Another project is to examine the role of the microvascular endothelial cells of the corpus luteum. The development of the ovarian corpus luteum is analogous to the development of a tumor, i.e., both involve angiogenesis. Cyclical development and regression of the corpus luteum is required for normal reproductive function. Although the formation and regression of the corpus luteum are dependent on endocrine hormones (LH and PGF2a), the early disruption of the vasculature during luteolysis is dependent on the activity of specific cytokines. Ongoing studies are designed to delineate the effects of cytokines (TGFB1, TNFa, IFNg) on the regulation of endothelial cell tube formation, chemokine production and apoptosis. We are exploring the interactions among endothelial cells, steroidogenic cells, fibroblasts and immune cells. These studies are anticipated to provide new insights into the cellular mechanisms that regulate the function (steroidogenesis) and lifespan (apoptosis) of the corpus luteum, as well to provide a novel approach to studies on tumor vascular development.