The expression level of the target protein in chondrocytes of each group was calculated by Western blot and semi-quantitative analysis, using methods we described previously [31 (link)]. The following antibodies were used: TNF-α antibody (1: 1000; Abcam, Cambridge, MA, USA), IL-6 antibody (1: 1000; Abcam, Cambridge, MA, USA), p53 antibody (1: 1000; Cell Signaling Technology, Inc., Danvers, MA, USA), β-actin antibody (1: 2000; Abcam, Cambridge, MA, USA), and secondary antibodies (1: 20 000; Merck Millipore, Darmstadt, Germany).