The impact of impaired DNA mobility on gene electrotransfer efficiency: analysis in 3D model

Fibroblasts transfection by electroporation in 3D reconstructed human dermal tissue

The understanding of the mechanisms involved in DNA electrotransfer in human skin remains modest and limits the clinical development of various biomedical applications, such as DNA vaccination. To elucidate some mechanisms of DNA transfer in the skin following electroporation, we created a model of the dermis using a tissue engineering approach. This model allowed us to study the electrotransfection of fibroblasts in a three-dimensional environment that included multiple layers of fibroblasts as well as the self-secreted collagen matrix. With the aim of improving transfection yield, we applied electrical pulses with electric field lines perpendicular to the reconstructed model tissue. Our results indicate that the fibroblasts of the reconstructed skin tissue can be efficiently permeabilized by applied millisecond electrical pulses. However, despite efficient permeabilization, the transfected cells remain localized only on the surface of the microtissue, to which the plasmid was deposited. Second harmonic generation microscopy revealed the extensive extracellular collagen matrix around the fibroblasts, which might have affected the mobility of the plasmid into deeper layers of the skin tissue model. Our results show that the used skin tissue model reproduces the structural barriers that might be responsible for the limited gene electrotransfer in the skin.

Importance of the electrophoresis and pulse energy for siRNA-mediated gene silencing by electroporation in differentiated primary human myotubes

BACKGROUND

Electrotransfection is based on application of high-voltage pulses that transiently increase membrane permeability, which enables delivery of DNA and RNA in vitro and in vivo. Its advantage in applications such as gene therapy and vaccination is that it does not use viral vectors. Skeletal muscles are among the most commonly used target tissues. While siRNA delivery into undifferentiated myoblasts is very efficient, electrotransfection of siRNA into differentiated myotubes presents a challenge. Our aim was to develop efficient protocol for electroporation-based siRNA delivery in cultured primary human myotubes and to identify crucial mechanisms and parameters that would enable faster optimization of electrotransfection in various cell lines.

RESULTS

We established optimal electroporation parameters for efficient siRNA delivery in cultured myotubes and achieved efficient knock-down of HIF-1α while preserving cells viability. The results show that electropermeabilization is a crucial step for siRNA electrotransfection in myotubes. Decrease in viability was observed for higher electric energy of the pulses, conversely lower pulse energy enabled higher electrotransfection silencing yield. Experimental data together with the theoretical analysis demonstrate that siRNA electrotransfer is a complex process where electropermeabilization, electrophoresis, siRNA translocation, and viability are all functions of pulsing parameters. However, despite this complexity, we demonstrated that pulse parameters for efficient delivery of small molecule such as PI, can be used as a starting point for optimization of electroporation parameters for siRNA delivery into cells in vitro if viability is preserved.

CONCLUSIONS

The optimized experimental protocol provides the basis for application of electrotransfer for silencing of various target genes in cultured human myotubes and more broadly for electrotransfection of various primary cell and cell lines. Together with the theoretical analysis our data offer new insights into mechanisms that underlie electroporation-based delivery of short RNA molecules, which can aid to faster optimisation of the pulse parameters in vitro and in vivo.

A micro-electroporation/electrophoresis-based vaccine screening system reveals the impact of vaccination orders on cross-protective immunity

The constant emergence of mutated pathogens poses great challenges to the existing vaccine system. A screening system is needed to screen for antigen designs and vaccination strategies capable of inducing cross-protective immunity. Herein, we report a screening system based on DNA vaccines and a micro-electroporation/electrophoresis system (MEES), which greatly improved the efficacy of DNA vaccines, elevating humoral and cellular immune responses by over 400- and 35-fold respectively. Eighteen vaccination strategies were screened simultaneously by sequential immunization with vaccines derived from wildtype (WT) SARS-CoV-2, Delta, or Omicron BA.1 variant. Sequential vaccination of BA.1-WT-Delta vaccines with MEES induced potent neutralizing antibodies against all three viral strains and BA.5 variant, demonstrating that cross-protective immunity against future mutants can be successfully induced by existing strain-derived vaccines when a proper combination and order of sequential vaccination are used. Our screening system could be used for fast-seeking vaccination strategies for emerging pathogens in the future.

Gene Electrotransfer Efficiency in 2D and 3D Cancer Cell Models Using Different Electroporation Protocols: A Comparative Study

Electroporation, a method relying on a pulsed electric field to induce transient cell membrane permeabilization, can be used as a non-viral method to transfer genes in vitro and in vivo. Such transfer holds great promise for cancer treatment, as it can induce or replace missing or non-functioning genes. Yet, while efficient in vitro, gene-electrotherapy remains challenging in tumors. To assess the differences of gene electrotransfer in respect to applied pulses in multi-dimensional (2D, 3D) cellular organizations, we herein compared pulsed electric field protocols applicable to electrochemotherapy and gene electrotherapy and different "High Voltage-Low Voltage" pulses. Our results show that all protocols can result in efficient permeabilization of 2D- and 3D-grown cells. However, their efficiency for gene delivery varies. The gene-electrotherapy protocol is the most efficient in cell suspensions, with a transfection rate of about 50%. Conversely, despite homogenous permeabilization of the entire 3D structure, none of the tested protocols allowed gene delivery beyond the rims of multicellular spheroids. Taken together, our findings highlight the importance of electric field intensity and the occurrence of cell permeabilization, and underline the significance of pulses' duration, impacting plasmids' electrophoretic drag. The latter is sterically hindered in 3D structures and prevents the delivery of genes into spheroids' core.