Nonviral gene delivery: what we know and what is next

Advances with the use of bio-inspired vectors towards creation of artificial viruses

IMPORTANCE OF THE FIELD

In recent years, there has been a great deal of interest in the development of recombinant vectors based on biological motifs with potential applications in gene therapy. Several such vectors have been genetically engineered, resulting in biomacromolecules with new properties that are not present in nature.

AREAS COVERED IN THIS REVIEW

This review briefly discusses the advantages and disadvantages of the current state-of-the-art gene delivery systems (viral and non-viral) and then provides an overview on the application of various biological motifs in vector development for gene delivery. Finally, it highlights some of the most advanced bio-inspired vectors that are designed to perform several self-guided functions.

WHAT THE READER WILL GAIN

This review helps the readers get a better understanding about the history and evolution of bio-inspired fusion vectors with the potential to merge the strengths of both viral and non-viral vectors in order to create efficient, safe and cost-effective gene delivery systems.

TAKE HOME MESSAGE

With the emergence of new technologies such as recombinant bio-inspired vectors, it may not take long before non-viral vectors are observed that are not just safe and tissue-specific, but even more efficient than viral vectors.

Evaluating the gene-expression profiles of HeLa cancer cells treated with activated and nonactivated poly(amidoamine) dendrimers, and their DNA complexes

Using dendrimers in cancer therapy as nonviral vectors for gene delivery seems promising. The biological performance of a dendrimer-based gene delivery system depends heavily on its molecular architecture. The transfection activity of dendrimers is significantly improved by processes activated in the heat degradation treatment of solvolysis. However, very little is known about the molecular mechanisms that dendrimers produce in cancer cells. We studied the changes in global gene-expression profiles in human cervical cancer HeLa cells exposed to nonactivated and activated poly(amidoamine) (PAMAM) dendrimers, alone or in complexes with plasmid DNA (dendriplexes). Real-time quantitative reverse transcriptase-polymerase chain reaction was used to confirm four regulated genes (PHF5A, ARNTL2, CHD4, and P2RX7) affected by activated dendrimers and dendriplexes. Activated and nonactivated dendrimers and dendriplexes alike induced multiple gene expression changes, some of which overlapped with their dendriplexes. Dendrimer activation improved transfection efficiency and induced additional gene expression changes in HeLa cells. Dendrimers and dendriplexes principally affect genes with the molecular functions of nucleic acid binding and transcription activity, metal-ion binding, enzyme activity, receptor activity, and protein binding. Our findings provide a deeper insight into the changes in gene expression patterns caused by the molecular structure of PAMAM dendrimers for gene-based cancer therapy.

Emerging nanotechnology approaches for HIV/AIDS treatment and prevention

Currently, there is no cure and no preventive vaccine for HIV/AIDS. Combination antiretroviral therapy has dramatically improved treatment, but it has to be taken for a lifetime, has major side effects and is ineffective in patients in whom the virus develops resistance. Nanotechnology is an emerging multidisciplinary field that is revolutionizing medicine in the 21st century. It has a vast potential to radically advance the treatment and prevention of HIV/AIDS. In this review, we discuss the challenges with the current treatment of the disease and shed light on the remarkable potential of nanotechnology to provide more effective treatment and prevention for HIV/AIDS by advancing antiretroviral therapy, gene therapy, immunotherapy, vaccinology and microbicides.

Modified nanoprecipitation method to fabricate DNA-loaded PLGA nanoparticles

OBJECTIVE

The objective of this study was to formulate DNA-loaded poly(d,l-lactide-co-glycotide) (PLGA) nanoparticles by a modified nanoprecipitation method.

METHODS

DNA-loaded PLGA nanoparticles were prepared by the modified nanoprecipitation method and the double emulsion/solvent evaporation method. The characterizations of DNA-loaded nanoparticles such as entrapment efficiency, morphology, particle size, zeta potential, structural integrity of the loaded DNA, and stability of the loaded DNA in PLGA nanoparticles against DNase I, in vitro release, cell viability and in vitro transfection capability were investigated.

RESULTS

The resulted PLGA nanoparticles by the modified nanoprecipitation method had uniform spherical shape, narrow size distribution with average particles size near 200 nm, negative zeta potential of -12.6 mV at pH 7.4, and a sustained-release property in vitro. Plasmid DNA could be efficiently encapsulated into PLGA nanoparticles (> 95%) without affecting its intact conformation using this modified nanoprecipitation method, which was superior to the double emulsion/solvent evaporation method. The PLGA nanoparticles were much safer to A549 cell compared to commercial Lipofectamine 2000 and could successfully transfer plasmid-enhanced green fluorescent protein into A549 cells.

CONCLUSION

In conclusion, the modified nanoprecipitation method could be applied as an efficient way to fabricate DNA-loaded PLGA nanoparticles instead of the conventional double emulsion/solvent evaporation method.

