Parkinson’s disease is a degenerative disease of the brain where there is progressive depletion of dopamine producing neurons in the substantia nigra, located in the brain. Stem cell therapy may possibly offer a solution as it aims at treating this disease by growing new cells to replace the older degenerated ones.
What are stem cells?
Stem cells are immature cells that have the potential to differentiate into any type of mature cell in the body. The sources of stem cells being researched are :
- Embryonic stem cells from fertilized eggs– they can be made to develop into any type of cell.
- Neural stem cells from embryonic or adult brain– they develop only into nerve cells.
- Mesenchymal stem cells from other tissues.
- Immature stem cells from human (umbilical) cord blood.
Replacement of the degenerated neurons, in a case of Parkinson’s disease, by stem cell transplantation is the basis of treatment that is being studied. The concept is to take stem cells and grow them into neurons, which can then be transplanted into the brain of the patient.
Possibilities of Stem Cell Therapy as a Parkinson’s Cure
The choice of treatment offered to a patient with Parkinson’s disease all have their own limitations.
- Drug therapy is the first line of treatment but they have various side effects and their efficacy decreases as the disease progresses.
- Surgery offers no significant additional benefits.
- Embryonic mesencephalic tissue transplantation has been tried but the results are unstable and there are not enough embryonic donors.
In this scenario, stem cell therapy offers hope, not only for treatment of symptoms of Parkinson’s disease, but possibly for the reversal and halting or slowing down the progression of the disease.
Dopamine cells have been successfully transplanted in the brain of patients with Parkinson’s disease which have led to initial improvement of symptoms such as tremor, slowness of movement, rigidity, and difficulties in balance and posture.
In vitro engineering of stem cells to dopamine neurons, prior to implantation in the brain of a patient with Parkinson’s disease, is being researched to overcome the ethical and practical issues of using fetal dopamine neurons.
The finding of neural stem cells in the adult brain has opened up possibilities of using the patients own neural stem cells to grow dopamine neurons for transplantation into his brain, thereby avoiding the issue of an immune reaction. However, other factors have to be considered such as whether surgery is advisable on the already diseased brain of a patient with Parkinson’s disease.
Limitations of Stem Cell Therapy as a Parkinson’s Cure
There are various ethical, practical, safety and technical issues associated with stem cell therapy.
- Shortage of suitable donor tissue is a major issue in cell replacement therapy in Parkinson’s disease.
- The ethical issue of using fetal dopamine neurons for transplantation into the brain of a patient with Parkinson’s disease.
- Authentic dopamine neurons with correct midbrain identity need to be developed to be able to treat Parkinson’s disease patient effectively.
- Treatment with transplanted dopamine cells gives good initial response but the transplanted cells may become diseased over time.