The female upper reproductive tract of fertile women harbour endogenous microbial profiles

Abstract Study question Do the Fallopian Tubes from fertile women harbor microbial communities and are they similar to the endometrial microbiome? Summary answer Fallopian tubes have their own microbiome which is greatly shared with endometrial microbial profiles of the same women. What is known already The vaginal milieu is known to have an active microbiome (>90% of Lactobacillus), but the microbial composition of the upper reproductive tract is not well established, especially in the Fallopian tubes. The first studies on the Fallopian tubes from women diagnosed with a benign disease or for prophylaxis suggest that this site supports an endogenous microbiome (Pelzer ES et al Oncotarget 2018; Miles SM et al Fertil Steril 2017). However, today we lack the knowledge of the microbial composition in Fallopian tubes in the non-diseased conditions (as biopsing these sites may hamper the tissue and future fertility). Study design, size, duration A pilot-study with 6 fertile women with benign uterine pathology submitted to abdominal hysterectomy or tubal ligation at Hospital Universitario Virgen de Arrixaca Murcia were included into the study. The samples were collected between January and July 2019. Participants/materials, setting, methods Fallopian tubes and endometrial samples were collected as previously described (Canha-Gouveia A et al Int J Mol Sci 2019) from women submitted to abdominal hysterectomy and women submitted a tubal ligation. After DNA extraction “Ion 16S Metagenomics Kit” (Ion Torrent) was used to exploit the V5 to V9 regions of the 16S rRNA gene. Primary data analysis was performed with Torrent Suite™ Software v5.12.1 and advanced analysis using Ion Reporter™ software v5.18.0.2. Main results and the role of chance In our study, distinct microbial community profiles in the Fallopian tubes confirm that this genital tract site harbors an endogenous microbiome and in big part is shared with the endometrial microbial profile (over 60% of the detected taxa). Since in humans the intramural portion of the uterine tube does not allow a real physical separation between the fallopian tube and uterine environments, the obtained results were expected. Nevertheless, 43 bacterial taxa were exclusively detected in the Fallopian tubes (FDR<0.05) that included Abiotrophia, Aeromonas, Aggregatibacter Weissella, Wolinella, and Zoogloea among others. Limitations, reasons for caution This is a pilot study with a limited number of samples, and more studies with a bigger sample size are warranted. Wider implications of the findings Distinct microbial community profiles in the Fallopian tubes from the uterus suggest that this upper reproductive site supports an endogenous microbiome, which can play a role in the fertilization process. Trial registration number not applicable