Reproductive biologists at the University of Massachusetts are working with an international team to better understand the basic processes of how sperm fertilizes an egg, which may one day lead to a better success rate of in vitro fertilization.
Pablo Visconti, a professor of veterinary and animal sciences at UMass, was the lead author of two recent papers on the subject published in “Proceedings of the National Academy of Sciences” and the “Journal of Biological Chemistry.” JBS named the study its “Paper of the Week.”
Visconti said in a press release that a male version of the birth control pill is still some ways off, but knowing how sperm fertilizes an egg and giving scientists the ability to enhance or block the process is a major step forward.
“Our laboratory is mainly interested in the basic science of how sperm acquire fertilizing capacity, but one interesting idea here is that this shortcut offers some translational possibilities for calcium ionophore use in IVF,” said Visconti in the press release. “This shortcut may address many of the difficult situations we encounter in IVF, in many species.”
The release stated that “Sperm are not fertile until they spend time in the specialized environment of the female reproductive tract, moving through a series of biochemically delicate stages known as capacitation.” Studies conducted over the past 50 years have shown scientists that this “signal transduction cascade” is a multi-stage process, and also that each mammalian species has distinct requirements for prosperity. Species-specific requirements must be discovered on a case-by-case basis, according to the press release.
Visconti and his team at UMass worked with Weill Cornell Medical College, University of Hawaii Medical School, Asahikawa Medical University Japan, Universidad Nacional de Rosario and Facultad de Medicina Argentina and Universidad Nacional Autónoma de México to conduct their experiments with mice sperm in vitro.
In the study published in PNAS, the teams “experimented with increasing intracellular calcium,” the release said, adding that, “Calcium is known to play a role late in the sperm capacitation process” involving other proteins and enzymes.
If too much calcium is used, though, it can overwhelm and immobilize the sperm. Visconti said in the press release that they managed to avoid this problem by simply washing the excess away.
Visconti’s co-authors Hiroyuki Tateno in Japan and Ryuzo Yanagimachi in Hawaii are credited with the idea of washing away the excess calcium ionophore.
“Until they conceived it, no one had thought of this trick. They did the first experiments,” Visconti said in the press release. “Later, our experiments demonstrated that by treating the sperm with calcium ionophore, we were activating these cells far downstream of the normal biological process. When the ionophore is washed away, the sperm retain just the calcium they need. They self-regulate the optimal calcium concentration and are ready to go on.”
According to the release, ionophore-treated sperm fertilized 80 percent of the eggs that developed into normal offspring in the study. The data shows that “ionophore-treated mouse sperm can fertilize ova” even when a “signaling pathway is inhibited,” the release said.
The Akiyama Science Foundation, the Agencia Nacional de Promoción Cientifica y Tecnológica of Argentina, CONACyT-Mexico, the University of Hawaii Foundation and the U.S. National Institutes of Health sponsored the research.
