Interactions of amphiphilic polyoxazolines formulated or not in lipid nanocapsules with biological systems: Evaluation from membrane models up to in vivo mice epidermis.

In this study, we evaluated the potential of amphiphilic polyoxazolines (POx) to interact with biological membranes thanks to models of increasing complexity, from a simple lipid bilayer using giant unilamellar vesicles (GUV), to plasma membranes of three different cell types, fibroblasts, keratinocytes and melanocytes, which are found in human skin. Upon assessing an excellent penetration into GUV membranes and cultured cells, we addressed POx's potential to penetrate the murine skin within an in vivo model. Exposure studies were made with native POx and with POx encapsulated within lipid nanocapsules (LNC). Our findings indicate that POx's interactions with membranes tightly depend on the nature of the alkyl chain constituting the POx. Saturated C16POx insert rapidly and efficiently into GUV and plasma membranes, while unsaturated C18:2POx insert to a smaller extent. The high amount of membrane-inserted saturated C16POx impacts cell viability to a greater extent than the unsaturated C18:2POx. The in vivo study, performed on mice, showed an efficient accumulation of both POx types in the stratum corneum barrier, reaching the upper epidermis, independently of POx's degree of saturation. Furthermore, the formulation of POx into lipid nanocapsules allowed delivering an encapsulated molecule, the quercetin, in the upper epidermis layers of murine skin, proving POx's efficacy for topical delivery of active molecules. Overall, POx proved to be an excellent choice for topical delivery, which might in turn offer new possibilities for skin treatments in diseases such as psoriasis or melanomas.

Electrotransfer of CpG free plasmids enhances gene expression in skin.

Skin is a very suitable target for gene therapy and DNA vaccination due to its accessibility, its surface and its ability to produce transgenes. Gene electrotransfer (GET) to the skin is under development for clinical applications for DNA vaccine or local treatment such as wound healing. Local treatments are effective if the expression of the plasmid affects only the local environment (skin) by inducing an efficient concentration over a prolonged period. In this study, we evaluate the control of expression in the skin of a plasmid coding a fluorescent protein by its CpG (cytosine-phosphate-guanine motif) content. Two fluorescent reporter genes are evaluated: tdTomato and GFP. The expression is followed on the long term by in vivo fluorescence imaging. Our results show that GET mediated expression in the skin can be controlled by the CpG content of the plasmid. Long term expression (>120 days) can be obtained at high level with CpG-free constructs associated with a proper design of the electrodes where the field distribution mediating the gene electrotransfer is present deep in the skin.

Electrochemotherapy guided by intraoperative fluorescence imaging for the treatment of inoperable peritoneal micro-metastases.

Surgery is often the first therapeutic indication in cancer. Patient survival essentially depends on the completeness of tumor resection. This is a major challenge, particularly in patients with peritoneal carcinomatosis (PC), where tumors are widely disseminated in the large peritoneal cavity. These small tumors can be difficult to visualize and are often positioned in delicate locations, further increasing the risk of producing serious tissue/organ damage during their ablation. We propose an innovative therapeutic approach based on intraoperative fluorescence (IF) guided electrochemotherapy (ECT) for the treatment of peritoneal micro-metastases. ECT combines the effects of tissue electro-permeabilization (EP) with the administration of an antimitotic agent (bleomycin) that has poor permeability across intact membranes. IF significantly improves the detection of small tumor lesions. ECT is clinically validated for the treatment of cutaneous tumors in animals and humans, but this is the first time that it has been used along with IF imaging for the targeted treatment of peritoneal metastases in a preclinical model. We set up a murine model of PC that develops secondarily to the resection of a distant primary tumor. Tumor growth and metastasis were finely monitored by non-invasive multimodal imaging (bioluminescence and 3D fluorescence/microCT). Once metastases were detected, mice were randomized into three groups: the ECT group (bleomycin injected intravenously followed by EP) and 2 control groups (bleomycin alone and EP alone). Twenty four hours after the intravenous injection of the tumor targeting agent Angiostamp™700, mice in all groups underwent an abdominal surgery for metastases exploration assisted by fluorescence imaging with the Fluobeam®700 portative device. EP was applied to every nodule detected by IF, except in the bleomycin control group. After surgery, the metastatic invasion was tracked by bioluminescence imaging. In mice treated with bleomycin or EP alone, the metastatic load progressed very rapidly and mice showed no significant difference in lifespan compared to non-operated mice (median lifespan: 27days vs. 25days, respectively). In contrast, the mice treated with ECT displayed a decreased metastatic load and an increased survival rate (median lifespan: 34days). These results provide evidence that IF guided ECT is an effective approach for the treatment of inoperable intraperitoneal micro-metastases.

