Researchers in Japan have successfully grown sperm for the first time in a study that could eventually help preserve the fertility of cancer patients and help infertile men have children.
In the experiment, published in Nature, small slices of testicular tissue (about 1-3mm in diameter) were cultured from mice and the retrieved sperm were injected into egg cells using a process called ICSI (intracytoplasmic sperm injection).
Around half (17) of the 35 egg cells inseminated by ICSI developed to the two-cell embryo stage, ten implanted correctly into the uterus, and five (two male and three female) mice were born. The pups went on to have families themselves. They also successfully performed the same procedure after the testicular cells had been frozen.
The researchers - Dr Takehiko Ogawa and colleagues at Yokohama City University, Japan - claim that sperm production is one of the longest and most complex processes in the body and that no one has managed to artificially mimic the whole cycle in mammals before. They discovered that the key lay in a simple change to standard culture conditions. Having shown that it is possible in one species, the researchers hope that they can extend the results to other species and eventually humans.
Reviewing the work, Professor Shahin Rafii, a geneticist, and Dr Marco Seandel, an oncologist, of Weill Medical College in New York, said: 'The preservation of fertility is a major concern for patients requiring… chemotherapy... that can inadvertently destroy germ cells.
'In men, this problem can be mitigated by banking sperm before treatment. The solution is less straightforward in prepubescent boys', they said, adding: 'In this scheme, boys would undergo testicular biopsy before chemotherapy or radiation therapy, to obtain tissue for cryopreservation'.
The procedure will also be useful for studying the molecular events that underlie sperm production, said Dr Martin Dym, a cell biologist at Georgetown University in Washington DC.
Dr Allan Pacey, a senior lecturer in andrology at the University of Sheffield, said: 'It is important to be cautious because sometimes species-specific differences in biology means that what works for one species does not work in another'. He added: 'It is clearly important to make sure that any sperm produced are safe and give rise to healthy offspring when used, and that they in turn have healthy offspring. We need to be cautious with this kind of work'.
Dr Ali Honaramooz a reproductive biologist at the University of Saskatchewan, Canada, said that it is just a matter of time. 'If the same methodology can be applied, with many minor changes, to other species, that's great', he said. 'If not, then it would take almost the same amount of work, but at least now you know that eventually it's going to work'.