Currently available therapies for multiple sclerosis (MS) delay disease 
progression via immunomodulation or immunosuppression. A persisting neurological 
deficit is mostly irreversible. Thus, a reparative treatment is urgently 
warranted. After positive results in animal models, clinical trials to promote 
endogenous remyelination with intravenous immunoglobulins (IVIg) or the growth 
factor IGF-1 were performed, unfortunately without clinical improvement. Another 
possibility to achieve remyelination is the transplantation of myelinating cells 
into the central nervous system. Proof of principle and demonstration of the 
functionality were shown in numerous experiments, and a first clinical trial in 
patients with MS has started. Although there are still several open questions, 
many are specific to MS and can not be answered in an animal model. This first 
trial will show if cell transplantation is a feasible concept in MS and whether 
the transplanted cells will survive and form new myelin. Schwann cells are 
currently the most promising cells to be transplanted, due to the advantages of 
an autologous transplantation from the patient's sural nerve biopsy, possibility 
to expand the cells in culture, and the possibility that they may escape the 
ongoing inflammatory reaction in MS. Other cell types are available, including 
stem cells, which are in the centre of a lively discussion. The results of the 
ongoing trial must be awaited before other transplant studies are performed to 
tackle other yet unresolved problems. At the time, it seems unlikely that cell 
transplantation will become clinical practice in the near future.