IL-1+OSM-induced <i>MMP1</i> expression is maximal at 24 h post-stimulation.

Human chondrocytes were treated with IL-1 (0.05 ng/mL) in combination with OSM (10 ng/mL) for the indicated time points and total RNA isolated. (A) RNA from three separate populations (#1, #2 and #3) was profiled using the Human HT-12v4 Expression Beadchip. The expression profile for MMP1 from the microarray dataset for each chondrocyte population is shown. (B) RNA from six separate chondrocyte populations was subjected to qPCR for MMP1, and relative expression levels (normalized to 18S rRNA) at the indicated times determined. The plots show mean ± SD (n = 6). Data from the populations used in the microarray analyses are highlighted by the solid symbols (#1, ▲; #2 ■; #3, ●). (C) Prior to stimulation with IL-1 (0.05 ng/ml) in combination with OSM (10 ng/ml), human chondrocytes were transfected with siRNA specific for the indicated genes, or a non-targeting control (siCon; all 100 nM), and mRNA expression levels (mean ± S.D., n = 6) of MMP1 measured 24 h post-stimulation by qPCR, relative to siCon treated cells, normalized to 18S rRNA. Statistical comparisons are versus IL-1 + OSM + siCon (Student’s two-tailed unpaired t test), where ***, p<0.001; **, p <0.01; *, p<0.05; ns = not significant. The data are pooled from three separate experiments, each using chondrocyte cultures from different donors.