TAU identifies method to increase chances of pregnancy through IVF

Doctors will be able to-select healthiest sperm for artificial insemination

Tel Aviv University (TAU) researchers established a method to track fast-moving sperm using 3D imaging technology both safely and accurately, according to a recent study published in Science Advances – a method which the study’s authors claim could help with in vitro fertilization (IVF) processes.

With the new advances, fertility doctors will be able to hand-select the healthiest and best-quality sperm for injection, increasing a woman’s chance of becoming pregnant and giving birth through artificial insemination.

“The IVF procedure was invented to help fertility problems,” explains Prof. Natan Shaked of the Department of Biomedical Engineering at TAU’s Faculty of Engineering, one of the study’s authors. “The most common type of IVF today is intra-cytoplasmic sperm injection (ICSI), which involves sperm selection by a clinical embryologist and injection into the woman’s egg. To that end, an effort is made to select the sperm cell that is most likely to create a healthy embryo.”

The selection of tracking high-speed moving sperm was made because during natural fertilization, the fastest sperm to navigate its way through a woman’s reproductive system to the egg normally “bears high-quality genetic material.”

“But this ‘natural selection’ is not available to the embryologist, who selects a sperm and injects it into the egg,” Prof. Shaked says. “Sperm cells not only move fast, they are also mostly transparent under regular light microscopy, and cell staining is not allowed in human IVF. Existing imaging technology that can examine the quality of the sperm’s genetic material may cause embryonic damage, so that too is prohibited. In the absence of more precise criteria, sperm cells are selected primarily according to external characteristics and their motility while swimming in water in a dish, which is very different from the natural environment of a woman’s body.

“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, does not require cell staining to enhance contrast, and has the potential for enabling the selection of optimal sperm in fertilization treatments.”

Shaked, alongside TAU doctoral student Gili Dardikman-Yoffe, chose to use light computed tomography (CT) technology to identify and track sperm cells for IVF treatment.

“We used weak light [and not X-rays], which does not damage the cell. We recorded a hologram of the sperm cell during ultrafast movement and identified various internal components according to their refractive index. This creates an accurate, highly dynamic 3D map of its contents without using cell staining,” said Shaked, adding that in standard CT scans the device rotates around the subject to get an accurate reading, but the sperms natural process of rotating to get momentum allows embryologists to use the method from a single vantage point and still be successful.

Using the technology, the researchers were able to obtain a clear four-dimensional image of the sperm – three dimensions with an accurate resolution down to less than half a micron and the speed that it is moving in down to the second sub-millisecond.

“Our new development provides a comprehensive solution to many known problems of sperm imaging,” Prof. Shaked says. “We were able to create high-resolution imaging of the sperm head while it was moving fast, without the need for stains that could harm the embryo. 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 TAU researchers also intend to attune the new processes to diagnose male fertility issues, and somewhere down the line they are hopeful the technology can be used to develop biomimetic micro-robots to carry and administer drugs throughout the body.