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Single Adult Stem Cell Can Self Renew, Repair Tissue Damage in
Live Mammal
December 15, 2008 (
www.LifeSiteNews.com ) - The first demonstration that a single adult stem
cell can self-renew in a mammal was reported at the American Society for Cell
Biology (ASCB) 48th Annual Meeting, Dec. 13-17, 2008 in San Francisco.
The transplanted adult stem cell and its differentiated descendants restored
lost function to mice with hind limb muscle tissue damage.
The ability to isolate and then transplant skeletal adult muscle stems cells
could have a wide impact in treating not only a variety of muscle wasting
diseases such as muscular dystrophy but also severe muscle injuries or loss of
function from aging and disuse.
The adult stem cells used in the study, conducted at Stanford University, were
isolated from a mixed population of satellite cells in the skeletal muscle of
mice.
The skeletal adult muscle stem cells (MusSC), which live just under the membrane
that surrounds muscle fibers, normally respond to tissue damage by giving rise
to progenitor cells that become myoblasts, fusing into myofibers to repair the
tissue damage.
The scientists transplanted the MusSC into special immune-suppressed "nude" mice
whose muscle satellite cells had been wiped out in a hind limb by irradiation.
The mice would only be able to repair injury if the transplanted MuSC "took."
The scientists, Alessandra Sacco and Helen Blau, had genetically engineered the
transplanted MusSC to glow under ultraviolet light, making it easy to trace.
"To be able to detect the presence of the cells by bioluminescence was really a
breakthrough," says Blau. "It taught us so much more. We could see how the cells
were responding, and really monitor their dynamics."
Sacco and Blau tracked each transplanted stem cell as it rapidly proliferated
and engrafted its progeny into the irradiated muscle tissue. The scientists then
injured the regenerated tissue, setting off massive waves of muscle cell growth
and repair, and subsequently showed that the MuSC and descendents rescued the
second animal's lost muscle healing function.
After isolating the luciferase-glowing muscle stem cells from the transplanted
animal, the scientists duplicated, or cloned, the cells in the lab. Like the
original MuSC, the cloned copies were intact and capable of self-renewal.
"We are thrilled with the results," says Sacco. "It's been known that these
satellite cells are crucial for the regeneration of muscle tissue, but this is
the first demonstration of self-renewal of a single cell."
In other experiments, the researchers transplanted between 10 and 500 luciferase-tagged
MuSC into the leg muscles of mice.
These cells also proliferated and engrafted, forming new myofibers and fusing
with injured fibers.
Unlike tumor cells, the transplanted stem cells achieved homeostasis, growing to
a stable, constant level and ceasing replication. The formation of tumors has
plagued attempts to use embryonic stem cells for similar cures, but appears to
largely be avoided when using adult stem cells.
After demonstrating that the transplanted stem cells proliferated and fully
restored the animal's lost function, Sacco and Blau recovered new stem cells
from the transplant with full stem cell potency, meeting the final "gold
standard" test for adult multipotent stem cells.
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