Vascular function in female reproduction

The vascular system develops through two distinct pathways commonly referred to as vasculogenesis and angiogenesis. The former involves formation of vascular networks from endothelial progenitor cells, which can originate from bone marrow and peripheral blood (Kassmeyer et al. 2009). In contrast, angiogenesis involves the growth of new blood vessels from preexisting ones. Vascular growth is a common feature of wound healing, inflammatory diseases and in the transition of tumours into a malignant state. Blood vessel growth is tightly regulated in the healthy adult; most organs do not need to form new blood vessels; however, one site where new blood vessel formation is normal in adulthood is the female reproductive tract. In non-pregnant and pregnant females, growth of new blood vessels is crucial for proper functioning of the ovary, endometrium and the placenta. Many disorders and diseases of the female reproductive tract (such as polycystic ovarian syndrome, unscheduled or excessive endometrial bleeding, endometriosis, pre-eclampsia and cancers) involve alterations in the growth and functioning of the vasculature (Smith 2001, Giudice & Kao 2004, Critchley et al. 2006, Jabbour et al. 2006, Fraser & Duncan 2008). Understanding the molecular processes that govern growth and function of blood vessels in physiological settings may help us to develop new therapies for those female reproductive tract pathologies that are promoted either by growth of new blood vessels or by altered functioning of established ones. There is much to be learnt from the female reproductive tract in the way it initiates and controls blood vessel growth cyclically every menstrual cycle and in pregnancy. Such knowledge may inform us about how to halt vessel growth in pathological contexts within the reproductive tract and elsewhere in the body. It may also inform us about how to initiate and regulate vascular growth and function during wound healing and following ischaemic injury such as myocardial infarction. Vasculogenesis is crucial for the establishment of the vascular bed of the placenta and is evident from days 18–20 post conception. In this Focus Issue, Burton et al. (2009) summarise the current knowledge about the molecular regulation of vasculogenesis and angiogenesis