Synovial Cell Cross-talk with Cartilage Plays a Major Role in the Pathogenesis of Osteoarthritis
Ontology highlight
ABSTRACT: We elucidated the molecular cross-talk between knee articular cartilage and paired synovium in n=3 individuals with knee osteoarthritis using the powerful tool of single-cell RNA-sequencing. Multiple cell types were identified based on profiling of 10,640 synoviocytes and 26,192 chondrocytes (11,579 chondrocytes from the diseased medial vs 14,613 chondrocytes from the relatively non-diseased lateral tibial plateau): 12 distinct synovial cell types and 7 distinct articular chondrocyte phenotypes from matched tissues. Intact cartilage was enriched for homeostatic and hypertrophic chondrocytes, while damaged cartilage was enriched for prefibro- and fibro-, regulatory, reparative and prehypertrophic chondrocytes. A total of 61 cytokines and growth factors were predicted to regulate the 7 chondrocyte cell phenotypes. Based on production by >1% of cells, 55% of the cytokines were produced by synovial cells (39% exclusive to synoviocytes and not expressed by chondrocytes) and their presence in osteoarthritic synovial fluid confirmed. The synoviocytes producing IL-1beta (a classic pathogenic cytokine in osteoarthritis), mainly inflammatory macrophages and dendritic cells, were characterized by co-expression of surface proteins corresponding to HLA-DQA1, HLA-DQA2, OLR1 or TLR2. Strategies to deplete these pathogenic intra-articular cell subpopulations could be a therapeutic option for human osteoarthritis.
Project description:Osteoarthritis (OA) is a degenerative joint disease characterized by progressive cartilage loss, bone remodeling, synovial inflammation, and significant joint pain, often resulting in disability. Injury to the synovial joint such as the anterior cruciate ligament (ACL) tear is the major cause of OA in young adults. Currently, there are no approved therapies available to prevent joint degeneration or rebuild articular cartilage destroyed by OA, primarily because our understanding of the cellular and molecular changes that contribute to joint damage is very limited. The synovial joint is a complex structure composed of several tissues including articular cartilage, subchondral bone, synovium, synovial fluid, and tensile tissues including tendons and ligaments. In the present study, using single-cell RNA sequencing (scRNA-seq), we examined the cellular heterogeneity in articular cartilage from mouse knee joints and determined the knee joint injury-induced early molecular changes in the chondrocytes that could contribute to OA.
Project description:Cartilage aging is a quintessential feature of knee osteoarthritis, and extracellular matrix (ECM) stiffening is a typical feature of cartilage aging. However, the mechanism of ECM stiffening to influence chondrocytes and downstream molecules is still poorly understood. Here, we mimicked the physiological and pathological stiffness of human cartilage by using polydimethylsiloxane-based substrates. We show that the epigenetic regulation of Parkin by histone deacetylase 3 (HDAC3) represents a new mechanosensitive mechanism by which the stiff matrix affects the physiology of chondrocytes. We found that ECM stiffening could accelerate the senescence of cultured chondrocytes in vitro, and also found that stiff ECM downregulated HDAC3, drove Parkin acetylation to activate excessive mitophagy, and accelerated chondrocyte senescence and osteoarthritis in mice. In contrast, intra-articular injection of adeno-associated virus expressing HDAC3 restored the young phenotype of aged chondrocytes stimulated by ECM stiffening and alleviated osteoarthritis in mice. Our findings indicate that changes in the mechanical properties of ECM initiate pathogenic mechanotransduction signals, promote the acetylation of Parkin and hyperactivate mitophagy, and damage the health of chondrocytes. These findings may provide new insights into how the mechanical properties of ECM regulate chondrocytes.
