See folks this new from NY Times :
By NICHOLAS WADE
n a possible glimpse at the brain surgery of the
future, biologists have
partly cured mice of a disease resembling multiple
sclerosis by
injecting restorative cells into their brains.
The cells migrated all over the brain and took the
correct action to repair
the neural disease, in this case a lack of the sheath
that covers certain
nerve cells and helps speed their conduction of
electrical signals.
The approach is founded on the
use of stem
cells, the special regenerative
cells with
which organs renew and repair
themselves.
Dr. Evan Y. Snyder and his
colleagues at
Harvard Medical School worked
with
neural stem cells, the progenitor
cells that
develop into all of the other
specialized cells
of the brain.
Dr. Snyder said that his experiment showed, in
principle, that neural stem
cells can migrate all over the brain and develop into
the right kinds of
specialized cells. Hence human neural stem cells could
serve to treat
diseases that affect the whole brain, like Alzheimer's
and multiple
sclerosis.
The subjects of Dr. Snyder's study, which was reported
in today's issue
of the Proceedings of the National Academy of Science,
were "shiverer"
mice, so called because they shiver uncontrollably
throughout their
generally short adult life.
The mice's problem is a mutation in the gene that makes
myelin, the
material that sheathes the long extensions of certain
nerve cells. Because
the gene is disrupted, the oligodendrocytes, the
special cells that do the
cladding, are ineffective.
In his experiment, Dr. Snyder injected neural stem
cells from a normal
mouse into newborn shiverer mice, into the brain region
from which the
stem cells originate. The new stem cells spread all
over the brain,
transformed themselves into oligodendrocytes and
churned out myelin to
wrap around the cells.
The shivering abated in more than half the treated
mice, and some
seemed fully normal.
It was long thought that people die with the same set
of brain cells that
they are born with. But recent findings have shown that
new brain cells
are continually created from neural stem cells, at
least in certain regions of
the brain. Dr. Snyder believes that neural stem cell
activity may be quite
high in normal adult brains and even higher in diseased
brains.
Even if neural stem cells do not migrate much in the
adult brain, it may be
possible to equip them with genes that reawaken the
migratory instincts
of their youth, Dr. Snyder believes. Stem cells are
particularly amenable
to genetic manipulation.
For a next step, he plans to repeat his experiment in
adult mice, then
perhaps with monkeys, and then in an appropriate
clinical setting. Dr.
Snyder envisions a new approach to many brain diseases,
based on the
use of neural stem cells. "It's very conceivable that
within this decade we
will have a genuine contribution to make to brain
repair," he said.
Dr. Snyder's optimism is shared by other biologists who
work on stem
cells, both in the brain and other organs, and who see
themselves as
opening up a new field of medicine based on the body's
own repair
system.
The use of stem cells, together with the signals that
control the cells'
behavior, is sometimes known as regenerative medicine.
"We do believe this represents a paradigm shift, that
it's a whole new
way of repairing the brain by trying to invoke
fundamental principles of
brain development," Dr. Snyder said.
Dr. Ron McKay, a neural stem cell expert at the
National Institutes of
Health, said Dr. Snyder's experiment was "pretty
impressive" in showing
how much of the shiverer mouse brains could be
re-sheathed in myelin.
It proved the concept, he said, that if neural stem
cells are injected at the
right stage in the brain's development, they will
develop into the
appropriate kind of specialized cell. "I am utterly
confident in the
correctness of the conclusion," he said.
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+--------| Salvador-Bahia-Brazil |------+
