Placental development requires trophoblast cells to proliferate, migrate and invade maternal uterine tissues to establish utero-placental blood flow. This is essential for the health and development of the fetus. Inadequate placental development can be observed in a number of pregnancy-related pathologies, including preeclampsia. The placental renin-angiotensin system (RAS) is highly expressed in early gestation placentae, when trophoblasts are at their most invasive. Binding of inactive prorenin to the (pro)renin receptor ((P)RR) can initiate the generation of angiotensin II (Ang II) via the classical RAS pathway. Ang II can then act on the angiotensin type-1 receptor (AT1R) to stimulate placental angiogenesis and trophoblast proliferation, migration and invasion. The binding of prorenin to the (P)RR can also induce intracellular signalling independently of Ang II/AT1R, yet this interaction and its functional consequences for placental development are unknown. We hypothesised that prorenin acting via (P)RR is a key regulator of early placental development.
A first trimester extravillous cell line, HTR-8/SVneo was transfected with siRNA targeting the ATP6AP2 gene to knockdown (P)RR expression. qPCR showed that siRNA transfection resulted in a 90% decrease in ATP6AP2 expression (P<0.0001) and western blotting showed an average reduction in intracellular (P)RR protein levels of 65% (P<0.01). The effect of (P)RR knockdown on HTR-8/SVneo cell function was assessed in real time using the xCELLigence DP instrument. The xCELLigence system uses electrical impedance to monitor cell proliferation, migration and invasion over time. Cells treated with (P)RR siRNA showed a 30% reduction in proliferation rates over 48 hours (P<0.0001) when compared with controls. Furthermore, treatment with (P)RR siRNA also showed a 48% reduction in HTR-8/SVneo migration rates (P<0.0001), and a 35% reduction in HTR-8/SVneo invasion rates (P=0.0039) over 48 hours. These results show that the (P)RR plays an important role in extravillous trophoblast proliferation, migration and invasion in early gestation placental development.