Submitted to: Society for the Study of Reproduction Annual Meeting
Publication Type: Abstract only
Publication Acceptance Date: 4/24/2006
Publication Date: 7/1/2006
Citation: Vallet, J.L., Freking, B.A. 2006. Comparison of placental microscopic fold development between large and small fetuses throughout gestation in swine [abstract]. Biology of Reproduction. (Supplement):163. (Abstract #409) Interpretive Summary:
Technical Abstract: Studies indicate that placental maternal and fetal blood flow occurs in a cross-countercurrent arrangement within microscopic folds of the maternal-fetal interface. Given this, widening the folded interface would increase the interaction between maternal and fetal blood. Experiments were undertaken to determine (1) whether the width of the folded pattern is altered in placenta of small fetuses, (2) whether hyaluronan is a component of the placental stroma, and (3) whether placental hyaluronan is altered in small fetuses. All gilts were unilaterally hysterectomized-ovariectomized (UHO) at 160 days of age and mated at estrus. In experiment one, gilts were killed on day 45, 65, 85 or 105, and sections of the uterine wall adjacent to the largest and smallest fetus in each litter were prepared for histology. The width of the folded interface and stromal layer above the folded interface were measured. The width of the folded interface increased and the width of the stromal layer decreased during gestation and was greater (P < 0.05) and less (P < 0.01), respectively, in placenta associated with the smallest fetus. To stain for hyaluronan, additional sections were treated with biotin-hyaluronan binding protein and avidin-peroxidase. Specific staining indicated that hyaluronan was a component of the placental stroma. In experiment two, 0.5 g placenta from the largest and smallest fetuses in each litter were collected from UHO gilts killed on days 25, 45, 65, 85 or 105 of gestation, homogenized in 10 ml 9.6 M urea, 5 mM K2CO3, 2% triton X-100, 0.5% dithiothreitol, and assayed for hyaluronan content. Hyaluronan increased from day 25 to 45 and day 85 to 105 and was greater (P < 0.05) in placenta from small fetuses on day 105. These results suggest that (1) increased width of the microscopic folds is a placental adaptation to reduced nutrient supply, (2) placental microscopic folds grow into the placental stroma and growth of each normally occurs simultaneously, and (3) in placenta of small fetuses, development of the stroma lags behind the microscopic folds, potentially limiting their development. These results suggest the hypothesis that disparate growth of the placental stroma and microscopic folds leads to failure of small fetuses to compensate for lack of nutrients, resulting in their loss during gestation.