A ground-breaking contraceptive pill for men could be just around the corner after a major breakthrough, scientists say. Researchers said they have identified a gene which temporarily renders sperm infertile once removed.
The American research team discovered a protein encoded by this gene, found solely in the testicular tissue of most mammals. It reduced sperm counts and deformed remaining sperm to make them incapable of fertilising an egg when altered.
The potentially historic breakthrough contraceptive pill would also have no hormonal side effects and could be additionally used on animals to quell overpopulation and replace castrations, it is said. And, crucially, the destabilisation of the infertility protein is not permanent - meaning sperm will recover once the person or animal stops taking the pills.
Scientists have hailed the discovery as potentially important for the 'future of the human race'. The research team, from Washington State University (WSU) in the USA, identified the expression of a gene called Arrdc5 in the testicular tissue of mice, pigs, cattle and humans.
Although other molecular targets have previously been sighted to develop male contraceptives, the Arrdc5 gene is specific to male testes and can be found in multiple mammalian species. The researchers found removing the gene led to significant infertility by causing a condition known as oligoasthenoteratospermia - or OAT.
This condition is the most common diagnosis of male infertility in humans; leading to a decrease in sperm produced as well as sperm being slower and distorted in shape, so the sperm is unable to fuse with an egg. The WSU team observed male mice lacking the gene and found they produced 28 per cent less sperm which moved 2.8 times slower than in normal mice.
Nearly all (98%) of the sperm in mice lacking the Arrdc5 gene was also deformed, with abnormal head and mid-pieces. The results of the study appear to indicate that the protein encoded by this gene is essential for normal sperm production.
The WSU team next plans to work on designing a drug that would inhibit the production or function of this protein. But disrupting the functions of this protein will not require any hormonal interference.
This a key hurdle considering the multiple roles testosterone plays beyond sperm production in men, including the building of bone mass and muscle strength as well as red blood cell production. The team also say that designing a drug which only targets this protein would further make it easily reversible as a contraceptive.
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Dr Jon Oatley, senior author and a professor in WSU’s School of Molecular Biosciences, said: "The study identifies this gene for the first time as being expressed only in testicular tissue and nowhere else in the body, and it’s expressed by multiple mammalian species. When this gene is inactivated or inhibited in males, they make sperm that cannot fertilize an egg, and that’s a prime target for male contraceptive development."
“You don't want to wipe out the ability to ever make sperm – just to stop the sperm that are being made from being made correctly. Then, in theory, you could remove the drug and the sperm would start being built normally again."
Dr Oatley, along with the study's first author Dr Mariana Giassetti, has already filed a provisional patent for the development of a male contraceptive based on this gene and the protein it encodes. As the gene is found across mammalian species, Dr Oatley says the discovery could also herald advances in animal contraception.
The scientists analysed available data on DNA and protein sequences in mammals. They said they found the gene in nearly every known mammal species.
This, say the WSU team, has the potential to open up development for male contraception in animals which could replace cruel castrations in livestock populations and help manage the overpopulation of some wild animals. However, the scientists insist they are for now focused on producing an effective contraceptive pill for men to hand them more control over their reproduction.
The study, published in the journal Nature Communications, further acknowledges that although many forms of birth control already exist for women, these are not always effective or widely available. Testament to this is the United Nation's estimation that more than half of the world's pregnancies remain unintentional.
Dr Oatley added: "Developing a way to curb population growth and stop unwanted pregnancies is really important for the future of the human race. Right now, we don't really have anything on the male side for contraception other than surgery, and only a small percentage of men choose vasectomies.
"If we can develop this discovery into a solution for contraception, it could have far-ranging impacts."
