X-Message-Number: 15734
From: "Mark Plus" <>
Subject: "Scientists Craft Mouse with Human Brain Cells"
Date: Sat, 24 Feb 2001 09:59:40 -0800



Saturday February 24 9:51 AM ET
Scientists Craft Mouse with Human Brain Cells

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 best used 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.''

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