Dysregulation of uterine fluid movement as a mechanism of contraception

Project Summary / Abstract Timely and coordinated hormonal levels are essential for establishing a natural early pregnancy. Therefore, hormonal contraceptives have been employed as a main approach for female contraception. Our lab has been studying uterine receptivity in mouse models. Uterine receptivity, a transient state in which the uterus can accept

an embryo to implant, is associated with two opposite major public health issues in reproductive women, infertility and contraception. Defective uterine receptivity is a key maternal factor for infertility while blocking uterine re- ceptivity is a main mechanism for female contraceptives. Although it is still not well-understood about the molec-

ular mechanism of how a uterus transforms into a receptive state for embryo implantation, it is well-established that progesterone (P4) signaling is essential for the establishment of uterine receptivity in all mammals studied. The action of P4 in the uterus is primarily mediated by progesterone receptor (PR), a nuclear transcription factor.

RU486 / Mifepristone is a mixed PR antagonist/agonist, has been used in numerous clinical applications, includ- ing in termination of early pregnancy and as an emergency contraceptive. Our dose-response and time-course study in mice, which have embryo attachment ~day 4.0 post-coitum (D4.0), reveals the inhibition/blockage of

embryo implantation by a single dose of RU486 (2-8 mg/kg) given on D2 @ 9 h ~ D3 @ 18 h, accompanied with excessive uterine fluid retention, prominently in the 4-8 mg/kg groups. Uterine fluid has not been systemically studied in infertile women. However, uterine fluid accumulation in hydrosalpinx patients and endometriosis pa-

tients is recognized to correlate with poor embryo implantation in IVF-ET. In mice, intraluminal infusion of non- toxic fluid (0.9% saline) impairs embryo implantation. These studies show the adverse effect of uterine fluid retention on embryo implantation. Since fluid retention is a “side effect” of hormonal contraceptives, and the

mechanisms for some of them, such as RU486, are not fully understood during different stages of early preg- nancy, we hypothesize that dysregulation of uterine fluid is a mechanism for hormonal contraceptives, such as RU486. We recently developed a novel method using Alexa Hydrazide (AH) to visualize uterine fluid absorption,

which is mainly through uterine luminal epithelium (LE) but not glandular epithelium (GE) during early pregnancy, and demonstrated the inhibition of uterine bulk absorption in D3.5 LE by 8 mg/kg RU486 treated on D1.5 and D2.5, supporting our hypothesis. Since uterine fluid movement is mainly through uterine epithelium and RU486

is a mixed PR antagonist/agonist, we have obtained a PR uterine epithelial conditional deletion mouse model, epiPR-/- (Pgrf/-Wnt7aCre/+), for testing the hypothesis in two aims. Aim 1. Determine time-course effects of RU486 on uterine fluid absorption during early pregnancy. Aim 2. Determine channels in fluid movement regulated by

RU486 during early pregnancy. The proposed research will add uterine fluid dysregulation as a mechanism for hormonal contraceptives and will provide molecular insights into channels in temporal uterine fluid dynamics during early pregnancy for contraception and for treating infertility related to uterine fluid dysregulation.