In the early 1970s, the first babies were born via in vitro fertilization (IVF). Now, a new imaging technique could assist couples struggling with infertility. The technique, which is in the early stages of development, was described recently in The Optical Society’s Biomedical Optics Express journal.
Currently, the gold standard for identifying viable sperm for IVF is computer-assisted semen analysis (CASA), which is able to ascertain the appearance, mobility and concentration of available sperm. Still, there are limits to this electronic-based imaging technique, and specialists work in two-dimensional technology rather than three.
Four researchers from some of Europe’s leading research institutions recently joined forces to develop a tracking system that can record 3-D images of sperm movement and motility over time. The team was led by Giuseppe Di Caprio, PhD, of the Institute for Microelectronics and Microsystems of the National Council of Research (NCR) and Harvard University. He was joined by researchers from the National Institute of Optics of the NCR and The Center for Assisted Fertilization.
The researchers utilize digital holographic microscopy (DHM) to create the moving images. During the process, the light of a laser beam is split in two. One beam passes through a dish containing live sperm cells. Then, after the first beam is magnified through a microscope, it and the second beam are recombined, generating a 3-D image that creates a pattern that can be captured on camera.
More Than Just Movement
By using DHM, which adds the dimension of time, the researchers discovered they could see more. One observation was that viable sperm are much more likely to move on the same plane than are less viable sperm, including those that have a bent tail or misshapen head, or are otherwise malformed.
“Abnormal sperm behavior is one of the most common important indicators for clinical male infertility, and of special relevance is sperm motility, i.e. curvilinear and linear velocity, wobble, etc. …,” says Di Caprio. “Our method is capable [of detecting] out-of-plane movements — not possible by using CASA — and [of correlating] this behavior to anomalous cell morphologies. Consequently, our technique creates a whole set of new quantitative parameters to perform cell sorting aimed at a more efficient IVF.”
The Next Step
This was the first in a series of studies by this research team helping define and track fertility for patients struggling with infertility. Di Caprio hopes the research can help scientists delve deeper into understanding the makeup of viable sperm.
“In the following steps, we are going to perform analysis on sperm cells with vacuoles — enclosed compartments filled with water plus organic and inorganic molecules — in order to determine if having vacuoles results in reduced fertility,” he says. “The long-term goal of such experiments and others using the new tracking system is to use the information to develop a microchip-scale method for sorting good sperm cells from ones that are less viable.”