Insulin-like growth factor 1 signaling in the placenta requires endothelial nitric oxide synthase to support trophoblast function and normal fetal growth

Abstract

Currently, there is no effective treatment for placental dysfunction in utero. In a ligated mouse model of fetal growth restriction (FGR), nanoparticle-mediated human insulin-like 1 growth factor (<i>hIGF1</i>) gene delivery (NP-Plac1-hIGF1) increased <i>hIGF1</i> expression and maintained fetal growth. However, whether it can restore fetal growth remains to be determined. Using the endothelial nitric oxide synthase knockout (eNOS^-/-) mouse model, a genetic model of FGR, we found that despite inducing expression of <i>hIGF1</i> in the placentas treated with NP-Plac1-hIGF1 (<i>P</i> = 0.0425), FGR did not resolve. This was associated with no change to the number of fetal capillaries in the placental labyrinth; an outcome which was increased with NP-Plac1-hIGF1 treatment in the ligated mouse model, despite increased expression of angiopoietin 1 (<i>P</i> = 0.05), and suggested <i>IGF1</i> signaling in the placenta requires eNOS to modulate placenta angiogenesis. To further assess this hypothesis, BeWo choriocarcinoma cell line and human placental explant cultures were treated with NP-Plac1-hIGF1, oxidative stress was induced with hydrogen peroxide (H₂O₂), and NOS activity was inhibited using the inhibitor <i>N</i>^G-monomethyl-l-arginine (l-NMMA). In both BeWo cells and explants, the protective effect of NP-Plac1-hIGF1 treatment against H₂O₂-induced cell death/lactate dehydrogenase release was prevented by eNOS inhibition (<i>P</i> = 0.003 and <i>P</i> < 0.0001, respectively). This was associated with an increase in mRNA expression of oxidative stress markers hypoxia inducing factor 1α (<i>HIF1α</i>; <i>P</i> < 0.0001) and <i>ADAM10</i> (<i>P</i> = 0.0002) in the NP-Plac1-hIGF1 + H₂O₂ + l-NMMA-treated BeWo cells. These findings show for the first time the requirement of eNOS/NOS in IGF1 signaling in placenta cells that may have implications for placental angiogenesis and fetal growth.