This Program area, directed by Dr. Koji Yoshinaga, supports basic research studies on uterine function involving molecular, cellular, tissue and organ level approaches. Particularly important are studies to elucidate the mechanism of action of steroid, lipid and protein hormones on the uterus, oviduct and vagina and how these hormones interact to promote cycle-regulated changes in uterine morphology and function. Critical to this Program are studies to elucidate the interactions between the implanting blastocyst and the uterus in the establishment of pregnancy. Processes important to the study of implantation include, but are not limited to uterine receptivity, decidualization, trophoblast invasion, neovascularization, tissue remodeling and formation of the placenta. The interplay of the immune and endocrine system families of hormones, growth factors and cytokines in promoting these processes is of particular interest. Studies on the causes of implantation-based infertility, subfecundity and poor pregnancy outcomes are clinically relevant aspects of this Program. An important component of this Program is the Interdisciplinary Collaborative Team on Blastocyst Implantation, comprised of funded investigators working on the immunobiology of implantation in a variety of animal models.