Nonviral Gene Transfer Systems Research Articles

Efficient episomal gene transfer to human hepatic cells using the pFAR4-S/MAR vector.

Liver-directed gene therapy, using mainly viral vectors for the genetic cell modification, is a promising therapeutic approach for many genetic and metabolic liver diseases. The recent successful preclinical trials with AAV vectors expose the benefits as well as the limitations of the system. We focused on the development of an alternative non-viral episomal gene transfer system, by inserting the DNA element Scaffold/Matrix Attachment Region (S/MAR) into the free of antibiotic resistance gene miniplasmid vector (pFAR4). We produced pFAR4 derivative experimental vectors, carrying the eGFP gene driven by the composite HCRHPi liver-specific promoter and either lacking (pFAR4-noS/MAR) or containing the S/MAR element in an upstream (pFAR-S/MAR-IN) or downstream (pFAR4-S/MAR-OUT) configuration in relation to the poly-A signal of the eGFP expression cassette. Upon transfer into Huh7 cells by lipofection, vector pFAR4-S/MAR IN showed significantly higher transfection efficiency and eGFP expression than the control vector or the pFAR4-S/MAR-OUT (p < 0.005), estimated by fluorescent microscopy and flow cytometry. Stable transfections were produced only with cultures containing vector pFAR4-S/MAR IN, through the expansion of single colonies, which displayed sustained GFP expression and plasmid copy number per cell of 2.3 ± 0.4, at 3months of culture. No vector integration events were detected in these cultures by FISH analysis, while the presence of free, circular plasmids was documented by plasmid rescue assay. The presence of S/MAR renders pFAR4 miniplasmid substantially more efficient regarding episomal gene transfer and is suitable for liver-directed studies towards gene therapy applications.

CRISPR/Cas9-Mediated Knockin Application in Cell Therapy: A Non-viral Procedure for Bystander Treatment of Glioma in Mice.

The use of non-viral procedures, together with CRISPR/Cas9 genome-editing technology, allows the insertion of single-copy therapeutic genes at pre-determined genomic sites, overcoming safety limitations resulting from random gene insertions of viral vectors with potential for genome damage. In this study, we demonstrate that combination of non-viral gene delivery and CRISPR/Cas9-mediated knockin via homology-directed repair can replace the use of viral vectors for the generation of genetically modified therapeutic cells. We custom-modified human adipose mesenchymal stem cells (hAMSCs), using electroporation as a transfection method and CRISPR/Cas9-mediated knockin for the introduction and stable expression of a 3 kb DNA fragment including the eGFP (selectable marker) and a variant of the herpes simplex virus 1 thymidine kinase genes (therapeutic gene), under the control of the human elongation factor 1 alpha promoter in exon 5 of the endogenous thymidine kinase 2 gene. Using a U87 glioma model in SCID mice, we show that the therapeutic capacity of the new CRISPR/Cas9-engineered hAMSCs is equivalent to that of therapeutic hAMSCs generated by introduction of the same therapeutic gene by transduction with a lentiviral vector previously published by our group. This strategy should be of general use to other applications requiring genetic modification of therapeutic cells.

Reducible PEG-POD/DNA Nanoparticles for Gene Transfer InVitro and InVivo: Application in a Mouse Model of Age-Related Macular Degeneration.

Non-viral gene delivery systems are being developed to address limitations of viral gene delivery. Many of these non-viral systems are modeled on the properties of viruses including cell surface binding, endocytosis, endosomal escape, and nuclear targeting. Most non-viral gene transfer systems exhibit little correlation between in vitro and in vivo efficiency, hampering a systematic approach to their development. Previously, we have described a 3.5 kDa peptide (peptide for ocular delivery [POD]) that targets cell surface sialic acid. When functionalized with polyethylene glycol (PEG) via a sulfhydryl group on the N-terminal cysteine of POD, PEG-POD could compact plasmid DNA, forming 120- to 180-nm homogeneous nanoparticles. PEG-POD enabled modest gene transfer and rescue of retinal degeneration in vivo. Systematic investigation of different stages of gene transfer by PEG-POD nanoparticles was hampered by their inability to deliver genes in vitro. Herein, we describe functionalization of POD with PEG using a reducible orthopyridyl disulfide bond. These reducible nanoparticles enabled gene transfer in vitro while retaining their in vivo gene transfer properties. These reducible PEG-POD nanoparticles were utilized to deliver human FLT1 to the retina in vivo, achieving a 50% reduction in choroidal neovascularization in a murine model of age-related macular degeneration.

