Parkinson's disease occurs as a result of a gradual loss of a specific type of nerve cell, located in an area of the brain called the substantia nigra. These nerve cells produce a natural chemical called dopamine (they are called dopaminergic neurons). The lack of dopamine makes patients with Parkinson’s disease have difficulty in moving freely, holding a posture, talking and writing.
Stem celli-based therapies for Parkinson's disease are not yet a routine clinical procedure. Scientists are agreed that more information is needed about the causes of Parkinson’s disease and the biology of stem cells before safe, effective and long-lasting therapies can be developed.
Because a single, well-identified type of cell is affected in Parkinson’s disease, stem cells offer great potential for treatment. The basis for such treatment would be to replace the cells that have died with other identical dopaminergic nerve cells, obtained from stem cells.
You may be aware of recent clinical trials where fetal brain tissue was transplanted into the brains of Parkinson's disease patients. These trials provide proof-of-principle for the approach, since in a few of these trials major and long-lasting improvements were seen in some patients. The trials also emphasized several issues that need to be resolved, one of which is the need to produce large amounts of pure, uniform cells for transplantation into patients. Stem cells provide one possible source, and dopaminergic-like cells have already been obtained from embryonic and fetal brain stem cells.
Further work is also needed to ensure that transplanted dopaminergic cells survive in the brain, integrate with existing cells to reform the circuits that sustain the correct functioning of the brain, and do not give rise to tumours.
Relevant links:
The National Institute for Neurological Disorders and Stroke
European Parkinson’s Disease Association
Parkinson’s Disease Society (UK)