Targeting the testicles could help create a male contraceptive without unwanted side effects, a new study suggests.
Chuen-yan Cheng at the Population Council鈥檚 Center for Biomedical Research in New York City, US, and colleagues, injected a drug into rats that prevents immature sperm cells from maturing properly.
The drug, called Adjudin, works by disrupting the interaction that takes place in the testicles between immature sperm cells and the nurse cells responsible for nurturing sperm to maturity. The germ cells need to adhere to the nurse cells for sperm to properly develop, and the drug prevents this bond from forming.
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But Cheng鈥檚 earlier studies showed that when taken orally, Adjudin did not specifically act on cells in the testicle 鈥� it caused liver inflammation and muscle atrophy in the rats. 鈥淓ven though it was very effective, we couldn鈥檛 make use of it,鈥� he explains.
Gel patch
To get around the problem, Cheng鈥檚 team has now coupled the Adjudin molecule to a mutant form of follicle-stimulating hormone (FSH), which targets receptor molecules found only in the testes.
The new approach allowed them to induce infertility in the adult rats using relatively low doses of the drug, which produced no obvious side effects, the researchers say.
Other types of male contraceptives currently being trialled involve hormone combinations that prevent sperm from being produced altogether. But these can have problematic side effects because hormones play such an important role throughout the body.
At the moment, Adjudin is injected into the rats鈥� bloodstream. 鈥淏ut injection won鈥檛 be acceptable for a male contraceptive in humans,鈥� admits Cheng. So, the team is now working to develop a gel patch that men could stick on their bodies.
鈥淲e are at a very early stage, but we are optimistic because in human males these FSH receptors are also only found in the testes,鈥� he says.
Journal reference: Nature Medicine (DOI: 10.1038/nm1420)
