Unraveling the genetic basis of azoospermia: transcriptome profiling analyses in a Greek population.

Objective: To investigate whether idiopathic nonobstructive azoospermia (iNOA) has its own transcriptomic signature.

Design: Testicular tissue biopsies were retrieved, processed, and prepared for ribonucleic acid (RNA) extraction from 26 consented patients diagnosed with iNOA. Samples were grouped into four pools based on the presence of testicular spermatozoa: two replicate pools for "No presence" (Null-spz-1 and Null-spz-2 pools), one for "High presence" (High-spz pool), and one for "Rare presence" (Rare-spz pool). A second set of replicate pools (CF-1 and CF-2) were used from patients with obstructive azoospermia (OA) and served as controls. RNA sequencing (RNA-seq) and comparative transcriptomics analysis were performed, followed by differential gene expression analysis focused on protein-coding genes only. Differentially expressed genes (DEGs) exclusively upregulated or downregulated were further analyzed using the Gene Ontology (GO), STRING, and Kyoto Encyclopedia of Genes and Genome bioinformatic platforms.

Setting: Private Fertility Clinic and Public University.

Patients: Males in whom iNOA was diagnosed.

Exposure: Testicular biopsies from men in whom iNOA was diagnosed.

Main outcome measures: Protein-coding DEGs.

Results: A significantly altered transcriptomic profile of protein-coding genes was identified in the testicular tissues from men with iNOA. A total of 3,858 genes exhibited dysregulated expression, with 1,994 genes being exclusively downregulated and 1,734 upregulated. Biological processes such as male gamete generation (GO:0048232) and meiotic cycle (GO:0051321) were significantly enriched by the downregulated DEGs whereas the upregulated DEGs enriched BPs such as regulation of cell death (GO:0010941), regulation of cell adhesion (GO:0030155), and defense response (GO:0006952). Interactome analysis identified hub genes among the downregulated DEGs, including PCNA, PLK1, MCM4, CDK1, CCNB1, AURKA, CCNA2, and CDC6, and among the upregulated DEGs, including EGFR, RELA, CTNNB1, MYC, JUN, SMAD3, STAT3 NFKB1, TGFB1, and ACTB. In addition, Kyoto Encyclopedia of Genes and Genome analysis demonstrated that pathways such as cell cycle (hsa04110) and oocyte meiosis (hsa04114) are primarily affected by the downregulated genes, whereas the upregulated genes mainly affected pathways such as the focal adhesion (hsa04510) and the PI3-Akt signaling pathway (hsa04151).

Conclusion: A distinct messenger RNA expression profile and altered transcriptomic activity were identified in the testicular tissues of men with iNOA.

Clinical trial registration number: University of Thessaly 1, 15.04.2016 and the Greek National Authority 701/15.9.2017.