Comparison of large-scale deletions of the sperm mitochondrial DNA in normozoospermic and asthenoteratozoospermic men

Background and objectiveMitochondria play a crucial role in energy metabolism for the survival and motility of sperm during fertilization. The aim of this study was to determine the association of large-scale mitochondrial DNA deletions with abnormal sperm motility and morphology in asthenoteratozoospermic patients. Materials and methodsIn this case-control study, 41 semen samples were collected from 18 normozoospermic healthy men and 23 asthenoteratozoospermic patients, according to the WHO guidelines. The swim-up technique was used for separation of spermatozoa on the basis of their motility. Long-range polymerase chain reaction (PCR) was used for screening of mitochondrial DNA (mtDNA) large-scale deletions, and primer shift PCR was used for confirmation of deletions. ResultsThe mean sperm motility, normal morphology, and progressive motility in asthenoteratozoospermic patients were significantly lower than in the normozoospermic group (P<0.0001). There was a positive significant correlation between motility and normal sperm morphology (P<0.0001, r=0.741). The results of long-range PCR revealed the existence of 4866-bp deletion along with the two common 4977-bp and 7436-bp deleted mtDNA in both groups. However, the frequency of multiple mtDNA deletions in the asthenoteratozoospermic group (15/23, 65.22%) was significantly higher than that in the normozoospermic group (7/18, 38.89%). Direct sequencing of the 534-bp PCR product revealed that it was amplified from the mtDNA with a 4866-bp deletion flanked by a seven-nucleotide direct repeat (5-ACCCCCT-3). ConclusionsOur findings suggested that these large-scale deletions of mtDNA may be genetic risk factors for poor sperm quality in asthenoteratozoospermia-induced male infertility. Thus, it is necessary to understand the mechanisms behind the generation of these deletions.