Figure 4

Downregulation of interleukin (IL)-1β-inducible matrix metalloproteinase (MMP) protein expression by mithramycin in cartilage explants. Human (a) or bovine (b) cartilage explants maintained in DMEM with 0.01% serum were either treated with mithramycin and IL-1β vehicles (water and PBS containing 0.1% BSA) or exposed to mithramycin (150 nM) and IL-1β (33 ng/ml) for 15 days, with renewal of the reagents every 2 days. The secreted media were concentrated by precipitation, and equal amounts of protein (human, 16 μg per lane; bovine, 20 μg per lane) were subjected to Western blotting. The MMP-3 and MMP-13 protein bands are shown.