Engineering the CNS stem cell microenvironment.

The loss of neural tissue underlies the symptomatology of several neurological insults of disparate etiology, including trauma, cerebrovascular insult and neurodegenerative disease. Restoration of damaged neural tissue through the use of exogenous or endogenous neural stem or progenitor cells is an enticing therapeutic option provided one can control their proliferation, migration and differentiation. Initial attempts at CNS tissue engineering relied on the intrinsic cellular properties of progenitor cells; however, it is now appreciated that the microenvironment surrounding the cells plays an indispensible role in regulating stem cell behavior. This article focuses on attempts to engineer the neural stem cell microenvironment by utilizing the major cellular components of the niche (endothelial cells, astrocytes and ependymal cells) and the extracellular matrix in which they are embedded.