PARIS, France (AFP) — Lab monkeys with Parkinson’s symptoms regained significant mobility after neurons made from human stem cells were inserted into their brains, researchers reported Wednesday in a study hailed as “groundbreaking”.

The promising results were presented as the last step before human clinical trials, perhaps as early as next year, the study’s senior author, Jun Takahashi, a professor at Kyoto University, told AFP.

Parkinson’s is a degenerative disease that erodes motor functions. Typical symptoms include shaking, rigidity and difficulty walking. In advanced stages, depression, anxiety and dementia are also common.

Worldwide, about 10 million people are afflicted with the disease, according to the Parkinson’s Disease Foundation.

Earlier experiments had shown improvements in patients treated with stem cells taken from human foetal tissue and likewise coaxed into the dopamine-producing brain cells that are attacked by Parkinson’s.

Dopamine is a naturally occurring chemical that plays several key roles in the brain and body.

But the use of foetal tissue is fraught with practical and ethical problems.

So Takahashi and his colleagues, in a medical first, substituted so-called induced pluripotent stem cells (iPSCs), which can be easily made from human skin or blood.

Within a year, some monkey’s who had could barely stand up gradually recovered mobility.

“They became more active, moving more rapidly and more smoothly,” Takahashi said by email. Animals that had taken to just sitting “start walking around in the cage.”

“These findings are strong evidence that human iPSC-derived dopaminergic neurons can be clinically applicable to treat Parkinson’s patients,” he said.

Experts not involved in the research described the results as encouraging.

The treatment, if proven viable, “has the potential to reverse Parkinson’s by replacing the dopamine cells that have been lost — a groundbreaking feat,” said David Dexter, deputy research director at Parkinson’s UK.

“Not only did the new cells survive… but they also integrated with the existing neuronal network,” he said.