Topical gene electrotransfer to the epidermis of hairless guinea pig by non-invasive multielectrode array

Intradermal DNA vaccine delivery using vacuum-controlled, needle-free electroporation

Intradermal delivery of DNA vaccines via electroporation (ID-EP) has shown clinical promise, but the use of needle electrodes is typically required to achieve consistent results. Here, delivery of a DNA vaccine targeting the Middle East Respiratory Syndrome Coronavirus (MERS-CoV) is achieved using noninvasive intradermal vacuum-EP (ID-VEP), which functions by pulling a small volume of skin tissue into a vacuum chamber containing noninvasive electrodes to perform EP at the injection site. Gene expression and immunogenicity correlated with EP parameters and vacuum chamber geometry in guinea pigs. ID-VEP generated potent humoral and cellular immune responses across multiple studies, while vacuum (without EP) greatly enhanced localized transfection but did not improve immunogenicity. Because EP was performed noninvasively, the only treatment site reaction observed was transient redness, and ID-VEP immune responses were comparable to a clinical needle-based ID-EP device. The ID-VEP delivery procedure is straightforward and highly repeatable, without any dependence on operator technique. This work demonstrates a novel, reliable, and needle-free delivery method for DNA vaccines.

Abnormal voxel-mirrored homotopic connectivity in first-episode major depressive disorder using fMRI: a machine learning approach

Objective

To explore the interhemispheric information synergy ability of the brain in major depressive disorder (MDD) patients by applying the voxel-mirrored homotopic connectivity (VMHC) method and further explore the potential clinical diagnostic value of VMHC metric by a machine learning approach.

Methods

52 healthy controls and 48 first-episode MDD patients were recruited in the study. We performed neuropsychological tests and resting-state fMRI scanning on all subjects. The VMHC values of the symmetrical interhemispheric voxels in the whole brain were calculated. The VMHC alterations were compared between two groups, and the relationship between VMHC values and clinical variables was analyzed. Then, abnormal brain regions were selected as features to conduct the classification model by using the support vector machine (SVM) approach.

Results

Compared to the healthy controls, MDD patients exhibited decreased VMHC values in the bilateral middle frontal gyrus, fusiform gyrus, medial superior frontal gyrus and precentral gyrus. Furthermore, the VMHC value of the bilateral fusiform gyrus was positively correlated with the total Hamilton Depression Scale (HAMD). Moreover, SVM analysis displayed that a combination of all clusters demonstrated the highest area under the curve (AUC) of 0.87 with accuracy, sensitivity, and specificity values of 86.17%, 76.74%, and 94.12%, respectively.

Conclusion

MDD patients had reduced functional connectivity in the bilateral middle frontal gyrus, fusiform gyrus, medial superior frontal gyrus and precentral gyrus, which may be related to depressive symptoms. The abnormality in these brain regions could represent potential imaging markers to distinguish MDD patients from healthy controls.

Reduction of plasmid vector backbone length enhances reporter gene expression

Gene therapy has a wide range of applications for various types of pathologies. Viral methods of gene delivery provide high levels of gene expression but have various safety concerns. Non-viral methods are largely known to provide lower levels of expression. We aim to address this issue by using plasmid DNA with smaller backbones to increase gene expression levels when delivered using non-viral methods. In this study we compare gene expression levels between two vectors with firefly luciferase encoding gene insert using liposome complexes and gene electrotransfer as delivery methods. A 2-fold reduction in plasmid vector backbone size, disproportionately enhanced gene expression levels more than 10-fold in rat tenocytes in vitro, and rat myocardium in vivo, while improvements in delivery to the skin were more moderate.

