The cardiovascular system is composed of the heart and circulatory system. It is responsible for delivery of oxygen- and nutrient-rich blood to the body’s cells, as well as for carrying away carbon dioxide and waste products generated by those same cells. Lining the heart, blood vessels, and lymphatic vasculature are endothelial cells that together form a semi-selective barrier and are critical for transcellular transport of macromolecules, hemostasis, immune responses, angiogenesis, metabolism of circulating factors, and vascular tone. Endothelial cell dysfunction is a major reason that cardiovascular disease remains a leading cause of morbidity and mortality worldwide.