Date: Fri 23-Apr-1999

Publication: Hea

Author: CURT

Quick Words:

replacement-body-parts

Full Text:

HEALTH MONITOR: Researchers Take Big Step Toward Growing Replacement Body

Parts

By Paul Recer

Associated Press

WASHINGTON, DC -- In what may be a major step toward learning how to grow

replacement body parts, researchers in Baltimore have isolated from adult bone

marrow a master cell that can be induced to grow bone or cartilage.

A study published today in the journal Science reports that researchers at

Osiris Therapeutics extracted a single mesenchymal stem cell from bone marrow

and then grew it into a colony of more than a million cells that could be

directed to produce either bone, cartilage or fat.

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.

Experts said the study is an important achievement for the new and rapidly

expanding field of stem cell research.

"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." The study using adult stem cells is important also because it

avoids the controversy of using stem cells from embryos, said Dr Mark F.

Pittenger, who led the team of Osiris researchers.

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 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 under way 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.

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.

Congress has banned federal financing of research using human embryos, and

some lawmakers oppose a National Institutes of Health plan to possibly pay for

embryonic stem cell research.

But Thomson, one of the first to isolate stem cells from human embryos, said

that although researchers have proven that some types of stem cells can be

obtained from adults, there is still a scientific need for embryonic stem cell

research. 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.