When human embryonic stem cells (hESCs) were injected into the monkeys` brain, it helped monkeys with Parkinson's disease-like symptoms ease their suffering, state Japanese scientists.
These cells were injected into monkeys whose brains had been damaged by a chemical that destroys dopamine-producing neurons and so causes Parkinson's symptoms.
In the study conducted by Jun Takahashi of Kyoto University in Japan and colleagues, two monkeys received hESCs that had been matured into an early form of neural cell.
Six months later, the monkeys had recovered 20 to 45 per cent of the movement they had lost before treatment.
Post-mortems a year after treatment showed that the cells had developed into fully functioning dopamine-secreting neurons.
Another monkey that received less-mature neural cells also showed improvements.
"Monkeys starting with tremors and rigidity [began] to move smoothly, and animals originally confined to sitting down were able to walk around," New Scientists quoted Takahashi as saying.
But it will probably be four to six years before clinical trials in humans begin, according to the team.