilage degradation during OA, while Utx loss promotes cartilage integrity through epigenetic stimulation of mitochondrial biogenesis and Igf2 transcription. This highlights a novel noncanonical role of Utx that regulates articular chondrocyte anabolism and OA development

Early changes within articular cartilage during human idiopathic osteoarthritis are poorly understood. However alterations to chondrocyte morphology occur with the development of fine cytoplasmic processes and cell clusters, potentially playing a role in cartilage degeneration. The aggrecanase ADAMTS-4 (A disintegrin and metalloproteinase with thrombospondin motifs-4) has been implicated as an important factor in cartilage degradation, so we investigated the relationship between chondrocyte morphology and levels of ADAMTS-4 in both non-degenerate and mildly osteoarthritic human cartilage. Human femoral heads were obtained following consent from patients undergoing hip arthroplasty following femoral neck fracture. Cartilage explants of normal (grade 0; G0) and mildly osteoarthritic (grade 1; G1) cartilage were labelled with the cytoplasmic dye CMFDA (5-chloromethylfluorescein-diacetate). Explants were cryosectioned (30μm sections), and labelled for ADAMTS-4 by fluorescence immunohistochemistry. Sections were imaged with confocal microscopy, allowing the semi-quantitative analysis of ADAMTS-4 and 3D visualisation of in situ cell morphology. With cartilage degeneration from G0 to G1, there was a decrease in the proportion of chondrocytes with normal rounded morphology (P<0.001) but an increase in the proportion of cells with processes (P<0.01) and those in clusters (P<0.001;[4(1653)]; femoral heads:cells). Although average levels of ADAMTS-4 for all cells was the same between G0 and G1 (P>0.05), a change was evident in the distribution curves for cell-specific ADAMTS-4 labelling. Cell-by-cell analysis showed that ADAMTS-4 levels were higher in chondrocytes with cytoplasmic processes compared to normal cells (P=0.044) however cells in clusters had lower levels than normal cells (P=0.003;[3(436)]). Preliminary data suggested that ADAMTS-4 levels increased with larger chondrocyte clusters. These results suggest complex heterogeneous changes to levels of cell-associated ADAMTS-4 with early cartilage degeneration – increasing in cells with processes and initially decreasing in clusters. Increased levels of ADAMTS-4 are likely to produce focal areas of matrix weakness potentially leading to early cartilage degeneration

Summary Statement. The deletion of gangliosides enhanced OA development by elevating MMP-13 and ADAMTS-5 expression and accelerating chondrocyte apoptosis. Gangliosides possibly play suppressive roles in IL-1α-induced inflammatory signaling cascades. Introduction. We have previously reported that glycosphingolipids (GSLs) play chondroprotective roles in the cartilage degradation process [1]. Gangliosides, one of the series of GSLs, are known to be important in intercellular signal transduction and cell-to-cell recognition [2]. Therefore, we hypothesised that gangliosides are important in cartilage metabolisms among the GSLs species. The purpose of this study was to determine the functional role of gangliosides in the development of OA in murine models. Materials & Methods. We adopted systemic GM3 synthase deficient mice (GM3S. −/−. ) which lack most of the gangliosides [3], and wild-type C57BL/6 mice as controls (WT). We applied instability-induced OA model (transecting the medial collateral ligament and removing the cranial half of the medial meniscus [4]) and age-associated OA model (following up to 15 months) with these mice. We also applied IL-1α-induced OA model with femoral head cartilage explants ex vivo. Histological evaluation and quantification of released proteoglycan (PG), secreted MMP-13, and NO in the cultured media were performed. In vitro experiments with chondrocytes extracted from articular cartilages of both genotypes (GM3S. −/−. , WT) were also performed to check the mRNA expression of cartilage degrading enzymes (MMP-13, ADAMTS-5). To test the functional roles of gangliosides, transient GM3S transfection was applied to WT chondrocytes and quantification of MMP-13 and ADAMTS-5 expression was performed. Results. Both age-associated and instability-induced OA models showed cartilage degradation in GM3S. −/−. mice were significantly more severe than WT mice. The results of IL-1α-induced OA model showed gangliosides deletion enhanced chondrocyte apoptosis and accelerated cartilage degradation. Femoral heads from GM3S. −/−. showed significantly higher concentration of MMP-13 and NO in the cultured media than those from WT. In vitro experiments revealed that ganglioside deletion enhanced MMP-13 and ADAMTS-5 expression in the chondrocytes stimulated with IL-1α. The expression of these enzymes was significantly suppressed by overexpressed GM3S in WT chondrocytes. Discussion/Conclusion. The deletion of gangliosides enhanced OA development by elevating MMP-13 and ADAMTS-5 expression and accelerating chondrocyte apoptosis. The results of this study raised the possibility that gangliosides, synthesised mainly from GM3, would play crucial roles in maintaining cartilage homeostasis among the GSLs species. Moreover, the result of overexpression experiment indicated that gangliosides play suppressive roles in IL-1α-triggered inflammatory signaling cascades. Although further studies are required to confirm our speculation, gangliosides may be the target molecules of a novel and effective strategy for the treatment of OA

