A comparison of mitochondrial and nuclear DNA status in testicular sperm from fertile men and those with obstructive azoospermia

Abstract

BACKGROUND: Mitochondria are vital to sperm as their motility powerhouses. They are also the only animal organelles with their own unique genome; encoding subunits for the complexes required for the electron transfer chain. METHODS: A modified long PCR technique was used to study mitochondrial DNA (mtDNA) in ejaculated and testicular sperm samples from fertile men undergoing vasectomy (n ⍧ 11) and testicular sperm from men with obstructive azoospermia (n ⍧ 25). Nuclear DNA (nDNA) fragmentation was measured by an alkaline gel electrophoresis (comet) assay. RESULTS: Wild-type mtDNA was detected in only 60% of fertile men's testicular sperm, 50% of their ejaculated sperm and 46% of testicular sperm from men with obstructive azoospermia. The incidence of mitochondrial deletions in testicular sperm of fertile and infertile men was not significantly different, but the mean size of the deletions was significantly less in testicular sperm from fertile men compared with men with obstructive azoospermia (P < 0.02). NDNA fragmentation in testicular sperm from fertile men and men with obstructive azoospermia was not significantly different. CONCLUSION: Multiple mtDNA deletions are common in testicular and ejaculated sperm from both fertile and infertile men. However, in males with obstructive azoospermia, the mtDNA deletions in testicular sperm are of a larger scale.Key words: human sperm/male infertility/mitochondrial and nuclear DNA/obstructive azoospermia/ROS

A multi-faceted approach to understanding male infertility: gene mutations, molecular defects and assisted reproductive techniques (ART)

“…Other studies have confirmed the persistence of multiple deletions in normozoospermic samples [139]. The ATPase6, ATPase8 and COII genes deletions have been reported previously in mtDNA of 49 asthenozoospermia patients [135]. However, there was a greater accumulation of multiple deletions present when the sperm quality was poor, with oligoasthenoteratozoospermic men harboring far more mtDNA deletions.…”

“…Recent reports have shown that mtDNA point mutations or multiple deletions, mtDNA single nucleotide polymorphisms (SNPs) and mtDNA haplogroups can greatly influence sperm quality and are associated with asthenozoospermia or oligoasthenozoospermia [128][129][130][131][132][133][134][135][136][137][138]. Among the mitochondrial deletions observed, the deletion of 4977 bp was the most prevalent and abundant one.…”

Testicular spermatozoa have statistically significantly lower DNA damage compared with ejaculated spermatozoa in patients with unsuccessful oral antioxidant treatment

“…In the study by O'Connell et al (32), 25 patients with obstructive azoospermia were shown to have lower nuclear DNA damage in testicular spermatozoa compared with spermatozoa from the proximal epididymis (16% and 26%, respectively) as assessed by an alkaline single-cell gel electrophoresis (Comet) assay. A negative effect of enzymes released from apoptotic and necrotic spermatozoa in the obstructed epididymis could be related to this damage.…”

Molecular Genetic of Human Male Infertility: From Genes to New Therapeutic Perspectives

“…Sperm motility and other parameters of sperm quality appear to be generally correlated with the intactness of the mitochondrial DNA sequence (mtDNA) since in infertile males mtDNA deletions have been found at a larger scale [188][189][190][191]. Recently, also an association between asthenozoospermia and a distinct mtDNA haplogroup T with some point mutations in mitochondrial t-RNAs was reported [192].…”