Cardiac Exosomes in myocardial Ischemic injury

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PROJECT SUMMARY / ABSTRACT Ischemic heart disease, the leading cause of mortality worldwide and at $475 billion/year also the costliest disease in the US, is highly heritable. Ischemia initiates specific biological processes that are highly dependent on genetic, transcriptional, and translational variation. In particular, regulation by noncoding RNAs (ncRNA), crucial components in the human genome, play a significant role in the biology of myocytes undergoing ischemia. Extracellular vesicles (EV) are emerging as new regulators of cell-to-cell communication carrying biological information, including proteins, lipids, and ncRNAs. The ncRNAs contained in EV, namely extracellular RNAs (exRNA), include microRNAs and other types of small RNAs and lncRNAs, some of which have been shown to be regulated by stressors and mediate functional effects in their recipient cells. Thus, exRNA offer tremendous potential as therapeutic molecules and biomarkers of disease. We have built a unique human tissue sample bank of over 230 patients experiencing myocardial ischemia while undergoing cardiac surgery with cardiopulmonary bypass (CPB). CPB is an applied human model of ischemia, as it is associated with obligatory ischemic myocardial injury evidenced by cardiac biomarker release, and therefore shares commonality with ambulatory myocardial infarction. Using this resource and as part of our NHLBI award, in the past four years we examined mRNA differential expression, lncRNAs, and microRNAs in ischemic human left ventricular myocardium, putting us in an ideal position to study the significance of exRNA in myocardial ischemic injury. We now propose to further explore the role of various short- and long ncRNAs by examining acute dynamic changes in ncRNAs in response to ischemia. Therefore, we will characterize the ncRNA transcriptome in the human and mouse heart, examine exRNA at various non-ischemic and ischemic time points in humans and mice, test for expressed quantitative trait loci (eQTL), and validate in a large population of cardiac surgical patients. Furthermore, we will use an ischemic mouse model to determine if the dynamically regulated exRNAs are present specifically in cardiomyocyte-derived EVs which will provide the framework for future interventional genetic studies. The results of this study will define the link between genetic variation, altered ncRNA expression and myocardial injury in human myocardial tissue and its associated ncRNA peripheral biomarkers. These ncRNA biomarkers can have an immediate clinical impact and advance the biological understanding, diagnosis and therapy of myocardial injury in humans.