Endometrial Hyperplasia Risk Is Increased by High-Fat Diet Via Estrogen-Driven Stromal Fibroblast Reprogramming Toward a Pro-Fibrotic State

The uterine endometrium is capable of scarless regeneration under coordinated estrogen and progesterone signaling across the menstrual cycle. Obesity suppresses progesterone production, leading to chronic estrogen exposure and increased endometrial hyperplasia (EH) risk. To define how obesity alters endometrial cell states, endometrial tissues from control and EH-predisposed mice fed either a control diet or a high-fat diet (HFD) were analyzed by single-cell RNA sequencing and tissue phenotyping. HFD reprogrammed endometrial stroma towards an inflammatory, pro-fibrotic state, reducing progesterone receptor-network-associated Aldh1a2+ fibroblasts and expanding estrogen receptor-network-associated Gsn fibroblasts. HFD further impaired macrophage recruitment and promoted hyperplastic epithelial signatures, consistent with increased disease severity in an EH mouse model. Stromal deletion of Estrogen Receptor established stromal estrogen signaling as a driver of HFD-induced extracellular matrix (ECM) accumulation. Collectively, these findings identify HFD-driven fibroblast reprogramming as a central mechanism linking estrogen dominance to stromal fibrosis, defective immune clearance, and heightened EH susceptibility. We propose that, in response to progesterone, fibroblast-mediated ECM remodeling is vital to normal endometrial homeostasis. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=161 SRC="FIGDIR/small/713224v1_ufig1.gif" ALT="Figure 1"> View larger version (47K): org.highwire.dtl.DTLVardef@125d0f7org.highwire.dtl.DTLVardef@1ba1714org.highwire.dtl.DTLVardef@41314borg.highwire.dtl.DTLVardef@b4585_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO HFD-induced estrogen dominance disrupts endometrial fibroblast homeostasis to predispose the endometrium to diseaseThis study demonstrates that HFD drives estrogen-dependent reprogramming of stromal fibroblasts, characterized by inflammation, stromal ECM accumulation and fibrosis, and a post-ovulatory shift from PGR-network-associated Aldh1a2+ Fibroblasts toward increasing ER-network-associated Gsn+ Fibroblasts. These fibroblast changes are accompanied by a reduction in endometrial macrophages and a transcriptomic shift of HFD epithelium toward hyperplastic epithelium seen in a mouse model of EH. Figure made with BioRender. C_FIG