Neonatal diethylstilbestrol exposure disrupts uterine epithelial apical-basal polarity and partial EMT state.

The developing female reproductive tract is highly sensitive to external hormonal stimulation, which can result in infertility and gynecologic diseases. To determine the underlying mechanisms, we used a mouse model to test the direct, cell type-specific effects of neonatal exposure to the estrogenic chemical, diethylstilbestrol (DES), on the developing uterus. We found that control uterine epithelium is in a partial epithelial-mesenchymal transition state that is lost following DES exposure. This is accompanied by evidence of premature differentiation including altered apical-basal cell polarity and absence of the Lgr5+ epithelial stem cell population required for uterine gland formation. Cell-cell communication between epithelial and mesenchymal cells is restructured, and Wnt signaling is aberrantly activated in the epithelium. The DES-exposed uterine mesenchyme has early signs of fibrosis through increased deposition of extracellular matrix (ECM) collagen. Mechanistically, DES exposure causes cell type-specific changes in chromatin accessibility and gene expression, most prominently in epithelial cells. These changes can be explained in part by cell-specific alterations in chromatin looping at enhancer regions in concert with alterations in ERα binding. These findings suggest that reprogramming cell type-specific differentiation trajectories and ECM characteristics underlie the long-term phenotypic effects of developmental exposure to DES and possibly other estrogenic endocrine disrupting chemicals. These changes lead to functional impairment of adult tissues and increased cancer risk.