Background
Expression of kisspeptin (protein) and Kiss1r (mRNA) was recently documented in the mouse uterus on D4 of pregnancy (the day of embryo implantation) suggesting that the uterine-based kisspeptin (KP)/kisspeptin receptor (KISS1R) signaling system regulates embryo implantation. Despite this important suggestion, it was never demonstrated that the uterus actually exhibits a functional KP/KISS1R signaling system on D4 of pregnancy. Thus, the goal of this study was to determine whether a functional KP/KISS1R signaling system exists in the mouse uterus on D4 of pregnancy. Findings: Since kisspeptin/KISS1R signaling triggers the phosphorylation of the mitogen-activated protein kinases p38 and ERK1/2, through immunohistochemical analyses, we determined whether exogenously administered kisspeptin could trigger p38 and ERK1/2 phosphorylation in the uterus on D4 of pregnancy. The
Conclusions
These results lead us to conclude that on D4 of pregnancy, the mouse uterus expresses a functional KP/KISS1R signaling system strengthening the possibility that this signaling system regulates embryo implantation. These findings strengthen the rationale for determining whether such a functional system exists in the uterus of the human female and if so, what role it might play in human pregnancy.