GLIAL HYALURONATE-BINDING PROTEIN EXPRESSION IN AGGREGATING BRAIN-CELL CULTURES

We analyzed the expression of glial hyaluronate-binding protein (GHAP) , an integral component of the extracellular matrix, in aggregating br ain cell cultures of fetal rat telencephalon using immunofluorescence. GHAP immunoreactivity appeared after 1 week in culture, simultaneous with the first deposits of myelin basic protein, and showed a developm ent-dependent increase. Comparison of glia-enriched and neuron-enriche d cultures showed that only glial cells express GHAP. Three peptide gr owth factors, epidermal growth factor, fibroblast growth factor and pl atelet-derived growth factor, which are known to stimulate the differe ntiation of glial cells, modulated the deposit of GHAP immunoreactivit y. The 3-dimensional structure of aggregate cultures promoted GHAP dep osition, suggesting that cell-cell interactions are required for extra cellular matrix formation. Furthermore GHAP production seemed to depen d on the developmental stage of the glial cells.