Cell cycle dependent transcription, a determinant factor of heterogeneity in cationic lipid-mediated transgene expression

Knockout of the lysosomal membrane protein, LAMP2C, improves transient gene expression in HEK293 cells via increased intracellular plasmid availability

Plasmid-based transfection can be used in many applications such as transient gene expression (TGE)-based therapeutic protein production. These applications preferentially require maximization of intracellular plasmid availability. Here, we applied a lysosome engineering approach to alleviate lysosome-mediated nucleic acid degradation and enhance the TGE in mammalian cells. By knocking out the lysosomal membrane protein LAMP2C, which is known to be the main player in RNautophagy/DNautophagy (RDA), we significantly improved transient fluorescent protein expression in HEK293 cells by improving the retention rate of transfected plasmids; however, this effect was not observed in CHO cells. Additional knockout of a lysosomal membrane transporter and another RDA player, SIDT2, was ineffective, regardless of the presence of LAMP2C. LAMP2C knockout enhanced TGE-based mAb production in HEK293 cells by up to 2.82-fold increase in specific mAb productivity. Taken together, these results demonstrate that HEK293 cells can be engineered to improve the usage of the transfected plasmid via knockout of the lysosomal membrane protein LAMP2C and provide efficient host cells in TGE systems for therapeutic protein production.

The analysis of protein recruitment to laser microirradiation-induced DNA damage in live cells: Best practices for data analysis

Laser microirradiation coupled with live-cell fluorescence microscopy is a powerful technique that has been used widely in studying the recruitment and retention of proteins at sites of DNA damage. Results obtained from this technique can be found in published works by both seasoned and infrequent users of microscopy. However, like many other microscopy-based techniques, the presentation of data from laser microirradiation experiments is inconsistent; papers report a wide assortment of analytic techniques, not all of which result in accurate and/or appropriate representation of the data. In addition to the varied methods of analysis, experimental and analytical details are commonly under-reported. Consequently, publications reporting data from laser microirradiation coupled with fluorescence microscopy experiments need to be carefully and critically assessed by readers. Here, we undertake a systematic investigation of commonly reported corrections used in the analysis of laser microirradiation data. We validate the critical need to correct data for photobleaching and we identify key experimental parameters that must be accounted for when presenting data from laser microirradiation experiments. Furthermore, we propose a straightforward, four-step analytical protocol that can readily be applied across platforms and that aims to improve the quality of data reporting in the DNA damage field.

Cellular uptake of modified mRNA occurs via caveolae-mediated endocytosis, yielding high protein expression in slow-dividing cells

Nucleic acids have clear clinical potential for gene therapy. Plasmid DNA (pDNA) was the first nucleic acid to be pursued as a therapeutic molecule. Recently, mRNA came into play as it offers improved safety and affordability. In this study, we investigated the uptake mechanisms and efficiencies of genetic material by cells. We focused on three main variables (1) the nucleic acid (pDNA, or chemically modified mRNA), (2) the delivery vector (Lipofectamine 3000 or 3DFect), and (3) human primary cells (mesenchymal stem cells, dermal fibroblasts, and osteoblasts). In addition, transfections were studied in a 3D environment using electrospun scaffolds. Cellular internalization and intracellular trafficking were assessed by using enhancers or inhibitors of endocytosis and endosomal escape. The polymeric vector TransIT-X2 was included for comparison purposes. While lipoplexes utilized several entry routes, uptake via caveolae served as the main route for gene delivery. pDNA yielded higher expression levels in fast-dividing fibroblasts, whereas, in slow-dividing osteoblasts, cmRNA was responsible for high protein production. In the case of mesenchymal stem cells, which presented an intermediate doubling time, the combination vector/nucleic acid seemed more relevant than the nucleic acid per se. In all cases, protein expression was higher when the cells were seeded on 3D scaffolds.