When joints sustain injury, the release of inflammation cytokines can cleavage matrix proteins and result in cartilage degradation and the subsequent osteoarthritis. RNA therapeutics emerging recently is a very promising approach to efficiently and specifically inhibit disease gene expression. However, the major challenge is how to deliver therapeutic RNA into joint and cartilage. Janus base nanotubes are self-assembled from synthetic Janus bases inspired from DNA base pairs. Based on the charge interaction, we are able to “sandwich” small RNAs among Janus base nanotubes to form tiny, nano-rod shaped delivery vehicles. Such vehicles can be engineered into different sizes and shapes. We have found that short and slim morphologies can greatly increase their penetration to extracellular matrix and delivery into “difficult-to-reach” tissues, such as cartilage and brain. Moreover, by delivering therapeutic siRNA, we have demonstrated its high-efficacy in inhibiting expression of an inflammatory regulator, Interleukin-1 receptor (IL-1R) in articular cartilage. Moreover, the inhibition effect is long-lasting so that joint inflammation and cartilage degradation caused by meniscus injury are greatly inhibited in a mouse model. Therefore, the Janus base nanotubes present a great potential in engineering into nano-structures for RNA delivery. Such approach may become an effective therapeutic against joint inflammation and arthritis

The arcOGEN study identified the 9q33.1 locus as associated with hip osteoarthritis (OA) in females. TRIM32 lies within this locus and may have biological relevance to OA; it encodes a protein with E3 ubiquitin ligase activity. Sanger sequencing of TRIM32 in the youngest 500 female patients with hip OA from the arcOGEN study identified genetic polymorphisms in the proximal promoter, and 3'untranslated region of TRIM32 that are disproportionately represented in female patients with hip OA compared to the control population. Reduced expression of TRIM32 was identified in femoral head articular chondrocytes from patients with hip OA compared to control patients. Trim32 knockout resulted in increased aggrecanolysis in murine femoral head explants. Murine chondrocytes deficient in Trim32 exhibited increased expression of mature chondrocyte markers following anabolic cytokine stimulation, and increased expression of hypertrophic chondrocyte markers following catabolic cytokine stimulation. Trim32 knockout mice demonstrated increased cartilage degradation and tibial subchondral bone changes after surgically-induced knee joint instability. Increased cartilage degradation and medial knee subchondral bone changes were also identified in aged Trim32 knockout mice. These results further implicate TRIM32 in the genetic predisposition to OA, and indicate a role for TRIM32 in the joint degeneration evident in OA. These results support the further study of TRIM32 in the pathophysiology of OA and development of novel therapeutic strategies to manage OA

Summary Statement. We observed that severe muscle weakness leads to OA, whereas a transient inflammatory stimulus did not have a significant effect on cartilage degradation. This arises the thought that a severe but transient inflammation may not be an independent risk factor for OA. Introduction. Biomechanical disturbances and joint inflammation are known risk factors, which may provoke or advance osteoarthritis (OA). However, the effect of interactions of such risk factors on the onset and progression of OA are still poorly understood. Therefore, the goal of this study was to investigate the in vivo effects of muscle weakness, joint inflammation, and the combination of these two risk factors, on the onset and progression of OA in the rabbit knee. Patients & Methods. Thirty 1-year-old skeletally mature female New Zealand White rabbits (weight: average 5.7kg, range 4.8–6.6kg) were used in this study. The animals were divided into four experimental groups: (i) surgical transection of the nerve branch of the common femoral nerve leading to the vastus lateralis muscle; (ii) muscle weakness of the quadriceps muscle induced by a chronic intramuscular injection of Botulinum toxin A (BTX-A) (3); (iii) intraarticular injection in the experimental knee joint with commercially available sterile Carrageenan solution to induce a transient severe inflammatory reaction (4); (iv) administration of both intraarticular injection of Carrageenan and intramuscular injection of BTX-A. In each animal, one hind limb was randomly assigned to the experimental intervention, while the contralateral side acted as its own control. Ninety days following intervention, muscle mass, joint diameter and cartilage histology of the femur, femoral groove, tibia and patella were assessed and microscopically analyzed using the OARSI histology score. Results. Transection of the femoral branch leading to the vastus lateralis as well as the administration of BTX-A led to a significant muscle mass loss for the vastus lateralis and the total quadriceps group, respectively. Similar results were seen in the combined Carrageenan/BTX-A group. There were no changes in total quadriceps muscle mass in the Carrageenan group. Knee joint diameters of the experimental limb were significantly increased in the Carrageenan and Carrageenan/BTX groups. VL transection and BTX-A injection did not cause significant increases in joint diameter. Histologic assessment of the cartilage showed that weakness of the vastus lateralis resulted in significantly higher OARSI scores in the patella and femoral groove, but not the tibiofemoral articulation. The administration of BTX-A caused significant cartilage damage in all 4 compartments (patella, femur, tibia, femoral groove). Intraarticular injection of Carrageenan did not cause significant cartilage damage in any compartment compared to the contralateral side. The combination of BTX-A and Carrageenan resulted in severe cartilage damage in the patella in all four compartments of the knee. The most severe damage was found on the medial side of the tibiofemoral joint and the lateral side of the patellofemoral joint. Conclusion. Severe muscle weakness over a three months period leads to the onset and progression of OA in the rabbit knee. A transient local inflammatory stimulus did not promote cartilage degradation, nor did it enhance cartilage degradation when it was combined with muscle weakness. This result is surprising and adds to the literature the idea that a severe but transient inflammation may not be an independent risk factor for OA

