MACROPHAGES IN CNS REMYELINATION - FRIEND OR FOE

Hematogenous macrophages and resident brain microglia are agents of de myelination in multiple sclerosis (MS) and paradoxically may also part icipate in remyelination. In vitro studies have shown that macrophage enrichment of aggregate brain cultures promotes myelination per se and enhances the capacity to remyelinate following a demyelinating episod e. It has been hypothesized that remyelination in MS is implemented by surviving dedifferentiated oligodendrocytes or by newly recruited pro genitors that migrate, proliferate and synthesize myelin in response t o signalling molecules in the local environment. We postulate that mac rophage-derived cytokines or growth factors may directly or indirectly promote oligodendroglial proliferation and differentiation, contribut ing to myelin repair in inflammatory demyelinating disease.