Cell therapy and transplantation in Parkinson's disease

Transplanted human fetal dopamine neurons can reinnervate the striatum in p atients with Parkinson's disease (PD). Recent findings using positron emiss ion tomography indicate that the grafts are functionally integrated and res tore dopamine release in the patient's striatum. The grafts can exhibit lon g-term survival without immunological rejection and despite an ongoing dise ase process and continuous antiparkinsonian drug treatment. In the most suc cessful cases, patients have been able to withdraw L-dopa treatment after t ransplantation and resume an independent life. About two-thirds of grafted patients have shown clinically useful, partial recovery of motor function. The major obstacle for the further development of this cell replacement str ategy is that large amounts of human fetal mesencephalic tissue are needed for therapeutic effects. Stem cells hold promise as a virtually unlimited s ource of self-renewing progenitors for transplantation. The possibility to generate dopamine neurons from such cells is now being explored using diffe rent approaches. However, so far the generated neurons have survived poorly after transplantation in animals.