RESUMEN
BACKGROUND: Applications of cell electropermeabilization are rapidly growing but basic concepts are still unclear. In particular, the impact of electric pulse repetition rate in the efficiency of permeabilization has not yet been understood. METHODS: The impact of electric pulse repetition rate in the efficiency of permeabilization was analyzed in experiments performed on potato tissue and partially transposed on mice liver. On potato tissue, pulses with durations of 100µs or 10ns are applied. The intensity of permeabilization was quantified by means of bioimpedance changes and electric current measurements and a new index was defined. RESULTS: For the two pulse durations tested, very low repetition rates (below 0.1Hz) are much more efficient to achieve cell permeabilization in potato tissue. In mice liver, using 100µs pulses, the influence of the repetition rate is more complex. Indeed, repetition rates of 1Hz and 10Hz are more efficient than 100Hz or 1kHz, but not the repetition rate of 0.1Hz for which there is an impact of the living mice organism response. CONCLUSIONS: We propose that the effects reported here might be caused by an electroporation-induced cell membrane 'electro-desensitization' which requires seconds to dissipate due to membrane resealing. GENERAL SIGNIFICANCE: This study not only reinforces previous observations, but moreover it sustains a new concept of 'electro-desensitization' which is the first unifying mechanism enabling to explain all the results obtained until now both in vitro and in vivo, with long and short pulses.
Asunto(s)
Permeabilidad de la Membrana Celular/fisiología , Impedancia Eléctrica , Solanum tuberosum/fisiología , Animales , Electroporación/métodos , Hígado/fisiología , Ratones , Pulso Arterial , Solanum tuberosum/citologíaRESUMEN
In vivo cell electropermeabilization can be used alone or in combination with a hydrophilic, nonpermeant cytotoxic drug such as bleomycin (electrochemotherapy) to efficiently treat tumors. We used magnetic resonance imaging to detect rapid structural modifications in tumors treated by electroporation-based methods. Water diffusion coefficient (ADC), transverse relaxation time (T(2)) and tumor volume of fibrosarcomas xenografted on syngenic mice were measured upon 3 groups of 6 treated mice within the 48 hrs following ECT done with a normal (BE) or a high dose of bleomycin (HBE), and after irreversible electroporation (IRE), and in three control groups. As expected, the tumor volume increased in the control groups at 48 hrs (p < 0.05) and the values of ADC and T2 did not varied significantly in the control groups except for ADC decrease and T2 increase observed between 3 hrs and 24 hrs (p < 0.03) in the group that received bleomycin only. Tumor volumes decreased significantly at 24 hrs in the IRE and HBE groups. The mean tumor ADC increased significantly at 24 hrs (117.6%, p < 0.03) in the BE group, probably reflecting apoptosis, while in the HBE group the mean tumor ADC increased earlier, at 10 hrs (119%, p < 0.03) because of the speed of the pseudoapopototic process. In the IRE group, the mean tumor ADC decreased significantly at 1 hrs (p < 0.05) and 3 hrs (p < 0.03), and T(2) decreased (p < 0.03), both probably reflecting cell swelling induced by the vascular lock. Thus ADC and T(2) changes in the treated tumors correlated with previous histological observations on the same tumor models. Noteworthy, ADC allowed the visualization of early and rapid changes in the treated tumors, when tumor volume monitoring was not yet able to detect any effect of the treatments.
Asunto(s)
Imagen por Resonancia Magnética , Neoplasias Experimentales/diagnóstico , Animales , Línea Celular Tumoral , Electroquimioterapia , Electroporación , Ratones , Neoplasias Experimentales/tratamiento farmacológico , Neoplasias Experimentales/patología , Resultado del Tratamiento , Carga TumoralRESUMEN
Immune cell recruitment during the treatment of sarcoma tumors in mice with irreversible electroporation was studied by immunohistochemistry. Irreversible electroporation is a non-thermal tissue ablation technique in which certain short duration electrical fields are used to permanently permeabilize the cell membrane, presumably through the formation of nanoscale defects in the membrane. Employing irreversible electroporation parameters known to completely ablate the tumors without thermal effects we did not find infiltration of immune cells probably because of the destruction of infiltration routes. We confirm here that immune response is not instrumental in irreversible electroporation efficacy, and we propose that irreversible electroporation may be, therefore, a treatment modality of interest to immunodepressed cancer patients.