In response to stimuli such as hypoxia, VEGF induces vasculogenesis and endothelial cell proliferation. Ang1–Tie2 interactions mediate vessel maturation and maintain vessel integrity through the recruitment of peri-endothelial cells. Ang2 blocks Ang1–Tie2 signaling, loosening vascular structure and exposing the endothelium to inducers of angiogenesis such as VEGF. In the presence of VEGF, endothelial cells migrate and proliferate to form new capillary sprouts and blood vessels. Ang2 expression in the absence of VEGF stimulation leads to vessel regression and apoptosis. RTK indicates receptor tyrosine kinase.
