Evolving concepts and issues in remyelination.

The ability of the central nervous system to undergo remyelination is now well established in both clinical and experimental situations. The focus of investigation has shifted from simple morphologic documentation to a detailed examination of the basic biologic processes controlling or limiting remyelination. Successful remyelination depends on an adequate number of oligodendrocytes, which may be provided either by proliferation of endogenous cells or by delivery of exogenous oligodendrocytes, which have been shown to be capable of remyelinating axons. It has recently been found that these transplanted cells are capable of significant migration to reach axons. The adhesion of myelinating cells to the demyelinated axon is probably another step in the process of remyelination and may require a form of cell adhesion molecule, although it is possible that the actual process of myelin wrapping depends on some other additional signal. Attempts to enhance remyelination will involve modulation of both the demyelinating event and these basic biological oligodendrocyte-axon interactions.