Аpplication of massive parallel reporter analysis in biotechnology and medicine

The development and functioning of an organism relies on tissue-specific gene programs. Genome regulatory elements play a key role in the regulation of such programs, and disruptions in their function can lead to the development of various pathologies, including cancers, malformations and autoimmune diseases. The emergence of high-throughput genomic studies has led to massively parallel reporter analysis (MPRA) methods, which allow the functional verification and identification of regulatory elements on a genome-wide scale. Initially MPRA was used as a tool to investigate fundamental aspects of epigenetics, but the approach also has great potential for clinical and practical biotechnology. Currently, MPRA is used for validation of clinically significant mutations, identification of tissue-specific regulatory elements, search for the most promising loci for transgene integration, and is an indispensable tool for creating highly efficient expression systems, the range of application of which extends from approaches for protein development and design of next-generation therapeutic antibody superproducers to gene therapy. In this review, the main principles and areas of practical application of high-throughput reporter assays will be discussed.

Nucleic acid therapies for CNS diseases: Pathophysiology, targets, barriers, and delivery strategies

Nucleic acid therapeutics have emerged as one of the very advanced and efficacious treatment approaches for debilitating health conditions, including those diseases affecting the central nervous system (CNS). Precise targeting with an optimal control over gene regulation confers long-lasting benefits through the administration of nucleic acid payloads via viral, non-viral, and engineered vectors. The current review majorly focuses on the development and clinical translational potential of non-viral vectors for treating CNS diseases with a focus on their specific design and targeting approaches. These carriers must be able to surmount the various intracellular and extracellular barriers, to ensure successful neuronal transfection and ultimately attain higher therapeutic efficacies. Additionally, the specific challenges associated with CNS administration also include the presence of blood-brain barrier (BBB), the complex pathophysiological and biochemical changes associated with different disease conditions and the existence of non-dividing cells. The advantages offered by lipid-based or polymeric systems, engineered proteins, particle-based systems coupled with various approaches of neuronal targeting have been discussed in the context of a variety of CNS diseases. The possibilities of rapid yet highly efficient gene modifications rendered by the breakthrough methodologies for gene editing and gene manipulation have also opened vast avenues of research in neuroscience and CNS disease therapy. The current review also underscores the extensive scientific efforts to optimize specialized, efficacious yet non-invasive and safer administration approaches to overcome the therapeutic delivery challenges specifically posed by the CNS transport barriers and the overall obstacles to clinical translation.

Current standards and pitfalls associated with the transfection of primary fibroblast cells

Cultured fibroblast cells, especially dermal cells, are used for various types of scientific research, particularly within the medical field. Desirable features of the cells include their ease of isolation, rapid cellular growth, and high degree of robustness. Currently, fibroblasts are mainly used to obtain pluripotent cells via a reprogramming process. Dermal fibroblasts, are particularly useful for gene therapies used for promoting wound healing or minimizing skin aging. In recent years, fibroblast transfection efficiencies have significantly improved. In order to introduce molecules (most often DNA or RNA) into cells, viral-based systems (transduction) or non-viral methods (transfection) that include physical/mechanical processes or lipid reagents may be used. In this article, we describe critical points that should be considered when selecting a method for transfecting fibroblasts. The most effective methods used for the transfection of fibroblasts include both viral-based and non-viral nucleofection systems. These methods result in a high level of transgene expression and are superior in terms of transfection efficacy and viability.

Less is more: Investigating the influence of cellular nanoparticle load on transfection outcomes in neural cells

Genetic engineering of cell transplant populations offers potential for delivery of neurotherapeutic factors to modify the regenerative microenvironment of the injured spinal cord. The use of magnetic nanoparticle (MNP)-based vectors has reduced the traditional reliance on viral methods and their associated obstacles in terms of scale up and safety. Studies utilizing magnetic assistive platforms for MNP-mediated gene delivery have found transfection efficiency in astrocytes (a major transplant and homeostatic neural cell type) to be both frequency- and amplitude-dependent. It is widely assumed that increased intracellular particle load will enhance transfection efficiency in a cell population. Therefore, we tested repeat delivery of MNP:plasmid complexes in conjunction with oscillating magnetic field parameters-a process termed "magneto-multifection"-in astrocytes of primary origin in an attempt to enhance transfection levels. We show (a) levels of transfection using magneto-multifection equal that seen with viral methods; (b) reporter protein expression using two reporter plasmids shows a diverse profile of single/dual transfected cells with implications for delivery of a "cocktail" of neurotherapeutic proteins; and (c) contrary to expectation, an inverse relationship exists between particle load and reporter protein expression.