Moderate Heat-Assisted Gene Electrotransfer as a Potential Delivery Approach for Protein Replacement Therapy through the Skin

Gene-based approaches for protein replacement therapies have the potential to reduce the number of administrations. Our previous work demonstrated that expression could be enhanced and/or the applied voltage reduced by preheating the tissue prior to pulse administration. In the current study, we utilized our 16-pin multi-electrode array (MEA) and incorporated nine optical fibers, connected to an infrared laser, between each set of four electrodes to heat the tissue to 43 °C. For proof of principle, a guinea pig model was used to test delivery of reporter genes. We observed that when the skin was preheated, it was possible to achieve the same expression levels as gene electrotransfer without preheating, but with a 23% reduction of applied voltage or a 50% reduction of pulse number. With respect to expression distribution, preheating allowed for delivery to the deep dermis and muscle. This suggested that this cutaneous delivery approach has the potential to achieve expression in the systemic circulation, thus this protocol was repeated using a plasmid encoding Human Factor IX. Elevated Factor IX serum protein levels were detected by ELISA up to 100 days post gene delivery. Further work will involve optimizing protein levels and scalability in an effort to reduce application frequency.

Synergistic effects of an atmospheric pressure plasma jet and pulsed electric field on cells and skin

Nonthermal atmospheric pressure plasmas produce reactive plasma species including charged particles and reactive oxygen nitrogen species, which are known to induce oxidative stress in living cells in liquid or tissue. In the meantime, pulsed electric fields have been widely used in reversible or irreversible electropermeabilization for either the delivery of plasmid DNA or inactivation of cancer cells. This work discusses the synergistic effects of nanosecond pulsed plasma jets and pulsed electric field on inactivation of pancreatic cancer cells in vitro and enhancement of plasmid DNA delivery to guinea pig skin in vivo. Higher inactivation rates of the cancer cells in suspension were obtained with combined treatment of 300-ns 50 kV/cm pulsed electric field and a 1-min exposure of a nanosecond pulsed, 250-μm plasma jet. Increased efficiency of gene electrotransfer to skin was also observed after a 3-min treatment of a nanosecond pulsed, 1-mm plasma jet. Application of the plasma alone at the same dosage did not have significant effect on gene delivery. These findings signify the dosage-dependent cell-response to both the electric fields and plasma. Importantly, the use of cold plasma to increase the sensitization of the biological cells in response to pulsed electric fields could be an effective approach to enhance the desired effects in electroporation-based applications.

Real-time impedance feedback to enhance cutaneous gene electrotransfer in a murine skin model

Electric field mediated gene delivery methods have the ability to efficiently transfect cells in vivo with an excellent safety profile. The method has historically used a fixed number of electric pulses with identical characteristics in induce delivery. Electrical treatment does not typically compensate for subject-to-subject variation and other differences. This study was designed to investigate if delivery/expression could be increased using a novel electropulsation method that compensated for variation using real-time electrical impedance measurements. The method involved delivering plasmid DNA encoding luciferase to murine skin. Tissue impedance in a 1-3 KHz range was measured before electric pulses were applied. Impedance was also measured after each successive pulse. Pulsation was stopped when impedance values were reduced by either 80% or 95% relative to prepulse values. Standard/fixed pulsing parameters were also used for comparison. The results indicated that up to 15-fold increases in luciferase expression could be obtained when electrical treatment was ceased based upon impedance reductions. Furthermore, peak expression levels of all treatment groups pulsed using the novel pulsing method were statistically higher than those that employed standard pulsing. These results strongly suggest that applying pulses until a defined impedance-based endpoint results in higher expression.

Moderate Heat-Assisted Gene Electrotransfer for Cutaneous Delivery of a DNA Vaccine Against Hepatitis B Virus

