Glial reaction and reactive glia

Abstract

This chapter describes both morphological and functional features of the glial response following lesions of the central nervous tissue. The sequence of stages and a combination of different cell activities are emphasized. Especially, the effect on neural regeneration is also described, including data on immature and nonmammalian brains. It discusses that the glial reaction is the central nervous system (CNS)-type of wound healing, and it has combined multilateral, beneficial, and adverse effects depending on the circumstances. The glial reaction to lesion is a result of evolution and neurohistogenesis, and it cannot be considered simply as a “misfortune.” The chapter reviews that the expression of glial fibrillary acid protein (GFAP) indicates astroglial activation in general, not only the “reactive glia” responding to a lesion. Although the reactive gliosis seems to be the main impediment for axonal regrowth, it has beneficial effects and its relation to axonal regeneration is more complex than a simple inhibition. Reactive astrocytes re-express some features of immature astroglia, but they are not “immature” cells. The inhibitory effect of the glial reaction is acquired, both phylogenetically and ontogenetically.