Local regulation of corpus luteum development and regression in the cow: Impact of angiogenic and vasoactive factors

The corpus luteum (CL) of the estrous cycle in the cow is a dynamic organ which has a life time of approximately 17-18 days. The main function of the CL is to secrete a large amount of progesterone (P) thereby supporting the achievement of pregnancy. As the CL matures, the steroidogenic cells establish contact with many capillaries and the matured CL is composed of many vascular endothelial cells that account for up to 50% of all CL cells. The bovine CL produces several major angiogenic and vasoactive foctors such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), angiopoietin-1 and -2 (ANPT-1 and -2), prostaglandin F_2α (PGF_2α), endothelin-1 (EDN1), angiotensin II (Ang II) and nitric oxide (NO). These factors regulate P secretion directly and/or indirectly within the CL. Moreover, different actions of PGF_2α in the early cycle CL (non-luteolytic) and the mid cycle CL (luteolytic) may provide insight into the luteolysis cascade in the cow. The aim of the present review is to describe the current concepts of the local mechanisms for the cascade of development and regression of the bovine CL as regulated by luteal angiogenic and vasoactive factors.