Dysregulation of MTFR2, ATP5IF1 and BAK1 in Sertoli cells relates to idiopathic non-obstructive azoospermia via inhibiting mitochondrial fission and inducing mitochondrial dysfunction

Abstract

Non-obstructive azoospermia (NOA) affects more than 10% of infertile men with over 70% patients are idiopathic with uncharacterized molecular mechanisms which is referred as iNOA. In this study, we checked the morphology of Sertoli cell (SC) mitochondria in testis biopsies from patients with iNOA and patients with obstructive azoospermia (OA) who have normal spermiogenesis. The expression of 104 genes controlling mitochondria fission and fusion were analyzed in three gene expression datasets including a total of 60 patients with NOA. The levels of 7 candidate genes were detected in testis biopsies from 38 patients with iNOA and 24 patients with OA who have normal spermatogenesis by RT-qPCR. Cell viability, apoptosis, mitochondria membrane potential, ATP production, oxygen consumption and mitochondria morphology were examined in primary human SCs. Mouse spermatogonial stem cells (SSCs) were used to detect the cell supporting capacity of SCs. We observed that patients with iNOA had elongated mitochondria. MTFR2 and ATP5IF1 were downregulated, whereas BAK1 was upregulated in iNOA testis and SCs. SCs from patients with iNOA had reduced viability, mitochondria membrane potential, ATP production, oxygen consumption rate (OCR), glycolysis and increased apoptosis. Knockdown MTFR2 in SCs increased the mitochondria size. Knockdown ATP5IF1 did not change mitochondrial morphology but increased ATP hydrolysis. Overexpression of BAK1 reduced membrane potential and upregulated cell apoptosis. The dysregulation of all these three genes contributed to the dysfunction of SCs which provides a clue for iNOA treatment.