Regulatory mechanism of transforming growth factor beta receptor type II degradation by interleukin-1 in primary chondrocytes.

International audienceInterleukin-1β (IL-1β), a key-cytokine in osteoarthritis, impairs TGFβ signaling through TβRII down-regulation by increasing its degradation. Here, we investigated the molecular mechanism that controls TßRII fate in IL-1ß treated cells. Chondrocytes were treated with IL-1ß in the presence of different inhibitors. TßRII and Cav-1 expression were assayed by Western blot and RT-PCR. We showed that IL-1ß-induced degradation of TßRII is dependent on proteasome and on its internalization in caveolae. In addition, IL-1ß enhances Cav-1 expression, a major constituent of lipid raft. In conclusion, we enlighten a new mechanism by which IL-1ß antagonizes TGFß pathway and propose a model of TßRII turnover regulation upon IL-1ß treatment

Modulation of transforming growth factor beta signalling pathway genes by transforming growth factor beta in human osteoarthritic chondrocytes: involvement of Sp1 in both early and late response cells to transforming growth factor beta

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Genetic Determinism of Primary Early-Onset Osteoarthritis

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Type II TGFβ receptor modulates chondrocyte phenotype

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Molecular mechanism of hypoxia-induced chondrogenesis and its application in in vivo cartilage tissue engineering.

International audienceCartilage engineering is one of the most challenging issue in regenerative medicine, due to its limited self-ability to repair. Here, we assessed engineering of cartilage tissue starting from human bone marrow (hBM) stem cells under hypoxic environment and delineated the mechanism whereby chondrogenesis could be conducted without addition of exogenous growth factors. hBM stem cells were cultured in alginate beads and chondrogenesis was monitored by chondrocyte phenotypic markers. Activities and roles of Sox and HIF-1α transcription factors were investigated with complementary approaches of gain and loss of function and provided evidences that HIF-1α is essential for hypoxic induction of chondrogenesis. Thereafter, hBM cells and human articular chondrocytes (HAC) underwent chondrogenesis by 3D and hypoxic culture for 7 days or by ectopic expression of HIF-1α. After subcutaneous implantation of 3 weeks into athymic mice, tissue analysis showed that hypoxia or HIF-1α overexpression is effective and sufficient to induce chondrocyte phenotype in hBM cells, without use of exogenous growth factors. Therefore, this study brings interesting data for a simple and affordable system in biotechnology of cartilage engineering

Anti-inflammatory and chondroprotective effects of the S-adenosylhomocysteine hydrolase inhibitor 3-Deazaneplanocin A, in human articular chondrocytes

International audience3-Deazaneplanocin A (DZNep) is an inhibitor of S-Adenosyl-L-Homocysteine Hydrolase (SAHH) known to inhibit EZH2, a histone methylase upregulated during osteoarthritis. In this study, we assessed its effects in human articular chondrocytes. Anti-inflammatory effects were assessed by Nitric Oxide (NO), Prostaglandin E2 (PGE2) and Metalloprotease (MMP) release in IL-1β-stimulated chondrocytes. MAPK and NFκB activation was analyzed by western blotting. Differentially expressed genes (DEG) regulated by DZNep were identified by whole-transcriptome microarray. DZNep inhibited SAHH activity and was not toxic. It counteracted NO, PGE2 and MMP release, and reduced MAPK activation induced by IL-1β. By whole-transcriptome analysis, we identified that DNZep counteracts the effect of IL-1β on the expression of 81 protein-coding genes, including CITED2, an MMP inhibitor. These genes are organized in a protein-protein network centred on EGR1, which is known to functionally interact with EZH2. Gene ontologies enrichment analysis confirmed that DZNep counteracts IL-1β-induced expression of genes involved in cartilage matrix breakdown (MMPs and ADAMTS). In addition, DZNep up-regulated cartilage specific genes, such as COL2A1 and SOX9, suggesting a chondroprotective effect of DZNep. DZNep exhibits anti-inflammatory effects, and regulates genes implicated in chondroprotective response in human articular chondrocytes, suggesting that inhibitors of S-adenosylmethionine-dependent methyltransferases could be effective treatments for OA

Description of Joint Alterations Observed in a Family Carrying p.Asn453Ser COMP Variant: Clinical Phenotypes, In Silico Prediction of Functional Impact on COMP Protein and Stability, and Review of the Literature

International audienceThe role of genetics in the development of osteoarthritis is well established but the molecular bases are not fully understood. Here, we describe a family carrying a germline mutation in COMP (Cartilage Oligomeric Matrix Protein) associated with three distinct phenotypes. The index case was enrolled for a familial form of idiopathic early-onset osteoarthritis. By screening potential causal genes for osteoarthritis, we identified a heterozygous missense mutation of COMP (c.1358C>T, p.Asn453Ser), absent from genome databases, located on a highly conserved residue and predicted to be deleterious. Molecular dynamics simulation suggests that the mutation destabilizes the overall COMP protein structure and consequently the calcium releases from neighboring calcium binding sites. This mutation was once reported in the literature as causal for severe multiple epiphyseal dysplasia (MED). However, no sign of dysplasia was present in the index case. The mutation was also identified in one of her brothers diagnosed with MED and secondary osteoarthritis, and in her sister affected by an atypical syndrome including peripheral inflammatory arthritis of unknown cause, without osteoarthritis nor dysplasia. This article suggests that this mutation of COMP is not only causal for idiopathic early-onset osteoarthritis or severe MED, but can also be associated to a broad phenotypic variability with always joint alterations