Angiogenesis induction by tumors, embryonic tissues, and lymphocytes.

Although it is well established that tumors can induce endothelial cell mitosis and angiogenesis leading to extensive neovascularization, little is known concerning the spectrum of normal cells or tissues that may have similar inductive capabilities. A variety of developmentally active tissues were tested: mouse embryonic organ rudiments, mouse and rabbit trophoblast and placenta, and blastemal fragments obtained from regnerating deer antlers. Assays for angiogenesis included grafts made to the chorioallantoic membrane of chick embryos and grafts placed intracorneally in adult rabbit eyes. Virtually all of these test tissues were negative, the only exceptions being some antler grafts and some grafts obtained from metanephric tubules of the embryonic mouse kidney.