title: Neural stem cells modified by a hypoxia-inducible VEGF gene expression system improve cell viability under hypoxic conditions and spinal cord injury.
abstract: METHODS
  An 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.
  
  
  OBJECTIVE
  To 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.
  
  
  BACKGROUND
  On 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.
  
  
  METHODS
  Hypoxia-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.
  
  
  RESULTS
  The 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.
  
  
  CONCLUSIONS
  These 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.
authors.affiliation: Department of Neurosurgery, Spine and Spinal Cord Institute, Yonsei University College of Medicine, Seoul, Republic of Korea.
authors.forename: Hong
authors.initials: H
authors.lastname: Lian Jin
authors.forename: William A
authors.initials: WA
authors.lastname: Pennant
authors.forename: Min
authors.initials: M
authors.lastname: Hyung Lee
authors.forename: Sung
authors.initials: S
authors.lastname: Su
authors.forename: Hyun
authors.initials: H
authors.lastname: Ah Kim
authors.forename: Meng
authors.initials: M
authors.lastname: Lu Liu
authors.forename: Jin
authors.initials: J
authors.lastname: Soo Oh
authors.forename: Joon
authors.initials: J
authors.lastname: Cho
authors.forename: Keung
authors.initials: K
authors.lastname: Nyun Kim
authors.forename: Do
authors.initials: D
authors.lastname: Heum Yoon
authors.forename: Yoon
authors.initials: Y
authors.lastname: Ha
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000235:genetics; D004195:Disease Models, Animal; D017930:Genes, Reporter; D015316:Genetic Therapy / Q000379:methods*; D006085:Graft Survival / Q000235:genetics*; D000860:Hypoxia / Q000235:genetics* / Q000473:pathology / Q000628:therapy*; D008297:Male; D051379:Mice; D058953:Neural Stem Cells / Q000502:physiology / Q000637:transplantation*; D010957:Plasmids / Q000008:administration & dosage / Q000627:therapeutic use; D011401:Promoter Regions, Genetic / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D012097:Repressor Proteins / Q000008:administration & dosage / Q000235:genetics; D013119:Spinal Cord Injuries / Q000235:genetics* / Q000601:surgery / Q000628:therapy*; D014157:Transcription Factors; D015854:Up-Regulation / Q000235:genetics; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis / Q000235:genetics*
chemical_list: C000632146:Ddit4 protein, rat; D012097:Repressor Proteins; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A; C467498:vascular endothelial growth factor A, rat