CircP4HA3/miR-5001-5p/THBS2 axis promotes chondrocyte senescence and cartilage degradation during osteoarthritis progression

BACKGROUND: Osteoarthritis (OA) is a degenerative joint disease characterized by cartilage degradation and impaired chondrocyte function. Increasing evidence suggests that circular RNAs (circRNAs) and microRNAs (miRNAs) play crucial roles in OA pathogenesis. METHOD: Deep sequencing identified differentially expressed circRNAs in OA and control cartilage tissues. CircP4HA3 was found to be upregulated in OA and was further investigated using in vitro and in vivo models. RNA-binding protein immunoprecipitation, luciferase reporter assays, western blot, immunofluorescence, and in situ hybridization were employed to analyze interactions between CircP4HA3, miR-5001-5p, and THBS2. Cartilage damage in the specimens was evaluated using microcomputed tomography (micro-CT), hematoxylin and Safranin O staining, and immunohistochemistry staining. RESULT: CircP4HA3 was significantly upregulated in OA cartilage, while miR-5001-5p was downregulated. THBS2, a miR-5001-5p target, was elevated in OA conditions. Functional assays demonstrated that CircP4HA3 knockdown promoted chondrocyte proliferation, extracellular matrix (ECM) production, and inhibited senescence. miR-5001-5p mimics suppressed THBS2, enhancing chondrocyte viability. CircP4HA3 knockdown further increased miR-5001-5p activity and decreased THBS2 levels, confirming their regulatory interplay. Furthermore, down-regulation of CircP4HA3 attenuated the THBS2-mediated activation of the MAPK signaling pathway. CONCLUSION: The CircP4HA3/miR-5001-5p/THBS2/MAPK axis plays a key role in chondrocyte function and OA progression, providing potential therapeutic insights.