Endothelin2 signaling in the neural retina promotes the endothelial tip cell state and inhibits angiogenesis

Endothelin signaling is required for neural crest migration and homeostatic regulation of blood pressure. Here we report that constitutive over-expression of Endothelin-2 (Edn2) in the mouse retina perturbs vascular development by inhibiting endothelial cell (EC) migration across the retinal surface and subsequent EC invasion into the retina. Developing endothelial cells exist in one of two states: tip cells at the growing front, and stalk cells in the vascular plexus behind the front. This division of endothelial cell states is one of the central organizing principle of angiogenesis. In the developing retina, Edn2 over-expression leads to over-production of endothelial tip cells by both morphologic and molecular criteria. Spatially localized over-expression of Edn2 produces a correspondingly localized endothelial response. Edn2 over-expression in the early embryo inhibits vascular development at mid-gestation, but Edn2 over-expression in developing skin and brain has no discernable effect on vascular structure. Inhibition of retinal angiogenesis by Edn2 requires expression of Endothelin receptor A (Ednra) but not Ednrb in the neural retina. Taken together, these observations imply that the neural retina responds to Edn2 by synthesizing one or more factors that promote the endothelial tip cell state and inhibit angiogenesis. The response to Edn2 is sufficiently potent that it over-rides the activities of other homeostatic regulators of angiogenesis, such as vascular endothelial growth factor.

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Rattner A, Yu H, Williams J, Smallwood PM, Nathans J