Abstract
In pregnant sheep, maternal:fetal exchange occurs across placentomes composed of placental cotyledonary and uterine caruncular tissues. Recently, we reported that fetal weights of obese (OB) ewes [fed a diet of 150% of National Research Council (NRC) recommendations] were approximately 30% greater than those of control (C) ewes (fed a diet 100% of NRC recommendations) at midgestation (MG), but fetal weights were similar in late gestation (LG). Transplacental nutrient exchange is dependent on placental blood flow, which itself is dependent on placental vascularity. The current study investigated whether the observed initial faster and subsequent slower fetal growth rate of OB compared with C was associated with changes in cotyledonary vascularity and expression of angiogenic factors (vascular endothelial growth factor, fibroblast growth factor-2, placental growth factor, angiopoietin-1 and -2). Cotyledonary arteriole diameters were markedly greater (P < 0.05) in OB than C ewes at MG, but while arteriole diameter of C ewes increased (P < 0.05) from MG to LG, they remained unchanged in OB ewes. Cotyledonary arterial angiogenic factors mRNA and protein expression were lower (P < 0.05) in OB than C ewes at MG and remained low from MG to LG. In contrast, mRNA levels of angiogenic factors in C ewes declined from high levels at MG to reach those of OB ewes by LG. The increase in cotyledonary arteriole diameter in early to MG may function to accelerate fetal growth rate in OB ewes, while the decreased cotyledonary arterial angiogenic factors from MG-LG may function to protect the fetus from excessive placental vascular development, increased maternal nutrient delivery, and excessive weight gain.