Dual Mechanism of Action: Exosomes from Human iPSC-Cardiomyocytes and Mesenchymal Stem Cells Restore Injured Myocardium

BackgroundTransplantation of mesenchymal stem cells or induced pluripotent stem cell derived cardiomyocytes improve heart function after myocardial infarction in pre-clinical models. Exosomes are extracellular vesicles, 30-150nm in size, which regulate the paracrine signal of the stem cells. We investigated the functional outcomes and biological effects of exosomes from pure populations of human bone marrow derived mesenchymal stem cells (MSCs) and induced pluripotent stem cell derived cardiomyocytes (iCMs) in a porcine acute myocardial infarction model. MethodsYorkshire swine were subject to proximal left anterior descending artery occlusion with a catheter balloon for 1 hour for ischemia-reperfusion injury. Ten 500ul injections containing 5 x 1011 exosomes isolated from the tissue culture media of iCMs or MSCs were delivered transendocardially into the peri-infarct region. Cardiac function was assessed by magnetic resonance imaging (MRI). Multi-omic analyses were performed in the ex vivo swine peri-infarct specimen to delineate the mechanism of action. ResultsCardiac MRI at weeks 2 and 4 showed significant improvement in heart function in iCM-derived exosomes while MSC-derived exosomes showed a trend towards improvement. A comparative analysis of transcriptomic sequencing of the porcine peri-infarct tissue and Next Generation Sequencing of the exosome cargo confirmed the dual mechanism of action. The marked improvements seen in cardiac function are conferred by miRNA carried by the exosomes, particularly by cardioprotective reduction in metabolism during acute myocardial injury while promoting concurrent cardiomyocyte cell cycle re-entry and proliferation. ConclusionsSignificant reduction in myocardial metabolism and increase in proliferation signal pathways were found in both exosome treatment groups; however, distinct sets of microRNAs were found to underlie the mechanism of action in each population of exosomes.