A significant number of human disease phenotypes are linked to mutations in over 4000 genes (as per OMIM Gene Map Statistics, 2020). This has created a base for therapeutic strategies that can modify nucleic acids within disease-affected cells, eg., gene therapy, and many genes have been investigated as potential candidates for such strategies. However, effects of transgene medicinal agents depend on the dosage, therefore, both for laboratory and therapeutic applications, a regulated gene expression is a potential requirement. In this context, pulsed electric field technology could be a candidate for non-invasive, biophysical activator of the induction of gene expression.
The aim of this study is to examine the use of microsecond pulsed electric field (μsPEF) stimulation as a proof-of-concept for potential non-ligand physically triggered inducer of gene expression in viable mammalian cells. We report here the response and activation of heterologous transcription system, which consists of NF-${\kappa}$B controlled synthetic promoter and a reporter gene (pNF-${\kappa}$B-SEAP) in viable human cervix carcinoma cells (Hep-2c) and Cricetulus griseus ovarian tissue (CHO-K1) cells. The conditions for treatment were selected based on published data [1, 2]. The rectangular electric pulses with different amplitude, fixed pulse frequency (1 Hz) and pulse duration (100 μs) was used. Results are reported in relative expression of SEAP in folds 24- and 48-hours post-pulsation. The cellular metabolic activity was assessed 24- and 48-hours post-pulsation and was expressed as a percentage relative to the untreated control cells.
PNF-${\kappa}$B-SEAP transfected Hep-2c cell line exposure to μsPEF of 0.25, 0.3 and 0.4 kV/cm resulted in increased levels of relative expression of SEAP (approximately 1.7-fold compared to the control) 24 hours post pulsation. However, μsPEF of 0.165 kV/cm showed the highest peak of relative expression of SEAP in Hep-2c cell line 24 hours post-pulsation - 2-fold in comparison to control. No gene expression activation was detected in Hep-2c cell line 48 hours post-pulsation. Conversely, no activation of gene expression was detected in all experimental setup in CHO-K1 cell line 24 hours post-pulsation, but μsPEF of 0.3 kV/cm resulted in increased levels of relative expression of SEAP (approximately 1.2-fold compared to the control) 48 hours post-pulsation. All experimental setup resulted in high viability of both cell lines.
We conclude the activation of NF-${\kappa}$B in Hep-2c cells is achieved by μsPEF treatment of cell suspension reaching the peak at 0.165 kV/cm 24 hours post-pulsation. The activation of CHO-K1 is achieved at lower levels at 0.3 kV/cm with a time delay and is detected 48 hours post-pulsation. Experimental setup of PEF application does not have a significant impact on viability of treated cells. To our knowledge, this is the first experimental study that demonstrates μsPEF can act as the inducer of target promoter.