Systemic and localized reversible regulation of transgene expression by tetracycline with tetR-mediated transcription repression switch.

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.

Materials And 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.