Self-assembled micronanoplexes for improved biolistic delivery of nucleic acids

A new method for biolistic delivery of nucleic acids using a combination of cationic micro- and nanoparticles is reported. The new method is simpler to perform than the conventional calcium/spermidine-based formulations and shows 11-fold improved nucleic acid binding capacity and dose-dependent performance both for in vitro and in vivo applications relative to either the conventional preparation or our recently reported direct cationic microparticle method. These features may enable higher throughput gene delivery and genetic immunization programs and open new venues for the biolistic delivery method.

Gold nanoparticles delivery in mammalian live cells: a critical review

Functional nanomaterials have recently attracted strong interest from the biology community, not only as potential drug delivery vehicles or diagnostic tools, but also as optical nanomaterials. This is illustrated by the explosion of publications in the field with more than 2,000 publications in the last 2 years (4,000 papers since 2000; from ISI Web of Knowledge, 'nanoparticle and cell' hit). Such a publication boom in this novel interdisciplinary field has resulted in papers of unequal standard, partly because it is challenging to assemble the required expertise in chemistry, physics, and biology in a single team. As an extreme example, several papers published in physical chemistry journals claim intracellular delivery of nanoparticles, but show pictures of cells that are, to the expert biologist, evidently dead (and therefore permeable). To attain proper cellular applications using nanomaterials, it is critical not only to achieve efficient delivery in healthy cells, but also to control the intracellular availability and the fate of the nanomaterial. This is still an open challenge that will only be met by innovative delivery methods combined with rigorous and quantitative characterization of the uptake and the fate of the nanoparticles. This review mainly focuses on gold nanoparticles and discusses the various approaches to nanoparticle delivery, including surface chemical modifications and several methods used to facilitate cellular uptake and endosomal escape. We will also review the main detection methods and how their optimum use can inform about intracellular localization, efficiency of delivery, and integrity of the surface capping.

PEGylated Adenoviruses: From Mice to Monkeys

Covalent modification with polyethylene glycol (PEG), a non-toxic polymer used in food, cosmetic and pharmaceutical preparations for over 60 years, can profoundly influence the pharmacokinetic, pharmacologic and toxciologic profile of protein and peptide-based therapeutics. This review summarizes the history of PEGylation and PEG chemistry and highlights the value of this technology in the context of the design and development of recombinant viruses for gene transfer, vaccination and diagnostic purposes. Specific emphasis is placed on the application of this technology to the adenovirus, the most potent viral vector with the most highly characterized toxicity profile to date, in several animal models.

Chemically modified cell-penetrating peptides for the delivery of nucleic acids

Short nucleic acids targeting biologically important RNAs and plasmids have been shown to be promising future therapeutics; however, their hydrophilic nature greatly limits their utility in clinics and therefore efficient delivery vectors are greatly needed. Cell-penetrating peptides (CPPs) are relatively short amphipathic and/or cationic peptides that are able to transport various biologically active molecules inside mammalian cells, both in vitro and in vivo, in a seemingly non-toxic fashion. Although CPPs have proved to be appealing drug delivery vehicles, their major limitation in nucleic acid delivery is that most of the internalized peptide-cargo is entrapped in endosomal compartments following endocytosis and the bioavailability is therefore severely reduced. Several groups are working towards overcoming this obstacle and this review highlights the evidence that by introducing chemical modification in CPPs, the bioavailability of delivered nucleic acids increases significantly.

Lipid-mediated delivery of RNA is more efficient than delivery of DNA in non-dividing cells

