The use of proteomics to map phenotypic heterogeneity of the endothelium

The inner lining of the vasculature consists of a heterogeneous population of endothelial cells. Phenotypes of these cells vary between different organs, between different parts of the vasculature in a given organ, and even between neighboring endothelial cells of the same organ and the same blood vessel type. Every single endothelial cell of the body is subjected to a seemingly infinite array of signals, including soluble factors, such as growth factors and chemokines, cell-cell and cell-basement membrane interactions, and other variables, such as pH, pO2, sheer stress from blood flow, stretch, and temperature, to name a few. All these variables in the endothelial cell microenvironment will influence the phenotype-thus function-of the cell, to the extent that its predetermined genetic makeup allows. Together, these diverse phenotypes (structural and functional) lead to vascular heterogeneity (e.g., at the level of the organ, tissue, and blood vessel). Hopefully, this phenomenon will become increasingly recognized in the clinical practice of medicine.