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 cell-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 neurons. These dopaminergic neurons can readily be obtained from embryonic stem cells in the laboratory, but there are still ethical and technical hurdles to using this source.
Dopaminergic neurons can also be obtained from fetal brain tissue. You may be aware of 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. Recent findings also highlight a further concern about cell transplantation therapies. The fetal transplants that some patients received began to show signs of being affected by Parkinson's disease. This showed that the disease from the patient was transmitted to the transplanted fetal cells.
Stem cells could also help Parkinson's patients by contributing to the discovery of new drugs, which would have a much wider impact than cell therapies. We can now get embryonic-like stem cells from adults through a method called "reprogramming". By reprogramming a sample of adult, specialised cells from a patient, we can make so-called induced pluripotent stem (iPS) cells. These iPS cells can make any type of cell found in the body, including dopaminergic neurons. Scientists are now making iPS cells from people with Parkinson’s disease and using them to produce neurons in the laboratory. The aim is to learn more about why these nerve cells die in Parkinson's disease, and to use the cells to test for substances that could be developed into new drugs.
Relevant links:
Michael J. Fox Foundation
Parkinson’s UK
The National Institute for Neurological Disorders and Stroke
European Parkinson’s Disease Association
