Cell transplantation in Parkinson's disease

Previous open-label clinical trials have provided proof of principle that intrastriatal transplants of fetal dopaminergic neurons can induce substantial and long-lasting functional benefits in patients with Parkinson's disease. However, in two recent NIH-sponsored double-blind trials functional improvements were only marginal and the primary endpoints were not met. Severe off-phase dyskinesias were observed in a significant proportion of the transplanted patients, raising doubts about the viability of the cell transplantation approach. The results from the two NIH-sponsored trials highlight several important issues that need to be carefully addressed before any further clinical trials are initiated. Several aspects of the transplantation procedure, tissue handling and storage, immunosuppressive treatment, and patient selection, clearly need to be improved and standardized. Furthermore, because the extent to which degeneration of dopaminergic neurons also affects striatal and cortical areas outside the putamen varies from patient to patient, the way the transplantation is made – the number of graft sites and their placement – might need to be tailored individually to each patient. With further improvement and refinement of the grafting procedure there is every reason to believe that cell transplantation can be developed into a safe and effective therapy for patients with Parkinson's disease.