The rodent vaginal microbiome across the estrous cycle and the effect of genital nerve electrical stimulation

PLoS One. 2020 Mar 12;15(3):e0230170. doi: 10.1371/journal.pone.0230170. eCollection 2020.

Abstract

Treatment options are limited for the approximately 40% of postmenopausal women worldwide who suffer from female sexual dysfunction (FSD). Neural stimulation has shown potential as a treatment for genital arousal FSD, however the mechanisms for its improvement are unknown. One potential cause of some cases of genital arousal FSD are changes to the composition of the vaginal microbiota, which is associated with vulvovaginal atrophy. The primary hypothesis of this study was that neural stimulation may induce healthy changes in the vaginal microbiome, thereby improving genital arousal FSD symptoms. In this study we used healthy rats, which are a common animal model for sexual function, however the rat vaginal microbiome is understudied. Thus this study also sought to examine the composition of the rat vaginal microbiota. Treatment rats (n = 5) received 30 minutes of cutaneous electrical stimulation targeting the genital branch of the pudendal nerve, and Control animals (n = 4) had 30-minute sessions without stimulation. Vaginal lavage samples were taken during a 14-day baseline period including multiple estrous periods and after twice-weekly 30-minute sessions across a six-week trial period. Analysis of 16S rRNA gene sequences was used to characterize the rat vaginal microbiota in baseline samples and determine the effect of stimulation. We found that the rat vaginal microbiota is dominated by Proteobacteria, Firmicutes, and Actinobacteria, which changed in relative abundance during the estrous cycle and in relationship to each other. While the overall stimulation effects were unclear in these healthy rats, some Treatment animals had less alteration in microbiota composition between sequential samples than Control animals, suggesting that stimulation may help stabilize the vaginal microbiome. Future studies may consider additional physiological parameters, in addition to the microbiome composition, to further examine vaginal health and the effects of stimulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Arousal / physiology
  • Bacteria / genetics
  • Electric Stimulation / methods
  • Estrous Cycle / physiology*
  • Female
  • Microbiota / genetics
  • Pudendal Nerve / physiology*
  • RNA, Ribosomal, 16S / genetics
  • Rats
  • Rats, Sprague-Dawley
  • Rodentia / microbiology*
  • Vagina / microbiology*
  • Vagina / physiology*

Substances

  • RNA, Ribosomal, 16S

Grants and funding

This study was supported by a pilot grant from the University of Michigan Medical School Host Microbiome Initiative Microbiome Explorer Program to TMB and MBB. The funders provided expertise in study design and microbiome analysis as part of the Microbiome Explorer Program but did not influence the preparation of the manuscript or decision to publish. There was no additional external funding received for this study.