Angiogenesis in the endometrium.
Human endometrial vasculature has the unique property of undergoing benign angiogenesis during each menstrual cycle under the influence of the ovarian steroids estradiol and progesterone. However, neither has intrinsic angiogenic activity and endometrial angiogenesis involves stimulation by ovarian steroids of angiogenic factor release by the epithelium and stroma which then act on the endothelium. In vitro models using cultures of isolated endometrial epithelium, stroma and endothelium now allow mechanistic questions to be addressed. Vascular endothelial growth factor and platelet-derived endothelial cell growth factor/thymidine phosphorylase at present appear to be key players in endometrial angiogenesis.