miR-199b-5p is a regulator of left ventricular remodeling following myocardial infarction

Myocardial infarction (MI), the globally leading cause of heart failure, morbidity and mortality, involves post-MI ventricular remodeling, a complex process including acute injury healing, scar formation and global changes in the survivingmyocardium. The molecular mechanisms involved in adverse post-infarct left ventricular remodeling still remain poorly defined. Recently, microRNAs have been implicated in the development and progression of various cardiac diseases as crucial regulators of gene expression. We previously demonstrated that in amurine model of pressure overload, amodel of heart failure secondary to aortic stenosis or chronic high blood pressure, elevated myocardial expression of miR-199b-5p is sufficient to activate calcineurin/NFAT signaling, leading to exaggerated cardiac pathological remodeling and dysfunction. Given the differences in left ventricular remodeling secondary to post-infarct healing and pressure overload, we evaluated miR-199b function in post-MI remodeling. We confirmed that the expression of miR-199b is elevated in the post-infarcted heart. Transgenic animals with cardiomyocyte- restricted overexpression of miR-199b-5p displayed exaggerated pathological remodeling after MI, re- flected by severe systolic and diastolic dysfunction and fibrosis deposition. Conversely, therapeutic silencing of miR-199b-5p in MI-induced cardiac remodeling by using an antagomir to specifically inhibit endogenous miR-199b-5p in vivo, resulted in efficient suppression of cardiac miR-199b-5p expression and attenuated cardiac dysfunction and dilation following MI. Mechanistically, miR-199b-5p influenced the expression of three predicted target genes in post-infarcted hearts, dual specificity tyrosine- phosphorylation-regulated kinase 1A (Dyrk1a), the notch1 receptor and its ligand jagged1. In conclu- sion, here we provide evidence supporting that stress-induced miR-199b-5p participates in post-infarct remodeling by simultaneous regulation of distinct target genes.