Source: NewScientist.com news service

By Helen Thomson

Adult human brain cells can generate new tissue when implanted into in the
brains of mice, new research reveals. The findings could pave the way to new
therapies for a host of neurodegenerative diseases, including Alzheimer's,
the researchers say.

Furthermore, lab tests show that the mature brain cells have the versatility
to divide many times in culture and develop into a wide range of specialised
cell types.

Researchers at the University of Florida, US, showed for the first time that
common human brain cells are adaptable and self-renewing - qualities
normally associated with stem cells.

Dennis Steindler and his colleagues transplanted adult human brain cells
into mice and found that they could successfully generate new neurons and
incorporate themselves in a variety of brain regions.

The researchers also coaxed a single adult brain cell to divide into
millions of new cells in culture. "We can, theoretically, take a single
brain cell out of a human being and generate enough brain cells to replace
every cell of the donor's brain," says Steindler.

Brain donor

The new source of human brain cells could be used to repair or replace
damaged tissue in degenerative disorders such as Alzheimer's and Parkinson's
disease, the researchers suggest.

"Anything that removes the need to use foetal or embryonic tissue [to clone
new tissue] is very interesting because that's where the controversy lies,"
says David Dexter, a specialist in Parkinson's disease at Imperial College,
London, UK, who was not involved in the study.

"Now we can use adult human brain cells for research. They can be donated,
like you would a heart or lung."

Growth promotion

The brain cells were acquired from adult patients undergoing surgery for
epilepsy and were extracted from grey matter, an area not known for
harbouring stem cells.

When the cells were bathed in a solution containing a growth-promoting
agent, the researchers noticed the emergence of neural progenitor cells.
Progenitor cells are similar to stem cells but are further along in their
development.

Steindler speculates that progenitor cells may pre-exist in grey matter and
they simply multiplied after being bathed in growth promoter, or being
transplanted into the mice.

Another possibility is that the "ageing clock" of the mature cells is
actually reversed when the donor cells arrive in their new environment,
returning them to their past lives as stem cells, he suggests.

Directed development

"One day we might be able to coax our own cell populations to provide us
with regenerative aid for disease," Steindler hopes.

However, although scientists can control what the brain cells develop into
in culture, they may not exhibit the same control inside the brain.
"Although the transplanted cells survive, we don't yet know how to tell some
cells to grow over here and others to grow over there. Until we can direct
the brain to wire them in the right places, they're going to be useless,"
Dexter warns.

But, the ability to produce huge numbers of brain cells outside of the brain
may serve as a useful instrument to test the safety of new drugs, Steindler
says.

Journal reference: Development (vol 133, p 3671)