By Andrew Quinn
SAN
FRANCISCO (Reuters) - U.S. researchers have produced laboratory mice with human
brain cells, marking a potential step toward developing treatments for human brain
disease like Alzheimer's but promising to fuel fresh debate over the evolving
ethics of bioengineering.
The research at California biotechnology company
StemCells Inc . breaks new ground by demonstrating that human brain stem cells
can be induced to grow within a mouse's skull, scientists said on Friday.
"We
are not recreating a human brain. We're really just trying to understand how these
stem cells can function, and how they can be used in the treatment of specific
diseases,'' said Ann Tsukamoto, vice president of scientific operations at StemCells
Inc.
Irving Weissman, a Stanford university professor involved in the two-year
research project, said the next step could be to produce mice with brains made
up almost entirely of human cells -- although he said there would have to be a
thorough ethical review before this step is taken.
"You would want to ask
the ethicist what percentage of the brain would be human cells before you start
worrying, and if you start worrying, what would you start worrying about,'' Weissman
said.
The California study involved isolating human stem cells in the laboratory
and then introducing them into mice. As the mice matured, the human stem cells
-- "master cells'' that can develop into any other type of cell -- grew into a
full range of specialized cells throughout each mouse brain.
"It looks
like human cells can follow the developmental instructions put in by the mouse
brain. They are making human components in what is clearly a mouse brain,'' Weissman
said.
The researchers believe that these mice could be used to test treatments
for human brain diseases such as Parkinsons and Alzheimer's, although these tests
have not yet been undertaken.
Tsukamoto added that the experiment also
demonstrated that StemCell Inc's process for isolating and developing human stem
cells was viable, and that cell banks could be established for future transplantation
into humans.
"We're of course moving this into the development phase, and
looking at which disease indications these cells would be bestused for in preclinical
trials,'' she said.
Both scientists stressed that their research, while
marking a new breakthrough in the controversial world of stem cell research, was
in no way aimed at blurring the lines between human and animal.
But Weissman
added that he had already requested a review panel to look at the research to
determine if there may be ethical problems in taking the work further.
"It
is not the objective to go make mice with human brains,'' Weissman said. ``(But)
it is in the domain of the ethicists, not the experimenters, to figure out what
our limits are." |
