Angiogenesis and vascular regression in the ovary

Angiogenesis is prominent during development and downregulated in the adult. Strictly controlled angiogenesis in the healthy adult occurs cyclically in the ovary and corpus luteum, which therefore make an excellent model with which to study vascular growth. Dysfunctional or uncontrolled angiogenesis is involved in a number of diseases and is responsible for growth and dissemination of tumours. This review focuses on the following aspects of the ovary: the gross and microscopical anatomy of the blood vessels, described mainly--but not exclusively--in the bovine; vascularization of the follicle before and after ovulation; angiogenesis in the developing and the mature corpus luteum as well as in the corpus luteum of pregnancy. The potential mechanisms of vascular regression during luteolysis and the potential role of vascular growth in dominance and atresia of follicles will be described. Furthermore, recent research on ovarian angiogenic and potential anti-angiogenic factors including fibroblast growth factor (FGF), vascular endothelial growth factor (VEGF), insulin-like growth factor (IGF), angiopoietin and metalloproteinase inhibitor will be presented. Finally, the role of hormones including FSH, LH, sexual steroids, prostaglandins, prolactin, oxytocin and activin/inhibin in ovarian angiogenesis will be summarized. Future research is likely to yield valuable information that can contribute to the development of novel therapeutic strategies for the treatment of diseases characterized by disregulated angiogenesis and vascular regression.