Vascular Organization: Lessons from Development and Disease.

Organ formation requires tight coordination with vascular growth. Intricate networks of blood vessels course through all organs and tissues and are composed of both endothelial cells (ECs) and associated mural cells. Despite decades of research into the biology of blood vessel formation and homeostasis, little is known about how the vasculature ensures its properly coordinated growth and intimate development with the cells of different organs. Even more mystifying is how a highly dynamic endothelium quiesces to differentiate into mature vessels, and how disruption of this mature quiescence results in pathological conditions. Interestingly, both intra- and interorgan vascular architecture hold critical importance to the maintenance of blood vessels, as the rate of flow and supply of supportive angiogenic factors can be altered with deleterious effects. In this article, we review the basic mechanisms of blood vessel formation and maintenance with an emphasis on organ-specific vascular development, and we examine the case of transient pulmonary arteriovenous malformations as a case study of vascular homeostatic mechanisms.