An estimated 350 million people are living with chronic Hepatitis B virus (HBV) worldwide. Preventative HBV vaccination in infants has reduced the disease burden; however, insufficient immunization programs and access obstacles leave vulnerable populations at risk for infection in endemic regions. Gene electrotransfer (GET) using a noninvasive multielectrode array (MEA) provides an alternative platform for DNA vaccination in the skin. DNA vaccines are nonlive and nonreplicating and temperature stable unlike their counterparts. In addition, their simple engineering allows them to be manufactured quickly at a low cost. In the current work, we present the combination of GET and moderate heating for delivery of a DNA vaccine against HBV. Our laboratory has previously shown the synergy between moderate tissue preheating at 43°C and GET with the MEA as a means to reduce both the applied voltage and pulse number to achieve similar if not higher gene expression than GET alone. In this study, we expand upon this work, by optimizing the plasmid dose to achieve the highest level of expression. Using the reporter gene luciferase, we found that an intradermal injection of 100 μL at 1 mg/mL induced the highest expression levels across all tested GET conditions. We then evaluated our moderate heat-assisted GET platform for the intradermal delivery of a plasmid encoding Hepatitis B surface antigen (pHBsAg) via a prime and prime plus boost vaccination protocol. At 18 weeks, following the prime plus boost protocol, we observed that a high-voltage low-pulse GET condition with moderate heating (45 V 36 p+heat) generated antibodies against Hepatitis B surface antigen (HBsAb) at peak measuring 230-fold over injection of plasmid DNA alone with moderate heating. HBsAbs remained robust over the 30-week observation period. These data suggest that moderate heat-assisted GET has the potential to induce strong immune responses, an attractive feature for development of an alternative vaccine delivery platform.

Monopolar gene electrotransfer enhances plasmid DNA delivery to skin

A novel monopolar electroporation system and methodologies were developed for in vivo electroporation intended for potential clinical applications such as gene therapy. We hypothesized that an asymmetric anode/cathode electrode applicator geometry could produce favorable electric fields for electroporation, without the typical drawback associated with traditional needle and parallel plate geometries. Three monopolar electrode applicator prototypes were built and tested for gene delivery of reporter genes to the skin in a guinea pig model. Gene expression was evaluated in terms of kinetics over time and expression distribution within the treatment site. Different pulsing parameters, including pulse amplitude, pulse duration, and pulse number were evaluated. Monopolar gene electrotransfer significantly enhanced gene expression compared to controls over the course of 21 days. Gene expression distribution was observed throughout the full thickness of the epidermis, as well as notable expression in the deeper layers of the skin, including the dermis, and the underlying striated muscle without any damage at the treatment site, which is a substantial improvement over previously reported expression confined to the epidermis only. Expression distribution observed is consistent with the electric field distribution model, indicating that our novel electrode geometry results in targeted electroporation and gene transfer. This is important, as it may facilitate translation of many electroporation-based clinical therapies including gene therapies, IRE, and ECT.

Safe and efficient novel approach for non-invasive gene electrotransfer to skin

Gene transfer into cells or tissue by application of electric pulses (i.e. gene electrotransfer (GET)) is a non-viral gene delivery method that is becoming increasingly attractive for clinical applications. In order to make GET progress to wide clinical usage its efficacy needs to be improved and the safety of the method has to be confirmed. Therefore, the aim of our study was to increase GET efficacy in skin, by optimizing electric pulse parameters and the design of electrodes. We evaluated the safety of our novel approach by assaying the thermal stress effect of GET conditions and the biodistribution of a cytokine expressing plasmid. Transfection efficacy of different pulse parameters was determined using two reporter genes encoding for the green fluorescent protein (GFP) and the tdTomato fluorescent protein, respectively. GET was performed using non-invasive contact electrodes immediately after intradermal injection of plasmid DNA into mouse skin. Fluorescence imaging of transfected skin showed that a sophistication in the pulse parameters could be selected to get greater transfection efficacy in comparison to the standard ones. Delivery of electric pulses only mildly induced expression of the heat shock protein Hsp70 in a luminescent reporting transgenic mouse model, demonstrating that there were no drastic stress effects. The plasmid was not detected in other organs and was found only at the site of treatment for a limited period of time. In conclusion, we set up a novel approach for GET combining new electric field parameters with high voltage short pulses and medium voltage long pulses using contact electrodes, to obtain a high expression of both fluorescent reporter and therapeutic genes while showing full safety in living animals.

