Low Density, but not High Density, C6 Glioma Cells Support Dorsal Root Ganglion and Sympathetic Ganglion Neurite Growth

Accumulating evidence suggests that an inhibitory influence of the environment on growth cones plays a crucial role in development and regeneration of neuronal projections. Oligodendrocyte‐associated neurite growth inhibiting substance is one of the most extensively studied molecules. Molecular biological studies, however, remain slow in progress. Although finding clonal cells that express such factors would facilitate the analysis of inhibitory influences on neurite growth, few cell lines have been reported to express neurite growth inhibitor. We therefore investigated the possibility of a clonal glial cell line to differentiate and express inhibitory or non‐permissive features for neurite outgrowth in culture. We chose the C6 glioblastoma cell line and examined neurite extension from chick dorsal root ganglion (DRG) explants. Neurites from embryonic day 9 DRG extensively grew on C6 cells that were cultured at low cell density, while they failed to grow on C6 cells cultured at high density, even in the presence of nerve growth factor in high concentrations. Membrane extract from high density C6 cells, when used as culture substratum, was less permissive for neurite outgrowth compared to extract from low density cells. Treatment of the membrane extract derived from high density C6 cells with trypsin made it less non‐permissive for neurite growth. These results suggest that C6 cells are induced to express a non‐permissive property for neurite outgrowth by culturing them at high density.