MMP9 and fibrosis: The increased cardiac fibrosis induced by MI was paralleled by significantly increased expression of the pro-fibrotic genes, connective tissue-derived growth factor (CTGF, Fig. 7e), periostin (Fig. 7f) and fibronectin (Fig. 7g); expression of matrix metalloproteinase (MMP)-9 also tended to increase in WT (P = 0.05, Fig. 7h).