Human Stem Cells Replace Damaged
Brain Cells
Human neural stem cells can replace and
take over the functions of damaged nervous system cells in a mouse
model of multiple sclerosis (MS) and related diseases, according
to a study presented at the American Neurological Association's
125th annual meeting, October 15 through 18 in Boston.
"Our results indicate that cell
replacement therapy using human neural stems cells could be an
effective therapy for MS patients," said lead author Seung U. Kim,
MD, a neurologist at the University of British Columbia in
Vancouver. The results are also significant for other neurological
disorders such as Parkinson's disease or stroke, in which
researchers hope neural stem cells will be able to replace damaged
cells.
Multiple sclerosis is a disorder of the
nerve fibers of the brain and spinal cord. In MS patients,
scarring (sclerosis) replaces myelin, a substance that normally
insulates the nerves and speeds electrical conduction through the
fibers.
Depending on which nerve fibers are
hindered, patients can experience problems ranging from weakness
and clumsiness to numbness, visual disturbances, and even
emotional and intellectual changes. Some patients experience MS as
cycles of relapse and remission; others progress to severe
debilitation and may die from the disease .
The myelin is itself part of neural
cells called oligodendrocytes, and one goal of Kim's research is
to replace the lost oligodendrocytes with new ones derived from
neural stem cells. Neural stem cells are immature cells that have
the potential to develop into various types of neurons (the
information-conveying cells of the nervous system) or different
varieties of glial cells (which support and nourish the neurons),
such as oligodendrocytes.
A first step in that direction was
achieved recently when Kim and his colleagues managed to induce
stem cells from the brains of human fetuses to continue to grow
and produce new cells in laboratory dishes, a process referred to
as "immortalization."
"In the present study, we transplanted
these human neural stem cells into the brains of mutant "shiverer"
mice, which have myelin disease throughout the brain and spinal
cord, and demonstrated remyelination of previously unmyelinated
fibers by the implanted cells," said Kim.
Since shiverer mice show functional
deficits such as tremor and a "shivering" gait, the researchers
intend to determine whether neural cell transplantation reverses
this motor dysfunction. Their preliminary observations of the
animals in this study indicated that there was considerable
reduction in tremor in many of the mice.
The implications of this line of
research go well beyond MS and other demyelinating
diseases.
"Since the neural stem cells exhibit
self-renewal and possess multilineage potential, they could be
utilized for cell replacement therapy for other neurological
diseases such as Parkinson's disease, Huntington's disease, motor
neuron diseases, Alzheimer's disease and stroke. Previous
transplantation studies in animal models of these diseases
indicate that cell replacement therapy is feasible," said
Kim.
Indeed, Kim and his group presented a
separate study at the ANA meeting showing that the same human
neural stem cells genetically modified to produce the
neurotransmitter dopamine and then implanted in the brain of a rat
model of Parkinson's disease were able to ameliorate the movement
problems of that disorder.
Р’В©American Neurological Association
(ANA)
17 October 2000