Ultrasound for speedy sperm

3 minute read

New research suggests a short burst of ultrasound could be all you need to shock sleepy sperm into action.

Slow swimmers may soon be a thing of the past, which could have significant impacts on IVF success rates.

A new Australian study, published in Science Advances, has shown just 20 seconds of ultrasound can increase sperm motility by up to 266%.

“This [study] has the potential to improve sperm function in the IVF laboratory setting so as to generate better fertilisation rates, embryo development and ultimately successful pregnancy,” said Professor Rob McLachlan, director of Andrology Australia.

Researchers from the department of mechanical and aerospace engineering at Monash University applied 20 seconds of 800mW and 40MHz ultrasonic exposure to individual sperm cells provided by three healthy donors, measuring a variety of sperm motility outcomes before and after the ultrasound treatment.

The ultrasound treatment improved sperm motility, based on the World Health Organization’s grading system. Sixty-one percent of nonprogressive or immotile sperm (straight-line swimming velocity less than 5μm/s) became slow progressive (between 5 and 25μm/s), and 11% became rapidly progressive (25μm/s or faster), while 47% of slow progressive sperm became rapidly progressive.

Over 80% of sperm cells also improved their curved line swimming velocity after ultrasound exposure. One particular sperm increased how far it could swim in 4.5 seconds from 4 to 140 micrometres after ultrasound – a 35-fold increase.

But the effects of ultrasound were most prominent in sperm cells that were completely immotile before treatment and began twitching – but not actually moving – after treatment. These cells experienced a 260% increase in their curved line swimming velocity, despite not increasing their straight-line velocity.

Researchers determined the ultrasound reduced the mitochondrial membrane potential of sperm cells, which could potentially be explained by increased ATP hydrolysis in the flagellum due to increasing how often the flagellum moved.

Having mobile sperm is a huge boost to the likelihood of conceiving, with pregnancy rates increasing 8% for every 10% increase in sperm motility. High sperm motility is also beneficial for patients considering assisted reproductive technology, as patients with more motile sperm can attempt traditional IVF rather than the more invasive intracytoplasmic sperm injection.

Current approaches for treating low sperm motility – drugs such as phosphodiesterase inhibitors – are toxic to the embryo and have potentially harmful effects on sperm, limiting their applicability in fertility clinics.

The potential for ultrasound to improve motility without any obvious side effects could reduce the costs associated with IVF and yield a greater number of higher-quality embryos, resulting in an overall improvement in IVF success rates, Associate Professor Alex Polyakov, an obstetrician, gynaecologist and fertility specialist from the University of Melbourne told media.

Professor Polyakov felt the results were “of great interest” but that it was crucial not to overestimate the technique’s utility.

“It is unclear whether a similar technique of stimulating the entire sperm sample with ultrasound waves would enhance the overall motility of the said sample,” he said.

Dr Frank Quinn, medical director of IVF Australia, agreed the results were encouraging, but also emphasised the importance of not putting the cart before the assisted conception horse.

“My only concern is the study does not address how long the motility lasts for after the ultrasound has been applied,” the Sydney-based gynaecologist and fertility specialist told media. 

“When eggs are inseminated with sperm as part of IVF treatment they need to remain motile for extended periods of time to fertilise the eggs. We don’t know and cannot assume this technology would improve outcomes with standard IVF.”

Science Advances 2024, online February 14

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