The design of appropriate gene delivery systems is essential for the successful application of gene therapy to clinical medicine. Cationic lipid-mediated delivery is a viable alternative to viral vector-mediated gene delivery in applications where transient gene expression is desirable. However, cationic lipid-mediated delivery of DNA to post-mitotic cells such as neurons is often reported to be of low efficiency, due to the presumed inability of the DNA to translocate to the nucleus. Lipid-mediated delivery of RNA is an attractive alternative to non-viral DNA delivery in some clinical applications, because transit across the nuclear membrane is not necessary. Here we report a comparative investigation of cationic lipid-mediated delivery of RNA versus DNA vectors encoding the reporter gene green fluorescent protein (GFP) in Chinese Hamster Ovary (CHO) and NIH3T3 cells following chemical inhibition of proliferation, and in primary mixed neuronal cell cultures. Using optimized formulations and transfection procedures, we assess gene expression by flow cytometry to specifically address some of the advantages and disadvantages of lipid-mediated RNA and DNA gene transfer. Despite inhibition of cell proliferation, over 45% of CHO cells express GFP after lipid-mediated transfection with RNA vectors. Transfection efficiency of DNA encoding GFP in proliferation-inhibited CHO cells was less than 5%. Detectable expression after RNA transfection occurs at least 3h earlier than after DNA transfection, but DNA transfection eventually produces a mean level of per cell GFP expression (as assayed by flow cytometry) that is higher than after RNA transfection. Transfection of proliferation-inhibited NIH3T3 cells and primary mixed neuronal cultures produced similar results, with RNA encoded GFP expression in 2-4 times the number of cells as after DNA encoded GFP expression. These results demonstrate the increased efficiency of RNA transfection relative to DNA transfection in non-dividing cells. We used firefly luciferase encoded by RNA and DNA vectors to investigate the time course of gene expression after delivery of RNA or DNA to primary neuronal cortical cells. Delivery of mRNA resulted in rapid onset (within 1h) of luciferase expression after transfection, a peak in expression 5-7h after transfection, and a return to baseline within 12h after transfection. After DNA delivery significant luciferase activity did not appear until 7h after transfection, but peak luciferase expression was always at least one order of magnitude higher than after RNA delivery. The peak expression after luciferase-expressing DNA delivery occurred 36-48 h after transfection and remained at a significant level for at least one week before dropping to baseline. This observation is consistent with our in vivo delivery results, which are shown as well. RNA delivery may therefore be more suitable for short-term transient gene expression due to rapid onset, shorter duration of expression and greater efficiency, particularly in non-dividing cells. Higher mean levels of expression per cell obtained following DNA delivery and the longer duration of expression confirm a continuing role for DNA gene delivery in clinical applications that require longer term transient gene expression.

Single cell optical transfection

The plasma membrane of a eukaryotic cell is impermeable to most hydrophilic substances, yet the insertion of these materials into cells is an extremely important and universal requirement for the cell biologist. To address this need, many transfection techniques have been developed including viral, lipoplex, polyplex, capillary microinjection, gene gun and electroporation. The current discussion explores a procedure called optical injection, where a laser field transiently increases the membrane permeability to allow species to be internalized. If the internalized substance is a nucleic acid, such as DNA, RNA or small interfering RNA (siRNA), then the process is called optical transfection. This contactless, aseptic, single cell transfection method provides a key nanosurgical tool to the microscopist-the intracellular delivery of reagents and single nanoscopic objects. The experimental possibilities enabled by this technology are only beginning to be realized. A review of optical transfection is presented, along with a forecast of future applications of this rapidly developing and exciting technology.

Dysopsonin activity of serum DNA-binding proteins favorable for gene delivery

Naked DNA is regarded as the safest and simplest method of gene delivery. However, normally intravenously injected naked plasmid DNA is rapidly eliminated from the blood. It has been hypothesized that opsonins, a category of serum DNA-binding proteins (SDBPs), label the injected plasmid DNA as foreign so that it may be recognized and rapidly removed from the bloodstream by liver nonparenchymal cells. Contrary to the hypothesis, our data indicate that some SDBPs across multiple species may have important dysopsonin properties, acting to reduce liver uptake. Formation of SDBP and DNA complexes was observed by agarose gel electrophoresis. An in vivo study involving hepatic artery and portal vein occlusion in a mouse model confirmed the activity of serum diminishing liver uptake of DNA. Data using hydrodynamic gene transfer in the mouse liver and in situ transfection in the mouse lung revealed that serum proteins bound to DNA do not affect the biological activity of the plasmid DNA. We have identified several SDBPs with potential dysopsonin properties. The SDBPs with dysopsonin properties and DNA complexes may be further modified and ultimately be developed into a novel DNA carrier system favorable for systemic gene delivery.

Degradable polyethylenimines as DNA and small interfering RNA carriers

Gene therapy is a powerful approach in the treatment of a wide range of both inherited and acquired diseases. Nonviral delivery systems have been proposed as safer alternatives to viral vectors because they avoid the inherent immunogenicity and production problems that are seen when viral systems are used. Many cationic polymers, including high-molecular-weight polyethylenimine (PEI) have been widely studied as gene-delivery carriers, both, in vitro and in vivo. However, interest has recently developed in degradable polymeric systems. The advantage of degradable polymer is its low in-vivo cytotoxicity, which is a result of its easy elimination from the cells and body. Degradable polymer also enhances transfection of DNA or small interfering RNA (siRNA) for efficient gene expression or silencing, respectively. This review paper summarizes and discusses the recent advances with degradable PEIs, such as cross-linked and grafted PEIs for DNA and siRNA delivery.

Nonviral gene delivery: principle, limitations, and recent progress

Gene therapy is becoming a promising therapeutic modality for the treatment of genetic and acquired disorders. Nonviral approaches as alternative gene transfer vehicles to the popular viral vectors have received significant attention because of their favorable properties, including lack of immunogenicity, low toxicity, and potential for tissue specificity. Such approaches have been tested in preclinical studies and human clinical trials over the last decade. Although therapeutic benefit has been demonstrated in animal models, gene delivery efficiency of the nonviral approaches remains to be a key obstacle for clinical applications. This review focuses on existing and emerging concepts of chemical and physical methods for delivery of therapeutic nucleic acid molecules in vivo. The emphasis is placed on discussion about problems associated with current nonviral methods and recent efforts toward refinement of nonviral approaches.

