Mutual communications between RhoA signaling and P4 signaling in luteal cells and the uterus during early pregnancy

Project Summary / Abstract Embryo implantation is an essential step for mammalian pregnancy. It requires timely mutual communication between a competent embryo and a transiently receptive uterus, in which progesterone (P4) and P4 receptor (PR) play an essential role. The first physical embryo-maternal interaction is established between trophoblasts and uterine luminal epithelial (LE) cells during embryo attachment for implantation initiation (~day 4.0 post-coitum (D4.0) in mice). How the LE senses the embryo remains largely unknown. RhoA is one of the most highly expressed genes in D3.5 and D4.5 mouse LE. RhoA is a GTPase with mechanosensing function. It is detected intensely in the apical membrane of D3.5 LE, the initial contact of an implanting embryo, and luteal cells, the site of P4 production during early pregnancy. RhoA uterine conditional knockout RhoAf/fPgrCre/+ (RhoAd/d) mice have P4 deficiency with diminished expression of StAR (the rate-limiting protein for P4 synthesis) in the luteal cells and embryo implantation failure. Exogenous P4 treatment upregulated StAR expression in the RhoAd/d luteal cells and partially rescued embryo implantation in the RhoAd/d mice, indicating that RhoA regulates P4 production and P4 can partially compensate for luteal cell StAR-deficiency and embryo implantation failure in the RhoAd/d mice. The mechanisms for P4-RhoA crosstalk remain unknown. To circumvent P4 deficiency in RhoAd/d mice, I ovariectomized RhoAf/f (control) and RhoAd/d mice and treated them with vehicle, P4, E2, or E2 + P4 for 24 hours. Masson’s Trichrome staining reveals altered responses to P4 in the ovariectomized RhoAd/d uterus. Based on literature and my preliminary data, I hypothesize that RhoA signaling and P4-PR signaling crosstalk in luteal cells and uterine endometrium to regulate embryo implantation. This hypothesis is being tested in two Specific Aims to determine mutual regulations of RhoA signaling and P4-PR signaling in the luteal cells for P4 synthesis (Aim 1) and in the uterus for establishing uterine receptivity (Aim 2), respectively. RhoAd/d in vivo mouse model, in vitro models of luteinized human granulosa-lutein cells and human uterine epithelial (UE) organoids coupled with 3D microfluidic female reproductive system (FRT)-on-a-chip, as well as pharmacological approaches will be employed. The successful completion of the ongoing and proposed studies in my F31 application will provide a comprehensive picture of interplays between two important signaling pathways, RhoA signaling and P4-PR signaling, in the luteal cells and uterine cells in regulating early pregnancy. It will also give insights into potential therapeutic targets to treat infertility and early pregnancy loss due to ovarian and uterine dysregulation. The fellowship training will take place at the University of Georgia in Dr. Xiaoqin Ye’s lab, which has the suitable environment (e.g., expertise, funding, equipment, etc.) for personal and professional growth. The training plan will also include dissemination of research at conferences and via publications to build my presentation skills, weekly reports and lab meeting presentations to improve my time and project management skills, as well as training for mentoring and leadership skills to foster my development as a well-rounded scientist.