A view from The NewScientist on the Parkinson's/stem cell debate.
Think again
Transplanting fetal brain cells to treat Parkinson's disease
remains an attractive therapy, as the trial producing "disastrous"
results is heavily criticised
A US experiment which produced "disastrous" results after
fetal cells were transplanted into the brains of Parkinson's
disease sufferers has been severely criticised by international
experts.
Five of 20 patients were left with uncontrollable and
untreatable jerky movements, which the US team says are
caused by the new dopamine-producing cells going into
overdrive.
Previous trials of fetal cell transplants in Parkinson's sufferers
in Europe have relieved symptoms in many patients without
producing severe side effects. These new "absolutely
devastating" results mean fetal transplant experiments have to
go right back to the drawing board, said Paul Greene, a
neurologist at Columbia University in New York, and one of the
researchers.
But leading European Parkinson's experts say the US
experiment was seriously flawed. "This study unfortunately
used a technique different to those used in previous primate
and human studies," says Lucy Annett of Cambridge
University, who has performed transplants in primates. "It had
not been properly validated by animal studies."
Anders Björklund, a world leader in human fetal cell transplants
at Lund University in Sweden, told New Scientist: "We are
convinced this study has no implications for ongoing fetal
transplant Parkinson's programmes."
Sham surgery
Over 20 European scientists wrote to the journal Science
seven years ago expressing their concern that the funding of a
large trial for this technique ignored other, perhaps more
promising, approaches.
The trial, conducted by a team from Columbia University,
involved transplanting fetal brain tissue into the brains of 20
long term Parkinson's sufferers. Controversially, 20 other
patients received sham surgery.
Some of the patients showed no improvement in symptoms.
For others, the improvements were slight. But after one year,
the patients that had showed the most improvement began to
develop severe dyskenesia - uncontrollable jerky movements.
These were more intense than their original symptoms.
The Columbia team say the embryonic cells had gone into
overdrive, and were producing too much dopamine. There is no
way to turn these cells off.
Technical trouble
Björklund says other experiments using much higher volumes of
fetal tissue have not produced these side effects. He says
technical problems with the trial make it impossible to estimate
how many of the dopamine-producing cells reached the vital
part of the patients' brains.
The surgical technique itself was unusual, he says. The
injections were made through the frontal cortex, requiring a
long needle. "There are concerns that the tissue may have
spilled over into the frontal cortex and have unpredictable
results," he says.
Long term storage of the fetal tissue before transplant, and a
lack of immuno-suppressive drugs, could also affect the
results, he says.
Björklund says the study does not in any way dim hopes to
use stem cells to cure Parkinson's. Stem cell experiments in
mice have already reported good results.
"Using stem cells will make it possible to carefully control the
amounts of dopamine-producing tissue being transplanted," he
says.
More at: New England Journal of Medicine (vol 344, p 710)
Science (vol 263, p 737)
Stem cells preferable to xenotransplantation to treat
Parkinsons's (20/02/01)
Gene treatment for Parkinson's (27.10.00)
Correspondence about this story should be directed to
latestnews@newscientist.com
1700 GMT, 13 March 2001
Emma Young |
