Injections appear to treat mouse multiple sclerosis
17 April 2003
HELEN R. PILCHER
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.
© 2003, Nature News Service