Epigenetic Disruption as a Molecular Signature in Idiopathic Nonobstructive Azoospermia

Idiopathic nonobstructive azoospermia (iNOA) is defined as the absence of sperm in the ejaculate with no identifiable cause after thorough physical, hormonal, and genetic evaluations. This study aimed to investigate the differential gene expression of key epigenetic regulators-<i>DNA methyltransferase (DNMT) 1 (DNMT1), DNMT3A, DNMT3B, and Zinc Finger CCHC-Type Containing 13 (ZCCHC13)</i>-in patients with iNOA compared with those with obstructive azoospermia (OA). Sixty infertile men diagnosed with azoospermia were equally divided into iNOA (case group) and OA (control group). Participants with iNOA were further subdivided into iNOA⁺ (successful sperm retrieval, <i>n</i> = 10) and iNOA⁻ (unsuccessful retrieval, <i>n</i> = 20) based on microdissection testicular sperm extraction (micro-TESE) outcomes. The relative expression of <i>DNMT1, DNMT3A, DNMT3B</i>, and <i>ZCCHC13</i> was analyzed in testicular tissue samples using quantitative real-time PCR. Expression levels of <i>DNMT1</i> and <i>ZCCHC13</i> were significantly lower in the iNOA group compared with OA (<i>p</i> = .01), while <i>DNMT3B</i> expression was significantly higher in iNOA, particularly in the iNOA⁻ subgroup (<i>p</i> < .0001). Receiver operating characteristic (ROC) analysis revealed DNMT3B had the highest diagnostic accuracy (AUC = 0.84, <i>p</i> < .0001), followed by ZCCHC13 (Area under the curve (AUC) = 0.69) and DNMT1 (AUC = 0.68). Our findings indicate that epigenetic dysregulation contributes to impaired spermatogenesis in iNOA, which can be molecularly distinguished from OA. Epigenetic biomarkers such as <i>DNMT3B</i> and <i>ZCCHC13</i> may offer reliable diagnostic tools for idiopathic cases of azoospermia and serve as potential targets for future epigenetic therapies.