Expression of heparanase is associated with breed-specific morphological characters of placental folded bilayer between Yorkshire and Meishan pigs.

The pig has a noninvasive epitheliochorial placenta, and trophoblast-endometrial epithelial bilayer development could impact on placental function. This work compared the morphological structures, the cell proliferation status as assessed by Ki67 staining, as well as the location and gene and protein expression of heparanase (HPSE) at the maternal-fetal interface between Yorkshire and Meishan pigs on Days 26, 50, and 95 of gestation. Histomorphometry showed that the widths of placental folds, endometrial stroma, and placental stroma in Meishan pigs were smaller than those in Yorkshire pigs during late gestation, while the complexity and the cell proliferation ability of the folded bilayer were greater in Meishan pigs in this period. The location and expression levels of HPSE mRNA and protein at the maternal-fetal interface were similar between the two breeds during early and midgestation. However, during late gestation, the mRNA and protein levels were higher in Meishan placentae. In addition, the HPSE mRNA was expressed by all the trophoblast cells, and the protein was located both at trophoblast and luminal epithelium cells in Meishan pigs during late gestation, while in Yorkshire pigs, the HPSE mRNA and protein were only identified in trophoblast cells located at the bottom and side of folds. The findings suggest that Meishan pigs may rely more upon the increase in the complexity of the folded bilayer within a reduced placenta to expand the exchange surface area and the HPSE may contribute to the development of the folded bilayer in pigs.