In Parkinson's disease, nerve cells in the part of the brain that controls muscle movement either die or become impaired. Normally, these cells produce a vital chemical known as dopamine, which allows smooth, co-ordinated function of the body's muscles and movement.

In this study, stem cells were developed into dopamine-producing neurons the missing nerve cells in Parkinson's disease. The mice that received neurons derived from their own clones showed significant signs of improvement. But when these neurons were grafted into mice that did not genetically match the transplanted cells, the cells did not survive and the mice did not recover.

The researchers say the therapy is promising because, as the cells originally came from the animal that was ill, they were not rejected by its immune system.

Scientists are pursuing the use of stem cell therapy for Parkinson's disease because it would allow the replacement of the dead dopamine-producing nerve cells with new, healthy cells. This should restore the supply of dopamine within the brain and allow it to work normally again.

"This is an exciting development, as for the first time, we can see that it may be possible to create a person's own embryonic stem cells to potentially treat their Parkinson's. Researchers in this area now need to carry out more studies to satisfy safety concerns and to make the process more efficient before these studies are carried out on people living with Parkinson's. Stem cell therapy offers great hope for repairing the brain in people with Parkinson's. It may ultimately offer a cure, allowing people to lead a life that is free from the symptoms of Parkinson's." – says Dr Kieran Breen, director of research and development at the Parkinson's Disease Society.

Professor Robin Lovell-Badge, an expert in stem cell research at the National Institute of Medical Research, said this was good research which showed using therapeutic cloning could be beneficial : "There was a very significant level of recovery. They only studied the mice for 11 weeks afterwards, which is not a huge amount of time to see how persistent the repaid would be."

However, the experts said much more research in both animals and humans was needed before the treatment could be offered to people with Parkinson's. The finding is able to provide scientists with a clue as to what causes Parkinson's - and could contribute to the search for new treatments.

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