Influence of Maternal Nutrition on Placental mRNA Expression of Angiogenic Factors (AF) and Their Receptors (AFR) in Adolescent Sheep at Days 50 and 75 of Pregnancy.

Abstract

Placental and fetal growth are severely compromised by late pregnancy in adolescent ewes overnourished throughout gestation. Switching ewes from a high to a moderate-control intake at d 50 of gestation prevents these negative pregnancy outcomes (Wallace et al. 1999, BOR 61:101-110). Moreover, recent analyses suggest that placental proliferation rate and vascularity are perturbed in high intake pregnancies as early as d 50. The aim here was to determine placental AF/AFR mRNA expression in control (C) and high-intake (H) ewes at d 50 and 75, and in ewes switched from a high to a control intake (H-C) at d 50 and euthanized on d 75. Singleton pregnancies (single sire) were established by embryo transfer to maximize feto-placental homeogeneity. Whole placentomes, collected at d 50 or 75 of gestation, were separated into fetal cotyledon (COT) and maternal caruncle (CAR) and frozen for quantitative real-time RT-PCR determination of placental AF/AFR mRNA. Maternal diet did not affect fetal or total placentome mass (g) at d 50 (103 ± 10 vs 94 ± 8 in H vs C; P>0.1) or at d 75 (537 ± 35 vs 557 ± 30 in H vs C; P>0.1). However, switching H ewes to C at d 50 increased placentome mass at d 75 (681 ± 46; P<0.05). Of 14 AF/AFR measured for mRNA expression, only the following differences were found. By d 50 in CAR, H-intakes decreased by one-third basic fibroblast growth factor receptor-2 (P<0.01) and angiopoietin (Ang)-1 (P<0.07) mRNA expression. By d 50 in COT, H-intakes increased by nearly two-fold Ang-2 (P=0.07) and vascular endothelial growth factor (VEGF) receptor-2 (KDR; P<0.05) mRNA expression. At d 75 for CAR, H-C increased endothelial nitric oxide synthase (eNOS) mRNA expression by over 50% (P<0.05), while H-intakes increased neuropilin-2 (NP2; P<0.05) and H-C returned NP2 to control levels. At d 75 for COT, H-intakes increased VEGF (P<0.05) and decreased placental growth factor (P<0.05) mRNA expression. Thus a complex picture of AF/AFR involved in the nutritional mediation of placental vascular growth is emerging. Future studies examining protein expression for AF/AFR are requisite to an improved understanding of the mechanisms by which placental vascular growth can be altered by maternal dietary intake during pregnancy. Funded by the Scottish Government and NIH HD045784.