Nihar Nayak, Ph.D., D.V.M.

Research in my laboratory is focused on understanding the mechanisms of endometrial angiogenesis and vascular remodeling during the menstrual cycle and pregnancy. We are particularly interested in understanding the mechanisms of spiral artery growth and remodeling in the primate uterus. These arteries are unique to the primate endometrium. They develop from the radial arteries of the myometrium and course through the endometrium, where they develop their coiled structure and vascularize primarily the upper endometrial zones. Their growth is primarily driven by progesterone in the luteal phase of the menstrual cycle and pregnancy. At the end of a nonfertile cycle, when progesterone levels fall, the spiral arteries severely constrict, leading to ischemia of the upper endometrial zones and menstrual breakdown of endometrium. During pregnancy, the trophoblasts invade the spiral arteries and replace the internal lining of these arteries, thereby regulate the vascular resistance and blood flow to the placenta and fetus. The degree of trophoblast invasion into these arteries appears to be a major determinant of pregnancy outcome. Inadequate invasion, particularly restricted endovascular invasion of spiral arteries, has been implicated in the pathophysiology of preeclampsia, preterm labor, and intrauterine growth restriction (lUGR). We believe that most of the pregnancy-related vascular complications manifested late in gestation, including preeclampsia, have their origins early in pregnancy. Our main goal is to identify the abnormalities in implantation that may lead to various pregnancy-related vascular complications.