title: Systemic and localized reversible regulation of transgene expression by tetracycline with tetR-mediated transcription repression switch.
abstract: BACKGROUND
  We recently developed a new tetracycline-inducible gene switch employing the tetracycline operator-containing hCMV major immediate-early promoter and the tetracycline repressor, tetR, rather than the previously used tetR-mammalian cell transcription factor fusion derivatives.
  
  
  METHODS
  The present study demonstrates that this tetR-mediated transcription repression system can function as a powerful gene switch for On-and-Off regulation of therapeutic gene expression in ex vivo gene transfer protocols. Firstly, for achieving regulated gene expression in a localized tissue environment, R11/OEGF cells, a stable line that expresses hEGF under the control of the tetR-mediated transcription repression switch, were transplanted into porcine full-thickness wounds enclosed by wound chambers.
  
  
  RESULTS
  By topically applying tetracycline in wound chambers at various concentrations or at different time points post-transplantation, the levels and timing of hEGF expression in transplanted wounds could be reversibly regulated by tetracycline. Over 3000-fold induction in hEGF expression was achieved in the local wound microenvironment. Secondly, R11/OEGF cells were intramuscularly injected into NCr outbread nude mice to test the efficacy of intermittent systemic gene delivery of a soluble peptide(s).
  
  
  CONCLUSIONS
  Basal circulating hEGF was undetectable and induced up to at least 1,500-fold after administration of tetracycline. Furthermore, the timing and duration of hEGF expression could be finely adjusted by the presence or the absence of tetracycline in the drinking water.
authors.affiliation: Laboratory of Tissue Repair and Gene Transfer, Plastic Surgery, Brigham and Women's Hospital, and Department of Surgery, Harvard Medical School, Boston, Massachusetts 02115, USA. FYao@RICS.BWH.Harvard.Edu
authors.forename: Feng
authors.initials: F
authors.lastname: Yao
authors.forename: Bohdan
authors.initials: B
authors.lastname: Pomahac
authors.forename: Scott
authors.initials: S
authors.lastname: Visovatti
authors.forename: Michael
authors.initials: M
authors.lastname: Chen
authors.forename: Starck
authors.initials: S
authors.lastname: Johnson
authors.forename: Hanka
authors.initials: H
authors.lastname: Augustinova
authors.forename: Tor
authors.initials: T
authors.lastname: Svensjo
authors.forename: Elof
authors.initials: E
authors.lastname: Eriksson
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents; D045744:Cell Line, Tumor; D003587:Cytomegalovirus / Q000235:genetics*; D004815:Epidermal Growth Factor / Q000235:genetics; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D018014:Gene Transfer Techniques; D006801:Humans; D008297:Male; D051379:Mice; D008819:Mice, Nude; D012516:Osteosarcoma; D011401:Promoter Regions, Genetic / Q000235:genetics; D012867:Skin / Q000293:injuries; D034421:Sus scrofa; D013752:Tetracycline; D019076:Transgenes / Q000235:genetics*; D014947:Wounds and Injuries / Q000503:physiopathology
chemical_list: D000900:Anti-Bacterial Agents; D004815:Epidermal Growth Factor; D013752:Tetracycline