Oligodendrocyte Progenitor - Transplantation

Transplantation

Apart from spontaneous remyelination, therapeutic myelin repair may be possible, though the type and source of cells for transplant is still unclear. Schwann Cells have shown to be successful in remyelinating the spinal cord of the rat, mouse, and macaque, though immortalized rodent Schwann cells show a tendency to form tumors when transplanted. In addition, transplanted olfactory myelinating cells are being explored as possible therapeutic remyelinating agents.

Oligodendrocyte progenitor transplants have been demonstrated to contribute to remyelination, but it is difficult to maintain such cells in reasonable concentrations at high puritiy. Finding a source for these cells, however, is impractical at the moment. Should adult cells be used for transplantation, a brain biopsy would be required for every patient, added to the risk of immune rejection. Embryonically derived stem cells have been demonstrated, to carry out remyelination under laboratory conditions, but carry ethical implications. Adult central nervous system stem cells have also been shown to generate myelinating oligodendrocytes, but are not readily accessible.

Even if a viable source of oligodendrocyte progenitors were found, identifying and monitoring the outcome of remyelination remains difficult though multimodal measures of conduction velocity and emerging magnetic resonance imaging techniques offer improved sensitivity verses other imaging methods. In addition, the interaction between transplanted cells and immune cells has yet to be fully characterized as does the effect of inflammatory immune cells on remyelination. If the failure of the endogenous remyelination mechanism is due to an unfavorable differentiation environment, then this will have to be addressed prior to any transplantation attempt.