Researchers at the University of Toronto (U of T) said they have discovered that, depending on their environment, sperm can actually adapt the way they swim.
Reza Nosrati, a PhD candidate at U of T, said in the beginning, the team was interested in selecting better quality sperm with higher DNA integrity.
Based on their experience in microfluidics (manipulating the flow of fluids in small spaces), the team built a device with long channels through which they could “race” the sperm.
By watching the sperm swim through these channels, the researchers discovered they tend to swim extremely close to the surface.
This discovery led them to wonder whether or not swimming close to the surface changed the way they swim, Nosrati said.
With the use of total internal reflection fluorescence, the team was able to observe the sperm up close. What they discovered was the sperm swim close to the surface and move in a horizontal slither motion.
What this means is the sperm move side to side, similar to the way snakes move. Previously, sperm had only been observed swimming in a “corkscrew” motion, where the head and the tail of the sperm rotate.
The sperm that can perform this slither motion are better in terms of swimming capability and are able to swim about 50 per cent faster, Nosrati said.
However, “the ultimate role of the sperm is transferring genetic information,” Nosrati said.
It’s this DNA integrity the researchers are looking to test next, in order to see if the slithering sperm are better carriers of genetic information. This information could prove extremely beneficial to people undergoing fertility treatments, which relies heavily on the selection of sperm with high DNA quality that can produce a viable embryo.
“The next step is we want to basically test this population for . . . DNA integrity to make sure it’s the better sperm,” Nosrati said. “We’re already starting to look to collaborate with some actual fertility clinics to ultimately test the selected population if they are a better population, to see what is the fertilization ability of those sperm and then if you can make small improvements even in the success rate of assisted reproduction technologies.”
In order to do the research, samples of both human and bull semen were used.
“It’s easier to establish the method with bull samples, and then for the final stage you go to human and then you deal with the actual sample,” Nosrati said. “It’s important to also test the approach with human because that’s the main problem you want to deal with.”
Nosrati said the research could have a big impact for couples undergoing fertility treatments.
“Because the success rate is really low right now, most of the couples which go to these clinics for fertilization, they need to do a couple of trials to get the actual embryo and then to have a successful process, and it’s very costly and not only costly but painful—I mean painful mentally,” he said. “And if you look at the success rate of the fertility treatment, it’s kind of plateaued to 33 per cent over the past 20 to 30 years and it shows we need a different way to select the sperm, to do fertilization in order to have a better success rate. And we hope that we get there.”
