Testicular microbiome in infertile men.
Authors:   the Department of Endoscopic Urology, Faculty of Pediatric Urology, RUDN University, Kadyrov Z.A. ,   Moscow, Russia, Faniev M.V. ,   the Department of Endoscopic Urology of the Department of Endoscopic Urology, RUDN University; Krasnodar, Russia, Prokopyev Ya.V. ,   the Department of Urology and Nephrology of the Kazan State Medical Academia – branch of the Federal State Budgetary Educational Institution of Further Professional Education of the Russian Medical Academy of Postgraduate Education of the Ministry of Health of the Russian Federation; Kazan, Russia, Faustova K.V. ,   the Department of Obstetrics and Gynecology of the Kazan State Medical Academia – branch of the Federal State Budgetary Educational Institution of Further Professional Education of the Russian Medical Academy of Post- graduate Education of the Ministry of Health of the Russian Federation; Kazan, Russia, Vodolazhsky D.I. ,   the laboratory of cell technologies of the Central Scientific Research Laboratory of the Medical Academy named after S.I. Georgievsky at Сrimea Federal University named after V.I. Vernadsky; Simferopol, Russia
Published: November 2023

Introduction. The concept of microbiome is a collective term for many microorganisms, such as bacteria, archaea, fungi, protists, and viruses, inhabiting various anatomical areas of the human body. The relevance of studying their quantitative and qualitative relationships is associated with the size of microbial populations, as well as the lack of awareness of the modern scientific community about the true role of most of them, including the connection between the microbiome diversity of male testicles and sperm with the presence of azoospermia and the development of idiopathic variants of infertility. The purpose: identification of the composition of the microbiome of testicular tissue in infertile men and determination of its clinical significance. Studying the influence of microbial populations of the urogenital tract of men on the development and course of diseases associated with infertility, such as azoospermia. Materials and methods. A literature review was performed based on data published in the PubMed (https://www.ncbi.nlm.nih.gov/pubmed/) and Scientific Electronic Library eLibrary.ru (https://elibrary.ru/) databases. The search was carried out using the following keywords: microbiome; microbiota; testicular tissue; azoospermia; sequencing; genome; male infertility. A total of 167 sources were analyzed. For this publication, 48 publications were selected. Results. Lactobacillus iners, Gardnerella vaginalis, Escherichia faecalis, Escherichia coli and Staphylococcus aureus are associated with the development of non-obstructive azoospermia. In men with different forms of azoospermia, a greater number of Bacteroidetes and Firmicutes phyla were observed, while Proteobacteria and Actinobacteria were significantly less common compared to healthy controls. Also, the microbial diversity between obstructive azoospermia (OA) and non-obstructive azoospermia (NOA) had a higher degree of similarity than the control group. Interestingly, the microbiome modifications found in men with NOA are similar to those previously identified in the gut of older adults, which can be considered as further evidence of microbiologically early aging of NOA men at the testicular level. Conclusions. Microbiome analysis demonstrated for the first time that human testicular tissue is not a microbiologically sterile environment, and also provided new data on the bacteriological composition of the male urogenital tract and allowed us to consider excluding any potential contribution of microbial communities present in neighboring anatomical regions. Therefore, larger studies are needed to confirm our preliminary findings that the testes of azoospermic men contain a more dysbiotic bacterial community.