Stable and reproducible transgene expression independent of proliferative or differentiated state using BAC TG-EMBED

Reproducible and stable transgene expression is an important goal in both basic research and biotechnology, with each application demanding a range of transgene expression. Problems in achieving stable transgene expression include multi-copy transgene silencing, chromosome-position effects, and loss of expression during long-term culture, induced cell quiescence, and/or cell differentiation. Previously, we described the “BAC TG-EMBED” method for copy-number dependent, chromosome position-independent expression of embedded transgenes within a BAC containing ~170 kb of the mouse Dhfr locus. Here we demonstrate wider applicability of the method by identifying a BAC and promoter combination that drives reproducible, copy-number dependent, position-independent transgene expression even after induced quiescence and/or cell differentiation into multiple cell types. Using a GAPDH BAC containing ~200 kb of the human GAPDH gene locus and a 1.2 kb human UBC promoter, we achieved stable GFP-ZeoR reporter expression in mouse NIH 3T3 cells after low-serum induced cell cycle arrest or differentiation into adipocytes. More notably, GFP-ZeoR expression remained stable and copy-number dependent even after differentiation of mouse ESCs into several distinct lineages. These results highlight the potential use of BAC TG-EMBED as an expression platform for high-level but stable, long-term expression of transgene independent of cell proliferative or differentiated state.

Pros and cons of pDNA and mRNA transfection to study mRNA translation in mammalian cells

Protein synthesis in eukaryotes is subject to stringent control. The misregulation of translation of certain mRNAs is often a hallmark of many diseases, including malignancies and autoimmune disorders. To understand why and how it happens, it is important to investigate the translational control of specific mRNAs. In this case, one could use reporter mRNAs in order to identify cis-acting elements responsible for regulation. Here we overview plasmid DNA (pDNA) and mRNA transfections, their pitfalls and limitations, as well as some emerging applications for mRNA transfection.

A novel nonviral gene delivery system: multifunctional envelope-type nano device

In this review we introduce a new concept for developing a nonviral gene delivery system which we call "Programmed Packaging." Based on this concept, we succeeded in developing a multifunctional envelope-type nano device (MEND), which exerts high transfection activities equivalent to those of an adenovirus in a dividing cell. The use of MEND has been extended to in vivo applications. PEG/peptide/DOPE ternary conjugate (PPD)-MEND, a new in vivo gene delivery system for the targeting of tumor cells that dissociates surface-modified PEG in tumor tissue by matrix metalloproteinase (MMP) and exerts significant transfection activities, was developed. In parallel with the development of MEND, a quantitative gene delivery system, Confocal Image-assisted 3-dimensionally integrated quantification (CIDIQ), also was developed. This method identified the rate-limiting step of the nonviral gene delivery system by comparing it with adenoviral-mediated gene delivery. The results of this analysis provide a new direction for the development of rational nonviral gene delivery systems.

Intracellular gene delivery is dependent on the type of non-viral carrier and defined by the cell surface glycosaminoglycans

Intracellular limiting steps and molecules involved in internalization and intracellular routing of non-viral gene delivery systems are still poorly understood. In this study, the intracellular kinetics of three different gene delivery systems calcium phosphate precipitates (CaP), polyethyleneimine (PEI) and N-[1-(2,3-dioleyl)propyl]-N,N,N-trimethylammonium chloride (DOTAP)) were quantified at cellular, nuclear, transcriptional and translational levels by using qRT-PCR. Additionally, a role of cell surface glycosaminoglycans (GAGs) was evaluated by performing the aforementioned studies in cells devoid of GAGs (pgsB-618) and cells lacking heparan sulphate (HS). The obtained data showed that the intracellular kinetics was dependent on the type of gene carrier and the weakest intracellular step varied between the carriers; rapid elimination of cell-associated pDNA in CaP, nuclear uptake in DOTAP and transcriptional and translational events in PEI mediated transfections. Overall, neither the amount of cell- nor nuclear associated pDNA correlated with transgene expression but the mRNA expression of the transgene correlated well with the expression at protein level. The nuclear uptake of pDNA in all cases was rapid and efficient thus indicating that the post-nuclear processes including transcription and translation steps have a critical role in defining the efficiency of non-viral gene delivery systems. Our study demonstrated that cell-surface GAGs are not essential for cell surface binding and internalization of gene delivery complexes, but they are able to define the intracellular routing of the complexes by leading them to pathways with high pDNA elimination.

