Born to die: blood vessel regression research coming of age.

Blood vessel network formation is a pivotal process of physiological development and pathological conditions such as tumor growth, diabetic retinopathy, and cardiovascular diseases.1,2 During neovascularization, vasculogenesis is followed by the well-described process of sprouting angiogenesis, including tip cell induction and selection, sprout elongation, and stalk formation, leading to the formation of a dense primary vascular network.1,2 To match vessel perfusion with the local metabolic demand of the tissue, initial sprouting angiogenesis is followed by vessel pruning and maturation to form a hierarchically defined vascular network of large arteries and veins branching into smaller capillaries.1,2 Although the phenomenon of vessel regression was described by Rouget in 18733 and further characterized by Ashton in 1960,4 the mechanisms of vessel pruning and the signaling pathways controlling this process are still largely undefined.