• Hong Lian Jin, William A Pennant, Hyung Lee Min M, Sung Su, Ah Kim Hyun H, Meng Lu Liu, Jin Soo Oh, Joon Cho, Nyun Kim Keung K, Heum Yoon Do D, and Yoon Ha.
• Department of Neurosurgery, Spine and Spinal Cord Institute, Yonsei University College of Medicine, Seoul, Republic of Korea.
• Spine. 2011 May 15; 36 (11): 857-64.

Study DesignAn in vitro neural hypoxia model and rat spinal cord injury (SCI) model were used to assess the regulation of therapeutic vascular endothelial growth factor (VEGF) gene expression in mouse neural stem cells (mNSCs) by the EPO (erythropoietin) enhancer or RTP801 promoter.ObjectiveTo increase VEGF gene expression in mNSCs under hypoxic conditions in SCI lesions but avoid unwanted overexpression of VEGF in normal sites, we developed a hypoxia-inducible gene expression system consisting of the EPO enhancer and RTP801 promoter fused to VEGF or the luciferase gene, then transfected into mNSCs.Summary Of Background DataOn the basis of the ischemic response in the injured area, poor cell survival at the transplantation site is a consistent problem with NSC transplantation after SCI. Although VEGF directly protects neurons and enhances neurite outgrowth, uncontrolled overexpression of VEGF in uninjured tissue may cause serious adverse effects. To effectively improve NSC survival in ischemic sites after transplantation, we evaluated mNSCs modified by a hypoxia-inducible VEGF gene expression system in an SCI model.MethodsHypoxia-inducible luciferase or VEGF plasmids were constructed using the EPO enhancer or RTP801 promoter. The effect of these systems on targeted gene expression and cell viability was evaluated in mNSCs in both hypoxic in vitro injury and a rat SCI model in vivo.ResultsThe gene expression system containing the EPO enhancer or RTP801 promoter significantly increased the expression of the luciferase reporter gene and therapeutic VEGF gene under hypoxic conditions. The Epo-SV-VEGF plasmid transfection group had significantly fewer apoptotic cells in vitro. This system also augmented cell viability in the in vivo SCI model.ConclusionThese results strongly suggest the potential utility of mNSCs modified by a hypoxia-inducible VEGF gene expression system in the development of effective stem cell transplantation protocols in SCI.

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