Estrogen promotes angiogenic activity in human umbilical vein endothelial cells in vitro and in a murine model

Background: Angiogenesis is a critical event in wound healing, tumor, growth, and the inflammatory vasculitides. Since women have a higher incidence of many vasculitic diseases, we examined the effects of female sex steroids, particularly estradiol, on human umbilical vein endothelial cell (HUVEC) behavior in vitro and on angiogenesis in vivo. Methods and Results: HUVECs were grown in estrogen-free medium before each assay. Exogenous 17β- estradiol (1 to 5 nmol/L.) increased cell attachment to laminin, types I and IV collagen, and fibronectin, as well as to tissue culture and plastic. After a confluent monolayer of cells was 'wounded' by scraping, estradiol-treated 10^-8 mol/L) cells migrated into the wound three times faster than untreated cells. Cell proliferation on plastic and on laminin increased threefold to fivefold respectively, in the presence of estradiol. Estradiol also enhanced the ability of HUVECs to organize into tubular networks when plated on a reconstituted basement membrane, Matrigel. Estradiol effects on both the 'wounding' assay and tube formation were blocked by the specific estrogen receptor antagonist ICI 182,780. Ovariectomy markedly decreased in vivo vascularization of Matrigel plugs coinjected with basic fibroblast growth factor in mice. With estrogen replacement, angiogenesis was increased to the levels observed in nonovariectomized mice. Conclusions: These studies demonstrate that, in vitro and in vivo, estradiol enhances endothelial cell activities important in neovascularization and suggest a promoting influence of estrogens on angiogenesis.