Figure 2. HRAS inhibited IL-1β-induced chondrocyte apoptosis and senescence. (A) Primary OA chondrocytes were isolated, treated with PBS or IL-1β and examined by light microscopy, toluidine blue staining and Collagen II immunofluorescence staining (IF). (B) HRAS knockdown or overexpression was achieved by transfection of si-HRAS or HRAS overexpressing vector into chondrocytes, respectively, and was confirmed using immunoblotting. Transfected chondrocytes were exposed to PBS or IL-1β and then examined for the MMP13 activity by a SensoLytes Plus 520 MMP13 assay kit (C), the protein levels of HRAS, ERK, p-ERK, MMP13 and Collagen II using immunoblotting (D), cell apoptosis using TUNEL assays (E) and Flow cytometer assays (F), the protein levels of Caspase 3, cleaved-Caspase 3, Caspase 7 and cleaved-Caspase 7 using immunoblotting (G), and the SA-β-Gal positive cells were determined by the SA-β-Gal staining (H). The data are presented as mean ± SD of three independent experiments. *P<0.05, **P<0.01, compared to control group; #P<0.05, ##P<0.01, compared to IL-1β + si-NC (negative control for si-HRAS) or IL-1β + NC vector (negative control for HRAS) group.