296. Loss of Placental NR4A2 may contribute to the pathogeneisis of pre-eclampsia

Abstract

Introduction Placental dysfunction is a key contributor in the development of pre-eclampsia. Recently, we identified NR4A2 mRNA to be altered in the maternal circulation in pregnancies complicated by severe, early onset fetal growth restriction and pre-eclampsia (PE). Objective The current study aimed to determine whether NR4A2 expression was altered in the human placenta with hypoxic insult and pre-eclampsia. Methods Isolated primary cytotrophoblasts (n = 5) and placental explant tissue (n = 4) from normal term placentas were cultured under normoxia (8% oxygen) and hypoxia (1% oxygen) for 24 h. Expression of NR4A2 was assessed by qPCR. Placental tissue was collected from severe early onset PE (n = 49) and gestation matched controls (n = 47) to test NR4A2 mRNA expression. NR4A2 protein was assessed in PE (n = 31) and preterm (n = 22) placenta by Western blotting. Primary cytotrophoblasts were transfected with NR4A2 siRNA (n = 3) to silence gene expression (under normoxia and hypoxia for 48 h). sFLT-1 secretion was assessed by ELISA and expression of the sFLT-1 variants (e15a and i13) and cell survival associated genes by qPCR. Normality (Gaussian distribution) was assessed in each case and appropriate post hoc analysis was performed. Results NR4A2 mRNA expression was significantly reduced with hypoxia in trophoblast, but not placental explants. Additionally, NR4A2 mRNA expression was significantly reduced in PE placenta. However, there was no difference in NR4A2 protein expression between PE and controls. Silencing NR4A2 significantly increased anti-angiogenic factor sFLT-1 secretion, but not sFLT-1 mRNA expression. Furthermore, loss of NR4A2 in the trophoblast reduced pro-survival IGF2 gene expression and increased NOX4 (oxidative stress marker) expression. Conclusion NR4A2 is reduced in the trophoblast with hypoxia and mRNA expression is low in the PE placenta. Signs of placental dysfunction were observed with the silencing of NR4A2 in the trophoblast and an increase in sFLT-1 secretion suggests potential roles for NR4A2 in the pathogenesis of PE.