Macrophage mannose receptor-specific gene delivery vehicle for macrophage engineering

Macrophages are the most plastic cells in the hematopoietic system and they exhibit great functional diversity. They have been extensively applied in anti-inflammatory, anti-fibrotic and anti-cancer therapies. However, the application of macrophages is limited by the efficiency of their engineering. The macrophage mannose receptor (MMR, CD206), a C-type lectin receptor, is ubiquitously expressed on macrophages and has a high affinity for mannose oligosaccharides. In the present study, we developed a novel non-viral vehicle with specific affinity for MMR. Mannan was cationized with spermine at a grafted ratio of ∼12% to deliver DNA and was characterized as a stable system for delivery. This spermine-mannan (SM)-based delivery system was evaluated as a biocompatible vehicle with superior transfection efficiency on murine macrophages, up to 28.5-fold higher than spermine-pullulan, 11.5-fold higher than polyethylenimine and 3.0-fold higher than Lipofectamine™ 2000. We confirmed that the SM-based delivery system for macrophages transfection was MMR-specific and we described the intracellular transport of the delivery system. To our knowledge, this is the first study using SM to demonstrate a mannose receptor-specific gene delivery system, thereby highlighting the potential of a novel specific non-viral delivery vehicle for macrophage engineering.

Nucleic-acid based gene therapeutics: delivery challenges and modular design of nonviral gene carriers and expression cassettes to overcome intracellular barriers for sustained targeted expression

The delivery of nucleic acid molecules into cells to alter physiological functions at the genetic level is a powerful approach to treat a wide range of inherited and acquired disorders. Biocompatible materials such as cationic polymers, lipids, and peptides are being explored as safer alternatives to viral gene carriers. However, the comparatively low efficiency of nonviral carriers currently hampers their translation into clinical settings. Controlling the size and stability of carrier/nucleic acid complexes is one of the primary hurdles as the physicochemical properties of the complexes can define the uptake pathways, which dictate intracellular routing, endosomal processing, and nucleocytoplasmic transport. In addition to nuclear import, subnuclear trafficking, posttranscriptional events, and immune responses can further limit transfection efficiency. Chemical moieties, reactive linkers or signal peptide have been conjugated to carriers to prevent aggregation, induce membrane destabilization and localize to subcellular compartments. Genetic elements can be inserted into the expression cassette to facilitate nuclear targeting, delimit expression to targeted tissue, and modulate transgene expression. The modular option afforded by both gene carriers and expression cassettes provides a two-tier multicomponent delivery system that can be optimized for targeted gene delivery in a variety of settings.

[Regulation and analysis of intracellular trafficking of nucleic acids based on quantitative and dynamic imaging]

In the 21st century the category of biomedicine is now expanding from low-molecular drugs to recombinant proteins, antibodies, and nucleic acids (e.q., siRNA and plasmid DNA). In this era also, development of a novel nanotechnology to control intracellular trafficking is highly desired. For a promising gene therapy, an efficient nuclear delivery vector is a minimum requirement. Quantitative and mechanism-based information on differences in transfection efficiency between viral and non-viral vectors would be highly useful to improve the effectiveness of non-viral vectors. In this review, we will summarize our recent progress in quantitative comparison and underlying mechanisms of the intracellular trafficking between adenovirus vectors and plasmid DNA (pDNA) transfected by non-viral vectors. Our analysis has revealed that poor post-nuclear delivery events, as well as the nuclear delivery process itself are key processes to focus on. Especially, less effective transcription and translation are most likely due to poor nuclear decondensation and excess electrostatic interaction between mRNA and the gene carrier, respectively. Meanwhile, we have developed a multi-functional envelope-type nano device (MEND), in which the pDNA/polycation core is encapsulated in the lipid bilayers. Based on feedback information concerning the rate-limiting processes of gene carriers, we controlled the number of lipid envelopes to enhance the decoating of encapsulated pDNA from the envelope structure. As an expanded application of this concept, we have developed a tetra-lamellar MEND (T-MEND), which is designed to overcome the endosome and nuclear membranes by step-wise membrane fusion.

