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Increased sperm mitochondrial DNA content in male infertility
P May-Panloup1, M-F Chrétien, F Savagner
1INSERM EMI-U 00-18, Laboratoire de Biochimie et Biologie Moléculaire, Laboratoire d'Histologie-Embryologie-Cytologie, UF de Biologie de la Reproduction, CHU d'Angers, F-49033 Angers, France.
Background:
There is increasing evidence that mitochondrial DNA (mtDNA) anomalies in sperm may lead to infertility. Point mutations, deletions and the presence of a specific mtDNA haplogroup have been associated with poor sperm quality, but little attention has been paid to the role of mtDNA content.
Methods:
Using density gradient separation and swim-up methods, we selected motile sperm from 32 normal and 35 abnormal sperm samples. The mtDNA/beta-globin gene ratio was determined by real-time quantitative PCR.
Results:
The average mtDNA/beta-globin ratio of sperm collected from 100% density layers was 1.4 for normal sperm, 6.1 for sperm samples presenting at least one abnormal criterion [among the three criteria established by World Health Organization (1999), i.e. sperm count, motility and morphology], and 9.1 for sperm samples presenting two or more of these abnormal criteria. These differences are very highly significant (P < 0.0001). The mtDNA numbers were also much greater in sperm collected from the 40% density gradient layers (mean: 17.1, P < 0.001), known to contain the most abnormal sperm of the sperm samples, than in those collected from the 100% layers known to contain sperm with the best fertilizing ability.
Conclusion:
Our results showed significant mtDNA amplification in sperm collected from abnormal sperm samples.