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.

IL-17A deficiency alleviate fluoride-induced injury by inhibiting immune response and apoptosis in testis

“…Testes have established effective self-protection through its immunosuppressive microenvironment, which is free from pathogens and in ammatory damage [40]. Once the microenvironment of the testes is imbalanced, it may lead to the occurrence of in ammation and lesion [41]. The overexpression of IL-17A, IL-6, IL-1β, and IL-23 may change the immunosuppressive microenvironment of the testes, causing testicular damage.…”

High prevalence of urogenital infection/inflammation in patients with azoospermia does not impede surgical sperm retrieval

“…As an immune‐privileged organ due to the blood–testis barrier, testicular tissue is generally believed to be sterile. However, just recently, a microbiome study evaluating testicular tissue from azoospermic and testicular cancer patients revealed that many different bacterial classes can be detected by NGS (Alfano et al, ). Of further interest was the fact that the amount of bacterial DNA was increased in patients with NOA compared to those with normal spermatogenesis (Alfano et al, ).…”

“…However, just recently, a microbiome study evaluating testicular tissue from azoospermic and testicular cancer patients revealed that many different bacterial classes can be detected by NGS (Alfano et al, ). Of further interest was the fact that the amount of bacterial DNA was increased in patients with NOA compared to those with normal spermatogenesis (Alfano et al, ). Finally, no significant differences were identified in NOA patients with positive sperm retrieval ( n = 5) and those without ( n = 5; Alfano et al, ).…”

“…Of further interest was the fact that the amount of bacterial DNA was increased in patients with NOA compared to those with normal spermatogenesis (Alfano et al, ). Finally, no significant differences were identified in NOA patients with positive sperm retrieval ( n = 5) and those without ( n = 5; Alfano et al, ). Although we did not apply NGS, we were never able to identify any pathogens in testicular swabs and testicular tissue by sensitive 16S rDNA analysis, except for one swab sample which was positive for Enterobacter cloacae and Leclercia adecarboxylata although the corresponding testicular tissue was negative.…”

“…Notably, in asymptomatic azoospermic patients undergoing testicular sperm extraction (TESE), histological analysis reveals focal immune cell infiltrates in the interstitial compartment in about 30% of cases (Chen, Duan, Haidl, & Allam, ; Fijak et al, ). However, only a few studies investigated pathogens in testicular tissues and provided suggestive evidence that the testis is not sterile (Alfano et al, ; Erles et al, ; Martorell et al, ; Sripada et al, ). In addition, it should be considered that various bacterial and viral species with undefined pathogenicity are detected in the semen of healthy males and patients presenting with sub/infertility (Mandar, Turk, Korrovits, Ausmees, & Punab, ; Neofytou, Sourvinos, Asmarianaki, Spandidos, & Makrigiannakis, ).…”