Project description:As the unique cell type in articular cartilage, chondrocyte senescence is a crucial cellular event contributing to osteoarthritis development. Here we show that clathrin-mediated endocytosis and activation of Notch signaling promotes chondrocyte senescence and osteoarthritis development, which is negatively regulated by myosin light chain 3. Myosin light chain 3 (MYL3) protein levels decline sharply in senescent chondrocytes of cartilages from model mice and osteoarthritis (OA) patients. Conditional deletion of Myl3 in chondrocytes significantly promoted, whereas intra-articular injection of adeno-associated virus overexpressing MYL3 delayed, OA progression in male mice. MYL3 deficiency led to enhanced clathrin-mediated endocytosis by promoting the interaction between myosin VI and clathrin, further inducing the internalization of Notch and resulting in activation of Notch signaling in chondrocytes. Pharmacologic blockade of clathrin-mediated endocytosis-Notch signaling prevented MYL3 loss-induced chondrocyte senescence and alleviated OA progression in mice. Our results establish a previously unknown mechanism essential for cellular senescence and provide a potential therapeutic direction for OA.
Project description:Joint injury and osteoarthritis affect millions of people worldwide, but attempts to generate articular cartilage using adult stem/progenitor cells have been unsuccessful. We hypothesized that recapitulation of the human developmental chondrogenic program using pluripotent stem cells (PSCs) may represent a superior approach for cartilage restoration. Using laser capture microdissection followed by microarray analysis, we first defined a surface phenotype (CD146low/negCD166low/negCD73+CD44lowBMPR1B+) distinguishing the earliest cartilage committed cells (pre-chondrocytes) at 5-6 weeks of development; pellet assays confirmed these cells as functional, chondrocyte-restricted progenitors. Flow cytometry, qPCR and immunohistochemistry at 17 weeks revealed that the superficial layer of peri-articular chondrocytes was enriched in cells with this surface phenotype. Isolation of cells with a similar immunophenotype from differentiating human PSCs revealed a population of CD166negBMPR1B+ putative pre-chondrocytes. Functional characterization confirmed these cells as cartilage-committed, chondrocyte progenitors. The identification of a specific molecular signature for primary cartilagecommitted progenitors may provide essential knowledge for the generation of purified, clinically relevant cartilage cells from PSCs. A total of 15 samples were analyzed. In the first comparison, there were 6 biological replicates for both the chondrogenic condensations and total limb cells. In the second comparison, three biological replicates of chondrocytes from the articular region were compared to the 6 replicates of the condensations.
Project description:Osteoarthritis (OA) of the hand is a common disease resulting in pain and impaired function. The pathogenesis of hand OA (HOA) is elusive and models to study it have not been described so far. Culture of chondrocytes is a model to study the development of cartilage degeneration, which is a hallmark of OA and well established in OA of the knee and hip. In the current study we investigated the feasibility human chondrocyte culture derived from proximal interphalangeal (PIP) finger joints of dissecting room cadavers. Index and middle fingers without signs of osteoarthritis were obtained from 30 cadavers using two different protocols. Hyaline cartilage from both articulating surfaces of the proximal interphalangeal (PIP) joint was harvested and digested in collagenase. Cultured chondrocytes were monitored for contamination, viability, and expression of chondrocyte specific genes. Chondrocytes derived from knee joints of the cadavers were cultured under identical conditions. Gene expression comparing chondrocytes from PIP and knee joints was carried out using Affymetrix GeneChip Human 2.0 ST arrays. The resulting differentially expressed genes were validated by real-time PCR and immunohistochemistry.Chondrocytes harvested up to 101 hours after death of the donors were viable. mRNA expression of collagen 2A1, aggrecan and Sox9 was significantly higher in chondrocytes as compared to cultured fibroblasts. Comparison of gene expression by chondrocytes from PIP and knee joints yielded 528 differentially expressed genes. Chondrocytes from the same joint region had a higher grade of similarity than chondrocytes of the same individual. These results were validated using real-time PCR and immunohistochemistry.We demonstrate for the first time a reliable method for culture of chondrocytes derived from PIP joints. PIP chondrocytes show a specific gene expression pattern and could be used as tool to study cartilage degeneration in HOA. Three samples of cultured chondrocytes from knee and proximal interphalangeal finger joints were compared. Gene expression of the four most differentially regulated genes was confirmed by real-time PCR in 10 independent samples.
