A new breakthrough has been discovered to help persons suffering from Parkinson's disease with the successfully growing brain cells from stem cells and grafted into animal brains.

With the cells surviving and functioning normally in monkeys, researchers said they have hurdled previous difficulties in transforming human embryonic stem cells to become the neurons that has been affected by the disease.

This development raises the prospect of transplanting freshly grown dopamine-producing cells into human patients to treat the disease.

Dr. Lorenz Studer at the Memorial Sloan-Kettering Cancer Centre in New York said previously they were no able to find the right signal for stem cells to differentiate into the right type of cells. But with the new study the new cells survived and reversed movement problems caused by Parkinson's in monkeys.

"The cells we produced in the past would produce some dopamine but in fact were not quite the right type of cell, so there were limited improvements in the animals. Now we know how to do it right, which is promising for future clinical use," Studer said.

As part of the new study, the researchers gave animals six injections of more than a million cells each, to parts of the brain affected by Parkinson's. This time the neurons survived, formed new connections and restored lost movement in mouse, rat and monkey models of the disease, with no sign of tumor development.

Parkinson's disease results when cells that produce dopamine die off in part of the brain called the substantia nigra causing tremors, rigidity and slowness of movement, including tiredness, pain, depression and constipation, which worsen as the disease progresses.

Scientist have tried to regrow the nerve cells lost in neurodegenerative diseases such as Parkinson's, Alzheimer's and amyotrophic lateral sclerosis (ALS) from stem cells, but this is the first time that researchers have found the specific chemical signals required to nudge stem cells into the right kind of dopamine-producing brain cells.

Kieran Breen, director of research at Parkinson's UK noted that the study has shown for the first time that it is possible to transplant nerve cells that work from human stem cells.

"We now have the right cells, but to put them into humans requires them to be produced in a specialised facility rather than a laboratory, for safety reasons. We have removed the main biological bottleneck and now it's an engineering problem," Studer concluded.