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Date: Thursday, April 3, 1997 FOR IMMEDIATE RELEASE Contact: National Institutes of Health, National Institute of Neurological Disorders and Stroke, Natalie Larsen, 301-496-5751
For decades, scientists believed that the adult central
nervous system could not repair itself, in part because it lacked
fundamental "stem cells," mother cells that can divide
to form other kinds of cells. A series of findings has now shown
that stem cells are present in the adult brain and spinal cord,
and that they can be grown in culture and directed to act in much
the same way as fetal stem cells. These findings provide new hope
for people with Parkinson's disease, spinal cord injury, and a
host of other disorders.
Recent advances in understanding adult CNS stem cells
are reviewed in the April 4, 1997, issue of Science by
Ronald D.G. McKay, Ph.D., chief of the Laboratory of Molecular
Biology at the National Institute of Neurological Disorders and
Stroke (NINDS) in Bethesda, Maryland. In another recent paper,
Dr. McKay and his colleagues provided the first detailed evidence
that adult and fetal stem cells behave in a uniform way. These
findings suggest that what scientists are learning about the complex
molecular steps controlling fetal development may be directly
applied to repair of the damaged adult nervous system.
"We need to understand the chemical signals,
or language, that cells use to control differentiation into different
types of cells," says Dr. McKay. "While previous evidence
suggested that there were stem cells in the adult, there was no
information about how to control them." Learning that adult
stem cells are essentially the same as fetal stem cells is the
latest in a string of findings revealing that the adult CNS is
actually quite malleable, or "plastic."
Stem cells are the beginning of the story of development,
"like the Garden of Eden," says Dr. McKay. A single
CNS stem cell can differentiate, or change during cell division,
into any of the three major cell types in the brain and spinal
cord: neurons, astrocytes, and oligodendrocytes. This differentiation
occurs naturally during fetal development, ultimately giving rise
to the marvelously complex human nervous system. For unknown reasons,
however, most CNS stem cells in adults do not normally differentiate.
Dr. McKay and others recently discovered that purified
CNS stem cells will divide in culture if given one of several
growth factors. This will allow scientists to move from a "hunter-gatherer"
stage, where they search out a limited supply of stem cells, to
a "settled agriculture" stage, where they can use systematic
technology to grow their own supply, Dr. McKay says.
The newly developed ability to culture large numbers
of purified stem cells allows scientists to study the specific
roles chemical signals play in brain development. For example,
Dr. McKay and his colleagues have found that one protein instructs
cultured stem cells to differentiate into neurons, while others
lead to astrocyte and oligodendrocyte development. This knowledge
should ultimately allow researchers to manipulate adult CNS stem
cells and use them to replace cells that have been lost to injury
or disease.
One of the most immediate applications for the new
knowledge about stem cells may be to improve treatment for Parkinson's
disease. Early fetal transplant studies have shown that transplanted
cells can survive in the brains of Parkinson's patients and partially
restore function. Using the new information from Dr. McKay and
others, researchers may now be able to culture stem cells to repair
damaged parts of the brain and spinal cord. These stem cells might
also be genetically altered to produce substances important to
normal CNS function. Eventually, scientists may even be able to
eliminate the need for transplants by pharmacologically manipulating
the stem cells normally present in the CNS.
This research may also lead to new ways of stopping
the growth of brain tumors. Putting genes that control cancer
susceptibility into a stem cell culture would allow scientists
to learn how these genes function in a controlled situation.
The next step, says Dr. McKay, is to learn why CNS
stem cells in adults do not differentiate as easily in the body
as they do in culture. Scientists also need to learn what adult
stem cells normally do in the CNS. Answering these questions may
not only point to ways of repairing the damaged nervous system,
but may also help researchers understand normal aging.
The NINDS, one of the National Institutes of Health
located in Bethesda, Maryland, is the nation's leading supporter
of research on the brain and nervous system and a lead agency
for the Congressionally designated Decade of the Brain.
(This release will be available on the World Wide Web at www.ninds.nih.gov).