Scientists have boosted the motility of sluggish sperm by up to 266%, by blasting the cells with noninvasive, 40-MHz ultrasound waves to induce movement. Capturing the technique's impact on individual sperm cells, the study opens the door to new non-invasive fertility treatments.
Encasing single sperm cells in microdroplets for the first time, researchers from Australia's Monash University have demonstrated how 20-second bursts of ultrasound 'revived' immotile sperm, spurring 59% of the treated individuals into action.
Assessing the 50 semen samples, which had been split into rapid, slow and immotile groups, together, the researchers found motility went from 64% before treatment to 90% following it. However, it remains unclear how sustained the increased activity is.
"This research by the Monash University Engineering team brings new hope to men with severe defects in sperm quality," said Associate Professor Luk Rombauts, Director of Clinical Research at Monash IVF. "The novel approach using ultrasound stimulation allows the movement of sperm to be enhanced by more than 250%. This opens up new treatment choices in particular for men who produce sperm that do not exhibit the usual swimming motion. In these men, it is difficult to distinguish between dead and immotile sperm."
Sperm motility is, of course, vital for improving the likelihood of successful fertilization, potentially reducing the need for expensive and invasive procedures such as intracytoplasmic sperm injection (ICSI). ICSI, in which a single sperm cell is injected directly into an extracted egg, is an extra, delicate and costly step during in vitro fertilization treatment. Boosting motility could help men with oligospermia – low sperm count – bypass this process.
"The ultrasound seems to result in a significant improvement in sperm motility," said Dr Frank Quinn, Medical Director for IVF Australia. "This technology would be useful for men with severe oligospermia and poor sperm motility and assist embryologists in selecting sperm to inject into eggs in IVF patients undergoing intracytoplasmic sperm injection. It would potentially be useful in couples who require surgical sperm retrieval to harvest sperm as part of an IVF treatment cycle. The sperm retrieved from testicular samples at best is only twitching and any device or application to increase sperm motility, and sperm selection and possibly enhance the outcome is enthusiastically monitored.
"My only concern is the study does not address how long the motility lasts for after the ultrasound has been applied," he added. "When eggs are inseminated with sperm as part of IVF treatment they need to remain motile for extended periods of time to fertilize the eggs."
The study suggests that the high-frequency treatment suspends any mitochondrial dysfunction, which can cause sluggish, poorly 'powered' sperm cells. While clinical application is a distant goal, the researchers now plan to investigate just how ultrasound affects cellular function in slow sperm, and whether motility in treated cells can be sustained.
"The new non-invasive technique that preserves sperm DNA integrity and viability provides IVF specialists with a better way to select healthy sperm," Rombauts said. "Improving sperm movement may also lead to better fertilization and embryo development rates and ultimately to more babies born, but this needs to be confirmed in further clinical studies."
The study was published in the journal Science Advances.
Source: Monash University via Scimex
