The long-term safety and efficacy of bilateral transplantation of human fetal striatal tissue in patients with mild to moderate Huntington's disease.

Huntington's disease (HD) is a fatal autosomal dominant neurodegenerative disease involving progressive motor, cognitive and behavioural decline, leading to death approximately 20 years after motor onset. The disease is characterised pathologically by an early and progressive striatal neuronal cell loss and atrophy, which has provided the rationale for first clinical trials of neural repair using fetal striatal cell transplantation. Between 2000 and 2003, the 'NEST-UK' consortium carried out bilateral striatal transplants of human fetal striatal tissue in five HD patients.

Is there a future for neural transplantation?

Traditionally neural transplantation has had as its central tenet the replacement of missing neurons that have been lost because of neurodegenerative processes, as exemplified by diseases such as Parkinson disease (PD). However, the effectiveness and widespread application of this approach clinically has been limited, primarily because of the poor donor supply of human fetal neural tissue and the incomplete neurobiological understanding of the circuit reconstruction required to normalize function in these diseases. So, in PD the progress from promising neural transplantation in animal models to proof-of-principle, open-labeled clinical transplants, to randomized, placebo-controlled studies of neural transplantation has not been straightforward.

The emerging technologies of neural xenografting and stem cell transplantation for treating neurodegenerative disorders.

Neural transplantation has normally been considered in the context of the neurodegenerative disorders, Parkinson's and Huntington's disease, which are characterized pathologically by the predominant loss of specific cells in the basal ganglia. This approach has now emerged from the experimental arena into the level of clinical trial, at least with respect to fetal human allografts. However the ethical and practical problems with using such tissue has led to the search for alternative sources of cells of which two of the most promising are cells from another species, such as the pig (xenografts), and stem cells.