Regulation of Uterine Spiral Artery Remodeling During Primate Pregnancy

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PROJECT SUMMARY/ABSTRACT: During early human pregnancy, placental extravillous trophoblasts (EVT) remodel the uterine spiral arteries (UAR) to promote utero-placental blood flow and fetal development. Impaired UAR underlies pregnancy disorders, e.g. fetal growth restriction and preeclampsia (PE), which result in maternal and neonatal morbidity/mortality. Conversely, excessive UAR, as in placenta accreta, impairs vasoregulation after delivery. Despite the importance of UAR to successful pregnancy little is known about UAR regulation. Using the baboon as a nonhuman primate translational model, we have shown that advancing the surge in estradiol (E2) from the second to the first trimester suppressed UAR and EVT expression of vascular endothelial growth factor (VEGF). Therefore, we propose that: (a) the low level of E2 in the first trimester promotes EVT VEGF expression and UAR and (b) the increase in E2 in the second trimester suppresses UAR by inhibiting EVT VEGF. Because E2 suppression of UAR was simply associated with a decrease in EVT VEGF expression, it is not known whether VEGF mediates this process. Therefore, in Aims 1A,B we propose to use contrast enhanced ultrasound (CEU)/microbubble (MB) targeting to deliver the VEGF gene to the placental basal plate of E2-treated baboons and the sFlt-1 gene which suppresses VEGF bioavailability to untreated baboons to test the hypotheses that VEGF: (a) mediates the E2-induced suppression of UAR and (b) promotes UAR during normal pregnancy. A defect in UAR impairs placental function, leading to an increase in placental sFlt-1 expression/decline in VEGF availability and consequently disruption of maternal systemic vascular function. Therefore, in Aim 1C, blood flow dynamics will be determined in baboons to test the hypothesis that the E2-induced increase in sFlt-1/decrease in VEGF bioavailability results in maternal systemic vascular dysfunction. Because placental dysfunction and vascular defects in pregnancy disorders occur in a fetal sexual dimorphic manner, in Aim 1D UAR and maternal vascular function will be determined in pregnancies with male and female fetuses to test the hypothesis that fetal gender impacts the latter processes. Although E2 typically upregulates VEGF, E2 decreased EVT VEGF expression. The divergent roles of E2 on VEGF expression may reflect expression/action of estrogen receptor (ER)α versus ERβ. Therefore, in Aim 1E we will culture baboon EVT to test the hypothesis that ERβ mediates E2-induced suppression of EVT VEGF expression, migration and invasion. The proposed study is highly significant as it focuses on the regulation of UAR which when defective underpins abnormal pregnancy. The experimental paradigm and targeted delivery of VEGF/sFlt-1 genes via CEU/MB are novel cutting-edge approaches that will establish the role of VEGF on normal and abnormal UAR in a primate with substantial translational application to humans. Elucidating the role of VEGF on UAR will represent a major scientific advance and provide a basis for therapeutic application of VEGF targeting in disorders of human pregnancy.