TENASCIN-C MESSENGER-RNA AND TENASCIN-C PROTEIN IMMUNOREACTIVITY INCREASE IN ASTROCYTES AFTER ACTIVATION BY BFGF

Tenascin-C is an extracellular matrix glycoprotein with trophic and re pulsive properties, involved in migratory processes in CNS. Previous r eports demonstrated that this molecule is produced and secreted by ast rocytes. Preliminary data on fibroblasts and astrocytes have suggested that bFGF may modulate tenascin-C expression. bFGF is a mitogenic gro wth factor, involved in cell differentiation and neovascularization. I n the present study, we examined whether bFGF modulates the expression of tenascin-C in hippocampal astrocytes from newborn rats. Our result s suggest that bFGF increases the production of tenascin-C by cultured hippocampal astrocytes. We found that both tenascin-C mRNA and protei n immunoreactivity were increased after bFGF treatment. Our results al so demonstrated that tenascin-C polypeptides were secreted into the ex tracellular medium. In agreement with previous studies, we suggest tha t secreted tenascin-C is mainly the high molecular weight form. In add ition, our results suggest that a cleavage of the high molecular weigh t form may occur in the extracellular medium causing production of pro teolytic fragments, that may modify the biological properties of tenas cin-C, The present results may be relevant to the understanding of les ion scarring and regeneration process.