Differential Expression of the Vascular Endothelial Growth Factor-Receptor System in the Gravid Uterus of Yorkshire and Meishan Pigs

Abstract

Litter size in the pig is limited by uterine capacity, which is dependent on uterine size, placental size, and vascularity. Placentae of U.S. pig breeds, such as the Yorkshire, exhibit marked growth from mid to late gestation, increasing their surface area of endometrial attachment. In contrast, placentae of the prolific Chinese Meishan pig exhibit little growth from mid to late gestation; instead, they exhibit a marked and progressive increase in the density of placental blood vessels. Vascular endothelial growth factor (VEGF) is a potent angiogenic and permeability-enhancing factor that is produced and secreted by placentae of several species, including the pig. The activity of VEGF is mediated through two specific receptors (VEGF-R1 and VEGF-R2), both of which are expressed by placental and endometrial tissues in pigs and are thought to play a role in mediating increased vascularization and/or permeability at the fetal-maternal interface. The objectives of the present study were to determine concentrations of VEGF in fetal blood and placental fluids as well as placental and adjacent endometrial mRNA expression of VEGF, VEGF-R1, and VEGF-R2 on Days 30, 50, 70, 90, and 110 of gestation in Yorkshire and Meishan pigs. Day 90 Meishan conceptuses exhibited marked increases (P < 0.05) in placental VEGF mRNA expression as well as fetal blood and allantoic fluid concentrations of VEGF, which remained elevated through Day 110. In contrast, Yorkshire conceptuses failed to exhibit increases in placental VEGF mRNA expression or concentrations of VEGF in fetal blood or allantoic fluid until Day 110. Receptor mRNA expression patterns differed between Meishan and Yorkshire conceptuses, but no difference was found in their expression levels. Placental efficiency (fetal weight/placental weight) was higher (P < 0.05) on Days 90 and 110 in Meishan than in Yorkshire conceptuses. The earlier increase in VEGF protein and mRNA expression in the Meishan versus the Yorkshire conceptus may explain the previously reported increased vascularity and increased placental efficiency of this breed compared the Yorkshire breed.

Six placenta permeability-related genes: molecular characterization and expression analysis in pigs

“…CDH5 is a major adhesive component of cell-to-cell contacts (Huber et al, 1996); its lowlevel expression may help to promote placenta permeability. Our study demonstrated that during porcine placenta development, the expression of VEGF was up-regulated, which is generally in agreement with the previous research results ( Vonnahme and Ford, 2004). VEGFs are crucial regulators of vascular development (Olsson et al, 2006) and also directly stimulate increased vascular permeability to water and large molecular weight proteins and vasodilatation (Bates and Harper, 2002).…”

Uteroplacental vascular development and placental function: an update

“…In the other model exhibiting increased placental vascularity (Romanov vs. Columbia genotype), the animals were subject to long-term genetic selection, resulting in increased litter size. This latter case resembles that of Meishan and Yorkshire pigs, in which the Meishans exhibit increased litter size and weight associated with increased placental vascularity and VEGF expression Wilson et al, 1998;Vonnahme and Ford, 2004). …”

Imprinting analyses of the porcine GATM and PEG10 genes in placentas on days 75 and 90 of gestation

“…Previous study on human placenta revealed that PEG10 gene was down-regulated at early hypoxic stage of placental growth, induced at 11-12 wk, and then the level of expression increased and maintained at a high level (Smallwood et al, 2003). Notably, fetal weight of pig increased dramatically after 33 days (Vonnahme et al, 2004). Thus, we presume that PEG10 play a vital role in the development of fetus.…”