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Published online: 10
July 2006; | doi:10.1038/news060710-1
Mice born from stem-cell sperm
Mouse sperm has been made in a dish, but the method
is too unreliable for use in humans.
Michael
Hopkin
For the first time, embryologists
have shown that sperm created from embryonic stem cells can
give rise to live offspring. The work, carried out by researchers
in Germany and Britain, culminated in the production of six
adult mice that owed their origins to sperm derived from these
'multipurpose' cells.
But the
technique certainly isn't perfect: the success rate was very
low, and the mice suffered genetic abnormalities. So there is
no immediate prospect of the method being adapted to treat
infertile men. But the discovery could lend valuable insights
into the process by which functioning sperm are
manufactured.
Ordinarily, sperm cells develop
from precursors known as 'spermatogonial stem cells' (SSCs) in
the testes. In the new research, a team led by Karim Nayernia
at the University of Göttingen, Germany succeeded in
converting stem cells taken from early mouse embryos into
SSCs, and from there into functioning sperm.
Both
sperm cells and eggs have been made from stem cells before.
But this research goes further.
The researchers
implanted the sperm artificially into eggs collected from
mice, and showed that the sperm were capable of fertilizing
the eggs, which produced living offspring when implanted into
surrogate mothers. "We have shown that the sperm cells are
functional, and can fertilize an oocyte," says
Nayernia.
 This could help in understanding
why some men do not produce sperm
properly.  |
John
Burn,
University of Newcastle upon
Tyne | | |
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| Dying young
Of 210 eggs injected
with the lab-reared sperm, only 65 began to undergo cell
division, and only seven live births resulted, with one of
these offspring failing to reach adulthood, the researchers
report in the journal Developmental Cell1.
The
other six mice were all smaller or larger than control mice
thanks to abnormal growth rates. All died within 5 months of
their birth; mice usually live for years. The problems are
probably introduced, the researchers say, during imprinting: a
change in the pattern of genes that are switched on, or
expressed, in the embryo.
Learning how sperm
are produced could ultimately help in treating infertile men
in whom this pathway is defective, suggests John Burn, head of
the Institute of Human Genetics at the University of Newcastle
upon Tyne, where Nayernia now works. "From a scientific point
of view, this should be seen as a milestone in understanding
how cells produce functioning sperm."
The technique could
also be honed to remove the need to use stem cells taken from
embryos, Burn suggests. One possibility, he says, is to use
stem cells from blood in the placenta or umbilical cord, which
is rich in these highly adaptable proliferating
cells.
Any human application is nevertheless a long way
away, other researchers warn. "It is more difficult to say
whether artificial sperm produced this way could ultimately be
used as a new treatment for male infertility," says Allan
Pacey, who studies male reproductive problems at the
University of Sheffield, UK. "There are many technical,
ethical and safety issues to be confronted before this could
even be considered."
Visit our newsblog to read and post comments about
this story.
References
- Nayernia K., et al. Dev. Cell,
11. 1 - 8 (2006).
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