3D sperm imaging could improve ICSI

A new three-dimensional (3D) imaging method can identify sperm moving at high speed and may help select the best sperm for use in assisted conception.

Researchers from Tel Aviv University have developed 3D imaging which provides new insights into the movement and structure of freely swimming individual human sperm cells.

'In our study, we sought to develop an entirely new type of imaging technology that would provide as much information as possible about individual sperm cells... and has the potential for enabling the selection of optimal sperm in fertilisation treatments,' said senior author Professor Natan Shaked.

In natural fertilisation, the egg is fertilised by the fastest sperm to reach it, and this competition is believed to ensure that sperm with the highest-quality genetic material are successful. When performing intracytoplasmic sperm injection (ICSI) clinical embryologists must try to select the best sperm to create a healthy embryo, but this not straightforward. Many existing imaging techniques carry the possibility of causing DNA damage, and so cannot be used to analyse the quality of the sperm in case mutations are caused and passed on to the offspring.  

The new method uses light computed tomography (CT) to image sperm cells. CT scanners in a medical environment take x-ray measurements while rotating around a subject, creating a 3D reconstruction of the body. 

To analyse sperm cells, the researchers took advantage of the natural dynamics of the sperm: while swimming forward, the head of a sperm is constantly rotating. Using harmless light instead of x-rays the team were able to create high-resolution, accurate 3D reconstructions of individual sperm cells, revealing details on the internal components and their correlation with the cell motion.

The method can also be used to assess male fertility by analysing the patient's live sperm. 

'To help diagnose male fertility problems, we intend to use our new technique to shed light on the relationship between the 3D movement, structure and contents of sperm and its ability to fertilise an egg and produce a viable pregnancy,' said Professor Shaked. 'The new technology can greatly improve the selection of sperm cells in vitro, potentially increasing the chance of pregnancy and the birth of a healthy baby.'

The study was published in Science Advances.