BDNF promotes the growth of human neurons in vitro through crosstalk with the Wnt/β-catenin signaling pathway

Background: Brain-derived neurotrophic factor (BDNF) plays an important role in neuronal growth; however, the downstream regulatory mechanisms remain unclear. In this study, we investigated whether BDNF exerts its neurotrophic effects through the Wnt/β-catenin signaling pathway in human embryonic spinal cord neurons in vitro. Methods: The research was carry out by human embryonic spinal cord neurons cultured in vitro, immunofluoresence labelling, BDNF plasmid transfection and siRNA interference, RT-PCR, Real time quantitative PCR and Western Blot. Results: We found that neuronal growth (soma size and average neurite length) was increased by transfection with a BDNF overexpression plasmid. Western blotting and real-time quantitative PCR showed that expression of the BDNF pathway components TrkB, PI3K, Akt and PLC-γ were increased by BDNF overexpression. Furthermore, the Wnt signaling factors Wnt, Frizzled and Dsh and the downstream target β-catenin were upregulated, whereas GSK-3β was downregulated. In contrast, when BDNF signaling was downregulated with BDNF siRNA, the growth of neurons was decreased. Furthermore, BDNF signaling factors, Wnt pathway components and β-catenin were all downregulated, whereas GSK-3β was upregulated. Then we treated neurons with 6-bromoindirubin-3’-oxime (BIO), a small molecule GSK-3β inhibitor. BIO reduced the effects of BDNF upregulation/downregulation on soma size and average neurite length, and suppressed the impact of BDNF modulation on the Wnt signaling pathway. Conclusions: Our findings suggest that BDNF promotes the growth of neurons in vitro through crosstalk with the Wnt/β-catenin signaling pathway, and that this interaction may be mediated by GSK-3β.