MMP9 and myocardial infarction: Assessment of gene expression in the infarct region 3 days post-MI by real-time quantitative reverse-transcription PCR (qRT-PCR) revealed increases in mRNA levels of inflammatory genes (Il1b, Tnfa, Il6) and ECM regulatory genes (Mmp3, Mmp9, Tnc, Postn, Col1a1, Col3a1) and reduced mRNA for the myofibroblast differentiation marker Acta2 in MI hearts compared with sham hearts (Figure 1F).