Cryptotanshinone interferes with chondrocyte apoptosis in osteoarthritis by inhibiting the expression of miR‑574‑5p

Chondrocyte apoptosis is an important factor in the development and progression of osteoarthritis (OA). Cryptotanshinone (CTS) can inhibit chondrocyte apoptosis, but the specific mechanism remains unknown. The aim of the present study was to explore how CTS may affect chondrocyte apoptosis. Reverse transcription‑quantitative PCR and western blotting were used to validate microRNA (miR)‑574‑5p, YY1‑associated factor 2 (YAF2), Bcl‑2 and Bax expression levels. H&E, Safranin O and TUNEL staining assays were used to evaluate the apoptosis of arthritic chondrocytes in vivo. A Cell Counting Kit‑8 assay and flow cytometry were performed to detect cell proliferation and apoptosis of chondrocytes in vitro. The methylation level of the miR‑574‑5p promoter was measured via methylation specific PCR. The degree of chondrocyte apoptosis and the expression levels of YAF2 and Bcl‑2 were decreased in the mice with OA, and were increased in the OA + CTS mice, while the expression levels of miR‑574‑5p and Bax showed opposite changes. Furthermore, the degree of chondrocyte apoptosis and the expression levels of the aforementioned key factors in chondrocytes were consistent with those observed in vivo. The methylation degree of the miR‑574‑5p promoter was increased by the addition of CTS, and was reduced after the addition of a methylation inhibitor, 5‑aza‑CdR, indicating that CTS could regulate the methylation of miR‑574‑5p promoter. The present study suggested that CTS could downregulate the expression of miR‑574‑5p by regulating its methylation, and thus, could improve YAF2 expression and affect chondrocyte apoptosis.