Stem cells help paralysed mice walk
Injections
appear to treat mouse multiple sclerosis.
17 April 2003
HELEN R. PILCHER
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The immune system
strips MS patients'
nerves of their
myelin insulation
(brown). |
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© SPL |
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Injections of cultured adult brain stem cells seem to
have helped mice with a form of multiple sclerosis to
recover from paralysis. Researchers hope that similar
therapies may one day treat human sufferers of the
disease.
Cells injected into the bloodstream found their way
to the animals' brains, where they repaired damaged and
inflamed areas. Four out of 15 mice with paralysed back
legs moved normally after treatment1.
"It's a great recovery," says team member Angelo
Vescovi of the Stem Cell Research Institute at the San
Raffaele Hospital in Milan, Italy. The other 11 mice
retained only minor tail paralysis.
Multiple sclerosis affects more than a million people
worldwide and is currently incurable. Symptoms include
fatigue, tremors and paralysis. It is thought to arise
when the immune system attacks the nervous system,
stripping brain cells of their fatty myelin coatings and
damaging the underlying nerve fibres, called axons.
It's a wrap
The transplanted cells carry specialized proteins on
their surface that help them to enter the brain. Once
inside, they can turn into any type of adult brain cell,
explains neuro-immunologist Gianvito Martino, also of
San Raffaele Hospital. Over 40% of them turn into cells
that make myelin. "These wrap around the naked axons
that are still there," Martino says, helping the nerve
cells to conduct electricity once again.
Paralysed mice became increasingly active just ten
days after receiving the intravenous injection of one
million cultured brain stem cells.
"It's clear that something very exciting is going
on," says stem-cell-transplant researcher Bill Blakemore
of the University of Cambridge, UK. How it's happening
is less clear. Blakemore doubts that the transplanted
cells produce new myelin coats in the damaged areas.
Scientists have attempted to transplant stem cells
into rats with multiple sclerosis before, with mixed
results. The ability of adult stem cells to produce many
cell types has raised hopes that transplants could treat
conditions from multiple sclerosis to stroke, without
recourse to ethically contentious embryonic stem cells.
Proceed with caution
Others warn that immediate clinical aspirations are
unrealistic. "They seem to have put a very effective
bandage on the early phase of the disease," says
neurologist Alastair Compston, also at Cambridge. But
this is very different to treating multiple sclerosis in
the long term, he points out. Many patients' symptoms
worsen without respite - mainly due to loss of nerve
fibres.
John Sinden, chief scientific officer at stem-cell
company ReNeuron in Guildford, UK, agrees that the
animal model does not accurately mimic chronic multiple
sclerosis. What's more, if cells are injected into the
bloodstream, "there may be a risk that transplanted
cells could stray into other parts of the body", he
says.
There is no evidence to suggest that this will be a
problem, counters Vescovi. Ten days after mice received
their injection, transplanted cells were found in the
lung, liver, spleen and kidney. But after ten more days
they had disappeared.
The team is planning trials later this year in
primates, using similar all-purpose cells from human
fetuses. Compared to adult cells, fetal brain stem cells
can be collected relatively easily and can be cultured
in large numbers for transplantation. |
