ACE2 and COVID-19: The multi-organ endothelial dysfunctions observed in COVID-19 patients are likely due to the ubiquitous expression of SARS-CoV-2 receptor ACE2 in organs such as the lung, gut, kidney, brain, testis, heart, and mainly in the vascular system, where high levels of the receptor are present in the endothelial cells of either small or large arteries and veins [156,157].