Vonnahme Kimberly A, Ford Stephen P
Department of Animal Science, University of Wyoming, Laramie, WY 82071, USA.
J Physiol. 2004 Jan 1;554(Pt 1):194-201. doi: 10.1113/jphysiol.2003.055061.
Selecting Yorkshire breeding stock for increased placental efficiency (PE; piglet weight divided by its placental weight) results in larger litters (i.e. approximately 3 more piglets litter-1) and reduced placental sizes. Placental vessel density increases progressively after day 50 of gestation in the pig, and is positively correlated with PE and placental expression of vascular endothelial growth factor (VEGF), a potent angiogenic and permeability factor. To elicit its vascular effects, VEGF must bind to its receptors (R), VEGF-R1 and VEGF-R2. The objective of this study was to compare placental and endometrial blood vessel density and placental VEGF, VEGF-R1 and VEGF-R2 mRNA expression in day 70 and 90 conceptuses from Yorkshire females selected for high PE, low PE, and from unselected controls. A greater (P < 0.05) PE was observed for conceptuses in the high PE selection group when compared to the low PE selection group. Placental blood vessel density increased (P < 0.05) from day 70 to 90 (1.8 +/- 0.1 versus 2.8 +/- 0.2) in association with increases (P < 0.05) in placental VEGF mRNA expression. No selection group differences were observed in expression of VEGF, VEGF-R1, or VEGF-R2 on day 70. By day 90, however, placentae of conceptuses from the high PE group expressed greater (P < 0.05) amounts of VEGF and VEGF-R1 mRNA than the unselected controls and the low PE group. These data demonstrate that increased placental expression of the VEGF receptor system is associated with increased placental vascular density observed with the advancement of gestation in the pig. Although placental blood vessel density was not increased in the high PE selection group, elevated levels of the VEGF receptor system suggest an effect on increasing placental and endometrial blood vessel permeability and/or proximity in the high PE group.
选择具有更高胎盘效率（PE；仔猪体重除以胎盘重量）的约克夏种畜，会使产仔数增加（即每窝约多3头仔猪），且胎盘尺寸减小。猪在妊娠50天后胎盘血管密度逐渐增加，且与PE以及血管内皮生长因子（VEGF，一种强大的血管生成和通透性因子）的胎盘表达呈正相关。为发挥其血管效应，VEGF必须与其受体（R）VEGF-R1和VEGF-R2结合。本研究的目的是比较来自高PE、低PE的约克夏母猪以及未选对照组的妊娠70天和90天胚胎的胎盘和子宫内膜血管密度，以及胎盘VEGF、VEGF-R1和VEGF-R2 mRNA表达。与低PE选择组相比，高PE选择组的胚胎观察到更高的（P < 0.05）PE。从妊娠70天到90天，胎盘血管密度增加（P < 0.05）（1.8 ± 0.1对2.8 ± 0.2），同时胎盘VEGF mRNA表达增加（P < 0.05）。在妊娠70天时，VEGF、VEGF-R1或VEGF-R2的表达在各选择组之间未观察到差异。然而，到妊娠90天时，高PE组胚胎的胎盘表达的VEGF和VEGF-R1 mRNA量比未选对照组和低PE组更高（P < 0.05）。这些数据表明，VEGF受体系统胎盘表达的增加与猪妊娠进展时观察到的胎盘血管密度增加有关。尽管高PE选择组的胎盘血管密度未增加，但VEGF受体系统水平升高表明对高PE组胎盘和子宫内膜血管通透性和/或接近度增加有影响。
