The possibility of replacing dead and dying dopamine-producing cells in the brain with transplanted tissue has been of interest to researchers for some time. It is hoped that the transplanted material will help to raise the dopamine levels in the brain to a more normal level, thereby reducing Parkinson’s symptoms.
This is still an area of experimentation and research but several different techniques have been or are being explored, including:
Stem cell implants
Each of the cells in our bodies contains the same DNA but only part of this is ‘differentiated’ or ‘turned on’ according to the part of the body the cell is to be used for. Stem cells are those which have all our genetic information stored in their DNA but as yet they are ‘undifferentiated’, that is they are not yet committed to becoming a specific kind of cell. They therefore have the potential to develop into any type of cell in the body, providing exciting possibilities in treating all kinds of illnesses.
Stem cells may be found in various parts of the body, for example embryonic tissue, the developing nervous system, the adult nervous system and bone marrow. Research is currently taking place in many countries using different types of stem cells:
- embryonic stem cells can be cultured in a laboratory, but ethical concerns make this a complex area of research
- adult stem cells are found in specific organs and tissues and are ready to be ‘differentiated’ or ‘turned on’ by the body and used for growth and repair of those organs and tissues. The hope is that they can be used for repair of other parts of the body.
Results have been mixed and some significant side effects experienced so much more research is needed for scientists to ascertain whether this will be a valid treatment for Parkinson’s. There are also ethical and technical considerations that need to be resolved.
Retinal pigment epithelial cell transplants
These cells are derived from tissue at the back of the eye which produce and release dopamine. Initial trials have shown some promise so further trials are now being carried out.
Xenografts (i.e. transplants of tissue from one species to another)
Results have been mainly negative to date, essentially due to problems with the rejection of implanted cells by the immune system. Research is ongoing.
Adrenal gland cell grafts
Although the adrenal gland is responsible for producing catecholamines (which includes dopamine) amongst other things, this type of transplant has been largely abandoned because of poor results and the complicated surgery.
