CHARLOTTESVILLE, Va. (CBS19 NEWS) -- Researchers have learned something new about how sperm and egg fuse, which could have implications for couples that are facing infertility issues.
According to a release, the unexpected discovery occurred at the University of Virginia School of Medicine, and it has the potential to boost the success rate of in-vitro fertilization without costing as much.
“The infertility experts here at UVA are very excited about this,” said researcher Jeffrey J. Lysiak, PhD. “This tells us a lot about fundamental biology, but we think it could also have important clinical applications.”
The release says the discovery changes the previously held notions of the role of the egg in the fertilization process, saying the idea that the egg is a passive partner is wrong.
The researchers instead learned there are molecular substances on the egg's surface that bind to corresponding substances on the sperm and facilitate their fusion.
“High school biology taught us a very sperm-centric vision of fertilization,” said UVA researcher Kodi Ravichandran, PhD. “And now it's very clear that it is a dynamic process where both the sperm and egg are equally and actively involved in the ultimate biological goal of achieving fertilization.”
Ravichandran and Lysiak started working together a few years go when they were studying immature sperm and they found some that appeared to be dead, but weren't, had a molecular marker on their surface that normally suggests a cell is dying.
Instead, the marker on the sperm, which usually tells the body to remove the dying cell, has a different, important function during fertilization.
The marker is called phosphatidylserine or PS. It is normally held inside a cell until it dies, but not in this case.
Regarding the egg, there are protein partners on its surface that actively engage the PS, and this recognition, along with other chemical interactions, promotes the fusion of the sperm and the egg.
The release says masking the PS or preventing the receptors on the egg from recognizing it on the sperm blocked fertilization.
For couples that are struggling with infertility issues, their doctors may one day try to enhance the exposure of the marker on the sperm and promote the chances of conception.
Doctors could also examine the sperm before use in in-vitro fertilization to pick ones that will more likely result in pregnancy based on the presence of PS, which could help prevent the need for multiple attempts and reduce the cost couples incur in multiple attempts.
When a man currently goes in for infertility tests, a basic semen analysis primarily looks at the number of sperm present, how it looks and its mobility, but Lysiak says that does not give doctors any idea of the sperm's ability to actually fertilize an egg.
The researchers have now created a new test that will determine the fertilization fitness of the sperm based on the exposure of PS.
They also believe that finding a way to mask PS on the sperm could lead to a form of male contraceptive, saying they have tried a few different ways in the lab and they have been surprised at how well it has blocked fusion.
Ravichandran and Lysiak are planning to explore more questions related to fertilization and potential therapeutic applications, saying there are still many things that are understood about fertilization even about 100 years of research.
The findings have been published in the scientific journal Nature Communications.