Coalesced thermal and electrotransfer mediated delivery of plasmid DNA to the skin

Efficient gene delivery and expression in the skin can be a promising minimally invasive technique for therapeutic clinical applications for immunotherapy, vaccinations, wound healing, cancer, and peripheral artery disease. One of the challenges for efficient gene electrotransfer (GET) to skin in vivo is confinement of expression to the epithelium. Another challenge involves tissue damage. Optimizing gene expression profiles, while minimizing tissue damage are necessary for therapeutic applications. Previously, we established that heating pretreatment to 43 °C enhances GET in vitro. We observed a similar trend in vivo, with an IR-pretreatment for skin heating prior to GET. Currently, we tested a range of GET conditions in vivo in guinea pigs with and without preheating the skin to ~43 °C. IR-laser heating and conduction heating were tested in conjunction with GET. In vivo electrotransfer to the skin by moderately elevating tissue temperature can lead to enhanced gene expression, as well as achieve gene transfer in epidermal, dermal, hypodermal and muscle tissue layers.

Electroporation of Skin Stratum Corneum Lipid Bilayer and Molecular Mechanism of Drug Transport: A Molecular Dynamics Study

The electroporation technique has been used significantly to increase drug permeation through the skin. This technique relies on the application of short-timed (microseconds to millisecond) electric fields (generally, order of 50--300 V) on the skin to create microscopic pores. However, the molecular mechanism of pore formation, resulting in an enhanced flux of active molecules through the skin, remains poorly understood. In this study, extensive atomistic molecular dynamics simulation of skin lipids [made up of ceramide (CER), cholesterol (CHOL), and free fatty acid (FFA)] has been performed at various external electric fields. We show for the first time the pore formation in the skin lipid bilayer during electroporation. We show the effect of the applied external electrical field (0.6-1.0 V/nm) on the pore formation dynamics in the lipid bilayer of different sizes (154, 616, and 2464 lipids) and compositions (CER/CHOL/FFA, 1:0:0, 1:0:1, 1:1:0, 1:1:1). The pore formation and resealing kinetics were different and were found to be highly dependent on the composition of the skin lipid bilayer. The pore formation time decreased with increase in the bilayer size. The pore sustaining electric field was found to be in the range of 0.20-0.25 V/nm for equimolar CER, CHOL, and FFA lipid bilayers. The skin lipid bilayer (1:1:1) sealed itself within 20 ns after the removal of the external electric field. We also present the molecular mechanism of enhancement of drug permeation in the presence of external field as compared to the passive diffusion. The molecular-level understanding obtained here could help in optimizing/designing the electroporation experiments for effective drug delivery. For a given skin composition and size of the drug molecule, the combination of pore formation time and pore growth model can be used to know a priori the desired electric field and time for the application of the electric field.

A review of genetic engineering biotechnologies for enhanced chronic wound healing

Traditional methods for addressing chronic wounds focus on correcting dysfunction by controlling extracellular elements. This review highlights technologies that take a different approach - enhancing chronic wound healing by genetic modification to wound beds. Featured cutaneous transduction/transfection methods include viral modalities (ie adenoviruses, adeno-associated viruses, retroviruses and lentiviruses) and conventional non-viral modalities (ie naked DNA injections, microseeding, liposomal reagents, particle bombardment and electroporation). Also explored are emerging technologies, focusing on the exciting capabilities of wound diagnostics such as pyrosequencing as well as site-specific nuclease editing tools such as CRISPR-Cas9 used to both transiently and permanently genetically modify resident wound bed cells. Additionally, new non-viral transfection methods (ie conjugated nanoparticles, multi-electrode arrays, and microfabricated needles and nanowires) are discussed that can potentially facilitate more efficient and safe transgene delivery to skin but also represent significant advances broadly to tissue regeneration research.

