Researchers Take Big Step
Toward Growing Replacement
Body Parts
April 2, 1999
WASHINGTON (AP) - Researchers
have isolated from adult bone marrow a
master cell that can be directed to grow
bone or cartilage, a laboratory feat that
experts call a major step toward learning
to make replacement parts for ailing or
aged bodies.
The researchers at Osiris Therapeutics in
Baltimore report in the journal Science
that they isolated a single cell, called a
mesenchymal stem cell, and then grew it
into a colony of more than a million cells
that could be induced to produce bone,
cartilage or fat.
Other experts in the rapidly expanding
field of stem cell research applauded the
achievement.
"The fact that they can (isolate) a
precursor cell like that, and direct it to
produce specific cell types, is quite an
advance," said Dr. James A. Thomson of
the University of Wisconsin, a noted
pioneer in stem cell research. "It may be
that such cells can eventually be used for
therapy and that would be quite exciting."
Stem cells are the body's building blocks.
Some, such as pluripotent stem cells,
come only from embryos and their use in
research is opposed by many people.
Other stem cells, such as the mesenchymal
cells used by Osiris, are produced in
adults.
But only the pluripotent stem cells from
embryos are thought to be capable of
growing into any tissue in the body. The
mesenchymal stem cells are the parent
lines for bone, cartilage, fat, tendon and
muscle.
The Osiris work helps move stem cell
research from the laboratory toward the
clinic, said Dr. David J. Anderson, a
Howard Hughes Medical Institute stem
cell researcher at the California Institute of
Technology.
"If you want to use stem cells to replace
damaged tissue, you have to first know
how to differentiate those cells in the lab
dish before you put them into a patient,"
he said.
In their work, Osiris researchers led by
Dr. Mark F. Pittenger grew a single
mesenchymal stem cell through more than
20 generations to create about a million
cells.
The researchers then altered the culture
medium and added proteins that caused
the specimens to grow into cell families, or
lineages, that would produce bone, tendon
or fat, Pittenger said. Other work
underway may lead to producing muscle
cell lines.
"We've arrived at conditions that allow us
a very strong degree of control," said
Pittenger. "When we direct these cells to
the (cartilage) lineage, almost all of the
cells grow to that lineage."
That means it's very likely that researchers
will eventually be able to inject specific
types of cells into patients, which then
would grow into replacement bone,
tendon or muscle, he said.
Laboratory research on animals is already
underway and human studies may be
possible in three years, he said.
If the technique proves successful,
researchers predict that precursor cells for
bone could be used to replace tissue lost
to cancer, osteoporosis, injury or dental
disease.
Research in rabbits and dogs already has
shown that gaps in leg bone caused by
surgery, such as for cancer, can be filled in
with tissue grown in the body from stem
cells.
Animal studies also are underway to
determine if stem cells injected into the
heart can replace scar tissue caused by
heart attack.
The study using adult stem cells is
important also because it avoids the
controversy of using stem cells from
embryos, Pittenger said.
There are no known adult stem cells for
some critical organs, such as kidney, heart
and lung, he noted. If replacements are to
be grown for these parts, Thomson said, it
would require embryonic stem cell
research.
Copyright 1999 The Associated Press.
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