Novel gemini pyridinium surfactants: synthesis and study of their surface activity, DNA binding, and cytotoxicity

New pyridinium gemini amphiphiles having ethane-1,2-dithiol spacer have been synthesized by regioselective electrophilic cobromination of alpha-olefins. Ethane-1,2-dithiol (1) and N-bromosuccinimide (6) on reaction with alpha-olefins (dodecene (2), tetradecene (3), hexadecene (4), and octadecene (5)) gave the respective 1,2-bis(2-bromoalkylthio)ethane (7-10). The bromoalkylthio ethers when reacted with pyridine (11) gave the respective gemini bispyridinium bromide (12-15). The surface properties of new geminis were evaluated by surface tension and conductivity measurements. These gemini surfactants have also been found to be having low cytotoxicity by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay on C6 glioma cells. The DNA binding capabilities of these amphiphiles have been determined below as well as above critical micelle concentration. The preliminary studies by agarose gel electrophoresis indicated chain length dependent DNA binding abilities which has further been proved by ethidium bromide exclusion experiments and transmission electron microscopy (TEM).

Evading the immune response upon in vivo gene therapy with viral vectors

Gene therapy has the potential to provide minimally invasive and long-term treatment for many inherited disorders that otherwise have poor prognoses and limited treatment options. The sustained therapeutic correction of genetic disease by viral gene transfer has been accomplished in patients with severe immune deficiencies, or by the transduction of an immune privileged site for the treatment of ocular disease. For other diseases and target tissues, immune responses to vectors or transgene products often present major obstacles for therapy. Innate and adaptive immunity, sometimes including pre-existing or memory responses, may contribute by varying degrees to immune-mediated rejection and immunotoxicity. This review provides an overview of the immune responses to in vivo gene transfer with the most commonly used viral gene therapy vectors, and discusses strategies and protocols employed in evading the immune system in order to provide optimal gene therapy.

Enhancement of reporter gene detection sensitivity by insertion of specific mini-peptide-coding sequences

Two important aspects of gene therapy are to increase the level of gene expression and track the gene delivery site and expression, and a sensitive reporter gene may be one of the options for preclinical studies and possibly for human clinical trials. We report the novel concept of increasing the activity of the gene products. With the insertion of the mini-peptide-coding sequence CWDDWLC into the plasmid DNA of a SEAP reporter gene, we observed vast increases in the enzyme activity in vitro in all murine and human cell lines used. In addition, in vivo injection of this CWDDWLC-SEAP-encoding gene resulted in the same increases in reporter gene activity, but these increases did not correspond to alterations in the level of the gene products in the serum. Minor sequence changes in this mini-peptide negate the activity increase of the reporter gene. We report the novel concept of increasing the activity of gene products as another method to improve the reporting sensitivity of reporter genes. This improved reporter gene could complement any improved vector for maximizing the reporter sensitivity. Moreover, this strategy has the potential to be used to discover peptides that improve the activity of therapeutic genes.

Induction of human alveolar epithelial cell growth factor receptors by dendrimeric nanostructures

Although nonviral dendrimeric nanostructures have been widely used as gene delivery systems, key questions about target cells responses to these nanostructures are yet to be answered. Here, we report the responsiveness of A431 and A549 cells upon treatment with polypropylenimine diaminobutane (DAB) dendrimers nanosystems. Complexation of DAB dendrimers with DNA reduced the zeta potential of nanostructures, but increased their size. Fluorescence microscopy revealed high transfection efficiency in both cell lines treated with DAB dendrimers with induced cytotoxicity evidenced by MTT assay. The A549 cells showed upregulation of epidermal growth factor receptor (EGFR) and its downstream signalling biomolecule Akt kinase upon treatment with DAB dendrimers, while no changes were observed in A431 cells. Based on our findings, the biological impacts of these nanosystems appeared to be cell dependent. Thus, the biological responses of target cells should be taken into account when these nanostructures are used as gene delivery system.

