The discovery applies not just to couples seeking care for infertility but also for the general population. This biomarker could become a more accurate predictor of male infertility than semen parameters, on which health care organizations and clinicians have long relied.
“Clinically, the diagnosis of male infertility really hasn’t changed in decades,” says UMass Amherst environmental epigeneticist Richard Pilsner, corresponding author of the study published in the journal Human Reproduction. “In the last 10 to 20 years, there have been major advances in the understanding of the molecular and cellular functions of sperm, but the clinical diagnosis hasn’t changed or caught up.”
Mitochondrial DNA is maternally inherited, and sperm mitochondrial DNA copy number (mtDNAcn) typically decreases eight-to-10 fold during spermatogenesis to ensure that it is low upon fertilization. The researchers accessed sperm samples from 501 couples from Michigan and Texas from 2005 to 2009 and found that men with higher sperm mtDNAcn had as much as 50% lower odds of cycle-specific pregnancy and 18% lower probability of pregnancy within 12 months.
“Remarkably, we saw a strong inverse association between sperm mitochondrial biomarkers and couples’ time-to-pregnancy,” Pilsner says. “Understanding what is causing the retention of mitochondrial copy number during spermatogenesis will help us come up with better platforms to intervene and to promote better reproductive success,” Pilsner says.