Obesity-induced endometrial stromal cell fibrosis and immunosuppression leads to increased endometrial hyperplasia disease severity - PROJECT SUMMARY Endometrial hyperplasia (EH) is the benign proliferation of the endometrial epithelium, which can cause abnormal uterine bleeding and infertility. The hormone imbalance of increased estrogen levels relative to progesterone levels, referred to as unopposed estrogen, promotes EH. Obesity causes an unopposed estrogen state and therefore contributes to EH formation. Obesity is increasing in incidence and is expected to continue with approximately 50% of women predicted to be obese by 2030. Previous results found that mice with high-fat diet (HFD)-induced obesity had increased estrogen-to-progesterone levels, indicating an unopposed estrogen state, but the obese mice did not develop EH. Instead, endometrium from HFD-treated mice showed increased stromal cell fibrosis. Single-cell RNA sequencing of the HFD- versus control diet (CD)-treated uteri then displayed the highest number of differentially expressed genes (DEGs) in endometrial stromal cell clusters. The clusters’ DEGs were enriched for immune cell pathways, including HFD’s upregulation of CD47, which is an immunosuppressive cell surface molecule. PTEN mutation is commonly seen in women with EH. Mice with endometrial epithelial Pten mutation treated with HFD developed worsened EH compared to CD Pten-mutants. It is still unknown how obesity induces endometrial stroma fibrosis and if stromal cell-induced immunosuppression contributes to Pten- mutant EH development and progression. Therefore, the goal of this work is to understand the mechanism by which obesity induces endometrial stromal cell fibrosis in a normally scarlessly regenerating tissue and if inhibiting endometrial CD47-induced immunosuppression impedes EH. I hypothesize that obesity-driven unopposed estrogen increases stromal estrogen signaling, which induces stromal cell fibrosis and stimulates immunosuppression in the endometrial microenvironment to worsen EH disease severity. In Aim 1, I test this hypothesis by confirming estrogen’s involvement in the formation of endometrial stromal cell fibrosis. When inhibiting estrogen signaling in endometrial stromal cells of a genetically engineered mouse model (GEMM), we predict that HFD-associated fibrosis will be prevented. In Aim 2, I will use another GEMM to determine if removing the HFD-associated upregulation of CD47, increases immune cell activation and subsequent clearance of hyperplastic cells, therefore reducing EH severity. These proposed studies will better elucidate the obesity- induced stromal alterations that contribute to EH pathogenesis. These findings can then be used for the development of stromal-specific treatment targets to prevent EH disease formation and progression in women with obesity. This proposed work will greatly expand my technical expertise in genetic, molecular, and cellular reproductive science research. With the support of my sponsor, scientific advisory committee, graduate program, and department, these research experiences, in addition to professional development training, will provide me with the knowledge and tools I need to pursue an academic career in the reproductive sciences.
