microRNA prediction and its expression in IL-1β-treated chondrocytes. (A) Six microRNAs were selected to target Sox9 using three classic prediction databases. Primary rat chondrocytes were treated with IL-1β (5 ng/ml) for 2, 4 and 6 h. Sox9 expression was analyzed by real-time PCR and western blot. (B and C) Sox9 expression was markedly decreased at the mRNA and protein levels with the increasing duration of IL-1β stimulation. The upper panels (C) are representative images of the western blot analysis. The lower panels are densitometric analyses performed with images of three independent experiments, respectively; n = 3,*P < 0.05 versus 0 h. (D) microRNAs expression in IL-1β-induced chondrocytes was analyzed by real-time PCR; n = 3,*P < 0.05 versus 0 h.