Morphological Heterogeneity of Endothelium

Vascular endothelium lines the entire cardiovascular system where it performs a series of vital functions by its control of microvascular permeability, vessel wall tone, coagulation and anticoagulation cascades, lipid homeostasis, inflammation, angiogenesis, and vasculogenesis. The vertebrate endothelial cells display a remarkable heterogeneity in terms of morphology, molecular makeup, and functional output. This heterogeneity was documented very early by electron microscopy studies that established morphologically recognizable endothelial phenotypes in vascular beds of different organs and, moreover, within the different vascular segments of each organ. This review discusses endothelial heterogeneity from a morphological standpoint and the latest developments in our understanding of the components, structure, and function of the endothelial specific organelles that form the hallmark of these phenotypes.