LAUSR

ABSTRACT Background Recent studies have revealed that circular RNAs (circRNAs) play crucial roles in the progression of osteoarthritis (OA). This study aimed to investigate the biological function and regulatory mechanism of circ_0008365 in OA. Methods OA cell model in vitro was established in chondrocytes by treatment with Interleukin-1β (IL-1β). The levels of inflammatory cytokines were measured by enzyme-linked immunosorbent assay (ELISA). The expression levels of circ_0008365, microRNA-324-5p (miR-324-5p) and bone morphogenetic protein type 2 receptor (BMPR2) were analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). Cell viability was detected by Cell Counting Kit-8 (CCK-8) assay. Cell apoptosis was assessed using flow cytometry and caspase3 activity assays. The protein expression was determined via a western blot assay. Dual-luciferase reporter assay, RNA immunoprecipitation (RIP) and RNA pull-down assays were used to analyze the correlation between targets. Results IL-1β level and miR-324-5p expression were increased, while circ_0008365 was downregulated in OA patients. IL-1β treatment-induced cell apoptosis, inflammation and extracellular matrix (ECM) degradation in chondrocytes. Besides, circ_0008365 overexpression partly relieved IL-1β-induced cell damage in chondrocytes. Circ_0008365 could interact with miR-324-5p, and BMPR2 was a downstream target of miR-324-5p. Overexpression of miR-324-5p or BMPR2 knockdown partly overturned the inhibiting effect of circ_0008365 on cell damage in IL-1β-induced chondrocytes. In addition, circ_0008365 inactivated NF-κB pathway via regulating miR-324-5p/BMPR2 axis. Conclusion Circ_0008365 reduced IL-1β-induced cell damage in chondrocytes via inactivating NF-κB signaling pathway and regulating miR-324-5p/BMPR2 axis. Abbreviations OA: osteoarthritis; BMPR2: bone morphogenetic protein type 2 receptor