New Bone Marrow Cells May Aid
Brain
The Associated Press
Nov 30 2000 3:54PM
WASHINGTON (AP) - Researchers
have discovered that transplanted
bone marrow cells can migrate to
the brain and turn into neurons, a
dramatic laboratory finding that
may offer hope of new therapies for
Parkinson's disease and other
brain disorders.
Two separate teams of
scientists, using different methods and
different strains of mice, have
demonstrated that transplanted bone
marrow cells can transform
themselves naturally into neurons - brain
cells that carry nerve impulses
- and install themselves seamlessly into
the brain.
However, it could take years
before the researchers can prove that such
transplants can be effective and
safe for treating human brain
disorders, they said.
The researchers said the finding
suggests that converting bone marrow
cells into brain neurons may be
part of a previously unknown natural
healing action the body uses to
replace failed brain cells.
``It may be a repair mechanism
that is going all the time at a low
level,'' said Helen M. Blau, a
professor at Stanford University and
senior author of one of two
studies appearing Friday in the journal
Science.
Blau said the repair mechanism
may not be powerful enough to correct
``a really severe insult, like
an injury or Parkinson's disease,'' but
medical science may find a way
to enlist this potential to replace
neurons destroyed by disease or
injury.
Dr. Eva Mezey of the National
Institute of Neurological Disorders and
Stroke, first author of the
other study in Science, agreed that the
researchers may have found a way
the body replaces neurons.
``On a certain level, there
might be a repair going on throughout life,''
said Mezey. She said there's no
awareness of the repair because the
process replaces a neuron as
soon as the cell fails. This process could
be similar to the way the body
constantly replaces dead skin cells with
new cells, she said.
The studies are the latest in a
hot new field of research exploring the
ability of adult stem cells to
transform themselves into other types of
cells and to fill new roles in
the body. Bone marrow consists of at least
two types of stem cells. Earlier
studies have shown these cells can
convert themselves into muscle,
bone and liver. There also have been
studies showing that neural stem
cells can convert into muscle or make
a variety of brain cells.
In Blau's study at Stanford,
researchers obtained bone marrow from a
strain of mice that carry in
each cell a protein that glows in the dark.
This bone marrow was injected
into the tail vein of mice whose natural
bone marrow had been killed by
radiation. Later, the mice were killed
and their brains examined.
Blau said her team was stunned
to find that some cells in the test
animals' brains glowed in the
dark, proving that bone marrow cells
from the donor mice had migrated
to the brains of the test mice and
changed into neural tissue.
``That was a total surprise to
us. We did not expect it,'' said Blau.
``We were going to do
experiments looking at muscle'' but curiosity
prompted them to look at the
brain as well.
``We spent two years convincing
ourselves that what we were seeing
was right,'' and even enlisted
scientists from other labs to confirm the
discovery, Blau said.
In Mezey's lab, the researchers
used bone marrow from male mice and
injected it into a strain of
female mice born without bone marrow. Using
the male cells provided a marker
since male cells contain a Y
chromosome and female cells do
not. The mice brains were examined
later and the researchers found
Y chromosome cells incorporated into
several brain structures.
Additional tests in both studies
indicated the new brain cells were
neurons. Both Blau and Mezey,
however, said more studies are needed
to prove that such neurons made
the right connections to become a
working part of the brain.
Blau is confident the adult
mouse bone marrow cells did convert into
brain cells.
``We couldn't tell (the
converted bone marrow cells) from its neighbors
in the brain unless we turned
off the lights,'' said Blau. In darkness,
the new cells glowed.
Before they can prove the method
is safe and effective in humans,
science must identify the
proteins or other factors in the body that
signal the bone marrow to
transform into brain cells, the researchers
said.
``What we need to learn is the
rules of the game,'' said Blau. ``We
need to know the factors, what
is calling those cells to the brain.''
Mezey said that once these
``rules'' are known, it may be possible to
treat brain disorders by
injecting protein factors that would signal bone
marrow cells to change into
neurons and, perhaps, repair damaged
brain cells. Under that
scenario, a patient's own bone marrow could be
prompted to help heal the brain,
she said.
On the Net:
Science:
http://www.eurekalert.org
National Institute of
Neurological Disorders and Stroke:
http://ninds.nih.gov/news-and-events/index.htm -
