Signaling mechanisms that modulate uterine 3D structure for pregnancy success

PROJECT SUMMARY/ABSTRACT
Although much is known about the embryo during early development, the structural uterine
environment in which the early embryo develops is not well understood. A poor uterine environment at the time
of blastocyst entry and attachment can cause long lasting detrimental effects on the health of the growing
embryo, leading to defects such as miscarriage, placental insufficiency, intra-uterine growth restriction,
preeclampsia and preterm birth. Using confocal imaging in combination with 3D image analysis we have
identified and quantified dynamic changes in murine uterine luminal structure in preparation for implantation.
When applied to mouse mutants deficient in progesterone signaling, mice with excess progesterone signaling
or mice deficient in WNT5A signaling, with known molecular implantation defects, this approach reveals
striking abnormalities in uterine structure at the time of implantation.
The goal of this proposal is to determine, embryo and progesterone driven mechanisms that
guide uterine folding in preparation for embryo implantation and pregnancy success. In Aim 1 we will
determine how the embryo itself affects the 3D structure of the uterus. Using a time-course we will determine
the temporal pattern of fold formation along the mesometrial-anti mesometrial axis. We will determine if the
embryo is required as a physical object or as a biological signaling center to cause structural changes in the
uterine lumen. In Aim2 we will test the hypothesis that progesterone influences receptivity of the endometrium
by shaping uterine 3D structure. First we will assess endometrial folding in human subjects in both the
estrogen dominant proliferative and progesterone dominant secretory phase of the menstrual cycle. We will
then use physiological, supra-physiological progesterone treatment, and a mouse model of superovulation with
increased progesterone levels, to determine how progesterone regulates folding. We will also use mouse
mutants deficient in progesterone signaling to determine if progesterone regulates folding developmentally or
during early pregnancy. Studies in Aim 3 will determine if progesterone affects uterine luminal shape by
interacting with the WNT5A signaling pathway. We will also test if aberrant localization of embryos and
aberrant axis alignment, in aberrantly structured folds, explains the entirety of poor pregnancy outcomes in
aberrant folding mutants (superovulated and mutants deficient in WNT5A signaling).
The methods developed in this proposal will be crucial to analyze the uterine structure in three-
dimensions for different implantation-defective genetic mutants, pathological conditions, and will help uncover
novel molecular and structural pathways involved in successful implantation. The long-term vision of my
research is to identify novel uterine 3D structure based mechanisms that govern endometrial receptivity with
the goal of developing new approaches to improve fertility outcomes for assisted reproduction and potential
clinical situations for patients with hormonal disruptions.

Grant Number: 5R01HD109152-04
NIH Institute/Center: NIH
Principal Investigator: Ripla Arora