Abstract 13837: Cardiomyocyte Progenitor Cell and Mesenchymal Stem Cell Exosomes Stimulate the Angiogenic Capacity of Endothelial Cells
Cardiac cell therapy results in increased capillary density, however only a small percentage of cells successfully engraft the myocardium. This suggests that paracrine factors are involved. These paracrine factors can include e.g. soluble proteins, growth factors and exosomes. Exosomes are small membrane vesicles which can facilitate communication between cells. Here, we focused on the effect of cardiomyocytes progenitor cell (CMPC) and mesenchymal stem cell (MSC) exosomes on the angiogenic capacity of endothelial cells (ECs). In addition, we studied the role of extracellular matrix metalloproteinase inducer (EMMPRIN) on exosomes. Exosomes were isolated from conditioned medium (CM) by centrifugation at 100.000xg or separated on a sucrose gradient. These exosomes were used in scratch wound, spheroid, and matrigel assays. In addition, exosomes were or were not treated with an extracellular matrix metalloproteinase inducer antibody. CMPCs and MSCs are able to produce exosomes of approximately 100 nm in size as was observed via EM and western blot analysis for exosomal marker flotillin-1 and have a density between 1.10 and 1.12 g.ml-1. In a scratch wound assay, CMPC and MSC exosomes stimulated wound closure of ECs by 52% (+/- 10% SEM) and 39% (+/- 4% SEM), respectively, compared to 4% (+/- 4% SEM, p < 0.05) when no exosomes were added. The angiogenic capacity of endothelial cells is enhanced in the presence of CMPC and MSC exosomes. CMPC and MSC CM depleted for exosomes displayed a 44% (+/- 16% SEM) and 62% (+/- 18% SEM) reduction in sprouting length for spheroids (p < 0.05). The number of junctions in a matrigel assay was increased when ECs are stimulated with exosomes. CMPC and MSC exosomes express EMMPRIN, a protein known to facilitate cellular migration. By blocking exosomes with an EMMPRIN antibody, wound closure was inhibited and resulted in reduced number of junctions in the spheroid assay. CMPC and MSCs release exosomes. Although there is no difference between both types of exosomes, they both enhance the angiogenic in vitro capacity of ECs via an EMMPRIN mediated mechanism. This could be a novel mechanism in which transplanted cells trigger or enhance migration and organization of endogenous ECs upon cardiac cell therapy leading to increased capillary formation.
- © 2011 by American Heart Association, Inc.