A versatile in vivo platform for reversible control of transgene expression in adult tissues

Temporal control of exogenous genes through artificial genetic circuits has advanced a range of biomedical interventions, including in vivo reprogramming. The doxycycline (Dox)-mediated Tet- ON system has been widely employed due to its highly reversible and tunable gene induction. Nonetheless, its effectiveness in vivo is limited by inherent resistance in some tissues. In the present study, mouse models were developed with the Tet-ON or complementary Tet-OFF system to thoroughly investigate the spatial and temporal control of transgene expression in adult tissues. The Tet-OFF system could induce gene expression in a broad spectrum of cell types, such as neuronal cells, cardiomyocytes, and skeletal muscle cells, in stark contrast with the Tet-ON system, which could only induce gene expression in particular tissues and cell types, mainly epithelial cells. Despite its broader reach, the Tet-OFF system exhibited slow inducibility and lacked tunability in the expression levels of transgenes. Capitalizing on the pharmacologic advantages of tetracycline (Tc), which has a shorter half-life in vivo and lower affinity for Tet repressor than Dox, we revisited its application. Remarkably, Tc enabled rapid, reversible, and graded control of transgene expression in the Tet-OFF system. Moreover, utilization of Tc mitigated the transcriptional perturbation associated with use of Dox. Our data suggest that the Tc-mediated Tet-OFF system not only enables more versatile control of transgene expression but may also offer a more biocompatible alternative, enhancing its suitability for applications such as tissue regeneration and organismal rejuvenation.