CircGNB1 drives osteoarthritis pathogenesis by inducing oxidative stress in chondrocytes.

Background: Circular RNAs (circRNAs) have risen to prominence as important regulators of biological processes. This study investigated whether circGNB1 functions as a competitive endogenous RNA to regulate the pathological process of oxidative stress in age-related osteoarthritis (OA).

Methods: The relationship between circGNB1 expression and oxidative stress/OA severity was determined in cartilages from OA patients at different ages. The biological roles of circGNB1 in oxidative stress and OA progression, and its downstream targets were determined using gain- and loss-of-function experiments in various biochemical assays in human chondrocytes (HCs). The in vivo effects of circGNB1 overexpression and knockdown were also determined using a destabilization of the medial meniscus (DMM) mouse model.

Results: Increased circGNB1 expression was detected in HCs under oxidative and inflammatory stress and in the cartilage of older individuals. Mechanistically, circGNB1 sponged miR-152-3p and thus blocked its interaction with its downstream mRNA target, ring finger protein 219 (RNF219), which in turn stabilized caveolin-1 (CAV1) by preventing its ubiquitination at the K47 residue. CircGNB1 inhibited IL-10 signalling by antagonizing miR-152-3p-mediated RNF219 and CAV1 inhibition. Consequently, circGNB1 overexpression promoted OA progression by enhancing catabolic factor expression and oxidative stress and by suppressing anabolic genes in vitro and in vivo. Furthermore, circGNB1 knockdown alleviated the severity of OA, whereas circGNB1 overexpression had the opposite effect in a DMM mouse model of OA.

Conclusion: CircGNB1 regulated oxidative stress and OA progression via the miR-152-3p/RNF219/CAV1 axis. Modulating circGNB1 could be an effective strategy for treating OA.