Hedgehog signaling in the maintenance of endometrial thickness and pregnancy - proposal summary the inner lining of the uterus, the endometrium, is an important determinant of gestational outcomes…

The National Institute of Child Health and Human Development awarded The Regents of the University of Colorado (University of Colorado-Denver) $124,125 on June 1, 2026, under the Child Health and Human Development Extramural Research program (CFDA 93.865) to investigate the role of the Hedgehog signaling pathway—specifically GLI2—in endometrial remodeling and placental development.

The project uses a mouse model with conditionally deleted uterine GLI2 to examine how the Hedgehog signaling pathway maintains endometrial thickness and supports successful pregnancy. Preliminary data demonstrates that GLI2 deficiency results in abnormal endometrial expansion during the estrous cycle, producing a thin endometrium. Although GLI2-deficient animals remain fertile, they produce smaller litters than controls. The research will determine whether subfertility occurs after implantation and before birth, closing a knowledge gap in understanding how cell signaling pathways other than steroid hormone signaling regulate endometrial thickening. The work addresses human clinical relevance: thin endometrium in humans increases risk for miscarriage, preterm delivery, and low birth weight, yet the underlying molecular mechanisms remain unknown.

Performance runs from June 1, 2026, through January 31, 2029, at the University of Colorado-Denver campus in Aurora, Colorado. The award is classified as a Project Grant, a form of assistance funding.

Hedgehog signaling in the maintenance of endometrial thickness and pregnancy - proposal summary the inner lining of the uterus, the endometrium, is an important determinant of gestational outcomes even prior to the implantation of an embryo. In humans, a thin endometrium increases risk for miscarriage, preterm delivery, and low birth weight. Currently, IT is unknown what causes a thin endometrium and how IT leads to the later gestational outcomes. Much of what is currently known about the endometrium relates to how the epithelium and underlying stroma respond to steroid hormone signals. We know substantially less about what other downstream cell signaling occurs to thicken the endometrium. Members of the hedgehog (HH) signaling pathway, including GLI2, change expression dramatically across the 4-7 day mouse estrous (menstrual) cycle and are known to have important roles in implantation. Prior work in the field has shown that decreased GLI2 expression in mouse placentas results in decreased blood flow to the fetus and changes in the structure of the labyrinth layer of the placenta. There is also decreased GLI2 expression in human placentas affected by preeclampsia. However, the cell and molecular role of GLI2 in either the cycling endometrium or gestational success is largely unknown. Therefore, the overarching objective of this proposal is to close this knowledge GAP by investigating the role of GLI2 in endometrial remodeling and placental development. In order to accomplish this, we developed a mouse model with conditionally deleted uterine GLI2. My preliminary data shows that the endometrium does not expand normally during the estrous cycle, resulting in a thin endometrium. These animals are still able to produce offspring, but each litter has fewer pups compared to controls. My preliminary work also shows that GLI2 deficiency does not affect the initial number of implantation sites, so the subfertility is likely occurring after implantation and before birth. Therefore, my central hypothesis is that GLI2 is necessary for supporting gestation by regulating cell proliferation at three important times: in the cycling uterus, at decidualization, and during syncytiotrophoblast expansion. To test this hypothesis, i will conditionally delete GLI2 in the uterus and in the placenta. In aim 1, i will use high-resolution imaging to analyze stromal and decidual proliferation at two estrous cycle phases and gestational timepoints, respectively, in order to identify perturbations with loss of uterine GLI2. Aim 2 will utilize the placenta-specific knockout of GLI2 to assess changes to fertility when endometrial GLI2 remains intact. I will also use this placenta GLI2 ablation model to measure proliferation of syncytiotrophoblasts, a key placental labyrinth cell type, using imaging techniques congruent to aim 1. Collectively, these data will significantly advance our understanding of the cell signaling underlying endometrial thickness and ability to maintain gestation. Additionally, IT will describe GLI2 as a common factor that is necessary in both endometrial and placental functions to prevent gestational failure. This proposal will have broad implications in understanding how a thin endometrium occurs and subsequently contributes to unfavorable gestational outcomes.