Activation of epidermal growth factor receptors in astrocytes: from development to neural injury.

The epidermal growth factor receptor (EGFR) pathway controls the phenotypic characteristics of astrocytes. In the developing central nervous system (CNS), activation of the EGFR pathway induces astrocyte differentiation, forming the cribriform structure that surrounds axons and providing a supportive environment for neurons. In the adult CNS, the EGFR pathway is absent from astrocytes but is highly up-regulated and activated following neuronal injury. Activation of the EGFR pathway triggers quiescent astrocytes to become reactive astrocytes. Although astrocytes regulated by the EGFR pathway play constructive roles in the developing CNS, astrocytes that become reactive in response to activation of the EGFR pathway appear to be destructive to neurons in the adult CNS. The reappearance and activation of EGFRs in astrocytes under pathological conditions may activate a developmental process in an adult tissue. Regulation of EGFR function in astrocytes may be a new therapeutic strategy for the treatment of neural disorders. (c) 2007 Wiley-Liss, Inc.