77 - Murine placentae supporting FGR male fetuses are more susceptible to angiogenic perturbation compared to placentae of FGR female fetuses in early hypertensive disease of pregnancy

Poster Number: 77
Publication Number: 77.473

Background: Hypertensive disease of pregnancy (HDP) causing uteroplacental insufficiency (UPI) is the most common cause of fetal growth restriction (FGR) in developed countries. We have published that placentae supporting FGR fetuses weigh more in early HTN (E15.5) compared to appropriate-growth (AGA) fetuses despite no change in fetal weight or CD31 vascular density within the labyrinth layer (Gibbins et al. 2018). Weight increase is mostly driven by placentae supporting female fetuses. In mid-(E17.5) and late-(E19) HTN, placentae supporting FGR and AGA fetuses weigh similarly, but FGR placentae increase their efficiencies as the vascular density decreases.

Objective: To determine expression profiles of key placental angiogenic proteins in early HTN (E15.5) that may lend to decreased vessel growth in later pregnancy.

Design/Methods: We used a well-established mouse model of HDP by implanting a micro-osmotic pump and infusing TXA2-analog in pregnant C57BL/6 dams on embryonic day E12.5. Sham-operated dams with vehicle infusion were controls. We harvested placentae at E15.5, extracted proteins, and performed Western immunoblotting on protein expression of: Wnt signaling (Wnt5A/B, Frizzled 7 receptor, beta-catenin), HIF signaling (HIF1-alpha and -beta and HIF2-alpha), placental growth factor, platelet-derived growth factor B and its receptors PDGFR-A and B, angiopoietin-1 and -2, VEGFR-1 and -2, Tie-2, eNOS, and FGF2, with GAPDH as loading control. We determined sex by PCR of Rbm31x/y genes. We measured band densities and protein abundance was normalized to GAPDH. Normality and equal variances of data allowed Student’s t-test to be used to compare means of sham and FGR groups separating sex with p< 0.05 as significant.

Results: Compared to E15.5 sham male placentae, FGR male placentae had decreased WNT5A/B, HIF1-α, eNOS, and VEGFR2 proteins (Figure 1). FGR male placentae also increased PDGFR-B and ANG2 proteins. FGR female placentae only increased ANG1 protein compared to AGA female placentae, with no changes in the other aforementioned angiogenic proteins.

Conclusion(s): Key signaling proteins that govern placental angiogenesis appear to be preserved in FGR female placentae compared to FGR male placentae in early HTN. FGR females upregulate angiopoietin-1 which is a critical vascular growth factor for vessel maturation, adhesion, migration, and survival. FGR male placentae had decreases in multiple classes of angiogenic proteins, which occur prior to overt placental vascular diminution in later gestation. The underlying mechanism for this sex-divergent compensation is currently unknown but warrants further investigation.