CCL4/CCR5 regulates chondrocyte biology and OA progression

Short-term overloading exercise attenuates articular chondrocyte features partly via synovium-cartilage interactions mediated by inhibin subunit beta A

Excessive mechanical loading leads to cartilage degeneration. However, short-term responses of the synovium and cartilage to overloading and interactions between these tissues remain poorly understood. We developed a mouse model to study excessive mechanical loading, combining treadmill exercise with weight attachment. Time-course RNA sequencing of the synovium and cartilage displayed transient upregulation of inflammation after single overloading, whereas it was prolonged by repeated overloading. Ingenuity pathway analysis identified Inhba, encoding inhibin subunit beta A, as an upstream molecule for the cartilage transcriptomic changes. Inhba was highly induced by single or repeated overloading in the synovium, and Inhba protein was detected in the superficial layer of the synovium. Supplementation with recombinant activin A, a homodimer of Inhba, exerted catabolic effects in mouse primary chondrocytes. Further insights into mechano-responses of the synovium and cartilage, including the role played by Inhba in the synovium-cartilage interaction, may contribute to the elucidation of osteoarthritis pathogenesis.

Elucidating the molecular mechanisms of CCR5-containing extracellular vesicles in vitro and in a rat model of experimental Rheumatoid arthritis

Extracellular vesicles from Rheumatoid arthritis (RA) derived synovial fibroblasts (EVsRASF) have been implicated in the pathogenesis of RA, acting as mediators of cell-to-cell communication. This study aimed to elucidate the role of the chemokine receptor CCR5 and EVs positive for CCR5 (EVsRASF) in RA, focusing on their impact on cartilage destruction and bone erosion in a rat model of Adjuvant-induced arthritis (AIA). In vivo experiments were conducted using AIA rats, treated with either EVsRASF, EVsRASF without CCR5 (EVsRASF-CCR5), or EVsM which encapsulated the CCR5 antagonist Maraviroc. The results demonstrated that EVsRASF-CCR5 reversed the catabolic effect of EVsRASF on hRA-CHs. EVsRASF accelerated cartilage destruction and bone erosion in the AIA rats, as evidenced by increased arthritis scores, joint damage, and NF-κB activation. In contrast, EVsRASF-CCR5 and EVsM treatment mitigated these effects, suggesting a detrimental role of CCR5 in EVsRASF-mediated RA pathogenesis. These findings highlight the critical role of CCR5 in mediating the pro-inflammatory and destructive effects of EVsRASF in RA, suggesting that targeting CCR5 may represent a novel therapeutic strategy for RA management. In conclusion, this study provides valuable insights into one of the molecular mechanisms underlying RA pathogenesis, emphasizing the importance of EVsRASF and CCR5 in mediating synovial inflammation and joint destruction. The results underscore the potential of CCR5 as a therapeutic target, opening avenues for the development of targeted interventions in RA treatment with synovial fibroblast derived EVs serving as a convenient, stabilizing vehicle for delivering Maraviroc into the RA affected joint tissues.