Nanocapsule-delivered Sleeping Beauty mediates therapeutic Factor VIII expression in liver sinusoidal endothelial cells of hemophilia A mice

Liver sinusoidal endothelial cells are a major endogenous source of Factor VIII (FVIII), lack of which causes the human congenital bleeding disorder hemophilia A. Despite extensive efforts, gene therapy using viral vectors has shown little success in clinical hemophilia trials. Here we achieved cell type-specific gene targeting using hyaluronan- and asialoorosomucoid-coated nanocapsules, generated using dispersion atomization, to direct genes to liver sinusoidal endothelial cells and hepatocytes, respectively. To highlight the therapeutic potential of this approach, we encapsulated Sleeping Beauty transposon expressing the B domain-deleted canine FVIII in cis with Sleeping Beauty transposase in hyaluronan nanocapsules and injected them intravenously into hemophilia A mice. The treated mice exhibited activated partial thromboplastin times that were comparable to those of wild-type mice at 5 and 50 weeks and substantially shorter than those of untreated controls at the same time points. Further, plasma FVIII activity in the treated hemophilia A mice was nearly identical to that in wild-type mice through 50 weeks, while untreated hemophilia A mice exhibited no detectable FVIII activity. Thus, Sleeping Beauty transposon targeted to liver sinusoidal endothelial cells provided long-term expression of FVIII, without apparent antibody formation, and improved the phenotype of hemophilia A mice.

The influence of size, lipid composition and bilayer fluidity of cationic liposomes on the transfection efficiency of nanolipoplexes

Among non-viral vectors, cationic liposomes are the most promising carriers in gene delivery. But the most critical issue about their application is their low transfection efficiency compared to viral vectors. In this study, we tried to make a comparison between transfection efficiency of different liposomal formulations and to investigate the effect of membrane fluidity and other physical properties of liposomes and lipoplexes such as size and charge ratio on the transfection efficiency in in vitro environment. Different gene delivery systems were developed by using liposomes composed of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) or 3-beta-[N-(N'N'-dimethylaminoethane)-carbamoyl] cholesterol (DC-CHOL) in combination with other lipids including 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), egg L-alpha-phosphatidylcholine (EPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE). These multilamellar vesicle (MLV) liposomes were extruded through 100 nm polycarbonate filters to produce small unilamellar vesicles (SUVs). Transfection activity of these lipoplexes in Neuro2A cells was tested using pRL-CMV encoding Renilla luciferase. We could not establish any direct correlation between high fluid membranes and high transfection efficiency because DOTAP:DPPE had a better result than DOTAP:DOPE while DC-CHOL:DOPE was more successful in gene transfer than DC-CHOL:DPPE. It was revealed that the use of these two helper lipids with different Tm (DPPE: 64 degrees C and DOPE: -11 degrees C) along with DOTAP increased transfection efficiency but formulation of these phospholipids with DC-CHOL was led to a significant reduction in transfection activity. Generally, DOTAP:DPPE, DC-CHOL:DOPE and DOTAP:DOPE:DPPE formulations showed the highest transfection activity. The results of this study showed that, in designing of liposome based non-viral vectors, different parameters such as size, lipid composition and the use of helper lipid should be considered.

Targeted delivery of nucleic-acid-based therapeutics to the pulmonary circulation

Targeted delivery of functional nucleic acids (genes and oligonucleotides) to pulmonary endothelium may become a novel therapy for the treatment of various types of lung diseases. It may also provide a new research tool to study the functions and regulation of novel genes in pulmonary endothelium. Its success is largely dependent on the development of a vehicle that is capable of efficient pulmonary delivery with minimal toxicity. This review summarizes the recent progress that has been made in our laboratory along these research directions. Factors that affect pulmonary nucleic acids delivery are also discussed.

Progress and prospects: the design and production of plasmid vectors

Plasmid DNA (pDNA) expression vectors are fundamental to all forms of non-viral gene transfer. In this review, we discuss principles of pDNA design and production including the impact of bacterially derived sequences on transgene expression and minicircle approaches to minimize their effects. The impact of inclusion of DNA elements such as scaffold matrix attachment regions (S/MARs), transcription factor (TF)-binding sites and tissue-specific promoters are described. The benefits of eliminating CG dinucleotides (CpGs) from the pDNA are also considered.

The tissue plasminogen activator gene promoter: a novel tool for radiogenic gene therapy of the prostate?

BACKGROUND

Radiation therapy is a treatment modality routinely used in cancer management so it is not unexpected that radiation-inducible promoters have emerged as an attractive tool for controlled gene therapy. The human tissue plasminogen activator gene promoter (t-PA) has been proposed as a candidate for radiogenic gene therapy, but has not been exploited to date. The purpose of this study was to evaluate the potential of this promoter to drive the expression of a reporter gene, the green fluorescent protein (GFP), in response to radiation exposure.

METHODS

To investigate whether the promoter could be used for prostate cancer gene therapy, we initially transfected normal and malignant prostate cells. We then transfected HMEC-1 endothelial cells and ex vivo rat tail artery and monitored GFP levels using Western blotting following the delivery of single doses of ionizing radiation (2, 4, 6 Gy) to test whether the promoter could be used for vascular targeted gene therapy.

RESULTS

The t-PA promoter induced GFP expression up to 6-fold in all cell types tested in response to radiation doses within the clinical range.

