Myelin remyelination

Woodruff R. H. and Franklin R. J. M. (1999). The expression of myelin protein mRNAs during remyelination of lysolecithin-induced demyelination. Neuropathol. Appl. Neurobiol. 25 226-235. 

It is conceivable that the process of remyelination mimics that of myelination during development, but the key factors affecting the differentiation and maturation of OPCs into myelinating oligodendrocytes do not perfectly trigger remyelination... 

In demyelination such as MS, PSA-NCAM is expressed on denuded axons and might act as an inhibitor of remyelination, whereas the myelinated part outside the plaque is PSA-NCAM negative (Charles et al., 2000 Coman et al., 2005). On the other hand, in MS a two- to threefold increase in OPC density and proliferation was found in the subventricular zone (SVZ), which correlated with enhanced numbers of PSA-NCAM(-i-) cells (Nait-Oumesmar et al., 2007). EAE in rodents is another important example of the activation of the SVZ and the involvement of progenitor cells expressing the polysialylated form of neural cell adhesion molecule (PSA-NCAM) in the repair process (Picard-Riera et al., 2002). 

Transferrin (Tf), the iron transport glycoprotein found in the biological fluids of vertebrates, is also synthesized by oligodendrocytes in the CNS. Overexpressing Tf in the brain of transgenic mice accelerates oligodendrocyte maturation, early maturation of the cerebellum and spinal cord, and myelination in the corpus callosum (Sow et al., 2006). The association of IGF-1 and transferrin favors remyelination in the myelin deficient rat (Espinosa-Jeffrey et al., 2006). 

Our knowledge of myelin constituents has greatly increased, as well as the role of a bidirectional dialogue between glial cells and neurons in myelination and demyeli-nation but, little is known of the mechanisms responsible for myelin repair. Why is remyelination incomplete with less myelin and shorter intemodes ... 

Simons M, Trajkovic K (2006) Neuron-gUa communication in the control of oligodendrocyte function and myelin biogenesis. J Cell Sci 119 4381-4389 Smith EJ, Blakemore WE, McDonald W1 (1979) Central remyelination restores secure conduction. Nature 280 395-396... 

Coman I, Barbin G, Charles P, Zalc B, Lubetzki C (2005) Axonal signals in central ner vous system myelination, demyelinadon and remyelination. J Neurol Sci 233 67—71. 

In addition, antibodies may play a beneficial role in MS by skewing the immune system away from a TH-1 biased response and toward a TH-2 cytokine pattern or by fostering myelin repair. It has been demonstrated that IgM antibodies to CNS antigens enhance remyelination in MS (Sospedra and Martin, 2005). The beneficial effect of pooled intravenous Ig in MS therapy supports a beneficial role for antibodies in MS. It is believed that this beneficial effect occurs through several mechanisms including inactivation of cytokines, Fc-receptor blockade, blocking of CD4 and MHC, and modulation of apoptosis (Sospedra and Martin, 2005). 

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