Fetal cell implant trial for Parkinson's disease has mixed results

Hopes that implantation of fetal cells into the brains of people withneurodegenerative disorders might lead to permanent improvements have been dealt a blow with the publication of a new study in the New England Journal of Medicine (March 8, 2001). This found that, while Parkinson's disease patients derived some benefit from the implantation of embryonic dopaminergic neurons in terms of motor control, this only occurred in younger patients and, in some cases, led to serious dyskinesic side effects such as those seen in patients on long-term dopamine agonist therapy.

The study was conducted by researchers at various centers in the USA, and represents the first occasion that the positive results seen in small studies were put to the test in a randomized, controlled trial. A total of 40 patients with severe Parkinson's, aged between 34 and 75, were randomized to receive a transplant of nerve cells into the brain or a sham surgery and were followed for at least one year. Autopsy results in two patients who died during the course of follow-up confirmed the growth of the transplants in the brain.

There was no significant difference between the two groups in terms of the development of their Parkinson's symptoms over the course of follow-up. However, after one year, patients younger than 60 in the transplantation group had a small decrease in rigidity and bradykinesia but no change in tremor or gait. Improvement was detected only early in the morning, after the patients had been without medication overnight, and there was no significant improvement in older patients in the transplantation group, despite the fact that PET scanning suggested the implanted cells were growing just as well in this group. This suggests that the aging brain may lose its ability to respond to the transplants.