Mechanisms and regulations of endometrial angiogenesis

Angiogenesis is defined as the formation of new blood vessels from the existing vasculature. Angiogenesis occurs regularly in the endometrium throughout the reproductive life of females as part of the rapid growth and regression of this tissue that occurs during the menstrual cycle. It is now clearly evident that angiogenesis plays a key role in reproductive processes such as embryo implantation, placentation, endometrial regeneration after menstruation, and in the ovary during folliculogenesis and corpus luteum formation. Given the complexity and continual change of the endometrial milieu, it seems highly likely that aberrations in the angiogenic process may contribute to various disorders, including endometrial cancer, endometriosis, menorrhagia and breakthrough bleeding – all significant and common gynaecological pathologies. This review provides an update on the mechanisms and regulation of endometrial angiogenesis, with particular reference to the role of angiogenesis in implantation and placentation, as well as two endometrial pathologies – endometriosis and breakthrough bleeding.