Astrocyte characterization in the multiple sclerosis glial scar.

Dense astrocytic scarring in chronic multiple sclerosis (MS) plaques produces an inhibitory environment which can impede tissue repair. Animal studies have shown that the antigenic phenotype of the most abundant cell type in the brain, the astrocyte, varies depending on astrocyte type and location. To identify the phenotype of scar astrocytes (SAs) in chronic lesions, markers of reactive astrocytes characterized in animal studies were investigated. To date these are the only established markers. Cerebral subventricular deep white matter from normal control, MS normal appearing white matter and lesions (acute, subacute and chronic) were examined by immunohistochemistry and immunoblotting. The antigenic profile of SAs revealed significant modification of astrocyte protein expression in chronic MS lesions. SAs express nestin, embryonic neural cell adhesion molecule, fibroblast growth factor receptor 4, epidermal growth factor receptor, nerve growth factor and a subpopulation of SAs also express basic fibroblast growth factor. These are in addition to the expected markers glial fibrillary acidic protein, vimentin, and the tenascins C and R. Therefore, an SA antigenic phenotype has now been defined. This knowledge may allow the development of therapeutic strategies that prevent scar formation and promote tissue repair.