Abstract 13545: Atlas of Exosomal Microrna Secreted From Human Ipsc-derived Cardiac Cell Types

Abstract

Exosomes are small particles secreted from cells through an endosomal sorting complexes required for transport (ESCRT)-mediated pathway that releases vesicles into the extracellular matrix following fusion of the endosomal multivesicular body to the plasma membrane. Initially thought to be a waste disposal system for the cell, exosomes are now recognized as important mediators in cellular communication, transporting nucleic acid, protein and lipid. We hypothesize that microRNA (miRNA) transcriptomic profiles isolated from exosomes are distinct for each cardiovascular lineage in healthy control patients. Using induced pluripotent stem cells (iPSC), established differentiation protocols and a high-yield mechanical-sorting device (ExoTIC), we characterized the transcriptomic profiles of exosomal secretions derived from cardiomyocytes (CM), cardiac fibroblasts (CF) and endothelial cells (EC). We identified 120 miRNAs from 94 miRNA genes to be secreted at appreciable levels. We discovered 1) let-7 miRNA precursors are depleted in iPSC secretomes; 2) only a subset of total cellular miRNAs are present; 3) a common core of miRNAs are secreted by all three cardiac cell types; and 4) distinct enrichment or depletion of different mature miRNAs in each exosome type. The exosomal transcriptomic profiles of each lineage was compared to a published atlas of miRNA from seventeen tissue types from the human body. miR-302c known to be specific to pluripotent cells and is enriched in iPSC exosomes and found in bone, reflecting hematopoietic stem cells. miR-1, critical for cardiac development and pathology, is secreted by iPSC-CM and enriched in striated muscle and myocardium. miR-151 is secreted by iPSC-CF and is expressed ubiquitously. The relative enrichment of miRNAs in different cardiac tissues could be used to quantifying the cellular content of heterogenous mixtures of iPSC-derived cardiac lineages. We developed a ratiometric cell purity assay that can sensitively detect iPSC contamination in iPSC-CM differentiations.