Identifying male infertility problems early may soon be possible after scientists uncover a new way to predict male reproductive health and pregnancy success.
A team of researchers based at the University of Massachusetts Amherst in the United States have identified a biomarker in sperm mitochondrial DNA.
And they believe this could be a more accurate predictor of male infertility than testing the parameters of semen such as sperm count, volume and motility.
Dr Richard Pilsner, environmental epigeneticist and study author, said: “Clinically, the diagnosis of male infertility really hasn’t changed in decades.
“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.”
In his study, published in the journal Human Reproduction, Dr Pilsner worked with a team to study sperm mitochondrial DNA.
Mitochondrial DNA is generally inherited from the mother and so the number of sperm mitochondrial DNA (mtDNAcn) typically decreases eight-to-10 fold during the development of mature sperm to ensure that it is low by the time of fertilizsation.
Previous research by Dr Pilsner and Dr Whitcomb found increased mtDNAcn and mitochondrial DNA deletions (mtDNAdel) were associated with decreased semen quality and lower odds of fertilization in men seeking fertility treatment.
Dr Pilsner said: “The logical next step was to determine if the associations between sperm mitochondrial biomarkers and fertilization among couples seeking infertility treatment could be extended to couples from the general population.”
So the research team accessed sperm samples from the Longitudinal Investigation of Fertility and the Environment (LIFE) study, which recruited 501 couples from Michigan and Texas from 2005 to 2009 to examine the relationships between lifestyle, including environmental chemicals, and human fertility.
25 Siblings and Me — how a search for my sperm donor father led me to meet a whole family of brothers and sisters
They assessed sperm mtDNAcn and mtDNAdel from 384 semen samples and analysed their association with the probability of pregnancy within one year.
They found men with higher sperm mtDNAcn had as much as 50 per cent lower odds of cycle-specific pregnancy and 18 per cent lower probability of pregnancy within 12 months.
“Remarkably, we saw a strong inverse association between sperm mitochondrial biomarkers and couples’ time-to-pregnancy,” said Dr Pilsner.
“Mitochondrial DNA in sperm seems to reflect some underlying physiological phenomenon that affects sperm function”, added Dr Whitcomb.
Now the team plan to carry out further research to examine the impact of changes in mtDNAcn and mtDNAdel and to examine the factors which may bring about the changes in sperm mitochondrial DNA such as environmental toxins.
Dr Pilsner said: “We need to take advantage of our understanding of the molecular toolkit that we have to develop a better predictor of male fertility, as well as fecundability.
“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.”
Research, Sperm, Male reproductive system, Mitochondrion
World news – GB – Scientists believe they have found a new way to predict male infertility