RAB5A Governs Synovial Fibroblast Extracellular Vesicles and Mediates Chondrocyte Degeneration in Osteoarthritis

Osteoarthritis is a degenerative joint disease characterized by synovial inflammation and cartilage destruction. This study aimed to investigate the function of RAB5A in regulating human fibroblast-like synoviocytes (HFLS) and its subsequent impact on chondrocyte degeneration. Differential expression and pathway analyses were performed according to the Gene Expression Omnibus (GEO) dataset. HFLS were stimulated with IL-1β, and RAB5A was knocked down via transfection. Inflammatory signaling, cytokine expression, and extracellular vesicles (EVs) secretion were assessed. Isolated EVs were characterized by nanoparticle tracking analysis, transmission electron microscopy, and Western blotting. The functional effects of HFLS-derived EVs on chondrocyte inflammation, extracellular matrix metabolism, apoptosis, and viability were evaluated. Bioinformatics analysis identified RAB5A as a key gene linked to the endocytosis pathway. In IL-1β-stimulated HFLS, RAB5A expression was upregulated. RAB5A knockdown reduced the activation of p38 and NF-κB pathways and suppressed pro-inflammatory factors and matrix degradation mediators. Furthermore, RAB5A deficiency impaired EV secretion and altered their cargo. Crucially, while EVs from control HFLS promoted chondrocyte catabolism, inflammation, and apoptosis, EVs from RAB5A-knockdown HFLS mitigated these degenerative phenotypes. Our findings demonstrate that RAB5A, by modulating the biogenesis and composition of HFLS-derived EVs, plays a critical role in driving chondrocyte degeneration, highlighting its importance as a key molecular regulator in osteoarthritis.