Vaginal epithelial estrogen receptor α coordinates glycogen deposition, microbial stability, and pH regulation in mice

Estrogen plays a central role in regulating the vaginal environment, but the specific contribution of epithelial estrogen receptor α (ESR1) to microbial and biochemical homeostasis has not been fully defined. In our previous work, we showed that epithelial ESR1 is indispensable for estrogen-induced epithelial proliferation, cornification, and MUC1 expression. Here, using mice with conditional deletion of Esr1 in vaginal epithelial cells, called epithelial Esr1d/d, we extend these findings to demonstrate that epithelial ESR1 also regulates glycogen deposition, luminal pH, and microbial stability. Compared to control littermates, epithelial Esr1d/d mice reduced glycogen abundance, elevated vaginal pH, and a compositional shift in the vaginal microbiome, marked by enrichment of Comamonadaceae and loss of Lactobacillus species, without significant differences in alpha diversity. These changes parallel features of postmenopausal dysbiosis in women. Together, our findings identify epithelial ESR1 as a master regulator of multiple pathways that sustain vaginal homeostasis, integrating epithelial metabolism, barrier function, and host-microbe interactions. This work provides a mechanistic framework to understand postmenopausal vaginal dysbiosis and suggests epithelial estrogen signaling as a potential therapeutic target for genitourinary syndrome of menopause.