Stem Cells Repair Brain?
Dr. Evan Y. Snyder of Children's Hospital and Harvard
Medical School in Boston, Massechussetts, U.S., said
a laboratory study shows that neural stem cells will
convert themselves into whatever type of cell the brain
needs to restore functions that have been lost to disease,
injury or birth defect.
"The neural stem cell has the ability to become a whole
range of cell types in the brain," said Snyder, lead
author of a study published 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."
Snyder cautioned that it will take at least another five
years of study before neural stem cell transplants can be
tried in humans.
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."
Neural stem cells are found in all parts of the brain
in all stages of development. They are able to convert
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 used a strain of mice called "shiverer," which 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 three weeks of
age, then develops 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's team injected mouse neural stem cells into the
brains of newborn shiverer mice. A control group did not
receive the cells. The injected cells apparently detected
the absent gene 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 mice showed
severe symptoms of their inherited disorder.
An examination of the mice' brains, 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, Snyder said, while earlier studies 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. 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 strokes,
Alzheimer's, 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 noted that all of the studies so far have been
done on newborn mice. He said his team is turning next
to conducting tests in mature mice to see if what works
in infant rodents will also work in adults.
