Testicular microbiome in azoospermic men-first evidence of the impact of an altered microenvironment.

Abstract

STUDY QUESTIONGiven the relevant role of the extracellular microenvironment in regulating tissue homeostasis, is testicular bacterial microbiome (BM) associated with germ cell aplasia in idiopathic non-obstructive azoospermia (iNOA)?SUMMARY ANSWERA steady increase of dysbiosis was observed among testis with normal spermatogenesis vs. iNOA with positive sperm retrieval and iNOA with complete germ cell aplasia.WHAT IS KNOWN ALREADYTissue-associated BM has been reported to be a biologically important extracellular microenvironment component for numerous body habitats, but not yet for the human testis.STUDY DESIGN, SIZE, DURATIONCross-sectional study, investigating tissue-associated BM in the testis of (i) five men with iNOA and negative sperm retrieval at microdissection testicular sperm extraction (microTESE); (ii) five men with iNOA and positive sperm retrieval at microTESE; and (iii) five normozoospermic men upon orchiectomy. Every testicular specimen was histologically classified and analyzed in terms of bacterial community.PARTICIPANTS/MATERIALS, SETTING, METHODSMassive ultra-deep pyrosequencing was applied to investigate testis microbiome. Metagenome was analyzed using Quantitative Insights Into Microbial Ecology (QIIME). Tissue-associated bacterial load was quantified by digital droplet PCR.MAIN RESULTS AND THE ROLE OF CHANCENormozoospermic men showed small amounts of bacteria in the testis, with Actinobacteria, Bacteroidetes, Firmicutes Proteobacteria as the dominating phyla; iNOA individuals had increased amounts of bacterial DNA (P = 0.02), associated with decreased taxa richness due to the lack of Bacteroidetes and Proteobacteria (P = 2 × 10−5). Specimens with negative sperm retrieval at microTESE depicted complete germ cell aplasia and a further decrease in terms of Firmicutes and Clostridia (P < 0.05), a complete lack of Peptoniphilus asaccharolyticus, but increased amount of Actinobacteria.LIMITATIONS, REASONS FOR CAUTIONThe limited number of specimens analyzed in this preliminary study deserves external validation. The paraneoplastic microenvironment could have an impact on the residential bacterial flora.WIDER IMPLICATION OF THE FINDINGSHuman testicular microenvironment is not microbiologically sterile, containing low amounts of Actinobacteria, Bacteroidetes, Firmicutes and Proteobacteria. A dysbiotic bacterial community was associated with iNOA and complete germ cell aplasia. Novel findings on testicular BM could support future translational therapies of male-factor infertility.STUDY FUNDING/COMPETING INTEREST(S)This work was supported by URI-Urological Research Institute free funds. Authors declared no conflict of interest.TRIAL REGISTRATION NUMBERN/A.