Post-pulse addition of trans-cyclohexane-1,2-diol improves electrotransfer mediated gene expression in mammalian cells.

Electric field mediated gene transfer is facing a problem in expression yield due to the poor transfer across the nuclear envelope. Trans-cyclohexane-1,2-diol (TCHD) was shown to significantly increase chemically mediated transfection by collapsing the permeability barrier of the nuclear pore complex. We indeed observed a significant increase in expression by electrotransfer when cells are treated post pulse by a low non toxic concentration of TCHD. This was obtained for different pulsing conditions, cell strains and plasmid constructs. An interesting improvement in cell viability can be obtained. This can significantly enhance the non-viral gene electrical delivery.

A double-pulse approach for electrotransfection.

Gene transfer and expression can be obtained by delivering calibrated electric pulses on cells in the presence of plasmids coding for the activity of interest. The electric treatment affects the plasma membrane and induces the formation of a transient complex between nucleic acids and the plasma membrane. It results in a delivery of the plasmid in the cytoplasm. Expression is only obtained if the plasmid is translocated inside the nucleus. This is a key limit in the process. We previously showed that delivery of a high-field short-duration electric pulse was inducing a structural alteration of the nuclear envelope. This study investigates if the double-pulse approach (first pulse to transfer the plasmid to the cytoplasm, and second pulse to induce the structural alteration of the envelope) was a way to enhance the protein expression using the green fluorescent protein as a reporter. We observed that not only the double-pulse approach induced the transfection of a lower number of cells but moreover, these transfected cells were less fluorescent than the cells treated only with the first pulse.

Minicircle DNA electrotransfer for efficient tissue-targeted gene delivery.

A major issue for successful human gene therapy or genetic vaccination is a safe high-transgene expression level. Plasmid-based (non-viral) physical methods of gene transfer offered attracting approaches but their low efficiencies have limited their use in human pre-clinical trials. One of the limits appears to be the size of the plasmid that must be transferred across the cell membrane to the nucleus for its processing. In the present work to enhance gene transfer and expression, we evaluated a new generation of DNA vector; the minicircle, combined with the electropulsation technique. Minicircle is a doubled-stranded circular DNA with reduced size as it is devoid of bacterial sequences. We showed that electrotransferred minicircle encoding green fluorescent protein had higher in vitro transfection level compared with full-length plasmid. We demonstrated that minicircle great efficiency was not because of cellular toxicity decrease but was correlated to more efficient vector uptake by cells. Vector electrotransfection was operated in vivo and, using fluorescence imaging, minicircle electrotransfer was shown to enhance the efficiency and duration of tissue-targeted gene delivery and expression. By combining powerful expression and delivery systems, we have provided a valuable method for new approaches in gene therapy and genetic vaccination.

Drug delivery by electropulsation: Recent developments in oncology.

Electro-permeabilisation allows the free access of polar compounds to the cytoplasm by a reversible alteration of the cell membrane. It is now used in clinics for the eradication of cutaneous solid tumors. New developments predict its future applications for other anti-cancer treatments.

Successful treatment of equine sarcoids with cisplatin electrochemotherapy: a retrospective study of 48 cases.

REASONS FOR PERFORMING STUDY: Sarcoids are the commonest form of equine skin tumour. Several therapeutic measures have been described but none is considered to be universally effective. Electrochemotherapy (ECT) is a new anticancer therapy that utilises electrical field pulses to induce increased cell membrane permeability to antitumour hydrophilic drugs, such as cisplatin. The increased intracellular concentration of the drugs has a significant therapeutic benefit. The procedure has not been previously reported in a large number of horses. OBJECTIVE: To validate ECT as a novel alternative treatment for equine sarcoids. METHODS: A retrospective study evaluating the efficacy of cisplatin ECT in the treatment of equine sarcoids was performed. Electrochemotherapy treatments were applied under general anaesthesia at 2 week intervals with or without prior excision or debulking. Electric pulses were directly applied to the lesions following intra-tumoural injections of an aqueous solution of cisplatin. RESULTS: One-hundred-and-ninety-four sarcoids on 34 horses, 2 ponies, 11 donkeys and one mule were treated with ECT. The 4 year nonrecurrence rate was 97.9% for animals (47/48) and 99.5% (193/194) for tumours. When ECT was used as a single treatment, a significant influence of tumour size (ρ= 0.55) on the number of treatments required for cure was shown. When prior surgery was performed, there was a significant influence (P<0.001) of the excision quality (complete or incomplete) and the healing mode (closed or open wound) on the number of treatments. The most common adverse effect was a slight oedematous reaction for lesions located on thin skin regions. CONCLUSION AND CLINICAL RELEVANCE: Results demonstrate that ECT, with or without concurrent tumour debulking, is an effective alternative for treatment of equine sarcoids.

