[Neural transplantation for the treatment of Parkinson's disease. Update and future].

: Cell transplantation to replace lost neurons is a recent approach to the treatment of progressive neurodegenerative diseases. Replacement of dopaminergic neurons in patients with Parkinson's disease (PD) was the first transplantation therapy to be tested in the clinical setting. In PD, cell replacement strategy has been based on the idea that neural graft-induced restoration of dopamine neurotransmission in the striatum could lead to substantial and long-lasting functional recovery. Since transplantation of embryonic dopaminergic cells was first reported in the early 1990s, several open-label clinical trials have confirmed the benefits of transplantation. But, the validity of these studies has been uncertain because of small patient numbers, variable inclusion criteria, and the absence of control groups. Two controlled trials have been recently designed and performed. Their designs incorporated a "sham-operated" versus a transplant group. The conclusions drawn by both teams are that fetal mesencephalic allograft can not, at present, be recommended as a treatment for severe PD. However, several lessons can be learnt and the efficacy can be improved employing more neurons and better targets, and/or neurotrophic factors.