Electroporation-Induced Stress Response and Its Effect on Gene Electrotransfer Efficacy: In Vivo Imaging and Numerical Modeling.

Objective: Skin is an attractive target tissue for gene transfer due to its size, accessibility, and its immune competence. One of the promising delivery methods is gene delivery by means of electroporation (EP), i.e., gene electrotransfer (GET). To assess the importance of different effects of electroporation for successful GET we investigated: stress response and transfection efficacy upon different pulse protocols. Moreover, numerical modeling was used to explain experimental results and to test the agreement of experimental results with current knowledge about GET.

Methods: Double transgenic mice Hspa1b-LucF (+/+) Hspa1b-mPlum (+/+) were used to determine the level of stress sensed by the cell in the tissue in vivo that was exposed to EP. The effect of five different pulse protocols on stress levels sensed by the exposed cells and their efficacy for gene electrotransfer for two plasmids pEGFP-C1 (EGFP) and pCMV-tdTomato was tested.

Results: Quantification of the bioluminescence signal intensity shows that EP, regardless of the electric pulse parameters used, increased mean bioluminescence compared to the baseline bioluminescence signal of the non-exposed skin. The results of numerical modeling indicate that thermal stress alone is not sufficient to explain the measured bioluminescence signal. Of the tested pulse protocols, the highest expression of EGFP and tdTomato was achieved with HV-MV (high voltage - medium voltage) protocols, which agrees also with numerical model.

Significance: Although EP is widely used as a method for gene delivery, we show that the field could benefit from the use of mathematical modeling by introducing additional parameters such as EP induced stress and electrophoretic movement of plasmids.