Department of Animal and Veterinary Science, Clemson University, Clemson, SC, 29634, USA.
Center for Human Genetics, Clemson University, Greenwood, SC, 29646, USA.
BMC Genomics. 2019 Mar 29;20(1):254. doi: 10.1186/s12864-019-5626-0.
Placental efficiency (PE) describes the relationship between placental and fetal weights (fetal wt/placental wt). Within litters, PE can vary drastically, resulting in similarly sized pigs associated with differently sized placentas, up to a 25% weight difference. However, the mechanisms enabling the smaller placenta to grow a comparable littermate are unknown. To elucidate potential mechanisms, morphological measurements and gene expression profiles in placental and associated endometrial tissues of high PE and low PE feto-placental units were compared. Tissue samples were obtained from eight maternal line gilts during gestational day 95 ovario-hysterectomies. RNA was extracted from tissues of feto-placental units with the highest and lowest PE in each litter and sequenced.
Morphological measurements, except placental weight, were not different (P > 0.05) between high and low PE. No DEG were identified in the endometrium and 214 DEG were identified in the placenta (FDR < 0.1), of which 48% were upregulated and 52% were downregulated. Gene ontology (GO) analysis revealed that a large percentage of DEG were involved in catalytic activity, binding, transporter activity, metabolism, biological regulation, and localization. Four GO terms were enriched in the upregulated genes and no terms were enriched in the downregulated genes (FDR < 0.05). Eight statistically significant correlations (P < 0.05) were identified between the morphological measurements and DEG.
Morphological measures between high and low PE verified comparisons were of similarly sized pigs grown on different sized placentas, and indicated that any negative effects of a reduced placental size on fetal growth were not evident by day 95. The identification of DEG in the placenta, but absence of DEG in the endometrium confirmed that the placenta responds to the fetus. The GO analyses provided evidence that extremes of PE are differentially regulated, affecting components of placental transport capacity like nutrient transport and blood flow. However, alternative GO terms were identified, indicating the complexity of the relationship between placental and fetal weights. These findings support the use of PE as a marker of placental function and provide novel insight into the genetic control of PE, but further research is required to make PE production applicable.
胎盘效率（PE）描述了胎盘和胎儿体重之间的关系（胎儿重量/胎盘重量）。在同窝仔猪中，PE 差异很大，导致同样大小的猪具有不同大小的胎盘，最大差异可达 25%。然而，使较小胎盘能够生长出相当大小的同窝仔猪的机制尚不清楚。为了阐明潜在的机制，比较了高 PE 和低 PE 胎-胎盘单位的胎盘和相关子宫内膜组织的形态测量和基因表达谱。在 95 日龄卵巢-子宫切除术期间，从 8 头母系小母猪身上获得组织样本。从每个窝中 PE 最高和最低的胎-胎盘单位的组织中提取 RNA，并进行测序。
除胎盘重量外，高 PE 和低 PE 之间的形态测量值没有差异（P>0.05）。在内膜中没有发现差异表达基因（DEG），而在胎盘中共鉴定出 214 个 DEG（FDR<0.1），其中 48%上调，52%下调。基因本体论（GO）分析表明，大量 DEG 参与催化活性、结合、转运蛋白活性、代谢、生物调节和定位。上调基因中有 4 个 GO 术语富集，下调基因中没有术语富集（FDR<0.05）。在上调基因中鉴定出 8 个具有统计学意义的相关性（P<0.05），与形态测量值之间。
高 PE 和低 PE 之间的形态测量值验证了比较的结果是生长在不同大小胎盘上的同样大小的猪，并且表明到第 95 天，较小胎盘对胎儿生长的任何负面影响都不明显。胎盘中有 DEG 的鉴定，而子宫内膜中没有 DEG 的鉴定，证实了胎盘对胎儿的反应。GO 分析提供了证据，表明 PE 的极端情况受到不同的调节，影响了胎盘转运能力的组成部分，如营养物质转运和血流。然而，也确定了替代的 GO 术语，表明了胎盘和胎儿体重之间关系的复杂性。这些发现支持将 PE 用作胎盘功能的标志物，并为 PE 的遗传控制提供了新的见解，但需要进一步研究才能使 PE 生产具有实用性。