High-level transgene expression by homologous recombination-mediated gene transfer

Gene transfer and expression in eukaryotes is often limited by a number of stably maintained gene copies and by epigenetic silencing effects. Silencing may be limited by the use of epigenetic regulatory sequences such as matrix attachment regions (MAR). Here, we show that successive transfections of MAR-containing vectors allow a synergistic increase of transgene expression. This finding is partly explained by an increased entry into the cell nuclei and genomic integration of the DNA, an effect that requires both the MAR element and iterative transfections. Fluorescence in situ hybridization analysis often showed single integration events, indicating that DNAs introduced in successive transfections could recombine. High expression was also linked to the cell division cycle, so that nuclear transport of the DNA occurs when homologous recombination is most active. Use of cells deficient in either non-homologous end-joining or homologous recombination suggested that efficient integration and expression may require homologous recombination-based genomic integration of MAR-containing plasmids and the lack of epigenetic silencing events associated with tandem gene copies. We conclude that MAR elements may promote homologous recombination, and that cells and vectors can be engineered to take advantage of this property to mediate highly efficient gene transfer and expression.

Quantitative analysis of condensation/decondensation status of pDNA in the nuclear sub-domains by QD-FRET

Recent studies indicate that controlling the nuclear decondensation and intra-nuclear localization of plasmid DNA (pDNA) would result in an increased transfection efficiency. In the present study, we established a technology for imaging the nuclear condensation/decondensation status of pDNA in nuclear subdomains using fluorescence resonance energy transfer (FRET) between quantum dot (QD)-labeled pDNA as donor, and rhodamine-labeled polycations as acceptor. The FRET-occurring pDNA/polycation particle was encapsulated in a nuclear delivery system; a tetra-lamellar multifunctional envelope-type nano device (T-MEND), designed to overcome the endosomal membrane and nuclear membrane via step-wise fusion. Nuclear subdomains (i.e. heterochromatin and euchromatin) were distinguished by Hoechst33342 staining. Thereafter, Z-series of confocal images were captured by confocal laser scanning microscopy. pDNA in condensation/decondensation status in heterochromatin or euchromatin were quantified based on the pixel area of the signals derived from the QD and rhodamine. The results obtained indicate that modulation of the supra-molecular structure of polyrotaxane (DMAE-ss-PRX), a condenser that is cleaved in a reductive environment, conferred euchromatin-preferred decondensation. This represents the first demonstration of the successful control of condensation/decondensation in specific nuclear sub-domain via the use of an artificial DNA condenser.

Barriers to non-viral vector-mediated gene delivery in the nervous system

Efficient methods for cell line transfection are well described, but, for primary neurons, a high-yield method different from those relying on viral vectors is lacking. Viral transfection has several drawbacks, such as the complexity of vector preparation, safety concerns, and the generation of immune and inflammatory responses when used in vivo. However, one of the main problems for the use of non-viral gene vectors for neuronal transfection is their low efficiency when compared with viral vectors. Transgene expression, or siRNA delivery mediated by non-viral vectors, is the result of multiple processes related to cellular membrane crossing, intracellular traffic, and/or nuclear delivery of the genetic material cargo. This review will deal with the barriers that different nanoparticles (cationic lipids, polyethyleneimine, dendrimers and carbon nanotubes) must overcome to efficiently deliver their cargo to central nervous system cells, including internalization into the neurons, interaction with intracellular organelles such as lysosomes, and transport across the nuclear membrane of the neuron in the case of DNA transfection. Furthermore, when used in vivo, the nanoparticles should efficiently cross the blood-brain barrier to reach the target cells in the brain.

