Abstract MP215: Endothelial Colony Forming Cell Derived Exosomes Promote Angiogenesis And Cardiac Repair Post Myocardial Infarction

Background: Despite improvements in therapeutics, ischemic heart disease remains a leading cause of death. Cardiac remodeling after myocardial infarction (MI), predominantly due to loss of cardiomyocytes and coronary vasculature, leads to a progressive decline in cardiac function resulting in heart failure. Current therapies for cardiac repair and heart failure are of limited benefit. Cell transplantation therapy upon MI is a very promising therapeutic strategy to replace dead myocardium, reducing scarring and improving cardiac performance. Methods and Results: Our research focuses on endothelial colony-forming cell-derived exosomes (ECFC-exosomes), which are actively secreted endocytic nanovesicles (30-100 nm) that transport functional miRNAs, proteins, mRNAs, and lipids, playing a key role in paracrine intercellular communication. We identified a novel ability of ECFC-exosomes to promote angiogenesis and cardiac tissue repair. Administration of ECFCs to mice following experimental end-organ ischemia resulted in ECFC-exosome-dependent increase in angiogenesis. ECFC-derived exosomes were taken up by endothelial cells leading to their proliferation and migration, tube formation, and formation of new vessels. Administration of ECFC-exosome to a murine model of MI prevented cardiac remodeling and heart failure. The acute MI resulted in severely decreased left ventricle ejection fraction (Sham 71.2% ± 5 .87, MI+Saline 32.9% ± 2.32) and fractional shortening (Sham 29.5% ± 3.20, MI+Saline 13.6% ± 2.87), and the administration of ECFC-exosomes prevented MI-induced cardiac dysfunction (ejection fraction: MI+ECFC-Exo 64.3% ± 8.74; fractional shortening: MI+ECFC-Exo: 26.4% ± 3.13). Next generation sequencing and bioinformatics analyses identified 136 miRNAs present in ECFC-exosome cargo, and factor inhibiting HIF-1α and PTEN as their potential targets in endothelial cells. Increased nuclear HIF-1α levels in response to ECFC-exosome administration, which may aid in the transcriptional function of HIF-1α, corroborated the role of exosomal miRNA in myocardial angiogenesis. We also found decreased levels of PTEN in response to ECFC-exosome treatment, which is a key negative regulator of PI3K/Akt pathways, survival pathways of heart. We also identified the relative angiogenesis expression profile of the peri-infarcted area in response to ECFC-exosome treatment. The ECFC-exosome administration upregulated the levels of VEGF, IGFBP-1 and PDGF, among others proangiogenic factors, and downregulated the levels of angiostatic factors as IP-10 and Thrombospondin-2. Conclusion: Our findings support the view that the ECFC-exosomes represent a novel therapeutic approach to improve cardiac repair after MI.