26 - Neural plasticity after cerebral ischemia

Summary

Introduction

Neural stem cells that fulfill all the classic criteria for stem cells, including (i) multipotency, (ii) highly proliferative potential and self-renewal and (iii) a limited capacity to regenerate after injury or disease, continue to exist in the adult central nervous system (CNS). This chapter describes how cerebral global ischemia increases the proliferation of neural stem cells in the dentate gyrus, producing new neurons and glia in two separate compartments, namely the granule cell layer and the dentate hilus. Our recent data show that focal ischemia, though it rarely damages hippocampal neurons, increases the proliferation of dentate gyrus stem cells. Regeneration in the dentate gyrus after cerebral ischemia represents an injury-induced neural plasticity.

Neural stem cells in the adult CNS

Locations of adult neural stem cells

There are only two types of neuron normally generated in the adult brain, i.e., dentate granule cells and olfactory bulb interneurons. The sources of neural stem cells for generating these neurons are located at the subventricular zone (SVZ) of the lateral ventricles and at the subgranular zone (SGZ) of the dentate gyrus, both believed to be developmental remnants of the embryonic germinal zone. Recent evidence suggests that a group of glial fibrillary acidic protein-expressing cells in the SVZ are the precursor cells for generating neuroblasts in the rostral migratory stream, and eventually neurons in the olfactory bulb. Proliferating SVZ cells form a chain and migrate longitudinally through the SVZ to join the rostral migratory stream into the olfactory bulb.