Placentation

Vonnahme KA, Hess BW, Hansen TR, McCormick RJ, Rule DC, Moss GE, Murdoch WJ, Nijland MJ, Skinner DC, Nathanielsz PW, Ford SP. (2003) Maternal undernutrition from early- to mid-gestation leads to growth retardation, cardiac ventricular hypertrophy, and increased liver weight in the fetal sheep. Biol Reprod. 69(1): 133-40.

Vonnahme KA, Ford SP. (2004) Placental vascular endothelial growth factor receptor system mRNA expression in pigs selected for placental efficiency. J Physiol. 554(Pt 1): 194-201.

Kwon H, Ford SP, Bazer FW, Spencer TE, Nathanielsz PW, Nijland MJ, Hess BW, Wu G. (2004) Maternal nutrient restriction reduces concentrations of amino acids and polyamines in ovine maternal and fetal plasma and fetal fluids. Biol. Reprod. May 12 [Epub].

Han HC, Austin KJ, Nathanielsz PW, Ford SP, Nijland MJ, Hansen TR. (2004) Maternal nutrient restriction alters gene expression in the ovine fetal heart. J. Physiol. May 7 [Epub].

Epidemiological studies in humans have revealed that sub-optimal nutrition of women during the first half of pregnancy alters placental as well as fetal growth and development, predisposing offspring to cardiovascular, metabolic, and endocrine diseases later in life. In sheep as in humans, the first half of gestation is critical for placental growth, differentiation and vascularization as well as fetal organogenesis. In ruminants, placental cotyledons attach to descrete areas of the uterine mucosa called caruncles. The caruncular- cotyledonary unit is called a placentome and is the functional area of physiological exchange between mother and fetus.

As gestation advances, placentomes may undergo very profound morphologic transformations from type A placentomes through types B, C, and D placentome types. As a placentome progresses from a type A through types B, C, and D, the fetal tissue occupies relatively more of the placentome, increasing the surface area of maternal-placental exchange. A central aim is to determine structure-function relationships.

We have compared placentomal differentiation in response to prolonged maternal under nutrition. in two groups of multiparous Ramboillet ewes selected for many years under two markedly different management systems. The first group of ewes was adapted to a nomadic existence (~250 miles/year), grazing from desert terrain to high mountain pastures (nomadic ewes) with poor quality forages. The second group of ewes was obtained from the University of Wyoming (UW) Flock, and adapted to a relatively sedentary lifestyle, and supplied with more than adequate nutritional imputs throughout their lives (UW ewes). Both UW and Baggs ewes were fed to 50% (nutrient restricted, NR) or 100% (control fed, CF) of NRC requirements from day 28 to 78 of gestation. Our model of nutrient restriction led to a progressive decrease in maternal body condition score and body weight from day 28 to day 78 in both Baggs and UW ewes, with UW ewes losing more body condition and a greater percentage of body weight than Baggs ewes during the nutrient restriction period. Further, while we found a ~30% reduction of fetal weight in the NR vs. CF UW ewes on day 78, no effect of nutrient-restriction was seen on fetal weight in Baggs ewes.