Effect of TGF-β superfamily members on MMP activity and expression level. NHLF were stimulated with 5 ng/ml TGF-β1 or 100 ng/ml BMP-4 or BMP-7 alone or with TGF-β1 in the presence of BMP-4 or BMP-7 for 72 h. Cell supernatants were collected to perform zymography (A and B) and ELISA (C). Representative gelatin zymograms and related graphic plot of the bands obtained in zymographs for the pro-forms of MMP-1 (A) and MMP-2 (B) were performed. Gelatinolytic activity of the pro- and active forms of MMP-1 (57/52 and 47/42 kDa) and pro- and active forms of MMP-2 (72 and 67 kDa) are indicated. MMP-13 release was quantified in the cell supernatants by specific ELISA (C). Data are mean ± SD of five independent experiments. *, p < 0.05, as compared to unstimulated cells and †, p < 0.05, as compared to TGF-β1-stimulated cells.