Helping sperm to become fertile


A new study explores the basic processes of sperm capacitation and may one day improve success rates of in vitro fertilization (IVF) by providing a shortcut to bypass certain fertility problems. This new fundamental knowledge of how sperm acquire the ability to fertilize an egg may allow scientists to enhance the process one day and to control it.

What is capacitation?

Sperm are not fertile until they spend time in the specialized environment of the female reproductive tract. Once there, they move through a series of biochemically delicate stages called capacitation. Since this was discovered over 50 years ago, scientists are now certain that not only does capacitation occur in many cascade stages, but that each species has its own different and specific requirements for success.

Creating a shortcut to capacitation

Any improved understanding of how the cascade works improves the success rate of IVF. Using mouse sperm for their experiment, researchers found that they could skip the early parts of the cascade by applying calcium, which naturally makes its appearance late in the cascade. Excess calcium will incapacitate the sperm so researchers found that if they washed away the excess calcium they could retain healthy sperm. They basically bypassed early capacitation stages by applying the calcium, washing it away and letting the sperm proceed. These sperm fertilized 80% of eggs which then developed into normal offspring.

Jump starting fertility

Pablo Visconti, lead UMass Amherst author, credits Hiroyuki Tateno in Japan and Ryuzo Yanagimachi in Hawaii with the idea of washing the excess calcium away. “Until they conceived it, no one had thought of this trick. They did the first experiments. Later, our experiments demonstrated that by treating the sperm with calcium ionophore, we were activating these cells far downstream of the normal biological process. And 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.”

Source: MedicalNewsToday, Proceedings of the National Academy of Sciences


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