Construction of cell penetrating peptide vectors with N-terminal stearylated nuclear localization signal for targeted delivery of DNA into the cell nuclei

Cellular uptake and nuclear localization are two barriers to gene delivery. Here, we designed new gene delivery carriers with an N-terminal stearylated (STR) nuclear localization signal (NLS), PKKKRKV, present in the Simian Virus 40 large T antigen with the aim to overcome limitations, such as cell membrane and nuclear pores, offering attractive possibilities to enhance gene delivery. Four vectors with different structures of N-stearylated nuclear localization signal-octaarginine peptide (STR-PKKKRKV-R(8) or STR-NLS-R(8), STR-VKRKKKP-R(8) or STR-reverse NLS-R(8), PKKKRKV-R(8) or NLS-R(8), and VKRKKKP-R(8) or reverse NLS-R(8)) were compared. The gene expression mediated by these vectors in dividing and non-dividing cells (both in 293T and HeLa cell lines) was investigated. The most efficient N/P ratio was 4 for STR-PKKKRKV-R(8,) STR-VKRKKKP-R(8,) and 0.25 for PKKKRKV-R(8), VKRKKKP-R(8.) The maximum transfection activity of these vehicles (VKRKKKP-R(8)) was up to 80% as effective as jetPEI™ and the vehicles did not exhibit cytotoxicity. Interestingly, N-stearylated peptides presented lower transfection activity compared to peptides without N-stearylation at lower N/P ratios (0.25 to 1). Confocal study showed that the vectors could effectively promote the nuclear translocation.

Improved transfection efficiency of an aliphatic lipid substituted 2 kDa polyethylenimine is attributed to enhanced nuclear association and uptake in rat bone marrow stromal cell

BACKGROUND

Lipid substitutions of cationic polymers are actively explored to enhance the efficiency of nonviral gene carriers. We recently took this approach to develop a novel gene carrier by grafting linoleic acid (LA) to relatively biocompatible 2 kDa polyethylenimine (PEI2). The resulting polymer (PEI2LA) displayed improved transfection efficiency over the unmodified PEI2. The intracellular kinetics and distribution of the respective polyplexes were investigated in the present study to gain a better understanding of the role of lipid modification in intracellular trafficking of gene carriers.

METHODS

A Cy5-labeled plasmid DNA (pDNA) expressing the green fluorescent protein (GFP) was complexed with PEI2, PEI2LA, and 25 kDa polyethylenimine (PEI25) to transfect rat bone marrow stromal cells (BMSC). Subcellular fractionation was performed to measure the amount of nuclear associated pDNA. pDNA uptake, GFP-expression and nuclear-associated pDNA were measured by both flow cytometry and confocal laser scanning microscopy.

RESULTS

PEI2LA mediated higher transgene expression and percentages of transfected cells than PEI25 and PEI2, respectively. There was a strong correlation between nuclear associated pDNA and transgene expression. PEI2LA polyplexes were significantly larger in size than PEI25. The amounts of pDNA associated with the nuclei were greater in PEI2LA than PEI25 polyplexes. The perinuclear pDNA distribution between GFP-expressing and nonGFP-expressing indicated that GFP-positive cells had a higher amount of pDNA associated with their nuclei.

CONCLUSIONS

Improved transfection efficiency of PEI2LA was attributed to enhanced association with the nucleus, which may be a result of hydrophobic interaction between the lipid moieties on the modified lipopolymer and the nuclear membrane.

Nonviral vectors for the delivery of small interfering RNAs to the CNS

While efficient methods for cell line transfection are well described, for primary neurons a high-yield method different from those relying on viral vectors is lacking. Viral vector-based primary neuronal infection has several drawbacks, including complexity of vector preparation, safety concerns and the generation of immune and inflammatory responses, when used in vivo. This article will cover the different approaches that are being used to efficiently deliver genetic material (both DNA and small interfering RNA) to neuronal tissue using nonviral vectors, including the use of cationic lipids, polyethylenimine derivatives, dendrimers, carbon nanotubes and the combination of carbon-made nanoparticles with dendrimers. The effectiveness, both in vivo and in vitro, of the different methods to deliver genetic material to neural tissue is discussed.

