Genetically engineered HEK cells as a valuable tool for studying electroporation in excitable cells.

Electric pulses used in electroporation-based treatments have been shown to affect the excitability of muscle and neuronal cells. However, understanding the interplay between electroporation and electrophysiological response of excitable cells is complex, since both ion channel gating and electroporation depend on dynamic changes in the transmembrane voltage (TMV). In this study, a genetically engineered human embryonic kidney cells expressing NaV1.5 and Kir2.1, a minimal complementary channels required for excitability (named S-HEK), was characterized as a simple cell model used for studying the effects of electroporation in excitable cells. S-HEK cells and their non-excitable counterparts (NS-HEK) were exposed to 100 µs pulses of increasing electric field strength. Changes in TMV, plasma membrane permeability, and intracellular Ca2+ were monitored with fluorescence microscopy. We found that a very mild electroporation, undetectable with the classical propidium assay but associated with a transient increase in intracellular Ca2+, can already have a profound effect on excitability close to the electrostimulation threshold, as corroborated by multiscale computational modelling. These results are of great relevance for understanding the effects of pulse delivery on cell excitability observed in context of the rapidly developing cardiac pulsed field ablation as well as other electroporation-based treatments in excitable tissues.

Cancer electrogene therapy with interleukin-12.

Electrogene therapy combines administration of plasmid DNA into tissue followed by local application of electric pulses. In electrogene therapy with interleukin-12 (IL-12), different routes of administration, different doses of plasmid DNA and different protocols for delivery of electric pulses were evaluated in numerous preclinical studies. Antitumor effectiveness was tested in different types of primary tumors, distantly growing tumors and induced metastases. Intratumoral IL-12 electrogene therapy has been proved to be very effective in local tumor control, having also a systemic effect. Intramuscular and peritumoral IL-12 electrogene therapy had also a pronounced systemic effect and when combined with other treatment strategies resulted in tumor cures. Antitumor effectiveness of IL-12 electrogene therapy is due to the induction of adaptive immunity and innate resistance and anti-angiogenic action. Translation of preclinical studies into clinical trials in human and veterinary oncology has started with encouraging results that would hopefully lead to further investigation of this therapy, also in combination with other cancer treatment modalities.

Perturbation of blood flow as a mechanism of anti-tumour action of direct current electrotherapy.

Anti-tumour effects of direct current electrotherapy are attributed to different mechanisms depending on the electrode configuration and on the parameters of electric current. The effects mostly arise from the electrochemical products of electrolysis. Direct toxicity of these products to tumour tissue is, however, not a plausible explanation for the observed tumour growth retardation in the case when the electrodes are placed into healthy tissue surrounding the tumour and not into the tumour itself. The hypothesis that the anti-tumour effectiveness of electrotherapy could result from disturbed blood flow in tumours was tested by the measurement of changes in blood perfusion and oxygenation in tumours with three different methods (in vivo tissue staining with Patent Blue Violet dye, polarographic oximetry, near-infrared spectroscopy). The effects induced by electrotherapy were evaluated in two experimental tumour models: Sa-1 fibrosarcoma in A/J mice and LPB fibrosarcoma in C57B1/6 mice. We found that perfusion and oxygenation were significantly decreased after electrotherapy. Good agreement between the results of different methods was observed. The effect of electrotherapy on local perfusion of tumours is probably the prevalent mechanism of anti-tumour action for the particular type of electrotherapy used in the study. The importance of this effect should be considered for the optimization of electrotherapy protocols in experimental and clinical trials. The non-invasive technique of near-infrared spectroscopy proved to be a reliable method for detecting perfusion and oxygenation changes in small solid tumours.