Direct visualization at the single-cell level of siRNA electrotransfer into cancer cells.

The RNA interference-mediated gene silencing approach is promising for therapies based on the targeted inhibition of disease-relevant genes. Electropermeabilization is one of the nonviral methods successfully used to transfer siRNA into living cells in vitro and in vivo. Although this approach is effective in the field of gene silencing by RNA interference, very little is known about the basic processes supporting siRNA transfer. In this study, we investigated, by direct visualization at the single-cell level, the delivery of Alexa Fluor 546-labeled siRNA into murine melanoma cells stably expressing the enhanced green fluorescent protein (EGFP) as a target gene. The electrotransfer of siRNA was quantified by time lapse fluorescence microscopy and was correlated with the silencing of egfp expression. A direct transfer into the cell cytoplasm of the negatively charged siRNA was observed across the plasma membrane exclusively on the side facing the cathode. When added after electropulsation, the siRNA was inefficient for gene silencing because it did not penetrate the cells. Therefore, we report that an electric field acts on both the permeabilization of the cell plasma membrane and on the electrophoretic drag of the negatively charged siRNA molecules from the bulk phase into the cytoplasm. The transfer kinetics of siRNA are compatible with the creation of nanopores, which are described with the technique of synthetic nanopores. The mechanism involved was clearly specific for the physico-chemical properties of the electrotransferred molecule and was different from that observed with small molecules or plasmid DNA.

Electrodes for in vivo localised subcutaneous electropulsation and associated drug and nucleic acid delivery.

BACKGROUND: Drug and nucleic acids can be delivered in vivo by an injection of the product followed by the application of a train of electric pulses. OBJECTIVE: The success of the method is linked to the proper distribution of the electric field in the target tissue. This is under the control of the design of the electrodes. METHODS: The field distribution can be obtained by computer simulation mainly by using numerical methods and simplifying hypothesis. The conclusions are validated by comparing the computed current and its experimental values on phantoms. A good agreement is obtained. RESULTS/CONCLUSION: Targeting the delivery to the skin can be obtained by using an array of very short needle electrodes, by pinching the skin between two parallel plate electrodes, or by using contact wire electrodes.

Control by pulse parameters of DNA electrotransfer into solid tumors in mice.

Electrotransfer (electroporation) is recognized as one of the most promising alternatives to viral vectors for transfection of different tissues in vivo for therapeutic purposes. We evaluated the transfection efficiency of reporter genes (green fluorescent protein and luciferase) in murine subcutaneous tumors using different combinations of high-field (HV) (600-1400 V cm(-1), 100 mus, 8 pulses) and low-field (LV) (80-160 V cm(-1), 50-400 ms, 1-8 pulses) pulses and compared it to protocol using eight identical pulses of 600 V cm(-1) and 5 ms duration (electro-gene therapy, EGT). Expression of GFP was determined using a fluorescent microscope and flow cytometry and expression of luciferase by measuring its activity using a luminometer. The EGT protocol yielded the highest expression of both reporter genes. However, a careful optimization of combinations of HV and LV pulses may result in similar transfection as EGT pulses. With the combination protocol, relatively high fields of LV pulses were necessary to obtain comparable transfection to the EGT protocol. Expression of reporter genes was higher in B16 melanoma than in SA-1 fibrosarcoma. Our data support the hypothesis that both electropermeabilization and electrophoresis are involved in electrotransfer of plasmid DNA, but demonstrate that these components have to happen at the same time to obtain significant expression of the target gene in tumors.

In vivo restoration of RhoB expression leads to ovarian tumor regression.

