Boos A, Janssen V, Mülling C
Institute of Veterinary Anatomy, University of Zurich, Winterthurerstrasse 260, CH-8057 Zurich, Switzerland.
Reproduction. 2003 Oct;126(4):469-80. doi: 10.1530/rep.0.1260469.
Placental growth can be achieved by either cellular proliferation or hypertrophy. Tissue regeneration and the nutrition of the fetus via embryotrophe require high rates of cellular turnover and the so-called pre-term 'maturation' of the placenta is correlated with a reduction of maternal crypt epithelial cells. Placentomes of 45 pregnant cows were collected from an abattoir to assess the role of proliferation and apoptosis in placental physiology and pathology. Placentomes were also taken from five cows undergoing premature Caesarean section and from ten naturally calving cows immediately after the expulsion of the fetus. Five of these animals had not released the fetal membranes after 12 h. Tissue sections of placentome were assessed for the Ki-67 protein; the TUNEL procedure was performed and verified by transmission electron microscopy. The maternal crypt epithelium and the fetal chorionic epithelium had a higher percentage of Ki-67-positive cells than the stroma. The percentage of Ki-67-positive cells increased significantly during pregnancy in fetal chorionic epithelium and was significantly decreased in fetal chorionic epithelium and maternal crypt epithelium after the expulsion of the fetus in comparison with tissue from month 9 of pregnancy. The number of apoptotic cells increased significantly during pregnancy in maternal crypt epithelium, maternal stroma and fetal chorionic epithelium as detected in slaughtered animals. Significantly more apoptotic fetal chorionic epithelial cells were found in animals retaining their fetal membranes in comparison with prepartum cattle during month 9 of pregnancy, at premature section and in animals releasing the fetal membranes completely. The results strongly indicate that bovine placentomes have cell type-specific rates of cellular turnover reflecting tissue growth, embryotrophe and placental maturation. Retention of fetal membranes is characterized by a large number of fetal chorionic epithelial cells undergoing apoptosis immediately after the expulsion of the fetus. This finding indicates that incomplete maturation of placentomes plays an important role in fetal membrane retention and that massive apoptosis after the expulsion of the fetus should be the consequence of diminished blood supply to the uterus, as verified in a recent study.
胎盘生长可通过细胞增殖或肥大实现。组织再生以及通过胚胎营养物质为胎儿提供营养需要较高的细胞更新率，而胎盘所谓的早产“成熟”与母体隐窝上皮细胞减少相关。从屠宰场收集了45头怀孕母牛的胎盘小叶，以评估增殖和凋亡在胎盘生理和病理中的作用。还从5头接受早产剖宫产的母牛以及10头自然分娩后立即排出胎儿的母牛身上获取了胎盘小叶。其中5头动物在12小时后仍未排出胎膜。对胎盘小叶的组织切片进行Ki-67蛋白评估；进行了TUNEL检测并通过透射电子显微镜进行了验证。母体隐窝上皮和胎儿绒毛膜上皮的Ki-67阳性细胞百分比高于基质。胎儿绒毛膜上皮中Ki-67阳性细胞百分比在怀孕期间显著增加，与妊娠9个月时的组织相比，胎儿排出后胎儿绒毛膜上皮和母体隐窝上皮中的Ki-67阳性细胞百分比显著降低。在屠宰动物中检测到，母体隐窝上皮、母体基质和胎儿绒毛膜上皮中的凋亡细胞数量在怀孕期间显著增加。与妊娠9个月时的产前母牛、早产剖宫产时以及完全排出胎膜的动物相比，在保留胎膜的动物中发现的凋亡胎儿绒毛膜上皮细胞明显更多。结果强烈表明，牛胎盘小叶具有反映组织生长、胚胎营养物质和胎盘成熟的细胞类型特异性细胞更新率。胎膜保留的特征是胎儿排出后大量胎儿绒毛膜上皮细胞立即发生凋亡。这一发现表明，胎盘小叶成熟不完全在胎膜保留中起重要作用，胎儿排出后大量凋亡应是子宫供血减少的结果，正如最近一项研究所证实的那样。
