Uterine epithelial ERα regulates preimplantation uterine immunity and sperm fitness - Project Summary/Abstract: Key early pregnancy events include fertilization, embryo development and transport, and embryo implantation. A prerequisite for fertilization in a natural pregnancy is the timely migration of sperm through the uterus to the oviduct/Fallopian tube. A prerequisite for embryo implantation is the transient readiness of the uterus, especially the uterine luminal epithelium (LE), for embryo attachment to form the initial maternal-embryo interface. Sperm are allogeneic and an embryo is semi-allogeneic to the biological mother-to-be and allogeneic to a surrogate woman. How the uterine immune status is temporally regulated to provide a conducive environment for sperm and embryo during early pregnancy remains a significant knowledge gap. Estrogen receptor α (ERα/Esr1) me- diates E2 signaling in the uterus. ERα deficiency in the uterine epithelium of epiERα-/- (Esr1fl/-Wnt7aCre/+) mice leads to defective semen liquefaction thus impaired sperm migration to the oviduct for fertilization, as well as a disrupted uterine environment for embryos leading to failed early pregnancy. Our preliminary data demonstrated massive infiltration of neutrophils in the un-liquified semen in the day 0.5 post-coitum (D0.5) epiERα-/- uterine lumen and uterus. mRNA-seq of isolated LE cells from D0.5 and D3.5 Esr1fl/- (control) and epiERα-/- uteri revealed upregulation of innate immune response pathways in the D0.5 epiERα-/- LE. Foremost among these is the IL-1β signaling, a potent neutrophil chemoattractant, consistent with increased neutrophil infiltration noted above. By D3.5, ERα-dependent innate immune dysregulation diminishes. Collectively, these preliminary data implicate an essential role of uterine epithelial ERα in temporally regulating the uterine immune environment during early pregnancy. The cellular and molecular mechanisms by which uterine epithelial ERα regulates preimplantation uterine immune environment remain largely unexplored. Our long-term goal is to understand the mechanisms regulating uterine functions during early pregnancy thus helping alleviate uterine health and clinical issues re- lated to infertility and early pregnancy loss. The specific goal of this application is to use the epiERα-/- mouse model to elucidate mechanisms of uterine epithelial ERα in regulating the uterine immune environment for sperm fitness (D0.5) and for transition (D0.5-D3.5) to a favorable immune environment for embryo implantation. Our central hypothesis is that uterine epithelial ERα temporally regulates a conducive uterine immune environment to support early pregnancy events. This will be tested in two aims using the epiERα-/- mouse model coupled with molecular and immunological approaches. Aim 1. Determine the cellular and molecular mechanism(s) by which uterine epithelial ERα temporally orchestrates immune status in the preimplantation uterus. Aim 2. Determine the immunological mechanisms by which uterine epithelial ERα controls sperm fitness. Immunohistochemistry, flow cytometry, and neutrophil depletion are among the employed approaches. The proposed work is significant because understanding mechanisms regulating uterine immune environment is critical for developing diagnostic and therapeutic approaches to detect and treat infertility and early pregnancy loss.
