The reconstruction of an astrocytic environment in glia-deficient areas of white matter.

Injection of ethidium bromide into X-irradiated spinal cord white matter produces a lesion in which demyelinated axons reside in an environment that is permanently depleted of glial cells. By transplanting defined populations of glial cells into this lesion it is possible to recreate normal or novel glial environments. In this study we have transplanted cultures of astrocytes into the X-irradiated ethidium bromide lesion in order to (1) assess the ability of these cells to relate to components within the lesion environment and thereby contribute to tissue reconstruction and (2) establish an astrocytic environment around demyelinated axons that resembles pathological states such as the chronic demyelinated plaques of multiple sclerosis. In order to focus attention on the interactions between astrocytes and demyelinated axons we developed a protocol for depleting astrocyte cultures of oligodendrocyte lineage cells and Schwann cells based on complement-mediated immunocytolysis and in vitro X-irradiation. In addition to establishing the ability of transplanted astrocytes to form an astrocytic matrix around demyelinated axons, this study has also revealed the diversity of cell types present within neonatal forebrain cultures.