Nonviral gene delivery to mesenchymal stem cells using cationic liposomes for gene and cell therapy

Mesenchymal stem cells (MSCs) hold a great promise for application in several therapies due to their unique biological characteristics. In order to harness their full potential in cell-or gene-based therapies it might be advantageous to enhance some of their features through gene delivery strategies. Accordingly, we are interested in developing an efficient and safe methodology to genetically engineer human bone marrow MSC (BM MSC), enhancing their therapeutic efficacy in Regenerative Medicine. The plasmid DNA delivery was optimized using a cationic liposome-based reagent. Transfection efficiencies ranged from ~2% to ~35%, resulting from using a Lipid/DNA ratio of 1.25 with a transgene expression of 7 days. Importantly, the number of plasmid copies in different cell passages was quantified for the first time and ~20,000 plasmid copies/cell were obtained independently of cell passage. As transfected MSC have shown high viabilities (>90%) and recoveries (>52%) while maintaining their multipotency, this might be an advantageous transfection strategy when the goal is to express a therapeutic gene in a safe and transient way.

Effects of carriers on transgene expression from plasmids containing a DNA sequence with high histone affinity

The intranuclear disposition of plasmid DNA is highly important for transgene expression. The effects of a left-handedly curved sequence with high histone affinity on transgene expression were examined in COS-7 cells with two kinds of carriers (Lipofectamine Plus and TransIT-LT1). Three plasmids containing the curved sequence at different positions were transfected. The transgene expression was affected by the position of the left-handedly curved sequence, and the sequence at appropriate locations enhanced the expression from plasmid DNAs. However, the position effects on the expression differed from those obtained by electroporation of the same plasmid DNAs in a naked form. In addition, the degree of expression enhancement seemed to depend on the carriers. These results suggest that the left-handedly curved sequence with high histone affinity could increase the transgene expression from a plasmid delivered with carriers.

Advances in non-viral gene delivery: using multifunctional envelope-type nano-device

BACKGROUND

Low transfection efficiency is an obstacle to the clinical use of non-viral gene vectors. Effective non-viral vectors require the ability to control intracellular trafficking of gene vectors for the delivery of exogenous DNA to the nucleus.

OBJECTIVE

To overcome multiple intracellular barriers, various types of devices must be integrated into one nano-particle so that each device performs its function at the appropriate location at the desired time. Such a strategy requires an understanding, based on quantitative information, of the rate-limiting processes that hinder intracellular trafficking.

METHODS

In this review, advancements in the development of multifunctional envelope-type nano-devices (MEND) are discussed. In particular, a novel method to quantitatively evaluate the rate-limiting steps in intracellular trafficking, based on a comparison of viral and non-viral gene-delivery systems, is described.

CONCLUSION

MENDs are useful to integrate various kinds of devices to overcome intracellular barriers into one particle. Comparison of intracellular trafficking between adenoviruses and non-viral vectors indicates that a postnuclear delivery process is an important rate-limiting step for efficient transfection with non-viral vectors.

Development of lipid particles targeted via sugar-lipid conjugates as novel nuclear gene delivery system

Efficient nuclear gene delivery is essential for successful gene therapy. This study developed a novel system that mimics the mechanism of nuclear entry of adenovirus (Ad) by means of a Multifunctional Envelope-type Nano Device (MEND). In this system, plasmid DNA (pDNA) was condensed with polycation, followed by encapsulation in a lipid membrane. To target MEND to the nuclear pore complex (NPC), sugar served as a NPC-mediated nuclear targeting device was modified on the surface of the lipid envelope. This was accomplished via synthesis of a sugar-cholesterol conjugate. After binding of the MEND to the NPC, the pDNA core was transferred into the nucleus in conjunction with a breakdown of the lipid envelope. Sugar-modified MEND showed higher transfection efficiency compared with unmodified MEND, in non-dividing and dividing cells. Confocal microscopy confirmed that nuclear transfer of pDNA was improved by sugar modification of MEND. Furthermore, destabilization of the lipid envelope significantly enhanced transfection activity: therefore, nuclear-delivery efficiency was closely related to lipid envelope stability. Moreover, quantitative evaluation of cellular uptake and nuclear transfer processes by real-time PCR confirmed that the surface sugars affected nuclear transfer, but not cellular uptake. In summary, a novel system for the nuclear delivery of pDNA was successfully developed by using a sugar-modified MEND and by optimizing the lipid envelope stability.

