Effects of exogenous sexual hormones on the vaginal microbiota and immune cells in mice

Abstract

The effect of progesterone (P) and estradiol (E) on several organs of an experimental animal model was evaluated. 2-months-old female BALB/c mice were inoculated with (P) (day -5) or E (day -2) to induce and maintain the different stages of the estrous cycle. The samples taken on days 0, 2, 6 and 8 post-injection of hormones were: blood, vaginal fluid (VF), vagina, spleen and bone marrow (BM). Most of the animals remained in diestrous-metaestrous stages until day 6 post-P-injection or in proestrous-estrous stages until day 8 post-E-injection. The numbers of enterobacteria, staphylococci and lactic acid bacteria in VF were higher in estrogenized animals. In VF, myeloid population (Gr-1+) was dominant compared to T (CD3+) and B (B220+) lymphoid populations, determined by flow cytometry. On most of days, the Gr-1+ cells of VF were higher in estrogenized mice. The hormonal treatments did not produce significant differences in the myeloid and T cell populations of BM or spleen. Only in spleen, a significant increase of mature B cells (B220HighCD24Low) and a decrease of immature B cells (B220LowCD24High) were observed in P-inoculated mice compared with those E-inoculated. These results allow the selection of the most suitable experimental conditions to further evaluate the mechanisms of interaction between beneficial vaginal lactobacilli and the host in a murine experimental model.