THE USE OF TRANSPLANTED GLIAL-CELLS TO RECONSTRUCT GLIAL ENVIRONMENTSIN THE CNS

Transplantation studies have demonstrated that glia-depleted areas of the CNS can be reconstituted by the introduction of cultured cells. Th us, the influx of Schwann cells into glia-free areas of demyelination in the spinal cord can be prevented by the combined introduction of as trocytes and cells of the O-2A lineage. Although Schwann cell invasion of areas of demyelination is associated with destruction of astrocyte s, the transplantation of rat tissue culture astrocytes (''type-1'') a lone cannot suppress this invasion, indicating a role for cells of the O-2A lineage in reconstruction of glial environments. By transplantin g different glial cell preparations and manipulating lesions so as to prevent meningeal cell and Schwann cell proliferation it is possible t o demonstrate that the behaviour of tissue culture astrocytes (''type- 1'') and astrocytes derived from O-2A progenitor cells (''type-2'') is different. In the presence of meningeal cells, tissue culture astrocy tes clump together to form cords of cells. In contrast, type-2 astrocy tes spread throughout glia-free areas in a manner unaffected by the pr esence of meningeal cells or Schwann cells. Thus, progenitor-derived a strocytes show a greater ability to fill glia-free areas than tissue c ulture astrocytes. Similarly, when introduced into infarcted white mat ter in the spinal cord, progenitor-derived astrocytes fill the malacic area more effectively than tissue culture astrocytes, although axons do not regenerate into the reconstituted area.