Genetic insights into non-obstructive azoospermia: Implications for diagnosis and TESE outcomes

Abstract

Background: Non-obstructive azoospermia (NOA) is considered one of the most severe forms of male infertility. Despite the limited range of testicular phenotypes, NOA exhibits considerable genetic heterogeneity. The aim of this study was to uncover the etiopathogenesis of NOA and provide insights into the outcomes of testicular sperm extraction (TESE).

Material method: To elucidate the potential causes of testicular pathogenesis, a cohort of 61 patients was analyzed. The genetic etiology was assessed using our developed gene panel, based on genes with prior functional studies conducted specifically in the context of testicular characterization.

Results: Our analytical approach, built upon these findings, enabled us to explore the potential genetic causes of NOA and assess their relevance to TESE outcomes. A potential causal defect was identified in 14 genes across a total of 26 individuals (42%). Of these, three genes-MEIOB, TERB1, and USP26-had been previously described in men, while eight genes-SPO11, RBBP7, STS, RBMXL3, ZCCHC13, HUWE1, ESR1, and ABCD1-had been reported in prior studies. Additionally, three genes-CEP85, NAP1L3, and CENPI-had been previously described only in knockout (KO) phenotype studies, and this study represents the first identification of these genes in men.

Conclusion: Interestingly, the histological findings of meiotic arrest were strongly linked to genes involved in meiosis, reinforcing the clinical diagnosis of patients in this cohort. Additionally, our study underscores the importance of refining diagnostic strategies that focus on genes associated with testicular phenotypes, which could enhance the accuracy of TESE success predictions.

Keywords: Genetic heterogeneity; Meiotic arrest; Monogenic disorders; Non-obstructive azoospermia; TESE outcomes.

Fig. 1

A Predicted protein–protein interaction analysis of proteins encoded by the 175 candidate genes in the NOA panel using STRING. Legend: protein–protein interaction network and functional enrichment analysis of the 175 candidate genes encoded in the NOA panel, highlighting meiotic and DNA repair genes within the figure. b Literature-based overview of NOA testicular phenotypes

Fig. 2

a, b, c, d, and e Histological micrographs of testis biopsy samples. f Correlation between testicular histology and successful TESE outcomes. Legend: a Sertoli cell-only syndrome (SCOS): The tubules contain only Sertoli cells, with no germ cells present. b Maturation arrest at the primary spermatocyte stage (MA) is characterized by tubule structures where spermatogonial cells are positioned near the base of the tubules. c Post-meiotic arrest (post-MA): The image shows seminiferous tubule structures where no sperm are observed, but numerous spermatids are present. d Hypospermatogenesis (HS): Tubule structures where no complete tubule formation is observed, but a few sperm cells are present. e Normal spermatogenesis (NS): The image shows seminiferous tubule structures where cells in various stages of spermatogenesis are observed. Yellow arrow: basement membrane, black arrow: spermatogonia, green arrow: primary spermatocyte, red arrow: late spermatocyte, blue arrow: spermatozoon, circle: empty seminiferous tubule lumen, and ST, seminiferous tubule