Positive correlation between the generation of reactive oxygen species and activation/reactivation of transgene expression after hydrodynamic injections into mice.

Purpose: Hydrodynamic injection has been shown to reactivate silenced transgene expression in mouse liver. In this study, the roles of inflammatory cytokines and reactive oxygen species (ROS) in the reactivation were examined.

Methods: Production of inflammatory cytokines and ROS by hydrodynamic injection of saline was examined in mice that had received a hydrodynamic injection of a plasmid expressing Gaussia luciferase.

Reactivation of silenced transgene expression in mouse liver by rapid, large-volume injection of isotonic solution.

Rapid, large-volume injection, or so-called hydrodynamic injection, of naked plasmid DNA gives high transgene expression in mouse liver, and this method has been applied to liver-directed gene transfer in humans with slight modifications. To prove that injection-induced biological changes are involved in hydrodynamic injection-induced, high-level transgene expression in mouse liver, isotonic solutions were injected into mice that had received a hydrodynamic injection of plasmid DNA. Transgene expression in the liver was increased by such injections irrespective of the cDNA, promoter, and type of solution.