Developmental origin of vaginal epithelium

The developmental origin of vaginal epithelium has been controversial for nearly a century, with speculation that vaginal epithelium originates from the Mullerian duct, Wolffian duct, and/or urogenital sinus. None of these possibilities have been definitively proven or disproven by direct scientific data. To define precisely the origin of vaginal epithelium, epithelial cells of the Mullerian duct, Wolffian duct, or urogenital sinus were fluorescently labeled in mouse embryos by crossing tdTomato-EGFP dual-reporter transgenic mice with transgenic mouse lines that express Cre-recombinase in each type of epithelium. In embryos and newborn mice, the vagina consisted of fused Mullerian ducts plus the sinus vagina of urogenital sinus origin. However, the proportion of the sinus vagina was significantly reduced as the Mullerian vagina grew caudally. By postpartum day 7, the Mullerian vagina extended to the caudal end of the body, whereas the sinus vagina remained only at the junction between the vagina and perineal skin. As the vagina opened in puberty, urogenital sinus epithelium was detected only in the vulva, but not in the vagina. Additionally, from embryo to adult stages, residual Wolffian duct epithelium was present in the dorsolateral stromal wall of the vagina, but not within vaginal or vulvar epithelium. In conclusion, adult mouse vaginal epithelium is derived solely from Mullerian duct epithelium. (C) 2010 International Society of Differentiation. Published by Elsevier Ltd. All rights reserved.