We’re still inching, slowly, towards a birth control pill for men. But now biologists have discovered the key to a contraceptive that would work in both men and women.
A team led by UC Berkeley professor Polina Lishko found that sperm tails can power-kick their way toward an egg thanks to an interaction between female hormones and the sperm’s protein receptors.
When sperm are close to the egg, receptors on their tails respond to the hormone progesterone, which is secreted by the egg. This triggers a reaction that allows the sperm to whip their tails and so penetrate the egg.
Understanding this hormonal interplay could be used to create a unisex birth control drug, say researchers, as either partner could take a drug that would block sperm from recognizing progesterone.
“That’s what makes this work really exciting,” Melissa Miller, a postdoctoral fellow at both UC Berkeley and UC San Francisco and the first author of the paper, tells Quartz. “Why is a unisex contraceptive important? It will give both parties an equal stake in control of their reproductive freedoms.”
Miller says the drug creation would have to be taken on by a pharmaceutical company. But based on the work by her and her colleagues, a product could be on the market within a couple of years.
She believes that similar research on creating a male contraceptive has been neglected because of the long-held belief that reproduction is the role of the women.
“Available contraceptives on the market are very gender specific,” she says. “There’s very little work done on the male gamete, on sperm. We’re really scratching the surface on what is yet to be understood with these cells.”
The findings, published in Science on March 17, also have important implications for understanding male fertility.
“About 80% of men who present infertilities are given what’s called a ‘idiopathic diagnosis,’ which is essentially medical terminology for ‘We really don’t understand why you’re infertile, we’re really sorry,’” says Miller.
Finally, the research is valuable because the same protein that acts as a progesterone receptor in sperm tails is also found elsewhere in the body. The researchers now want to evaluate its effects elsewhere. For example progesterone could interact with the receptors to affect pain sensation in neurons, or muscle contractions in lungs.
Miller says she has “absolutely no doubt” that such interactions are taking place throughout the body, and it’s simply a matter of further research to determine the exact effects.