Glial function (and dysfunction) in the normal & ischemic brain

Astrocytes are the most abundant cell type in the central nervous system (CNS). Once considered to be of fairly homogeneous phenotype throughout the brain and spinal cord, they are now understood to be heterogeneous in both structure and function. They are important in brain functions as diverse as ion and fluid balance in the interstitial space, contributing to integrity of the neurovascular unit (blood-brain barrier), neurotransmitter regulation, metabolism of energy substrates and possibly even axonal regeneration. After ischemic or hemorrhagic brain/spinal cord injury, formation of an astrocytic scar adjacent to the ‘lesion’ is a characteristic histopathologic feature, and this astrogliosis can be demonstrated by immunohistochemistry, usually using primary antibodies to glial fibrillary acidic protein (GFAP). Astrocytes interact with microglia and oligodendroglia in novel ways that will be discussed in this review.