Viable artificial sperm have been created using stem cells for the first time in a scientific breakthrough that could lead to new treatments for infertile men.
Fertility researchers created sperm-producing germ cells in a lab and transferred them into infertile mice, which after the treatment were able to produce healthy offspring.
The development, which was described by experts as “hugely exciting”, could help thousands of infertile men become fathers if the method proves similarly effective in humans.
Japanese scientists at Kyoto University used stem cells from mouse embryos to create primordial germ cells, which drive the production of sperm in men.
When transplanted into the testicles of infertile mice, the cells produced normal-looking sperm.
Researchers led by Dr Katsuhiko Hayashi injected the sperm into mouse eggs and implanted them into female mice, which give birth to healthy pups.
The babies, when they grew up, were capable of reproducing naturally, according to a study in the Cell journal.
Previous experiments to make sperm from embryonic stem cells have not been so successful, and in most cases led to unhealthy offspring which soon died.
Fertility expert Dr Allan Pacey, senior lecturer in andrology at the University of Sheffield, said: "This is quite a step forward in developing a process by which sperm could be made for infertile men, perhaps by taking as a starting point a cell from their skin or from something like bone marrow.
“Clearly more work needs to be done to refine this process, but it's hugely exciting."
The technique may not fall foul of British laws which ban the use of lab-made mature sperm in fertility treatments because the scientists only created germ cells which produced sperm naturally.
Dr Pacey said: “The philosophy of the law is to stop that kind of thing happening. But in this case you're not technically creating sperm, so it might be that you can sidestep this regulation. It all depends on definition.”
Dr Jane Stewart, British Fertility Society spokesperson and consultant gynaecologist at Newcastle Fertility Centre said the ability to create human sperm-producing cells in the lab would be a “landmark achievement” in fertility treatments.
She said: “This publication in an animal model marks a further step towards this goal, however as the authors clearly point out much work remains to be done.”
© Press Association