Electroporation as a vaccine delivery system and a natural adjuvant to intradermal administration of plasmid DNA in macaques

In vivo electroporation (EP) is used to enhance the uptake of nucleic acids and its association with DNA vaccination greatly stimulates immune responses to vaccine antigens delivered through the skin. However, the effect of EP on cutaneous cell behavior, the dynamics of immune cell recruitment and local inflammatory factors, have not been fully described. Here, we show that intradermal DNA vaccination combined with EP extends antigen expression to the epidermis and the subcutaneous skin muscle in non-human primates. In vivo fibered confocal microscopy and dynamic ex vivo imaging revealed that EP promotes the mobility of Langerhans cells (LC) and their interactions with transfected cells prior to their migration from the epidermis. At the peak of vaccine expression, we detected antigen in damaged keratinocyte areas in the epidermis and we characterized recruited immune cells in the skin, the hypodermis and the subcutaneous muscle. EP alone was sufficient to induce the production of pro-inflammatory cytokines in the skin and significantly increased local concentrations of Transforming Growth Factor (TGF)-alpha and IL-12. Our results show the kinetics of inflammatory processes in response to EP of the skin, and reveal its potential as a vaccine adjuvant.

Novel Instruments for the Implementation of Electrochemotherapy Protocols: From Bench Side to Veterinary Clinic

Electrochemotherapy (ECT) is a medical strategy that allows an increased efficacy of chemotherapy agents after the application of permeabilizing electric pulses having appropriate characteristics (form, voltage, frequency). In the past 10 years, the clinical efficacy of this therapeutic approach in several spontaneous models of tumors in animals has been shown. Moreover, some of the molecular and cellular mechanisms responsible for this phenomenon have been elucidated. Our group has been deeply involved in the development of new ECT protocols for companion animals, implementing the use of the technique as first line treatment, and evaluating different chemotherapy agents in laboratory animals as well as pets. This article summarizes the most important advances in veterinary ECT, including the development of novel equipment, therapeutic protocols, and their translation to humans. J. Cell. Physiol. 232: 490-495, 2017. © 2016 Wiley Periodicals, Inc.

Electrotransfer parameters as a tool for controlled and targeted gene expression in skin

Skin is an attractive target for gene electrotransfer. It consists of different cell types that can be transfected, leading to various responses to gene electrotransfer. We demonstrate that these responses could be controlled by selecting the appropriate electrotransfer parameters. Specifically, the application of low or high electric pulses, applied by multi-electrode array, provided the possibility to control the depth of the transfection in the skin, the duration and the level of gene expression, as well as the local or systemic distribution of the transgene. The influence of electric pulse type was first studied using a plasmid encoding a reporter gene (DsRed). Then, plasmids encoding therapeutic genes (IL-12, shRNA against endoglin, shRNA against melanoma cell adhesion molecule) were used, and their effects on wound healing and cutaneous B16F10 melanoma tumors were investigated. The high-voltage pulses resulted in gene expression that was restricted to superficial skin layers and induced a local response. In contrast, the low-voltage electric pulses promoted transfection into the deeper skin layers, resulting in prolonged gene expression and higher transgene production, possibly with systemic distribution. Therefore, in the translation into the clinics, it will be of the utmost importance to adjust the electrotransfer parameters for different therapeutic approaches and specific mode of action of the therapeutic gene.

Recellularized human dermis for testing gene electrotransfer ex vivo

Gene electrotransfer (GET) is a proven and valuable tool for in vivo gene delivery to a variety of tissues such as skin, cardiac muscle, skeletal muscle, and tumors, with controllable gene delivery and expression levels. Optimizing gene expression is a challenging hurdle in preclinical studies, particularly for skin indications, due to differences in electrical conductivity of animal compared to human dermis. Therefore, the goal of this study was to develop an ex vivo model for GET using recellularized human dermis to more closely mimic human skin. Decellularized human dermis (DermACELL(®)) was cultured with human dermal fibroblasts and keratinocytes for 4 weeks. After one week of fibroblast culture, fibroblasts infiltrated and dispersed throughout the dermis. Air-liquid interface culture led to epithelial cell proliferation, stratification and terminal differentiation with distinct basal, spinous, granular and cornified strata. Firefly luciferase expression kinetics were evaluated after GET of recellularized constructs for testing gene delivery parameters to skin in vitro. Elevated luciferase expression persisted up to a week following GET compared to controls without electrotransfer. In summary, recellularized dermis structurally and functionally resembled native human skin in tissue histological organization and homeostasis, proving an effective 3D human skin model for preclinical gene delivery studies.

