The search for a male birth control has been such a tease. Researchers have been struggling for years to develop a working drug, and have so far come up short. The most optimistic prospect is Vasalgel, which has shown to be effective in animal trials. Other seemingly promising alternatives have faced development barriers—last year, for instance, a groundbreaking study on a male contraceptive injection ended early because the participants couldn't handle the annoying side effects, like mood swings and acne.
Researchers at the University of California, Berkeley, have started testing out a new approach. Sperm is able to fertilize an egg thanks to tadpole-like tail that can help it drill into the egg; this motion occurs when the calcium channel of the sperm is activated when it nears the egg and encounters progesterone. The UC Berkeley researchers say they've discovered a way to turn this mechanism, known as CatSper, off.
"Calcium, at high concentrations within the cell, does two very important things. One, it changes the way in which the sperm tail moves, resulting in a much stronger propulsion, which the cell needs to progress through the female reproductive tract and to penetrate the protective outer layers of the egg," Melissa Miller, one of the authors of the study, elaborated. "And two, it stimulates the release of enzymes that help to drill holes in the outer layers of the egg to allow the sperm access to the egg. This cascade of events is triggered, in humans, by the hormone progesterone." Previous studies have found that mutations in certain CatSper proteins are linked with infertility.
Since it's known that progesterone can activate CatSper, the researchers wanted to find out if there were compounds that could block it. They found that concentrations of lupeol, a common molecule found in plants like olives, mangos, and grapes, could prevent calcium ions from giving sperm the boost it needs to penetrate an egg.
This could discovery could lead to a unisex birth control method that works by blocking progesterone activation. In women, the application would work similarly to Plan B, except that it would only be effective before fertilization, or within six hours of sex. In men, it could work analogously to the pill. "If we think of sperm as a delivery man, it doesn't matter if his truck breaks down when he is still at the post office or if he is en route—he still can't deliver his package," Miller said.
Unlike the male contraception injection that was tested last year, there could be a lot less potential for adverse side effects with this method, though it's impossible to be sure "until we have a drug in hand and are able to perform safety studies," Miller explained. "Though, targeting CatSper for contraceptive development is incredibly promising, as CatSper is exclusively expressed in sperm cells, which would limit the possibly of adverse side effects."