PROJECT SUMMARY/ABSTRACT Hemochorial placentation occurs in many mammalian species including primates and rodents. It ensures the most intimate contact between maternal and embryonic compartments and requires specialized adjustments. Among these adjustments is the need for extensive remodeling of the maternal uterine spiral arteries. Uterine vascular modifications are required for the delivery of nutrients to the fetus. Central to the vascular remodeling process is a specialized population of trophoblast cells referred to as invasive trophoblast cells and in the human, extravillous trophoblast. These cells migrate from the placenta into the uterus where they contribute to the restructuring of the uterine spiral arteries, which facilitate the delivery of nutrients to the placenta and fetus. Disruptions in this fundamental process lead to diseases of pregnancy and placentation, including the “Great Obstetrical Syndromes” (preeclampsia, intrauterine growth restriction, preterm birth, abruptio placentae). Many of these disorders are associated with coagulopathies. In this research proposal we investigate roles for two anti-coagulation factors, tissue factor pathway inhibitor (TFPI) and thrombomodulin (THBD), as a regulators of invasive trophoblast lineage development and uterine spiral artery remodeling. Our proposed research uses the rat as an experimental model because it exhibits deep intrauterine trophoblast invasion and extensive uterine spiral artery remodeling similar to human placentation. We will utilize rat and human trophoblast stem cells to evaluate molecular mechanisms involved in differentiation of the invasive trophoblast lineage. Hypotheses for the conserved involvement of TFPI and THBD in placentation will be tested in vivo using rat models created by genome editing and through lentiviral-mediated trophectoderm gene manipulation. This study will facilitate elucidation of molecular pathways controlling the invasive trophoblast cell lineage and uterine spiral artery remodeling and create a platform for understanding the pathogenesis of diseases impacting placentation.