FIGURE 9.

Effects of ELF3 on MEK/ERK-dependent MMP13 expression in mouse primary chondrocytes. Mouse primary chondrocytes were isolated from articular cartilage from wild type (WT) C57BL/6 and Elf3 knock-out (KO) 5–6-day-old mice. A, after overnight incubation in serum-free medium, cells were pretreated with vehicle (DMSO) or the indicated concentrations of U0126 for 45 min before incubation with 1 ng/ml IL-1β in the presence of the inhibitor. At 24 h after IL-1β stimulation, total RNAs were isolated, and MMP13 mRNA was analyzed by RT-qPCR. Each value was normalized to GAPDH in the same sample and shown as mean ± S.E. (error bars). B, phospho-ERK1/2 (P-ERK1/2) and total ERK1/2 (ERK1/2) protein levels were analyzed by Western blotting using cell lysates prepared from wild type and Elf3 knock-out primary chondrocytes stimulated with 1 ng/ml IL-1β for the indicated times after overnight incubation in serum-free conditions. Western blots were reprobed for β-tubulin as a loading reference control. *, p < 0.05 versus the IL-1β-stimulated controls.