Vascular cells, cardiomyocytes, cardiac fibroblasts, and cardiac progenitor cells reportedly secrete miRNA-containing exosomes in culture systems.23 Functional studies focusing on exosomes in human biological fluids are still lacking. Such studies are of importance to characterize the relevance of exosome-based communication in human pathophysiology. We have reported the vascular regenerative potential of exosomes prepared from biological fluids collected from cardiovascular patients.