Ovarian cancers are very aggressive cancers most often diagnosed when metastasis has already occurred in the entire peritoneal cavity. Ovarian adenocarcinoma cells present an undetectable level of RhoB GTPase. Using preclinical ovarian cancer models, we aimed to evaluate the potential use of RhoB cDNA as a tumor suppressor gene in gene therapy. RhoB restoration in vitro, through recombinant adenovirus transduction, resulted in the apoptosis of endogenous RhoB protein low-expressing cell lines (OVCAR-3 and IGROV-1) through the activation of the intrinsic apoptotic caspase cascade. We showed that a single injection of 10(8) p.f.u. of adenoviral vector encoding a reporter gene into the peritoneal cavity of ovarian tumor bearing mice can induce the gene modification of a large quantity of cells throughout the cavity. We thereby tested the effect of AdRhoB injections to treat ovarian cancer-bearing mice. The ectopic expression of RhoB, following its introduction via viral transduction into nude mice in vivo, was highly effective in suppressing tumor growth of ovarian cancer xenografts. Therapeutic agents designed to correct defects of RhoB at the molecular level may thereby provide innovative treatment options for patients not responding to standard therapies.

Efficiency of high- and low-voltage pulse combinations for gene electrotransfer in muscle, liver, tumor, and skin.

Gene electrotransfer is gaining momentum as an efficient methodology for nonviral gene transfer. In skeletal muscle, data suggest that electric pulses play two roles: structurally permeabilizing the muscle fibers and electrophoretically supporting the migration of DNA toward or across the permeabilized membrane. To investigate this further, combinations of permeabilizing short high-voltage pulses (HV; hundreds of V/cm) and mainly electrophoretic long low-voltage pulses (LV; tens of V/cm) were investigated in muscle, liver, tumor, and skin in rodent models. The following observations were made: (1) Striking differences between the various tissues were found, likely related to cell size and tissue organization; (2) gene expression is increased, if there was a time interval between the HV pulse and the LV pulse; (3) the HV pulse was required for high electrotransfer to muscle, tumor, and skin, but not to liver; and (4) efficient gene electrotransfer was achieved with HV field strengths below the detectability thresholds for permeabilization; and (5) the lag time interval between the HV and LV pulses decreased sensitivity to the HV pulses, enabling a wider HV amplitude range. In conclusion, HV plus LV pulses represent an efficient and safe option for future clinical trials and we suggest recommendations for gene transfer to various types of tissues.

In vivo gene silencing in solid tumors by targeted electrically mediated siRNA delivery.

RNA interference (RNAi)-mediated gene silencing approaches appear very promising for therapies based on the targeted inhibition of disease-relevant genes. The major hurdle to the therapeutic development of RNAi strategies remains, however, the efficient delivery of the RNAi-inducing molecules, the short interfering RNAs (siRNAs) and short hairpin RNAs (shRNAs), to the target tissue. With respect to cancer treatment the development of efficient delivery methods into solid tumors appears as a critical issue. However, very few studies have addressed this problem. In this study we have investigated the contribution of electrically mediated delivery of siRNA into murine tumors stably expressing an enhanced green fluorescent protein (EGFP) target reporter gene. The silencing of EGFP gene expression was quantified over time by fluorescence imaging in the living animal. Our study indicates that electric field can be used as an efficient method for siRNA delivery and associated gene silencing into cells of solid tumors in vivo.

Electrically-assisted nucleic acids delivery to tissues in vivo: where do we stand?

Electropulsation (electroporation) is a physical method for delivery of various molecules into the cells in vitro and in vivo. It is an expanding field due to its applicability in cancer therapy, where combined application of electric pulses and chemotherapeutic drugs is used for treatment of cutaneous and subcutaneous nodules of different malignancies. Another application of electropulsation in vivo is electrogene therapy, where after injection of naked plasmid DNA and delivery of electric pulses directly to the tissue the expression of gene of interest can be obtained. However, the transfection efficiency of this methodology in vivo is still lower than with viral vectors. Nevertheless, due to the lack of immunogenicity of the method, easiness of the preparation of large quantities of endotoxin free plasmid DNA, control and reproducibility of the method and the development of electropulsators approved for the clinical use, electrically-assisted nucleic-acid delivery holds a great potential for the clinical application. This aim of this minireview is to critically discuss the main limitations and obstacles associated with electrogene therapy and the failures and problems as well as the successes. Topics on electric field distribution in the tissue, electrode geometries, construction of plasmid, modulation of extracellular space, tissue damage, pro-inflammatory and immune response as well as blood flow modification associated with application of electric pulses and injection of naked DNA are presented with possible directions how to overcome these limitations. Furthermore, for successful electrogene therapy in clinical setting it is of utmost importance to elucidate the mechanisms of DNA transfer into the cells of tissues in vivo. This will enable appropriate selection of electric pulse parameters and plasmid DNA constructs for each particular intended use. In the long run, this review should encourage other scientists to consider electrically assisted gene delivery for gene therapy as it matures.

