Potential biomarkers of infertility associated with microbiome imbalances

The aim of this study was to investigate the possible relationship between vaginal/rectal microbiome disbalances and miRNA expression with infertility.

Observational, exploratory, preliminary study. A total of 287 multiple IVF failure infertile patients were recruited. Twenty fertile women, not IVF failure, were recruited as the control group. Swab samples were collected from the vagina and rectum. Microbial composition by NGS and miRNA expression by real-time PCR of vaginal and rectal samples was measured. Immunometabolic markers from blood (insulin, vitamin D, LDL-cholesterol, ANA, TPO, Tg, and ASCA antibodies) and saliva (sIgA) were analyzed.

Infertile patients showed a lower bacterial richness and increased Firmicutes/Bacteroidetes ratio at rectal level and an increased Lactobacillus brevis/Lactobacillus iners ratio in vaginal samples regarding the fertile group. In the same rectal swab samples, we found that miR-21-5p, which is associated with tight junction disruption and yeast overgrowth, is upregulated and that miR-155-5p, which is associated with inflammation, is overexpressed in the unexplained infertile group (*p < .05). These deregulated miRNAs were also upregulated in the vaginal samples from the same patients (*p < .05).

miRNAs could be potential biomarkers of the inflammatory impact of microbiome disbalances in unexplained infertile women.