Bone marrow stem cells can transform
into lung, liver
by Michael O'Leary
SEATTLE -- May 4, 2001
(Cancer Digest) -- Researchers have shown for the first time
that transplanted bone marrow stem cells can not only reconstitute
bone marrow, but also may play a role in healing specialized
cells lining the intestines, lung and skin.
The study, done in
mice, is the first evidence that stem cells in bone marrow can
generate other tissues and organs.
A research team led
by Dr. Saul Sharkis, director of Johns Hopkins Oncology Center,
in collaboration with colleagues at Yale University School of
Medicine, reported the findings in the May 4, 2001, issue of
Cell. He says the results hold promise for repairing tissues
damaged by disease or certain treatments.
"This study suggests
that an infusion of stem cells after toxic cancer treatments
may be able to repair damaged tissue throughout the body,"
Sharkis said in a prepared statement. "These cells might
even serve as treatments for a variety of diseases characterized
by tissue and organ damage, such as diabetes and cystic fibrosis."
A stem cell holds a
unique property among cells in the body. When it divides, it
produces two types of cells, rather than identical copies of
itself. One daughter cell remains a stem cell, while the other
matures into a specialized cell type needed in that part of the
body.
Researchers thought,
until recently, that stem cells in bone marrow would only divide
to form a new bone marrow stem cell, and a cell that would develop
into one of the many specialized cell types that make up the
blood and immune systems. Likewise, stem cells found in other
tissues in the body that need to be continually replenished,
such as skin, were thought to be capable of generating only the
cell types needed for skin.
In the National Institutes
of Health-funded study, the researchers treated female mice with
high doses of radiation, which destroyed the bone marrow and
the lining of tissues and organs such as the intestine and lung.
They then transplanted
each mouse with a single purified bone marrow stem cell from
a male mouse that had been tagged with a fluorescent dye, allowing
investigators to track and recover cells made by the single transplanted
stem cell after transplantation.
In all five female
mice, they found the male chromosome not only in the bone marrow
and blood, as expected, but also in tissue lining the lungs,
esophagus, stomach, small and large intestine, liver and skin.
The findings surprised
researchers, says co-author Dr. Diane Krause, assistant professor
of laboratory medicine and pathology at Yale University School
of Medicine.
"It's astounding
that there are cells in our bone marrow that can become so many
different cell types," said Krause. "The challenges
now are to elucidate how these changes occur and to harness these
findings to develop therapies for many different human diseases
and injuries."
How the finding affects
the national debate surrounding research into embryonic stem
cells remains to be seen. For her part, Krause stressed only
continued research into both adult-derived stem cells and embryonic
stem cells will be able to answer the question of whether they
are functionally the same.
"Because this
field is very much in its infancy, we need to keep working with
embryonic stem cells. Our findings are very exciting, but, in
order for the field of stem cell research to move ahead, work
on both embryonic and adult-derived stem cells needs to be pursued,"
she said.
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