CONCLUSIONS

These results suggest that the t-PA promoter may be incorporated into gene therapy strategies driving therapeutic transgenes in conjunction with radiation therapy.

Death ligands designed to kill: development and application of targeted cancer therapeutics based on proapoptotic TNF family ligands

The identification of molecular markers associated with cancer development or progression, opened a new era in the development of therapeutics. The successful introduction of a few low molecular weight chemicals and recombinant protein therapeutics with targeted actions into clinical practice have raised great expectations to broadly improve cancer therapy with respect to both overall clinical responses and tolerability. Targeting the apoptotic machinery of malignant cells is an attractive concept to combat cancer, which is currently exploited for the proapoptotic members of the TNF ligand family at various stages of preclinical and clinical development. This review summarizes recent progress in this rapidly progressing field of "biologic" therapies targeting the death receptors of TNF, CD95L, and TRAIL by means of its cognate protein ligands, receptor specific antibodies, and gene therapeutic approaches. Preclinical data on newly derived variants and fusion proteins based on these death ligands, designed to act in a tumor restricted manner, thereby preventing a systemic, potentially harmful action, will also be discussed.

Phase I trial of interleukin-12 plasmid electroporation in patients with metastatic melanoma

PURPOSE

Gene-based immunotherapy for cancer is limited by the lack of safe, efficient, reproducible, and titratable delivery methods. Direct injection of DNA into tissue, although safer than viral vectors, suffers from low gene transfer efficiency. In vivo electroporation, in preclinical models, significantly enhances gene transfer efficiency while retaining the safety advantages of plasmid DNA.

PATIENTS AND METHODS

A phase I dose escalation trial of plasmid interleukin (IL)-12 electroporation was carried out in patients with metastatic melanoma. Patients received electroporation on days 1, 5, and 8 during a single 39-day cycle, into metastatic melanoma lesions with six 100-mus pulses at a 1,300-V/cm electric field through a penetrating six-electrode array immediately after DNA injection. Pre- and post-treatment biopsies were obtained at defined time points for detailed histologic evaluation and determination of IL-12 protein levels.

RESULTS

Twenty-four patients were treated at seven dose levels, with minimal systemic toxicity. Transient pain after electroporation was the major adverse effect. Post-treatment biopsies showed plasmid dose proportional increases in IL-12 protein levels as well as marked tumor necrosis and lymphocytic infiltrate. Two (10%) of 19 patients with nonelectroporated distant lesions and no other systemic therapy showed complete regression of all metastases, whereas eight additional patients (42%) showed disease stabilization or partial response.

CONCLUSION

This report describes the first human trial, to our knowledge, of gene transfer utilizing in vivo DNA electroporation. The results indicated this modality to be safe, effective, reproducible, and titratable.

Current status of gene therapy for rheumatoid arthritis

Gene therapy offers great possibilities for treating rheumatoid arthritis (RA). Traditional surgical and pharmaceutical methods of treating RA have met with limited therapeutic success and have failed to produce a cure, but the past several years have seen extensive progress toward development of a gene therapy for arthritis. Numerous vectors and therapeutic genes have been investigated in animal models of arthritis, and the potential of gene therapy to treat or manage RA has been demonstrated in several clinical studies. Gene therapy offers the possibility of overcoming many of the limitations of current biologic therapies by providing long-term, high-level localized expression of therapeutic genes, potentially in as little as a single dose. In this review, we explore the advances in gene therapy for RA and summarize the recent preclinical and clinical data. In addition, we provide an overview of vectors and targets for RA gene therapy.

A simple and reliable electroporation method for human bone marrow mesenchymal stem cells

Adult human mesenchymal stem cells (hMSCs) are able to differentiate into a range of specific cell types in vitro and in vivo, and thus hold tremendous potential for use in regenerative medicine. Despite this promise, deficient understanding of the mechanisms that regulate their differentiation has precluded their widespread use. Genetic manipulation of hMSCs by introduction of transgenes is an indispensable tool for gaining insight into these mechanisms. Like most primary cultures, hMSCs are difficult to transfect with conventional techniques, and although some viral transduction techniques are highly efficient, the protocols require extensive optimization and contain significant health risks. We were generally unable to achieve high transfection efficiencies with lipofection-based reagents that we found, in contrast to electroporation, adversely affected hMSC proliferation and differentiation. Here we report a simple and reliable electroporation protocol that results in transfection efficiencies up to 90% that are comparable to most viral methods while maintaining hMSC stemness. Most importantly, our protocol does not rely on a specific electroporator with preset programs and unique buffers, and is thus much simpler, cheaper, and easier to optimize. Furthermore, we show sustained transgene expression lasting several weeks that was useful for assessing the effects on hMSC function and in transient expression gene therapy.

