Stem Cell Transplants Fail to Cure Parkinson’s disease

A controversial study on the treatment of Parkinson's disease (PD) has come to a disappointing end. Previous open clinical trials had suggested that transplantation of human embryonic dopamine neurons into the brains of patients with Parkinson's disease was beneficial. However, a recent study published in the New England Journal of Medicine has found that in a controlled trial, no significant improvement was noted in patients with transplanted neurons. Freed et al. transplanted precursors of dopaminergic cells in fragments of mesencephalon isolated from human fetuses into the brains of patients with PD. Twenty patients received the operation, in which four holes were drilled in their skulls, and twenty others underwent sham surgery, in which the drill did not go all the way through the skull. Encouragingly, some of the implanted cells were found to have survived and differentiated on histologic examination or positron-emission tomography (PET). However, there was no correlation between these findings and motor improvements in the patients. No significant improvement was noted in elderly patients who had undergone the transplantation. However, younger patients, who make up about 40% of Parkinson's patients, showed a slight improvement of symptoms, but this only lasted for one year after the surgery.

The study had generated considerable controversy, as many people felt that it was unethical to perform sham operations in patients because of the pain and the risk of complications associated with the surgery.


  1. Freed et al. New England Journal of Medicine. 2001; 344:710-719.