Identification of microRNA‑363‑3p as an essential regulator of chondrocyte apoptosis in osteoarthritis by targeting NRF1 through the p53‑signaling pathway.

Osteoarthritis (OA) is a degenerative joint disease that affects the physical, and mental health of middle‑aged and elderly people. The aims of the present study were to determine the biological function and molecular mechanisms of miR‑363‑3p in chondrocyte apoptosis. Exploration of the molecular mechanisms of OA may be helpful in the understand of the causes, and facilitating the prevention and treatment of OA. In the present study, the expression of nuclear respiratory factor1 (NRF1) was downregulated in the articular cartilage of OA rats in vivo and lipopolysaccharide (LPS)‑treated chondrocytes in vitro. MicroRNAs (miRNA) are regulators of gene expression in the progression of OA. TargetScan software was used to predict that NRF1 was a potential target for miRNA (miR)‑363, and this was confirmed in subsequent experiments. The expression of miR‑363‑3p was negatively correlated with the expression of NRF1, and its expression was significantly upregulated in OA model rats and in LPS‑induced chondrocytes compared with the expression in the respective controls. In addition, the overexpression of miR‑363‑3p increased the levels of interleukin (IL)‑1β, IL‑6 and tumor necrosis factor‑α in vivo, and was demonstrated to promote chondrocyte injury and apoptosis by Safranin O staining and TUNEL. Moreover, the inhibition of miR‑363‑3p expression increased the expression of NRF1 and protected chondrocytes from apoptosis in vitro and in vivo, whereas the overexpression of miR‑363‑3p downregulated NRF1 expression and promoted LPS‑induced chondrocyte apoptosis through the p53 pathway in vitro. The results of this study suggested that miR‑363‑3p‑mediated inhibition of NRF1may be associated with chondrocyte apoptosis in OA.