Perspectives on Transdermal Electroporation

Transdermal drug delivery offers several advantages, including avoidance of erratic absorption, absence of gastric irritation, painlessness, noninvasiveness, as well as improvement in patient compliance. With this mode of drug administration, there is no pre-systemic metabolism and it is possible to increase drug bioavailability and half-life. However, only a few molecules can be delivered across the skin in therapeutic quantities. This is because of the hindrance provided by the stratum corneum. Several techniques have been developed and used over the last few decades for transdermal drug delivery enhancement. These include sonophoresis, iontophoresis, microneedles, and electroporation. Electroporation, which refers to the temporary perturbation of the skin following the application of high voltage electric pulses, has been used to increase transcutaneous flux values by several research groups. In this review, transdermal electroporation is discussed and the use of the technique for percutaneous transport of low and high molecular weight compounds described. This review also examines our current knowledge regarding the mechanisms of electroporation and safety concerns arising from the use of this transdermal drug delivery technique. Safety considerations are especially important because electroporation utilizes high voltage pulses which may have deleterious effects in some cases.

Improved Specificity of Gene Electrotransfer to Skin Using pDNA Under the Control of Collagen Tissue-Specific Promoter

In order to ensure safe, efficient and controlled gene delivery to skin, the improvement of delivery methods together with proper design of DNA is required. Non-viral delivery methods, such as gene electrotransfer, and the design of tissue-specific promoters are promising tools to ensure the safety of gene delivery to the skin. In the scope of our study, we evaluated a novel skin-specific plasmid DNA with collagen (COL) promoter, delivered to skin cells and skin tissue by gene electrotransfer. In vitro, we determined the specificity of the COL promoter in fibroblast cells. The specific expression under the control of COL promoter was obtained for the reporter gene DsRed as well as for therapeutic gene encoding cytokine IL-12. In vivo, the plasmid with COL promoter encoding the reporter gene DsRed was efficiently transfected to mouse skin. It resulted in the notable and controlled manner, however, in lower and shorter expression, compared to that obtained with ubiquitous promoter. The concentration of the IL-12 in the skin after the in vivo transfection of plasmid with COL promoter was in the same range as after the treatment in control conditions (injection of distilled water followed by the application of electric pulses). Furthermore, this gene delivery was local, restricted to the skin, without any evident systemic shedding of IL-12. Such specific targeting of skin cells, observed with tissue-specific COL promoter, would improve the effectiveness and safety of cutaneous gene therapies and DNA vaccines.

Application of increased temperature from an exogenous source to enhance gene electrotransfer

The presence of increased temperature for gene electrotransfer has largely been considered negative. Many reports have published on the lack of heat from electrotransfer conditions to demonstrate that their effects are from the electrical pulses and not from a rise in temperature. Our hypothesis was to use low levels of maintained heat from an exogenous source to aid in gene electrotransfer. The goal was to increase gene expression and/or reduce electric field. In our study we evaluated high and low electric field conditions from 90 V to 45 V which had been preheated to 40 °C, 43 °C, or 45 °C. Control groups of non-heated as well as DNA only were included for comparison in all experiments. Luciferase gene expression, viability, and percent cell distribution were measured. Our results indicated a 2-4 fold increase in gene expression that is temperature and field dependent. In addition levels of gene expression can be increased without significant decreases in cell death and in the case of high electric fields no additional cell death. Finally, in all conditions percent cell distribution was increased from the application of heat. From these results, we conclude that various methods may be employed depending on the end user's desired goals. Electric field can be reduced 20-30% while maintaining or slightly increasing gene expression and increasing viability or overall gene expression and percent cell distribution can be increased with low viability.