Visualization of the transgene distribution according to the administration route allows prediction of the transfection efficacy and validation of the results obtained.

Gene transfer to the lung can be achieved via a systemic, that targets the endothelium, or local, that targets the epithelium, delivery route. In the present study, we followed the distribution of a plasmid after transfection using some of our phosphonolipids, which have previously shown their efficiency in transfecting mouse lungs. The plasmid was radiolabeled and varying combinations of plasmid/phosphonolipid were administered by intravenous injection, or by endotracheal spray. The distribution of radioactive labeling was observed over a time course using a gamma-camera. These images were then correlated with the results for luciferase expression levels in the lungs. In each case, lungs were well targeted. However, whereas an intravenous injection reaches all of the lung immediately, progressive diffusion occurs when the plasmid/phosphonolipid is administered via an aerosol. Elimination of the radioactivity associated with plasmid occurs via the urinary tract after intravenous injections, and via the feces using the aerosol delivery approach. The radioactivity detected in the lungs correlated strongly with transgene expression. Thus, such an imaging technique is a powerful strategy to predict the formulation that will generate the best transfection efficiency. This study reveals that scintigraphic imaging permits both validation of the administration method and the results obtained for each animal, thereby reducing the statistical variability of in vivo experiments.