Figure 3. Effects of fibroblasts on proMMP-2 activation. Fibroblasts were cultured on 30 µg/cm² type I collagen-coated dishes in serum-free DMEM for 48 hrs at 37°C. Then, the collected culture media were incubated with (lanes 1 and 2) or without (lane 3) the fibroblasts cultured on type I collagen-coated dishes for 18 hrs at 37°C in the absence (lane 1) or presence (lanes 2 and 3) of 1 nM rhIL-1. The culture media (30 µL) were subjected to gelatin zymography. Similar results were seen in four independent experiments.