Endothelial Cell Heterogeneity: A Developmental Biologist's Perspective

Endothelium, the tissue that lines the lumen of the myriad blood vessels and capillaries of the body, was long thought to be passive and virtually inert. Over time it has come to be recognized as exceedingly diverse as well as highly interactive with its surroundings. We trace back this concept of diversity within the broad definition of endothelial cells to its earliest recognition and review some of the work that has led to the current explosion of studies documenting endothelial cell heterogeneity.