The Role of Wnt Signaling Pathway on the Expression of TGFβ 1 and TGFβ 2 in Cultured Rat Cortical Astrocytes

Introduction: Astrocytes, the most abundant glia in the central nervous system, modulate neuronal survival and function. Astrocytic functions are mediated by synthesis and secretion of wide ranges of polypeptides through mechanism (s) poorly understood. Among these, TGFβs are synthesized and released by the astrocytes. In this study, the involvement of Wnt signaling pathway on the synthesis of TGFβs by the astrocyte was investigated. Materials and Methods: Cultured rat astrocytes were therefore treated either with Wnt3a (20 ng/ml) alone for 24 hours or in combination with sFRP-1 (400 ng/ml) for a further 24 hours. Cells were then harvested and examined for the expression of TGFβs and the Wnt target gene, cyclin D1. Results: In this study, we were able to show that 1) treatment Wnt3a alone for 24 hours induced the expressions of TGFβs and cyclin D1 2) The effect of Wnt was inhibited by pre-treatment with sFRP-1, that is, sFRP-1 pre-treatment significantly blocked the Wnt-induced expressions of TGFβs and cyclin D1. Conclusion: This study therefore provides the first evidence for the involvement of Wnt signaling pathway in the synthesis of TGFβ proteins by cortical rat astrocytes.