Transplantation options for therapeutic central nervous system remyelination

Persistent demyelination, in addition to being the major pathology of multiple sclerosis and the leucodystrophies, is also a feature of spinal cord trauma where there is evidence that it contributes to the functional deficit. In experimental animals it is possible to remyelinate demyelinated CNS axons by transplanting cultures containing central or peripheral myelinogenic cells. Using functional testing we have been able to show that transplant-mediated remyelination results in restoration of function lost as a consequence of demyelination. Glial cell transplantation may therefore provide a therapeutic strategy for remyelinating areas of chronic demyelination. This article reviews issues that have to be addressed before glial transplantation can be undertaken in humans. These include: what cells to use, where would the cells come from, and can we predict how much remyelination will be achieved? It concludes that the most promising approach will be to use neural multipotential stem cells isolated from embryonic CNS, expanded in vitro as neurospheres and then committed to oligodendrocyte lineage differentiation prior to implantation. However, even with such preparations, which have considerable myelinating potential, the extent of remyelination that will be achieved cannot currently be predicted with any degree of certainty.