Scientists discover new way to isolate high-quality quality sperm to help improve IVF success rate

The past 50 years have seen a rise in infertility rates with one in every six couples experiencing the problem now. Though infertility is often incorrectly considered to be a women’s issue in many societies, experts suggest both men and women are equally responsible for the increasing rates. Low sperm count, poor sperm quality, reduced sperm motility and sperm DNA fragmentation are some of the possible causes of male infertility.

Though IVF (in vitro fertilization) and other assisted reproductive technologies are now available to help such couples conceive, the success rate of the procedure always comes down to the quality of the sperms and eggs.

Now, a group of researchers at Monash University, Australia say that acoustic waves and fluid dynamics can be used to isolate good quality sperm from a semen sample and increase the success rate of the IVF procedure.

The findings of the study are published in the peer-reviewed journal Lab on a Chip.

Sperm isolation for IVF and ICSI 

Sperm isolation is a crucial step in the IVF process. Normally, semen contains anywhere between 15 to 200 million sperms per mL. However, apart from sperm concentration and count, other factors like sperm motility and integrity of sperm DNA also play a role in the success of IVF procedures. Only the most motile and structurally intact sperms can reach the egg from the cervix and fertilise it.

During IVF, sperms are isolated from fresh ejaculate that is taken on the day of oocyte (immature egg cell) retrieval and about 50,000 to 100,000 sperms/mL of sample are used to fertilise the oocyte then. Low sperm count or quality would hence negatively affect the fertilisation rate.

In the case of ICSI (intracytoplasmic sperm injection), only a single isolated sperm is used to fertilise the oocyte in the lab. This sperm is isolated from the good-quality sperms that are initially separated from the raw semen sample. The whole process involves a series of steps including washing, centrifugation and then manual selection of the best quality sperm. It takes about three hours to complete.

Acoustic waves and their role in the new study

Acoustic waves are mechanical waves that occur when pressure travels through a medium -- either solid, liquid or gas. These waves can be perceived as sound by the human ear.

For the study, the researchers applied an acoustic field of 19.28 MHz and 1-2 W at an angle of 30 degrees in the direction of the flow of semen samples. They noted that the field separated good quality sperm from the main flow towards a small channel where they get collected, while the rest of the sperm stay in the mainstream sample.

The sperm that was isolated had a considerably increased motility — about 83 percent — as compared to the 62 percent motility in the original sample and the 36 percent motility in the sample that was left after the separation process.

Overall, about 50 to 60 percent improvement in sperm motility was observed. About 40 percent increment was also seen in the integrity of the sperm DNA.

The procedure, though new, was found to be pretty quick. It processed about 140 sperms every second and was able to isolate about 60,000 high-quality sperms in less than an hour. The current gold standard for sperm isolation is four times slower than this.

“We hope that with further testing, our acoustofluidic sperm selection process can provide new opportunities and be of benefit to the assisted reproduction industry, and help remove the fear, anxiety and negative stereotypes associated with infertility," said Dr Nosrati, supervisor of the study and a lecturer at the Department of Mechanical and Aerospace Engineering at the Monash University, in a news release by the University.

For more information, read our article on Infertility. 

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