The diversity and disparity of the glial scar

Injury or disease to the CNS results in multifaceted cellular and molecular responses. One such response, the glial scar, is a structural formation of reactive glia around an area of severe tissue damage. While traditionally viewed as a barrier to axon regeneration, beneficial functions of the glial scar have also been recently identified. In this Perspective, we discuss the divergent roles of the glial scar during CNS regeneration and explore the possibility that these disparities are due to functional heterogeneity within the cells of the glial scar—specifically, astrocytes, NG2 glia and microglia. The glial scar plays critical but divergent roles during regeneration of the mammalian CNS. Here the authors propose that in-depth analysis of the functionally heterogeneous populations of reactive glia within the scar is needed to fully understand the glial scar’s dual nature.