Background: MicroRNAs (miRs) regulate nearly all biological pathways. Because the dysregulation of miRs can lead to disease progression, they are being explored as novel therapeutic targets. However, the cell type-specific effects of miRs in the heart are poorly understood. Thus, we assessed miR target regulation using miR-92a-3p as an example. Inhibition of miR-92a is known to improve endothelial cell function and recovery after acute myocardial infarction.
Methods: miR-92a-3p was inhibited by locked nucleic acid (LNA)-based antimiR (LNA-92a) in mice after myocardial infarction. Expression of regulated genes was evaluated 3 days after myocardial infarction by RNA sequencing of isolated endothelial cells, cardiomyocytes, fibroblasts, and CD45+ hematopoietic cells.
Results: LNA-92a depleted miR-92a-3p expression in all cell types and derepressed predicted miR-92a-3p targets in a cell type-specific manner. RNAseq showed endothelial cell-specific regulation of autophagy-related genes. Imaging confirmed increased endothelial cell autophagy in LNA-92a treated relative to control animals. In vitro inhibition of miR-92a-3p augmented EC autophagy, derepressed autophagy-related gene 4a, and increased luciferase activity in autophagy-related gene 4a 3'UTR containing reporters, whereas miR-92a-3p overexpression had the opposite effect. In cardiomyocytes, LNA-92a derepressed metabolism-related genes, notably, the high-density lipoprotein transporter Abca8b. LNA-92a further increased fatty acid uptake and mitochondrial function in cardiomyocytes in vitro.
Conclusions: Our data show that miRs have cell type-specific effects in vivo. Analysis of miR targets in cell subsets disclosed a novel function of miR-92a-3p in endothelial cell autophagy and cardiomyocyte metabolism. Because autophagy is upregulated during ischemia to supply nutrients and cardiomyocyte metabolic-switching improves available substrate utilization, these prosurvival mechanisms may diminish tissue damage.
Keywords: angiogenesis; autophagy; cardiovascular protection; cell signaling; metabolism; microRNA; myocardial infarction.