Human embryonic stem cells have been used to treat a model of Parkinson's disease in mice, rats and monkeys, pointing to a possible new way of treating the condition.
Researchers from the Memorial Sloan-Kettering Cancer Centre in New York as well as other US institutions used stem cells to create dopamine neurons which have similar characteristics to brain cells affected by Parkinson's disease. The researchers then introduced these new cells to the animals' brains.
The animals survived the procedure and the researchers observed a reversal of tremors and reduced erratic movements in mice and rats. The scientists then treated two monkeys that had been given Parkinson's-like lesions and were able to successfully graft neurons into their brains, demonstrating the possibility of scaling up the technique.
Dr Lorenz Studer, one of the study's leading researchers said: 'Previously we did not fully understand the particular signals needed to tell stem cells how to differentiate into the right type of cells. 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'.
In addition to reversing the movement problems associated with Parkinson's, the study, published in Nature, showed that no cancer or uncontrolled cell growth was observed after the cells had been grafted onto the animals, which are two major concerns in stem cell therapy.
Dr Studer and colleagues are now planning to create the new cells on a larger scale over a 12-month period and hope to perform the technique on around 100 patients after thorough safety testing. Regarding human trials Dr Studer said: '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'.
Although the findings of this study are promising, more work is required before stem cells can be used to treat Parkinson's in humans as the human brain is much more complex than those of the animals tested. It remains to be seen how the use of stem cells demonstrated in this study might affect higher functions such as speech or complex memory.
Dr Kieran Breen, director of research at Parkinson's UK said: 'Stem cell therapy may still be some way off. However, this study has shown for the first time that is possible to transplant nerve cells that work from human stem cells'.
Around 120,000 people have Parkinson's disease in the UK. While the disease mostly affects people over the age of 50, one in 20 of those affected by it is under the age of 40.