IL-1β and dynamic compression influences aggrecan expression but not collagen type II. Effects of 15% dynamic compressive strain on (a) aggrecan and (b) collagen type II expression in unstrained (-) and strained (+) constructs cultured under no treatment conditions or with 10 ng/ml IL-1β and/or 10 μmol/l SB203580 for 6, 12 and 48 hours. The ratio of the relative expression levels of the target gene was calibrated to the mean value for the unstrained (untreated) control and normalized to GAPDH. Ratios were expressed on a logarithmic scale (arbitrary units). Bars represent the mean and standard error of the mean of 10 replicates from three separate experiments. Two-way analysis of variance with post hoc Bonferroni-corrected t-tests was used to compare data: *P < 0.05 and ***P < 0.001 between unstrained and strained values; and +P < 0.05 between untreated and IL-1β in unstrained constructs.