TRIM32 is a candidate gene at the 9q33.1 genetic susceptibility locus for hip osteoarthritis (OA). Increased cartilage degradation typical of OA has previously been demonstrated in Trim32 knockout mice. Our aim is to investigate the role of TRIM32 in human and murine articular tissue. TRIM32 expression in human articular cartilage was examined by immunostaining. TRIM32 expression was compared in femoral head chondrocytes from patients with and without primary hip OA (n=6/group) and examined by Western blotting. Aggrecanolysis by femoral head explants from Trim32 knockout (T32KO) and wild-type (WT) mice was compared following stimulation with IL1α or retinoic acid (RA) and was assessed by DMMB assay (n=4/group). Expression of chondrocyte phenotype markers was measured by qPCR and compared between articular chondrocytes from WT and T32KO mice following catabolic (IL1α/TNFα) or anabolic (Oncostatin-M (OSM)/IGF1) stimulation. TRIM32 expression was demonstrated in human articular cartilage; TRIM32 expression by chondrocytes was reduced in patients with hip OA (p=0.03). Greater aggrecanolysis occurred in cartilage explants from T32KO mice after treatment with no stimulation (p=0.03), IL1α (p=0.02), and RA (p=0.001). Unstimulated T32KO chondrocytes expressed reduced Col2a1 (p=8.53×10. −5. ), and Sox9 (p=2.35×10. −6. ). Upon IL1α treatment, T32KO chondrocytes expressed increased Col10a1 (p=0.0003). Upon anabolic stimulation, T32KO chondrocytes expressed increased Col2a1 (OSM: p=0.001; IGF: p=0.001), and reduced Sox9 (OSM: p=0.0002; IGF: p=0.0006). These results indicate that altered TRIM32 expression in human articular tissue is associated with OA, and that Trim32 knockout results in increased cartilage degradation in murine femoral head explants. Predisposition to cartilage degeneration with reduced Trim32 expression may involve increased chondrocyte hypertrophy upon catabolic cytokine stimulation and dysregulation of Col2a1 and Sox9 expression upon anabolic stimulation

Cartilage neoangiogenesis holds a key role in the development of osteoarthritis (OA) by promoting cartilage degradation with proteoglycan loss, subchondral bone sclerosis, osteophyte formation and synovial hyperplasia. This study aimed to assess the in vivo efficacy of bevacizumab, an antibody against vascular endothelial growth factor (VEGF) in an OA animal model. 24 New Zealand white rabbits underwent anterior cruciate ligament transection in order to spontaneously develop knee OA. Animals were divided into four groups: one receiving a sham intraarticular knee injection (saline) and three groups treated with 5, 10, and 20 mg intraarticular bevacizumab injections. The biological effect of the antibody on cartilage and synovium was evaluated through histology and quantified with the Osteoarthritis Research Society International (OARSI) scores. Immunohistochemical analysis was conducted to investigate type 2 collagen, aggrecan, and matrix metalloproteinase 13 (MMP-13) expression in both cartilage and synovium. Intraarticular bevacizumab led to a significant reduction of cartilage degeneration and synovial OA alterations. Immunohistochemistry showed a significantly reduced MMP-13 expression in all experimental groups, with the one receiving 20 mg bevacizumab showing the lowest. Furthermore, the antibody showed to increment the production of aggrecan and type 2 collagen after administration of 5, 10, and 20 mg. The group treated with 20 mg showed the highest levels of type 2 collagen expression, while aggrecan content was even higher than in the healthy cartilage. Intraarticular bevacizumab has demonstrated to effectively arrest OA progression in our model, with 20 mg being the most efficacious dose. By inhibiting cartilage and synovial neoangiogenesis, bevacizumab may serve as a possible disease-modifying osteoarthritis drug (DMOAD) in the next future