Modulation of neuronal survival and axonal growth in vivo by tetracycline-regulated neurotrophin expression

Gene Ther. 2001 Jun;8(12):954-60. doi: 10.1038/


Vector systems for the regulated and reversible expression of therapeutic genes are likely to improve the safety and efficacy of gene therapy for medical disease. In the present study, we investigated whether the expression of genes transferred into the central nervous system by ex vivo gene therapy can be regulated in vivo leading to controlled neuronal survival and axonal growth. Primary rat fibroblasts were transfected with a retrovirus containing a tetracycline responsive promoter for the expression of the neurotrophin nerve growth factor (NGF) or green fluorescent protein as a control (GFP). After lesions of basal forebrain cholinergic neurons, NGF-mediated neuronal rescue and axonal growth could be completely controlled over a 2-week period by the addition or removal of the tetracycline modulator doxycycline in the animals' drinking water. Further, continued expression of the reporter gene GFP could be reliably and repeatedly turned on and off in the injured CNS for at least 3 months post-grafting, the longest time point investigated. These data constitute the first report of regulated neuronal rescue and axonal growth by controlled neurotrophin gene delivery and long-term, regulated expression using ex vivo CNS gene therapy.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Analysis of Variance
  • Animals
  • Anti-Bacterial Agents / therapeutic use*
  • Axons / metabolism
  • Central Nervous System Diseases / therapy*
  • Doxycycline / therapeutic use*
  • Female
  • Fibroblasts / metabolism
  • Gene Expression / drug effects
  • Genetic Therapy / methods*
  • Genetic Vectors / administration & dosage
  • Green Fluorescent Proteins
  • Luminescent Proteins / genetics
  • Neurons / metabolism
  • Polysaccharides / genetics*
  • Promoter Regions, Genetic / drug effects*
  • Rats
  • Rats, Inbred F344
  • Retroviridae / genetics
  • Spinal Cord
  • Time Factors


  • Anti-Bacterial Agents
  • Luminescent Proteins
  • Polysaccharides
  • Green Fluorescent Proteins
  • neurotropin
  • Doxycycline