Scientists have developed a method to temporarily halt the production of sperm cells without damaging surrounding tissues, an advance that could lead to a safe, long-acting and reversible male contraceptive.
Existing contraceptive methods are mostly female-centred or permanent. Since there are few effective male contraceptive options that are reversible, men rely mainly on condoms and vasectomies.
While vasectomy offers a long-term solution and can be reversed, many men are hesitant to undergo the procedure. This, in large part, is why developing non-hormonal methods that can temporarily halt sperm production is considered the holy grail of contraceptive research.
Now a proof-of-concept study conducted on mice over six years shows that interrupting a natural checkpoint in meiosis, the process responsible for producing sex cells, can temporarily halt sperm production.
Researchers found that JQ1, a small molecule originally developed as a research tool for studying cancer, could interfere with a specific stage of meiosis and stop the formation of sperm cells. They showed for the first time that sperm production could be safely and reversibly stopped by targeting meiosis.
“We are practically the only group that is pushing the idea that contraception targets in the testis are a feasible way to stop sperm production,” geneticist Paula Cohen, an author of the study published in the journal PNAS, said.
“Our study shows that mostly we recover normal meiosis and complete sperm function and, more importantly, that the offspring are completely normal.”
The researchers found that JQ1 disrupted meiosis by eliminating cells in the first stage of cell division and preventing the gene activity needed for later stages of sperm development.
In male mice given JQ1 for three weeks, sperm production stopped completely and critical aspects of meiosis, including chromosome behaviour, were disrupted.
When the treatment was discontinued, recovery followed, and within six weeks sperm production returned to normal levels.
The mice could breed after the treatment was stopped, producing healthy offspring that were also capable of reproduction.
“It shows that we recover complete meiosis, complete sperm function, and more importantly, that the offspring are completely normal,” Dr Cohen said.
In future studies, the researchers hope to develop a new form of male birth control delivered as an injection every three months.
“While acknowledging the need for robust future safety assessments of any candidate drugs,” they said in the journal, “these studies provide a blueprint for developing new contraceptive approaches that act safely and selectively within the germline.”