Tissue engineering for bone defect healing: an update on a multi-component approach

The need for an interdisciplinary approach in order to establish new therapeutic strategies for the therapy of bone defects has been acknowledged by the scientific community for many years. This awareness makes itself felt when looking at the multitude of approaches--ranging from cell-based to scaffold-based strategies and also including the use of osteogenic growth factors and genetic engineering--that are currently being combined to assess their potential to develop effective concepts for the treatment of extensive loss of osseous tissue. With a strong focus on the preclinical research in this field, the goal of this review is to give an update on the multi-component approaches that are currently being investigated in tissue engineering of bone.

Whole animal in vivo imaging after transient, nonviral gene delivery to the rat central nervous system

We previously showed that a vector:lipid delivery system, comprised of a plasmid DNA vector and cationic lipid (lipoplex), when injected into the cerebrospinal fluid (CSF) of rats can deliver reporter genes in vivo efficiently and with widespread expression to the Central Nervous System (CNS). To further characterize this delivery system, we now present experiments that demonstrate the in vivo time-to-peak expression of the reporter gene, firefly luciferase. We infused a formulated lipoplex containing the lipid MLRI [dissymmetric myristoyl (14:0) and lauroyl (12:1) rosenthal inhibitor-substituted compound formed from the tetraalkylammonium glycerol-based DORI] and pNDluc, a luciferase vector, into CSF in the cisterna magna (CM) of the rat. Luciferase activity was followed over time by bioluminescence imaging after injection of luciferin. Our results show that luciferase activity in the CNS of rats is widespread, peaks 72 hours after injection into CM and can be detected in vivo for at least 7-10 days after peak expression. We further show that in contrast to injection into CSF, enzyme activity is not widely distributed after injection of the vector into brain parenchyma, emphasizing the importance of CSF delivery to achieve widespread vector distribution. Finally, we confirm the distribution of firefly luciferase in brain by immunohistochemical staining from an animal that was euthanized at the peak of enzyme expression.

Microfluidic based single cell microinjection

We report a microfluidic based approach for single cell microinjection in which fluid streams direct a cell onto a fixed microneedle in contrast to moving a microneedle towards an immobilized cell, as done in conventional methods. The approach simplifies microinjection and offers the potential for flow through automated microinjection of cells.

[Development of various multifunctional envelope-type nano device MEND based on novel assembly technologies]

Non-viral vectors need to overcome several barriers such as the plasma membrane, the endosomal membrane and the nuclear membrane for efficient gene delivery to the nucleus of target cells. To overcome these obstacles, the delivery system must be equipped with various functional devices. However, it is difficult to package all these needed devices into a single system to exert each of their functions at the appropriate time and at the correct location. Thus, our group proposed a new packaging concept, "Programmed Packaging". A multifunctional envelope-type nano device (MEND) was developed for use as an efficient non-viral system for the delivery of plasmid DNA (pDNA), oligodeoxynucleotide (ODN) and siRNA. Various types of MEND were developed as to strategy and situations. For example, the octaarginine (R8)-modified MEND (R8-MEND) encapsulating pDNA showed significantly high transfection activity comparable to adenovirus, and the up-take pathway of the R8-MEND was macropinocytosis, which can avoid lysosomal degradation. The R8-MEND successfully delivered a gene to hair follicles of mouse skin by in vivo topical application. Consequently, our group succeeded in the development of the MEND based on the Programmed Packaging, and found this to be a promising new delivery system of pDNA and functional nucleic acids.

Evaluation of gene promoters for liver expression by hydrodynamic gene transfer

OBJECTIVE

Gene therapy represents a promising treatment for hepatic disease. Most approaches today use viral methods to target tissues. While nonviral gene therapy is less prominent, hydrodynamic gene delivery represents a promising approach to direct gene expression to the liver. The purpose of the present study was to evaluate promoters for efficient gene expression in hepatocytes in vivo by hydrodynamic delivery and to test the findings in a model of hemophilia A.

MATERIALS AND METHODS

Human cytomegalovirus (hCMV), chicken beta-actin/CMV enhancer (CAG), elongation factor-1 alpha (EF1alpha), and phosphoglycerokinase (PGK) promoters were subcloned into plasmids with a luciferase reporter gene. In vitro calcium phosphate-mediated transfection of 2 x 10(5) HEK 293 cells was followed by in vivo whole animal bioluminescence and luminometry after hydrodynamic tail vein injection of plasmid DNA. Six-month-old FVB factor VIII (FVIII)-deficient mice were similarly injected with CBA- or EF1alpha-promoted constructs containing the FVIII heavy and light chains and expression was examined.

