In vivo electroporation threshold determination

To determine electric field distribution around needle electrodes inserted into rabbit liver tissue, a three-dimensional finite element model was built. Using numerical calculations of electric field distribution and biological observations in in vivo experiments, the authors determined the magnitude of electric field intensity for the reversible and irreversible electropermeabilization of rabbit liver tissue in vivo. The reversible threshold determination, obtained at electric field intensity of 362±21 V/cm (avg±std), was based on previous observation that bleomycin at large intracellular concentrations produces an apoptotic-like cell death. The irreversible threshold determination, obtained at electric field intensity equal or lower than 637±43 V/cm, was based on the in vitro observations that with increasing the electric field intensity permanent damage is inflicted to the plasma membrane and therefore cell viability is lost. Besides the determination of the reversible and irreversible thresholds, the authors´ results are important because they carry practical implications for electrochemotherapy of liver tumors in clinical situation, and of other visceral tumors for which needle electrodes applicators were already developed, as well as for the in vivo gene transfection by means of electroporation