MMP9 and Myocardial fibrosis: Chaturvedi et al. showed that exercise-induced exosomes from cardiomyocytes (cardiosomes) miR-29b and miR-455-1 downregulate the expression of matrix metalloprotein (MMP9) to inhibit myocardial fibrosis and myocyte uncoupling (Chaturvedi et al., 2015).