Project description:Osteoarthritis is a common joint disorder that causes debilitating conditions among the elderly. Risk factors of osteoarthritis include age, which is often associated with the thinning of articular cartilage. We generated conditional knockout mice that lack salt-inducible kinase 3 (Sik3) specifically in chondrocytes after birth by tamoxifen administration. Deletion of Sik3 at 2 or 8 weeks after birth increased the thickness of articular cartilage by increasing the chondrocyte population. Additionally, Sik3 deletion protected cartilage against osteoarthritis development. We identified the edible Pteridium aquilinum ingredient, pterosin B, as a compound that inhibits the Sik3 pathway. Intraarticular injection of pterosin B protected cartilage against osteoarthritis development. Sik3 deletion or pterosin B treatment inhibited activation of the hypertrophic program through the histone deacetylase 4 (Hdac4) pathway, increased Prg4 expression in chondrocytes, and protected cartilage against osteoarthritic attack. Collectively, our results suggest Sik3 is a regulator that regulates homeostasis of articular cartilage thickness and a target for treatment of osteoarthritis, and that pterosin B can be the lead compound for relevant drugs.
Project description:Cartilage destruction in osteoarthritis (OA) results from disturbed chondrocyte metabolism. Here, we used microarrays to show that TGF alpha and CCL2 are simultaneously upregulated in a rat model of OA and cooperate to drive cartilage degradation. The goals of the experiments included here were to a) characterize gene expression in knee joint articular chondrocytes at various stages of development of OA (2 and 8 weeks after surgical induction of OA), and b) to establish trends in gene expression among groups of genes related to the TGF alpha-EGFR axis, over time, in OA. The model chosen to study these results has been previously validated (Appleton, CT et al, 2007, Arthritis Rheum) and used to describe similar gene expression results at a different time point (4 weeks) after induction of OA. The rat model of OA involves surgical destabilization of the knee joint, followed by forced low-intensity mobilization over several weeks; a sham surgery is used as the control (representing a healthy non-OA knee joint) wherein a surgical incision is made but not structural (i.e. ligamentous) modification is made to the joint. Altogether, our data indicate that TGF and CCL2 cooperate to drive cartilage degradation in osteoarthritis. A total of 12 samples were analyzed. 3 replicates were used per condition: OA surgery at 2 weeks, OA surgery at 8 weeks, Sham (control) surgery at 2 weeks and Sham surgery at 8 weeks. Expression of OA samples was assessed relaitve to Sham (control) expression levels.
Project description:Autologous chondrocyte transplantation (ACT) is a routine technique to regenerate focal cartilage lesions. However, patients with osteoarthritis (OA) are lacking an appropriate long-lasting treatment alternative, partly since it is not known if chondrocytes from OA patients have the same chondrogenic differentiation potential as chondrocytes from donors not affected by OA. Articular chondrocytes from patients with OA undergoing total knee replacement (Mankin Score >3, Ahlbäck Score >2) and from patients undergoing ACT, here referred to as normal donors (ND), were isolated applying protocols used for ACT. Their chondrogenic differentiation potential was evaluated both in high-density pellet and scaffold (Hyaff-11) cultures by histological proteoglycan assessment (Bern Score) and immunohistochemistry for collagen types I and II. Chondrocytes cultured in monolayer and scaffolds were subjected to gene expression profiling using genome-wide oligonucleotide microarrays. Expression data were verified by using quantitative RT-PCR. Chondrocytes from ND and OA donors demonstrated accumulation of comparable amounts of cartilage matrix components, including sulphated proteoglycans and collagen types I and II. The mRNA expression of cartilage markers (COL2A1, COMP, aggrecan, CRTL1, SOX9) and genes involved in matrix synthesis (biglycan, COL9A2, COL11A1, TIMP4, CILP2) was highly induced in 3D cultures of chondrocytes from both donor groups. Genes associated with hypertrophic or OA cartilage (COL10A1, RUNX2, periostin, ALP, PTHR1, MMP13, COL1A1, COL3A1) were not significantly regulated between the two groups of donors. The expression of 661 genes, including COMP, FN1, and SOX9, were differentially regulated between OA and ND chondrocytes cultured in monolayer. During scaffold culture, the differences diminished between the OA and ND chondrocytes, and only 184 genes were differentially regulated. Only few genes were differentially expressed between OA and ND chondrocytes in Hyaff-11 culture. The risk of differentiation into hypertrophic cartilage does not seem to be increased for OA chondrocytes. Our findings suggest that the chondrogenic capacity is not significantly affected by OA and OA chondrocytes fulfill the requirements for matrix-associated ACT. Experiment Overall Design: Gene expression profiles of monolayer cultures (ML; passage 2) and Hyaff-11 scaffold cultures (3D; 14 days in vitro) of chondrocytes from 3 normal donors (ND; underwent ACT treatment) and 3 donors suffering from Osteoarthritis (OA; underwent knee replacement surgery) were determined. Comparative analyses between 3D and ML cultures (3D vs. ML) were performed to assess differentiation capacity of ND and OA chondrocytes. Furthermore, OA-related differences were determined comparing OA and ND monolayers as well as scaffold cultures (each OA vs. ND).