[Development of multifunctional envelope type artificial viral-like gene delivery system]

This review introduces a new concept "Programmed Packaging" to develop a non-viral gene delivery system. Based on this concept, multifunctional envelope type nano devices (MEND) were developed for in vitro, in situ and in vivo conditions. A quantitative study to identify a rate limiting step in intracellular trafficking was also shown between viral and non-viral vectors, which indicated an important role of controlled intranuclear disposition for development a safe and efficient non-viral gene delivery system. This review will provide a future direction of non-viral gene delivery system.

Multifunctional envelope-type nano device for non-viral gene delivery: Concept and application of Programmed Packaging

In this review, a new concept called "Programmed Packaging" is proposed for developing non-viral gene delivery systems. A Multifunctional Envelope-type Nano Device (MEND) was developed based on this concept, which can enter into cells via macropinocytosis and facilitate transfection activities as efficiently as an adenovirus. Intracellular trafficking of MEND was optimized in order to prevent lysosomal degradation and to enhance nuclear translocation. A quantitative analytical method (CIDIQ) was also established to evaluate each step in intracellular trafficking of genes as well as carriers. A comparative study between Lipofectamin and an adenovirus showed that intra-nuclear disposition, which includes the transcriptional process, translational process, etc., can be the limiting step for Lipofectamin PLUS. These studies indicated the importance of controlling intra-nuclear disposition in the development of an efficient non-viral gene delivery system.

The location of the left-handedly curved DNA sequence affects exogenous DNA expression in vivo

The intranuclear disposition of a plasmid is extremely important for transgene expression. The effects of a left-handedly curved sequence with high histone affinity on plasmid expression were examined in vivo. A naked luciferase-plasmid was delivered into mouse liver by a hydrodynamics-based injection, and the luciferase activities were quantitated at various time points. The location of the left-handedly curved sequence determined the transgene expression, without affecting the amount of intranuclear exogenous DNA. The plasmid containing the curved sequence at the location that results in the exposure of the TATA box out of the nucleosome core showed the highest expression. These results suggest that sequences with high histone affinity could control transgene expression from plasmids in vivo.

Quantitative and mechanism-based investigation of post-nuclear delivery events between adenovirus and lipoplex

Quantitative and mechanism-based information on differences in transfection efficiency between viral and non-viral vectors would be highly useful for improving the effectiveness of non-viral vectors. A previous quantitative comparison of intracellular trafficking between adenovirus and LipofectAMINE PLUS (LFN) revealed that the three orders of magnitude lower transfection efficiency of LFN was dominantly rate limited by the post-nuclear delivery process. In the present study, the contribution of transcription and translation processes to the overall differences in the transgene expression efficiency of nucleus-delivered DNA was independently evaluated by quantifying mRNA. As a result, transcription efficiency (E_transcript) of LFN, denoted as transgene expression divided by the amount of nuclear pDNA was about 16 times less than that for adenovirus. Furthermore, translation efficiency (E_translate), denoted as transfection activity divided by mRNA expression was approximately 460 times less in LFN. Imaging of the decondensed form of DNA by in situ hybridization revealed that poor decondensation efficiency of LFN is involved in the inferior E_transcript. Moreover, the inferior translation efficiency (E_translate) of LFN was mainly due to electrostatic interactions between LFN and mRNA. Collectively, an improvement in nuclear decondensation and the diminution of the interaction between vector and mRNA is essential for the development of new generations of non-viral vectors.