Activated Vitamin D(3) and Pro-activated Vitamin D(3) Attenuate Induction of Permanent Changes Caused by Neonatal Estrogen Exposure in the Mouse Vagina

Exposure of mice to a high dose of estrogens including diethylstilbestrol (DES) during the neonatal period modifies the developmental plan of the genital tract, which leads to various permanent changes in physiology, morphology and gene expression. These changes include development of an abnormal vaginal epithelium lined with hyperplastic mucinous cells accompanied by Tff1 gene expression in mice. Here, the influence of vitamin D on the direct effect of estrogen on the developing mouse vagina was examined. The mid-vagina of neonatal mice was cultured in a serum-free medium containing estradiol-17β (E(2)) and various concentrations of 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D) ex vivo and then was transplanted under the renal capsule of ovariectomized host mice for 35 days. Exposure to E(2) alone caused the vaginal tissue to develop estrogen-independent epithelial hyperplasia and to express TFF1 mRNA, while addition of a low nanomolar amount of 1,25(OH)(2)D added at the same time as E(2) to the culture medium attenuated the effects of estrogen. Expression of vitamin D receptor was also evident in the neonatal mouse vagina. Interestingly, addition of 25-hydroxyvitamin D(3), a pro-activated form of vitamin D, at the micromolar level was found to be potent in disrupting the developmental effects of E(2), while cholecalciferol was not at least at the dose examined. Correspondingly, expression of Cyp27B1, a kidney-specific 25-hydroxyvitamin D hydroxylase, was evident in the neonatal mouse vagina when examined by RT-PCR. In addition, simultaneous administration of 1,25(OH)(2)D successfully attenuated DES-induced ovary-independent hyperplasia in the vagina in neonatal mice in vivo. Thus, manipulation of vitamin D influenced the harmful effects of estrogens on mouse vaginal development.