Scientists have successfully eased the symptoms of Parkinson's disease in monkeys with the help of human stem cell transplants.
During the course of study, published in the Proceedings of the National Academy of Sciences, the scientists isolated stem cells from the brains of aborted foetuses, and grew them into large numbers in the laboratory.
Thereafter, they injected the cells into the brains of monkeys with a severe form of chemically induced Parkinson's disease.
Before the treatment, the monkeys could not walk unaided, struggled to use their hands, and sometimes were unable to move at all. However two months after the treatment, they started walking, feeding themselves, and move more normally.
"They're not as good as normal monkeys, but the improvement is still dramatic," Nature magazine quoted team-member and neuroscientist Richard Sidman from the Harvard Institutes of Medicine, Boston, Massachusetts, as saying.
The study shows that that stem cells not only replace cells, but also persuade the brain to heal itself.
"People used to think that stem cells transplants would work by replacing missing cells. But these results suggest they may do more than that. They may actually switch on the brain's own innate repair mechanisms," says neuroscientist John Sinden from the UK stem-cell company ReNeuron.
Evan Snyder from the California based Burnham Institute for Medical Research says that much more basic research needs to be conducted before clinical trials are carried out.
"It's becoming clear that transplanted neural stem cells exert their behavioural effects through a series of mechanisms," he says.
"There's a whole network of activity and crosstalk," he adds.