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 re-grow 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.
Dr Studer and his colleagues, whose work is published in the journal Nature, found the specific chemical signals required to nudge stem cells into the right kind of dopamine-producing brain cells.
In a series of experiments, the team gave animals six injections of more than a million cells each, to parts of the brain affected by Parkinson's. The neurons survived, formed new connections and restored lost movement in mouse, rat and monkey models of the disease, with no sign of tumour development. The improvement in monkeys was crucial, as the rodent brains required fewer working neurons to overcome their symptoms. This study has shown for the first time that it is possible to transplant nerve cells that work from human stem cells. (19)
Dopamine-producing nerve cells derived from embryonic stem cells and implanted into the brain of a monkey with Parkinson's disease
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