IL-1β-induced SOCS1 expression in primary human articular chondrocytes (HACs). HACs isolated from OA cartilage were activated with IL-1β, and the level of SOCS1 expression was checked with RT-PCR. IL-1β increased the expression of SOCS1 mRNA after 4 hours at mRNA and protein levels (A). Quantitative real-time PCR analysis demonstrated that SOCS1 mRNA levels significantly increased with IL-1β stimulation in a dose-dependent manner (B; n = 4; P < 0.01). Data were expressed as means ± SEM. *Corrected P < 0.05 by Mann–Whitney test with Bonferroni correction.