Blasting sluggish sperm with ultrasound waves gets them moving

Exposing immobile sperm to ultrasound waves gets them moving, a lab study has shown. Sperm that don’t move properly are a key cause of infertility, as it is harder for them to reach the egg. With further research, this technique could help improve the success rate of in vitro fertilisation (IVF).

Previous research has suggested that high-frequency ultrasound increases the motility of sperm. However, this work didn’t involve isolating the sperm to assess which individual cells benefited, which could then point doctors towards the optimal ones to use in fertility treatments.

In the latest research, Ali Vafaie and his colleagues at Monash University in Melbourne, Australia, separated 50 semen samples into three groups according to their sperm motility: rapid, slow and immotile, based on guidelines that assess swimming velocity.

After separating the individual sperm cells from the semen samples, the researchers measured the motility of the cells before and after they were exposed to ultrasonic sound waves at a power of 800 milliwatts and a frequency of 40 megahertz.

Following 20 seconds of ultrasound exposure, 59 per cent of the immotile sperm became slow moving, with some even starting to swim rapidly. The change in sperm motility peaked at a 266 per cent increase.

Overall, immotile sperm made up 36 per cent of the samples at the start of the study, declining to just 10 per cent post-treatment. It is unclear how long the increase in movement lasted.

The researchers think exposure to ultrasound improves any dysfunction in the sperm’s mitochondria, the power stations of cells, which contributes to their improved motility.

The approach may one day increase the success of IVF, which requires motile sperm for conception, potentially avoiding the need for multiple costly rounds of the procedure.

But first, Vafaie says a research group would need to test the effectiveness of the approach on sperm from those who are experiencing infertility due to poor sperm mobility specifically. Scientists also need to assess whether it is safe to create embryos from ultrasound-exposed sperm, he says.