Expression of vascular endothelial growth factor (VEGF) and placental growth factor (PIGF) in conceptus and endometrium during implantation in the rhesus monkey

The aim of this study was to analyse the expression of transcripts and proteins for vascular endothelial growth factor (VEGF) and placenta growth factor (PIGF) in different compartments of the early conceptus at primary implantation sites during lacunar (n = 6), early villous (n = 9) and villous placenta (n = 6) stages of gestation in the rhesus monkey. During the lacunar stage, VEGF expression was observed in the cytotrophoblast cells lining the extraembryonic cavity, but these cells did not express PIGF. With further development, cytotrophoblast cells lining villi, forming columns, and constituting anchoring villi, expressed both VEGF and PIGF during early villous and villous placenta stages. In addition, chorion, amnion and villous stromal cells expressed both VEGF and PIGF proteins and mRNA. During the lacunar stage, all epithelial cells in maternal endometrium generally expressed VEGF, while PIGF expression was observed in the plaque epithelium only. As gestation advanced, the expression of VEGF and PIGF from plaque cells decreased, and in surface and glandular epithelium the expression of VEGF increased, while the expression of PIGF remained unaltered. Decidual stromal cells expressed VEGF and PIGF only at low levels during the lacunar stage, while the expression of both increased during the early villous and the villous placenta stages of implantation. It appears from the present study that the expression of VEGF and PIGF are regulated in a temporal and spatial manner during early stages of implantation and that their concerted actions in placental and maternal compartments play a critical role in the evolving pregnancy in the rhesus monkey.