ABSTRACT
Clinical trials with transplantation of human embryonic mesencephalic tissue into the caudate and putamen (striatum) of Parkinson’s disease (PD) patients were initiated in 1987. About 350 patients have been operated upon since then.1 At that time, it was not known whether neuronal replacement could be effective in the diseased human brain. The main objective of scientific efforts in the past 15 years have been to provide proof-of-principle that: the grafted dopamine neurons can survive and form connections in the PD patient’s brain; the patient’s brain can integrate and use the grafted neurons; and the grafts can induce a measurable clinical improvement.2 Dopaminergic neurons isolated from human fetuses were transplanted to the striatum of PD patients, on one or both sides. The researchers who conducted the open trials in several medical centers reported on significant clinical benefits and demonstrated that the transplanted cells survived for years and produced dopamine.1,2 However, practical and ethical issues such as the need for up to eight fetuses to provide sufficient numbers of dopaminergic neurons for one PD patient limited this specific treatment.3-5 Recent reports on double-blind controlled trails of fetal nigral
transplantation raised serious questions on the safety and the efficacy of this procedure. They reported that improvement was not significant in most of the patients, while high percentages of the treated patients developed severe uncontrolled movements (tardive dyskinesia).6,7
Moreover, Olanow’s team found some evidence to suggest that an immunological reaction was destroying or disabling the tissue grafts.7
