Effects of Sirt1 siRNA on chondrocytes under stimulation with IL-1β. The chondrocytes were treated with IL-1β for 24 hours after the transfection with Sirt1 siRNA. A, Western blot for Sirt1 and representative data were from repeated experiments. B, Western blots for Bmal1, Per2, and Rev-erbα after Sirt1 siRNA treatment. C, The proliferation of chondrocytes was determined using the CCK-8 assay after the Sirt1 silence or IL-1β treatment. D, Real-time PCR for MMP1, MMP3, MMP13, and ADAMTS5 mRNA in chondrocytes. The values were at a relative expression level to the control expression. E, Western blots for MMP13 and ADAMTS 5 after Sirt1 siRNA treatment. Bars represent a mean and SE of n = 5/group. control, control siRNA; siBmal1, Sirt1 siRNA.