Mechanisms of cell membrane electropermeabilization: a minireview of our present (lack of ?) knowledge.

Cell electropulsation is routinely used in cell Biology for protein, RNA or DNA transfer. Its clinical applications are under development for targeted drug delivery and gene therapy. Nevertheless, the molecular mechanisms supporting the induction of permeabilizing defects in the membrane assemblies remain poorly understood. This minireview describes the present state of the investigations concerning the different steps in the reversible electropermeabilization process. The different hypotheses, which were proposed to give a molecular description of the membrane events, are critically discussed. Other possibilities are then given. The need for more basic research on the associated loss of cohesion of the membrane appears as a conclusion.

Inhibition of gene expression in mice muscle by in vivo electrically mediated siRNA delivery.

Owing to their capacity to induce strong, sequence-specific, gene silencing in cells, short interfering RNAs (siRNAs) represent new potential therapeutic tools. This development requires, however, new safe and efficient in vivo siRNA delivery methods. In the present technical report, we show that electrically mediated siRNA transfer can suppress transgene expression in adult mice muscles. Using electropulsation for siRNA delivery opens the way for a targeted gene silencing on a broad range of tissues. Clinical applications of electropulsation for delivery of other classes of molecules are under trials. We reported that gene silencing was efficiently obtained in vivo in an adult mammal (mouse) with chemically synthesized siRNA after its electrical delivery. The associated gene silencing was followed on the same animal and lasted at least 11 days. Gene silencing was obtained in muscles not only on young adult mice but also on much older animals. No tissue damages were detected under our electrical conditions. Therefore, this method should provide an efficient approach for a localized delivery of siRNAs in various tissues and organs.

Optical imaging of in vivo gene expression: a critical assessment of the methodology and associated technologies.

Following and quantifying the expression of reporter gene expression in vivo is very important to monitor the expression of therapeutic genes in targeted tissues in disease models and/or to assess the effectiveness of systems of gene therapy delivery. Gene expression of luminescent or fluorescent proteins can be detected directly on living animals by simply observing the associated optical signals by means of a cooled charged-coupled device camera. More accurate resolution can be obtained with more sophisticated technologies. Time-course and quasi-quantitative monitoring of the expression can be obtained on a given animal and followed on a large time window. The present paper describes the physical and technological methodologies and associated problems of in vivo optical imaging. Several examples of in vivo detection of gene delivery are described.

In vitro and in vivo electric field-mediated permeabilization, gene transfer, and expression.

Electropulsation is one of the non-viral methods successfully used to transfer genes into living cells in vitro as in vivo. This approach shows promise in the field of gene and cellular therapies. The present paper first describes the factors controlling electropermeabilization to small molecules (< 4 kDa) and then the processes supporting DNA transfer in vitro. The description of in vitro events brings the attention of the reader to the processes occurring before, during, and after electropulsation of DNA and cells. Their developments for the in vivo processes are reported in the final part where the present and potential clinical applications are described.

[Calcium and electropermeabilized cells]. / Calcium et cellules électropermeabilisées.

Trains of short and intense electric pulses may induce a reversible local permeabilization on the membrane of the treated cells. Hydrophilic species can then almost freely cross the envelope and either enter or escape from the cytoplasm. The purpose of the present study was to investigate the possibility of introducing well defined amounts of Ca2+ ions within the cell. Chinese hamster ovary cells were used as a model system. When the pulsing buffer contained high levels of free Ca2+, the survival of cells was strongly affected. A 1 mM level was well tolerated. When cells were pulsed under moderated field conditions, it was observed that Ca2+ entered cells very rapidly (second time range). But the basic cytoplasmic level was set back spontaneously within a few minutes. The perspectives of this electrical injection are discussed for basic cell biology and high-throughput biotechnology.