Angiogenesis in the ovary

In adult tissues, capillary growth (angiogenesis) occurs normally during tissue repair, such as in the healing of wounds and fractures. Inappropriate capillary growth is associated with various pathological conditions, including tumour growth, retinopathies, haemangiomas, fibroses and rheumatoid arthritis in the case of rampant capillary growth, and nonhealing wounds and fractures in the case of inadequate capillary growth. The female reproductive organs exhibit marked, periodic growth and regression, accompanied by equally striking changes in their rates of blood flow. It is not surprising, therefore, that they are some of the few adult tissues in which angiogenesis occurs as a normal process. Ovarian follicles and corpora lutea have been shown to contain and produce angiogenic factors. These angiogenic factors appear to be heparin-binding and to belong to the fibroblast growth factor (FGF) and vascular endothelial growth factor (VEGF) families of proteins. In addition, factors regulating gap junctional communication may play a critical role in coordinating the interactions between luteal vascular and nonvascular tissues. Further elucidation of the specific physiological roles of these factors in follicular and luteal growth, development and function will ultimately lead to improved methods for regulating fertility in mammals.