We’re One Step Closer To The Pill For Men
This study of the proteins in sperm tails could pave the way for male birth control. But not yet
We may be one step closer to an oral contraceptive for men, according to a new study in the journal Science. Researchers say they have found the protein responsible for propelling sperm toward an egg, and they suspect they may be able to harness the protein to increase fertility—and temporarily block it.
“This gives us an understanding of another pathway that is involved in human sperm activity,” said Melissa Miller, a postdoc at UC Berkeley and UC San Francisco and coauthor on the paper. “What’s really cool is that we have an actual target for unisex contraceptive development.”
We’ve been searching in vain for a unisex contraceptive since at least 1974, when scientists announced a dubious oral contraceptive for men and unexpectedly set off a sperm-science arms race that continued throughout the ’80s. Then in 2001, scientists thought they’d finally cracked the code of male fertility, with the discovery of a protein called CatSper that helps sperm swim.
It seemed like only a matter of time before men had an oral contraceptive to call their own. But for 15 years, nothing happened. Now, scientists think they’ve finally figured out how CatSper fits into male fertility, and how we might be able it to use to develop a Pill for dudes.
For the study, Miller and her colleagues attached microscopic electrodes to a human sperm tail in a petri dish and bombarded it with hormones. Sperm tails are covered in tiny protein receptors, including the famous CatSper proteins, which sort of catch the egg’s “scent” via hormones released by the egg, such as progesterone. These signals help the sperm find its way to the egg and, as the sperm gets closer, its receptors begin working overtime—activating a “power kick” within the tail that whips the sperm ahead of its competition and into the egg.
“If the receptor protein doesn’t recognize progesterone, you would be infertile,” Miller says. Which tells us two things. First, if we’re looking to cure male infertility, we may want to focus on those receptors and their relationship with the enzyme progesterone. And, perhaps even more interestingly, if we want to develop a Pill for guys we may want to focus on intentionally blocking those receptors, so the sperm get lost on their way to the egg.
A word of caution, however. This research is still at the basic science stage. We’re dealing with sperm in a petri dish wired up to microscopic electrodes. Long before we see a male birth control pill built on this research, we’d have to see an in vitro test with a real egg (and getting funding for that in the United States is not easy), followed by animal trials and human trials.
But in the meantime, scientists can use this information to better understand how cells interact with proteins, perhaps leading to more immediate medical applications. “Now that we know the players, the next step is to look in other tissues that express these proteins to see whether progesterone acts on them in a similar manner to affect pain threshold adjustment in pain sensing neurons … or the excessive smooth muscle contractions found in asthma,” Miller says.
“This may be a universal pathway in all cells.”