Tel Aviv University (TAU) researchers have developed a safe and accurate 3D imaging method to identify sperm cells that move at high speed.
Research, a study published in Progress of Science on April 10th, led by Prof. Natan Shaked from the Biomedical Engineering Department at the TAU Faculty of Engineering along with TAU doctoral student, Gili Dardikman-Yoffe.
This new technology can give doctors the ability to choose high-quality sperm to be injected into eggs during IVF treatment, potentially increasing a woman’s chances of getting pregnant and giving birth to a healthy baby.
The IVF procedure was created to help with fertility problems. The most common type of IVF today is intra-cytoplasmic sperm injection (ICSI), which involves sperm selection by clinical embryologists and injection into a woman’s egg. For this reason, an attempt is made to select the sperm cells most likely to make healthy embryos. “
Natan Shaked, Professor, Department of Biomedical Engineering, Faculty of Engineering, TAU
Under natural fertilization in a woman’s body, the fastest sperm to reach the egg should contain high-quality genetic material. This progressive movement allows the “best” sperm to overcome the real obstacles of the female reproductive system.
“But this ‘natural selection’ is not available to embryologists, who choose sperm and inject it into the egg,” Prof. Shaked “Sperm cells are not only fast-moving, they are also mostly transparent under ordinary light microscopy, and cell staining is not permitted in human IVF.
“Existing imaging technology that can check the quality of sperm genetic material can cause embryonic damage, so it is also banned. In the absence of more precise criteria, sperm cells are chosen primarily according to their external characteristics and motility when swimming in water in the dish, which is very different from the natural environment of a woman’s body.
“In our research, we are trying to develop a completely new type of imaging technology that will provide as much information as possible about individual sperm cells, does not require cell staining to increase contrast, and has the potential to enable optimal sperm selection in fertilizing treatments.”
The researchers chose light computed tomography (CT) technology for the unique task of imaging sperm cells.
“In a standard medical CT scan, the device rotates around the subject and sends X-rays that produce several projections, ultimately creating a 3D image of the body,” said Prof. Shaked “In the case of sperm, instead of turning the device around this small subject, we rely on the natural feature of the sperm itself: its head continues to rotate during forward movement.
“We use weak light (and not X-rays), which does not damage cells. We record holographic sperm cells during ultra-fast motion and identify various internal components according to their refractive index. This creates an accurate, highly dynamic 3D map of the contents without using cell staining. “
Using this technique, the researchers obtained clear and accurate CT images of sperm at very high resolutions in four dimensions: three dimensions in space with a resolution of less than half a micron (one micron equals one millionth of a meter) and the exact time dimension (motion) of a sub second millisecond.
“Our new development provides a comprehensive solution to many known sperm imaging problems,” said Prof. Shaked “We are able to make high-resolution imaging of the sperm head when moving fast, without the need for stains that can harm the embryo. This new technology can greatly improve sperm cell selection in vitro, which has the potential to increase the chances of pregnancy and the birth of healthy babies.
“To help diagnose male fertility problems, we intend to use our new technique to explain the relationship between 3D motion, the structure and contents of sperm and its ability to fertilize an egg and produce a proper pregnancy,” Prof. Shaked concluded. “We believe that such imaging capabilities will contribute to other medical applications, such as developing efficient biomimetic micro robots to carry drugs in the body.”