Scientists grow new stem cells in a living mouse

LONDON (Reuters) - Scientists have
succeeded in generating new stem cells in
living mice and say their success opens up
possibilities for the regeneration of damaged
tissue in people with conditions ranging from
heart failure to spinal cord injury.
The researchers used the same "recipe" of
growth-boosting ingredients normally used
for making stem cells in a petri dish, but
introduced them instead into living laboratory
mice and found they were able to create so-
called reprogrammed induced pluripotent
stem cells (iPS cells).
"This opens up new possibilities in
regenerative medicine," said Manuel Serrano,
who led the study at the Spanish National
Cancer Research Centre in Madrid.
Stem cell experts who were not directly
involved in the study said its success was
exciting, but noted that the technique as it
stands could not be used in humans since the
reprogrammed cells also lead to tumors
forming in the mice.
"Clearly nobody wishes to do this for
therapeutic purposes because this leads to
the formation of tumors called teratomas,"
said Ilaria Bellantuono, a reader in Stem Cell
and Skeletal Ageing at Britain's University of
But she added that Serrano's work was a "a
proof of concept" that opened up the
opportunity to investigate ways to partially
reprogram cells in the body up to a certain
"In principle, these partially dedifferentiated
cells could then be induced to differentiate to
the cell type of choice inducing regeneration
in vivo without the need of transplantation,"
she said.
Stem cells are the body's master cells and
are able to differentiate into all other types
of cells. Scientists say that by helping to
regenerate tissue, they could offer new ways
of treating diseases for which there are
currently no treatments - including heart
disease, Parkinson's and stroke.
There are two main types of stem cells -
embryonic stem cells, harvested from
embryos, and adult or iPS cells, cells taken
from skin or blood and reprogrammed back
into stem cells.
Serrano, who spoke to reporters in a briefing
ahead of his study's publication in the
journal Nature on Wednesday, said one of his
most striking findings was that the iPS cells
generated in the living mice seem to be more
similar to embryonic stem cells than to iPS
cells created in petri dishes.
Specifically, he said, the iPS cells
reprogrammed in living mice showed the
potential to differentiate into more cell types
than standard iPS cells or embryonic stem
cells - suggesting that reprogramming cells in
a living mammal produces cells with greater
potential, or what scientists call more
Chris Mason, a professor of regenerative
medicine at University College London, said
he had no doubt that being able to
reprogram cells in the body to different cell
types would be useful in producing future
therapies capable of transforming patients'
lives, but said there were many more years of
research ahead before that would be
"The cells that will be useful will not be the
pluripotent stem cells (iPS cells), but their
more specialized ('adult') offspring," he said.
"This.. is an interesting proof of concept of
the first step in the process, but it still needs
these iPS cells to be safely converted to
useful 'adult' cell types in the body."
He said the major challenge in this potential
approach to treating patients in the future
would be tightly controlling every step of the
process to make sure it delivered benefits
while also avoiding complications.