Exposure of juvenile female mice to isoflavone causes lowered expression of estrogen-related receptor gamma gene in vagina

In our previous study, the vaginal opening (VO) day of C57BL/6 mice was accelerated several days by chronic exposure to a 0.05% isoflavone (IF) fortified diet. The purpose of this study was to investigate whether the acceleration of VO by IF (1) has a critical window, (2) is modified by IF exposure combined with 17β-estradiol (E2), and (3) has any relation with gene expressions of estrogen-related receptors (ERRs). As a result, we determined that the critical window for the acceleration of VO was between 15 and 21 days postnatal. The combined effect of E2 and IF was thought to be additional in the acceleration of VO. The gene expression of ERRγ was significantly decreased in vagina by IF. The reduction of ERRγ may have two possible sequelae: disarrangement of vaginal development and high risk of vaginal cancer. In conclusion, IF exposure has a critical window for acceleration of VO and may have adverse effect on mouse vagina.