Stem cells transformed into brain cells to treat Parkinson's disease

Why not for stroke? Who's testing it for stroke?
http://www.guardian.co.uk/science/2011/nov/06/stem-cells-brain-parkinsons-disease?newsfeed=true

Brain cells that die off in Parkinson's disease have been grown from stem cells and grafted into monkeys' brains in a major step towards new treatments for the condition.

US researchers say they have overcome previous difficulties in coaxing human embryonic stem cells to become the neurons killed by the disease. Tests showed the cells survive and function normally in animals and reverse movement problems caused by Parkinson's in monkeys.

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

"Previously we did not fully understand the particular signals needed to tell stem cells how to differentiate into the right type of cells," said Dr Lorenz Studer at the Memorial Sloan-Kettering Cancer Centre in New York.

"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."

Parkinson's disease takes hold as cells that produce dopamine die off in part of the brain called the substantia nigra. This causes tremors, rigidity and slowness of movement, though patients may also experience tiredness, pain, depression and constipation, which worsen as the disease progresses.

The main treatments for Parkinson's are drugs that aim to control the symptoms by increasing the levels of dopamine that reach the brain and stimulating the parts of the brain where dopamine works. Some patients have wires surgically implanted into their brains that deliver electrical pulses to alleviate movement problems.

For around a decade, scientists have been trying to regrow nerve cells lost in neurodegenerative diseases such as Parkinson's, Alzheimer's and amyotrophic lateral sclerosis (ALS) from stem cells. However experiments in which dopamine neurons were created from mouse stem cells have not been successfully reproduced in humans. There have also been safety concerns, with signs that dopamine neurons developed from human stem cells can trigger the growth of tumours. As a result, clinical trials in humans have yet to start.