Prostaglandin F2α stimulates angiogenesis at the embryo-maternal interface during early pregnancy in the pig

Abstract

Blood vessel formation is a critical process for successful pregnancy establishment and placenta formation. Angiogenic factors such as vascular endothelial growth factor (VEGF), angiopoietins (ANGPTs) or fibroblast growth factor 2 (FGF2) are known to be involved in angiogenesis. However, the mechanism regulating their expression in the porcine endometrium and trophoblast has not been described during early pregnancy establishment. Recently, we reported an important role for prostaglandin F2α (PGF2α) in supporting processes accompanying the peri-implantation period in the pig. The aim of the present study was to determine the effect of PGF2α on angiogenic factor gene and protein expression at the embryo-maternal interface and on capillary-like structure formation by endometrial endothelial cells. In the present study, we used various in vitro models involving endometrial tissue explants, primary porcine trophoblast and endometrial endothelial cells, as well as a swine umbilical vein endothelial cell line (G1410). ANGPT1, ANGPT2 and FGF2 gene expression was analyzed in porcine endometrial explants and in primary trophoblast cells incubated with PGF2α (100 nM, 1 μM). VEGFA gene expression and protein secretion by porcine primary trophoblast cells were studied in vitro using primary trophoblast cells. A network formation assay using the G1410 cell line and primary endothelial cells of endometrial origin was performed to assess the effect of PGF2α on capillary-like structure formation. We found that PGF2α stimulated VEGFA gene expression (1 μM) and secretion of this protein (100 nM) by porcine trophoblast cells (P < 0.05). In endometrial explants, PGF2α increased the expression of the ANGPT1, ANGPT2 and FGF2 genes (P < 0.05). PGF2α stimulated the formation of capillary-like structures acting on porcine endometrial endothelial cells on days 15 and 20 of pregnancy and in the G1410 cell line (P < 0.05). PGF2α-stimulated endothelial cell network formation was diminished by using a MEK kinase inhibitor in G1410 cells. Our results indicate an important role for PGF2α in the regulation of angiogenesis at the embryo-maternal interface. PGF2α promotes angiogenesis in the porcine endometrium by activating the MAPK signaling pathway. The stimulating effect of PGF2α on the formation of capillary-like structures by endothelial cells, together with our previous findings, supports the hypothesis that PGF2α is an important factor promoting the development of the placenta during early pregnancy in the pig.

Keywords: Conceptus; Endometrium; Pig; Pregnancy; Prostaglandin F2α; Prostaglandin F2α receptor.