Epidermal growth factor promotes chick embryonic angiogenesis.

The response of the early extraembryonic vasculature to epidermal growth factor (EGF) was studied. Millipore filter discs containing 10ng-1 microgram of EGF were placed onto the advancing edge of the area vasculosa of 3-day chick embryos, and the effect examined macroscopically and histologically 24 hours after disc application. The capillary density at the site of application increased significantly, and the effect was seen to be dose-dependent; a similar but more marked response was observed in the vessel cross-sectional area per unit length. This change in vascularity was accompanied by tortuous folding of the mesoderm and endoderm (which normally lie parallel to the ectoderm in a trilaminar arrangement) into the yolk substance: this may indicate precocious development of all three layers (ectoderm, mesoderm and ectoderm) of the membrane, and the proliferative effects of EGF may not be confined to the vascular endothelium.