RESULTS

In vitro transfection demonstrated a hierarchy of expression: hCMV-intron>CAG>EF1alpha>hCMV>>PGK. In vivo luminometry demonstrated that the CAG construct produced 2.6x, 3.0x, 3.4x, and >1000x the expression of the hCMV-intron, EF1alpha, hCMV, and PGK constructs respectively. FVIII plasmid injected hemophilic mice demonstrated higher levels of FVIII expression with CAG versus EF1alpha, confirming the reporter gene studies. All FVIII-deficient mice injected with EF1alpha-FVIII or CAG-FVIII plasmids survived after tail clipping.

CONCLUSIONS

The CAG promoter/enhancer combination is an excellent alternative to the human CMV promoter for hydrodynamic gene delivery to the liver.

Poly(lactic-co-glycolic acid) nanosphere as a vehicle for gene delivery to human cord blood-derived mesenchymal stem cells: comparison with polyethylenimine

Polyethylenimine (PEI) is one of the most extensively studied non-viral vectors but its cytotoxicity limits its clinical value. PLGA nanospheres are biocompatible and can facilitate sustained release of plasmid DNA. This study compares the cytotoxicity and long-term transgene expression between PLGA nanosphere and PEI. PLGA nanospheres were significantly less cytotoxic than PEI at various concentrations. PLGA nanospheres induced significantly higher transgene expression in vitro for a longer duration (21 days) than PEI. We conclude that PLGA nanospheres have potential as gene delivery vehicles for use in gene therapy for diseases in which a long-term therapeutic gene expression regimen is necessary.

Application of an environmentally sensitive fluorophore for rapid analysis of the binding and internalization efficiency of gene carriers

Nonviral gene carriers must associate with and become internalized by cells in order to mediate efficient transfection. Methods to quantitatively measure and distinguish between cell association and internalization of delivery vectors are necessary to characterize the trafficking of vector formulations. Here, we demonstrate the utility of nitro-2,1,3-benzoxadiazol-4-yl (NBD)-labeled oligonucleotides for discrimination between bound and internalized gene carriers associated with cells. Dithionite quenches the fluorescence of extracellular NBD-labeled material, but is unable to penetrate the cell membrane and quench internalized material. We have verified that dithionite-mediated quenching of extracellular materials occurs in both polymer- and lipid-based gene delivery systems incorporating NBD-labeled oligonucleotides. By exploiting this property, the efficiencies of cellular binding and internalization of lipid- and polymer-based vectors were studied and correlated to their transfection efficiencies. Additionally, spatiotemporal information regarding binding and internalization of NBD-labeled gene carriers can be obtained using conventional wide-field fluorescence microscopy, since dithionite-mediated quenching of extracellular materials reveals the intracellular distribution of gene carriers without the need for optical sectioning. Hence, incorporation of environmentally sensitive NBD-oligos into gene carriers allows for facile assessment of binding and internalization efficiencies of vectors in live cells.

A unique and highly efficient non-viral DNA/siRNA delivery system based on PEI-bisepoxide nanoparticles

Delivery of DNA and siRNA into mammalian cells is a powerful technique in treating various diseases caused by single gene defects. Herein, we report a highly efficient delivery system using 1,4-butanediol diglycidyl ether (bisepoxide) crosslinked polyethylenimine (PEI) nanoparticles (PN). The nanoparticle/DNA complexes (nanoplexes) exibited approximately 2.5- to 5.0-fold gene transfer efficacy and decreased cytotoxicity in cultured cell lines, compared to the native PEI (25 kDa) (gold standard) and commercially available transfection agents such as Lipofectamine 2000 and Fugene. The bisepoxide crosslinking results in change in amine ratio in PEI; however, it retains the net charge on PN unaltered. A series of nanoparticles obtained by varying the degree of crosslinking was found to be in the size range of 69-77 nm and the zeta potential varying from +35 to 40 mV. The proposed system was also found to deliver siRNA efficiently into HEK cells, resulting in approximately 70% suppression of the targetted gene (GFP).

New bearings in pharmacotherapeutic strategies: Pharmacogenetics and gene therapy

<zakljucak> Slicno drugim, novim terapijskim konceptima i genska terapija je puno obecavala, ali za sada je jos u razvoju. Glavni izazov ostaje unosenje pravog gena na pravo mesto, u pravu celiju i obezbedjenje adekvatne ekspresije, uz minimalna nezeljena dejstva. Iako se najvise radi na virusnim vektorima, smatra se da buducnost genske terapije cine znatno bezbedniji nevirusni sistemi. Bilo je izvesnih promasaja u genskoj terapiji, sto je dovelo do sumnje i zabrinutosti u siroj populaciji. Medjutim, razvoj genske terapije je realnost, kao i cinjenica da ona ima svoje mesto u medicini. Vazno je istaci da genskoj terapiji treba pristupati sa izuzetno visokim stepenom naucne, strucne i eticke odgovornosti, jer se ne moze iskljuciti mogucnost genetskih manipulacija opasnih za ljudsko zdravlje.