Fig. 9. DEX upregulates MKP-1 through a GC-receptor-mediated transcriptional mechanism. Primary dermal fibroblasts were transduced with Runx2 retrovirus or left unmodified for controls and cultured in osteogenic media with (+) and without (–) 10 nM DEX. (A) MKP-1 mRNA expression was investigated by quantitative RT-PCR at 1, 3 and 7 days post-transduction and expressed on a logarithmic scale [mean + s.e.m., n=12; ANOVA: P<1E-11; ^*different from unmodified cell control, different from Runx2, different from Runx2+DEX (P< 0.05)]. (B) MKP-1 protein levels were examined at 1, 3 and 7 days post-transduction by western blot analysis. GAPDH was used as a loading control. Blots are representative of data from three separate experiments in triplicate. (C) MKP-1 mRNA expression was investigated by quantitative RT-PCR at 3 days post-Runx2 transduction after treatment with vehicle (ethanol), DEX (10 nM) or concomitant DEX/RU486 (100 nM) for 72 hours. Fold induction is shown relative to control samples without (–) DEX treatment [mean ± s.e.m., n=3; ANOVA: P<0.05; ^#different from Runx2+DEX+RU486 (P< 0.05)].