Glial cell heterogeneity in the mammalian spinal cord.

The vertebrate spinal cord is comprised of a complex array of different populations of neurons and axon tracts. Recent studies suggest that this complex neuronal cytoarchitecture is complemented by a similarly complex glial cytoarchitecture. Cultures of neonatal rat spinal cord contain multiple different classes of astrocytes. These distinct classes of astrocytes have particular morphologies and arise from separate precursors that proliferate in response to different mitogens. It seems likely that the individual classes of astrocytes will have regional localization and will be involved in specific functions in the intact spinal cord. In contrast to the significant diversity seen among astrocytes, spinal cord oligodendrocytes in the embryonic animal appear to be a relatively homogenous population of cells that proliferates in response to known growth factors at particular stages of maturation. An important future challenge in glial cell biology is to define clearly the functional roles of individual populations of astrocytes in the developing adult, and injured spinal cord. Such information may ultimately lead to the ability to modulate astrocytic function at a cellular level during aberrant development and following injury to the adult spinal cord.