Characterization of human cardiac mesenchymal stromal cells and their extracellular vesicles comparing with human bone marrow derived mesenchymal stem cells

Cardiac regeneration with adult stem-cell (ASC) therapy is a promising field to address advanced cardiovascular diseases. In addition, extracellular vesicles (EVs) from ASCs have been implicated in acting as paracrine factors to improve cardiac functions in ASC therapy. In our work, we isolated human cardiac mesenchymal stromal cells (h-CMSCs) by means of three-dimensional organ culture (3D culture) during ex vivo expansion of cardiac tissue, to compare the functional efficacy with human bone-marrow derived mesenchymal stem cells (h-BM-MSCs), one of the actively studied ASCs. We characterized the h-CMSCs as CD90^low, c-kit^negative, CD105^positive phenotype and these cells express NANOG, SOX2, and GATA4. To identify the more effective type of EVs for angiogenesis among the different sources of ASCs, we isolated EVs which were derived from CMSCs with either normoxic or hypoxic condition and BM-MSCs. Our in vitro tube-formation results demonstrated that the angiogenic effects of EVs from hypoxia-treated CMSCs (CMSC-Hpx EVs) were greater than the well-known effects of EVs from BM-MSCs (BM-MSC EVs), and these were even comparable to human vascular endothelial growth factor (hVEGF), a potent angiogenic factor. Therefore, we present here that CD90^lowc-kit^negativeCD105^positive CMSCs under hypoxic conditions secrete functionally superior EVs for in vitro angiogenesis. Our findings will allow more insights on understanding myocardial repair.