Abstract 802: Cardiomyocyte-derived Exosomal MicroRNAs Regulates Post-Infarction Inflammation and Myofibroblast Phenoconversion

• DOI: 10.1161/res.125.suppl_1.802
• Publication Date: 2019-10-16T17:53:59Z
• Authors: Gaetano Santulli; Celestino Sardu; Jun Shu; Alessandro Matarese; Xujun Wang
• Keywords: 0303 health sciences; 03 medical and health sciences

Background: The inclusion of microRNAs (miRNAs) in extracellular microvesicles/exosomes (named cardiosomes when deriving from cardiomyocytes) allows their active transportation and ensures cell-cell communication.

Aim: We hypothesize that cardiosomal miRNAs play a pivotal role in the activation of myofibroblasts following ischemic injury.

Methods: Using bioinformatic approaches and an established murine model of myocardial infarction (MI, achieved via ligation of the left anterior descending coronary artery), we tested our hypothesis by measuring in isolated fibroblasts and cardiosomes the expression levels of a set of miRNAs, upregulated in cardiomyocytes post-MI and involved in myofibroblast phenoconversion.

Results: We found that miR-92a and miR-195 were significantly upregulated (absolute values) in cardiosomes as well as in fibroblasts isolated at different time points after MI compared with SHAM conditions. These miRs were demonstrated to be both predicted (bioinformatics) and biologically validated (luciferase assays) targets of SMAD7. Moreover, primary isolated cardiac fibroblasts were activated both when incubated with cardiosomes isolated from ischemic cardiomyocytes and when cultured in conditioned medium of post-MI cardiomyocytes, whereas no significant effects were observed following incubation with cardiosomes or medium from sham cardiomyocytes. Myofibroblast activation was assessed measuring the expression of aSMA, periostin, collagen I/III, FAP, fibronectin ED-A. Both miRs also regulated the inflammatory response (evaluated in terms of IL-6 and CXCL1). The addition of an inhibitor of exosome release (GW4869 10 μM for 12 h) significantly attenuated all these responses. The mechanistic contribution of miR-92a and miR-195 was further confirmed using specific miR mimics and inhibitors.

Conclusions: Taken together, our findings indicate for the first time that two cardiomyocyte-specific miRNAs (miR-92a and miR-195), transferred to fibroblasts in form of exosomal cargo, are essential in the activation of myofibroblasts in MI.