Mice born using lab-grown sperm from frozen testicles

Healthy mice have been born using
sperm grown in the lab from a sample of cryopreserved testicular tissue.

The samples of tissue were
taken from baby mice and, after being frozen for up to seven months, were grown
in the lab to produce mature sperm cells that were used to fertilise mouse
eggs.

Researchers hope the technique
can be used to preserve the fertility of boys undergoing cancer treatment, who
are not able to provide a sperm sample. Some forms of cancer treatment may
reduce men's fertility, so they can opt to have their sperm cryogenically
frozen, but this is not a possibility for children yet to undergo puberty.

'The cryopreservation of
testicle tissue may be a realistic measure for preserving fertility', the researchers
wrote in Nature Communications.

The team, from Yokohama City
University, took 30 tissue samples from the testes of five-day-old mice, then cryopreserved
them. After thawing the tissue and growing it in the lab, mature sperm cells
began to develop in 17 of the samples.

The sperm cells, and immature sperm
precursors called spermatids, were then injected into mouse egg cells. The 156
resulting embryos were transferred into female mice, and eight healthy mouse
pups were born. These mice were healthy, able to mate normally and produced
their own offspring.

The researchers noted that
samples of rat testicles could not successfully produce sperm in the lab after
being thawed, so it is possible that the technique does not work in other
animals. However, the team are now beginning to develop a method that will work
for human samples.

Professor Takehiko Ogawa, who led
the study, told the BBC:
'This is the first time in animals. I predict it will take at least a couple of
years before it is done in humans, it's not so easy'.

'We are now working on human
samples, which are very different from mice tissue, I have to find some trick
to make it work, so it's very difficult to predict how long that will take'.

Dr Allan Pacey, andrology lecturer from the University of Sheffield, told the BBC: 'We would
need to check that lab-made sperm were genetically normal and that any babies
born are going to be healthy and fertile themselves. But based on this research
in mice, the data looks encouraging and I hope that proper trials in humans
will soon begin'.