From: Gina Miller (nanogirl@halcyon.com)
Date: Tue Jun 08 1999 - 01:45:27 MDT
Master cells may restore destroyed brain tissue, study shows
Copyright © 1999 Nando Media
Copyright © 1999 Associated Press
By PAUL RECER
WASHINGTON (June 7, 1999 5:00 p.m. EDT http://www.nandotimes.com) -
Injections of neural stem cells, a so-called master cell that can mature
into any type of brain tissue, may be able to restore neurons killed by
diseases that affect the whole brain, laboratory studies with mice suggest.
Dr. Evan Y. Snyder of Children's Hospital and Harvard Medical School in
Boston said the laboratory study shows that the neural stem cells will
convert themselves into whatever type of cell the ailing brain needs,
restoring functions that have been lost to diseases like Alzheimer's, injury
or birth defect.
"The neural stem cell has the ability to become a whole range of cell types
in the brain," said Snyder, the lead author of a study appearing Tuesday in
Proceedings of the National Academy of Sciences. "The neural stem cell can
accommodate all different regions of the brain and insert itself
appropriately into the fabric of the brain."
Dr. Gerald D. Fischbach, director of the National Institute of Neurological
Disorders and Stroke, one of the National Institutes of Health, said in a
statement that Snyder's study shows that neural stem cells are capable of
moving to all parts of the brain.
"Stem cells that can develop into a variety of different types of nerve
cells and glial cells (a type of brain tissue) would be extremely valuable
in the therapy of acute and chronic neurological disorders," Fischbach said.
Neural stem cells are found in all parts of the brain in all stages of
development. They are capable of converting to neurons, glial cells and
other types of cells in the central nervous system.
Snyder said that his team is researching using a neural stem cell culture
that was developed 13 years ago from cells removed from the brain of a
newborn mouse. He said the same cell line can be used in all types of mice.
The study in Proceedings used a strain of mice called "shiverer." This breed
has a genetic flaw that prevents its body from making a protein that is
needed to form myelin, the tissue that insulates nerve fibers.
A shiverer mouse develops tremors within a three weeks of age and goes on to
develop other symptoms similar those seen in human patients with multiple
sclerosis. MS is a crippling and sometimes fatal disease caused by the
progressive loss of the myelin covering of nerve fibers in the brain and the
spine.
Snyder said his team injected the mouse neural stem cells into the brains of
newborn shiverer mice. A control group of mice did not receive the cells. He
said the injected stem cells apparently detected the absent gene in the
shiverer mice and converted into oligodendrocytes, which are brain cells
that produce myelin.
Among the shiverer mice that received the stem cells, 60 percent appeared to
behave like normal mice, while the untreated shiverer mice showed severe
symptoms of their inherited disorder.
An examination of the animal's brains, said Snyder, showed that a much
higher percentage than normal of the inject stem cells converted into
oligodendrocytes, which then made the missing myelin. The brains of some of
the tested mice even appeared to have normal myelin tissue covering nerve
fibers, he said.
Snyder said that earlier studies in mice showed that the stem cells also
selectively converted into neurons to replace neurons that were missing or
removed.
"We have shown that these cells will migrate to wherever in the brain they
are needed," he said. "If there are missing neurons, these cells will
convert into new neurons. It is possible that these stem cells will replace
any damaged or missing cells in the brain."
Snyder said this means that transplanting human neural stem cells could
become part of the therapy for Alzheimer's, strokes, multiple sclerosis and
a whole group of brain birth defects. The researcher, however, said that
stem cell transplantation is not a "silver bullet" that by itself will cure
those disorders.
"The brain is very complex, and this means ... repairing the brain is not
going to be simple," he said.
Snyder cautioned that it will take at least another five years of study
before neural stem cell transplants can be tried in humans. For instance, he
noted that all of the studies so far have been done on newborn mice. Snyder
said his team is turning next to conducting tests in mature mice to see if
what works in infant rodents will also work adults.
Gina "Nanogirl" Miller
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