2002 ASCB Annual Meeting Press Book - page 6

December 14-18, 2002, San Francisco, CA
Bone Marrow Stem Cells
Renew Muscle and Brain
It was long thought that once cells differentiate, that is,
once they begin expressing the genes of a specialized cell
type, they cannot change—their identity is fixed and irre-
versible. This dogma has been challenged in the past few years
with the discovery of “stem cells” in the adult. Recent studies
have suggested that adult bone marrow cells and their prog-
eny may be extremely plastic. Stanford University’s Helen Blau
has been at the forefront of this work, her results strengthen-
ing the idea that these naturally occurring changes in cell
fate may be ongoing at some level throughout life, and that
they may be involved in repair of damage, a function that could
potentially be strengthened.
The question remained whether adult bone marrow cell
plasticity was a rare event or whether it figured significantly
in the normal upkeep and repair of the organism. Blau’s lat-
est results in transplanting fluorescently-labeled bone mar-
row cells in mice revealed a robust response in muscle fibers,
far stronger than any previously reported. She also found that
her mice with labeled bone marrow cells contributed to what
appear to be fully developed neurons involved in balance and
motor function.
In a series of experiments, Blau’s research group trans-
planted mouse bone marrow cells containing a gene for the
green fluorescent protein (GFP) into irradiated mice. The trans-
planted cells, which glow green, could be readily tracked over
time to assess the location and morphology of the new cells.
The GFP+ marked cells were found in the brain (in the olfac-
tory bulb) and in muscle. All appeared morphologically simi-
lar to their neighbors. In certain muscles, as many as 5 per-
cent of total muscle fibers contained GFP+ cells. This per-
centage is significantly higher than any reported for other
muscles to date. In neurons, numerous GFP+ Purkinje cells
with their characteristic cell bodies, axons, and full dendritic
trees were detected, suggesting that bone marrow cells can
yield fully functional neurons in adult mice. These results
suggest that cells for the repair of nervous system damage
may be readily obtained from the marrow and that one day it
may be possible to mobilize these cells to go from the blood
stream to specific tissues in need of repair.
In all, Blau says, “Our data suggest that adult stem cells
in blood may contribute throughout life to brain and brawn in
a previously unrecognized manner. Once the underlying
mechanisms are elucidated, we may be able to exploit them to
target specific organs and diseases.”
Contact: Helen M. Blau, Donald E. and Delia B. Baxter Pro-
fessor, Director, Baxter Laboratory for Genetic Pharmacology,
Stanford University, Stanford, CA 94305-5175, (650) 723-
Adult Stem Cells: From Bone Marrow to Brain and Brawn.
H.M. Blau
At the ASCB meeting: Presentation 2354, Minisymposium
26: Stem Cells. Author presents: Wednesday, December 18,
4:25 —4:45 PM.
Wild-type mice
received adult donor
bone marrow
marked with GFP, a
label. In muscle
tissue (top), the GFP
expressed in some
skeletal myofibers in
longitudinal section
indicates that
myofibers spanning
hundreds of microns
in length have
incorporated cells
derived from bone marrow. The banded distribution of GFP is
due to the internal contractile machinery of skeletal muscle. In a
mature Purkinje neuron (above) in adult mouse brain, the GFP
label reveals the clear contribution from the donor adult bone
marrow cells.
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