Project description:Steroid and xenobiotic receptor (SXR) and its murine ortholog pregnane X receptor (PXR) are nuclear receptors that are expressed mainly in the liver and the intestine. They function as xenobiotic sensors by inducing genes involved in detoxification and drug excretion. Recent evidence showed that SXR and PXR are also expressed in bone tissue where they mediate bone metabolism. Here we report that systemic deletion of PXR results in aging-dependent wearing of articular cartilage of knee joints. Histomorphometrical analysis showed remarkable reduction of width and an enlarged gap between femoral and tibial articular cartilage in PXR knockout mice. We hypothesized that genes induced by SXR in chondrocytes have a protective effect on articular cartilage and identified Fam20a (family with sequence similarity 20a) as an SXR-dependent gene induced by the known SXR ligands, rifampicin and vitamin K2. Lastly, we demonstrated the biological significance of Fam20a expression in chondrocytes by evaluating osteoarthritis-related gene expression of primary articular chondrocytes. Consistent with epidemiological findings, our findings indicate that SXR/PXR protects against aging-dependent wearing of articular cartilage and that ligands for SXR/PXR have potential role in preventing osteoarthritis caused by aging.
Project description:Steroid and xenobiotic receptor (SXR) and its murine ortholog pregnane X receptor (PXR) are nuclear receptors that are expressed mainly in the liver and the intestine. They function as xenobiotic sensors by inducing genes involved in detoxification and drug excretion. Recent evidence showed that SXR and PXR are also expressed in bone tissue where they mediate bone metabolism. Here we report that systemic deletion of PXR results in aging-dependent wearing of articular cartilage of knee joints. Histomorphometrical analysis showed remarkable reduction of width and an enlarged gap between femoral and tibial articular cartilage in PXR knockout mice. We hypothesized that genes induced by SXR in chondrocytes have a protective effect on articular cartilage and identified Fam20a (family with sequence similarity 20a) as an SXR-dependent gene induced by the known SXR ligands, rifampicin and vitamin K2. Lastly, we demonstrated the biological significance of Fam20a expression in chondrocytes by evaluating osteoarthritis-related gene expression of primary articular chondrocytes. Consistent with epidemiological findings, our findings indicate that SXR/PXR protects against aging-dependent wearing of articular cartilage and that ligands for SXR/PXR have potential role in preventing osteoarthritis caused by aging. ADC5 cells were infected with adeno-SXR or adeno-DsRed and cultured in phenol red-free DMEM with charcoal/dextran-treated FCS (5%) containing rifampicin (10 μM), vitamin K2 (10 μM), or ethanol. Total RNA was extracted from the cells using the ToTALLY RNA Kit (Ambion, Austin, TX). Profiling of mRNA was performed on Affymetrix Mouse Gene 1.0 ST arrays (Affymetrix Inc., Santa Clara, USA) according to the Gene Chip labeling assay manual version 4.