Influence of protein kinase RIPK4 expression on the apoptosis and proliferation of chondrocytes in osteoarthritis

The present study aimed to investigate the expression of receptor-interacting protein kinase 4 (RIPK4) and its effect on the apoptosis and proliferation of chondrocytes in osteoarthritis (OA). A total of 28 OA cartilage tissues and 20 normal cartilage tissues were collected to detect the expression of RIPK4 by using reverse transcription-quantitative polymerase chain reaction and western blot analysis. Chondrocytes were isolated from OA cartilage tissues and divided into OA, NC, si-RIPK4, Wnt3a, and si-RIPK4+Wnt3a groups, and those isolated from normal cartilage tissues were considered the Normal group. Chondrocytes proliferation was detected by MTT assay, cell apoptosis was indicated using flow cytometry and Wnt/β-catenin signaling pathway related-proteins were investigated using western blot analysis. RIPK4 mRNA and protein expression levels in OA cartilage tissues and OA chondrocytes were increased compared with normal controls (all P<0.05). Additionally, OA chondrocytes showed reduced cell proliferation, increased cell apoptosis and upregulated expression levels of Wnt/β-catenin signaling pathway related-proteins (all P<0.05). Once transfected with si-RIPK4, the proliferation ability of chondrocytes was enhanced, but apoptosis was notably decreased. Furthermore, the expression levels of Wnt/β-catenin signaling pathway related-proteins were significantly downregulated (all P<0.05). Results indicated that Wnt3a reversed the effect of si-RIPK4 on chondrocyte proliferation and apoptosis (all P<0.05). Thus, silencing RIPK4 promoted the proliferation and inhibited the apoptosis of chondrocytes. In addition, silencing RIPK4 blocked the Wnt/β-catenin signaling pathway, thus contributing to alleviating the OA pathogenesis.