213. Detection of Integration Sites of CD19 Chimeric Antigen Receptor Gene in a Non-Viral Gene Transfer System

BACKGROUND: Chimeric antigen receptor (CAR)-modified T cells targeting CD19 have exhibited marked activity in hematological malignancies, such as acute lymphoblastic leukemia, chronic lymphocytic leukemia, and B-cell lymphomas. Many of these results have been obtained using CD19-CAR T cells established by retro- or lentiviral vectors. We developed a non-viral gene-transfer method using the piggyBac transposon system wherein the CD19-CAR gene was integrated into the genome by cut paste mechanism of the transposase. In this system, the expression of CAR was permanent, and the in vitro and in vivo cytotoxic activity on several cancer cell lines was confirmed. In the process of such gene transfer, however, insertional mutagenesis and subsequent activation of proto-oncogenes are a concern. In this report, we aimed to detect the integration sites of CAR genes to evaluate the safety of our CD19-CAR T cells. METHOD: CD19-CAR T cells were produced by transfecting two plasmids containing piggyBac and a CD19-CAR gene by electroporation. We detected the integration sites of CAR genes by inverse polymerase chain reaction and subsequent next-generation sequencing using MiSeq. An analytic pipeline was developed to identify and to classify the integration sites. Proto-oncogenes were defined according to the Cancer Gene Census of the Catalogue of Somatic Mutations in Cancer database. RESULTS: We detected 181 independent integration sites of which five were in exons (CASP10, F2R, CYP51A1-AS1, ULBP2, and SLC24A2) and 113 in introns. The integration sites demonstrated no preference for specific sites. Five integration sites (2.8%) were in the introns of known proto-oncogenes (CDK6, MAML2, RAD51B, RUNX1, and EP300). This percentage of integrations into proto-oncogenes is comparable with that of random integration (2.4%) and lower than that of retro- and lentiviral vectors (6.3-10.4%) according to previous report using marker genes (Galvan et al. J Immunother 2009). CONCLUSION: We confirmed that our piggyBac-mediated transduction system randomly transduced the CAR gene into the genomic DNA. Therefore, this system is considered safer than viral vector system in terms of genotoxicity for CAR transduction into human T cells; however, the possibility of leukemic transformation caused by insertional mutagenesis should be carefully monitored by in vivo clonal analysis.

“Evolving nanoparticle gene delivery vectors for the liver: What has been learned in 30 years”

Nonviral gene delivery to the liver has been under evolution for nearly 30years. Early demonstrations established relatively simple nonviral vectors could mediate gene expression in HepG2 cells which understandably led to speculation that these same vectors would be immediately successful at transfecting primary hepatocytes in vivo. However, it was soon recognized that the properties of a nonviral vector resulting in efficient transfection in vitro were uncorrelated with those needed to achieve efficient nonviral transfection in vivo. The discovery of major barriers to liver gene transfer has set the field on a course to design biocompatible vectors that demonstrate increased DNA stability in the circulation with correlating expression in liver. The improved understanding of what limits nonviral vector gene transfer efficiency in vivo has resulted in more sophisticated, low molecular weight vectors that allow systematic optimization of nanoparticle size, charge and ligand presentation. While the field has evolved DNA nanoparticles that are stable in the circulation, target hepatocytes, and deliver DNA to the cytosol, breaching the nucleus remains the last major barrier to a fully successful nonviral gene transfer system for the liver. The lessons learned along the way are fundamentally important to the design of all systemically delivered nanoparticle nonviral gene delivery systems.

300. AAV Vector-Mediated In Vivo Reprogramming of Various Cell Types in Adult Mice

The 2006/7 discovery that somatic cells of different tissue origins can be converted into induced pluripotent stem cells (iPSC) by mere introduction of a cocktail of “reprogramming” factors, such as Oct4, Klf4, Sox2 and c-Myc (OKSM), has revolutionized the field of regenerative medicine. A major part of this success story is due to the fact that delivery of the OKSM combination (or variants thereof) to cultured target cells can be accomplished using virtually any of the existing non-viral or viral gene transfer systems. Here, we specifically engineered Adeno-associated viral (AAV) vectors for OKSM delivery, based on their superior safety profile and their typical persistence as episomal DNA that is lost during cell division, which we considered beneficial for reprogramming. A third advantage is that AAV vectors can be pseudotyped with natural or synthetic viral capsids exhibiting high specificities and efficiencies in a given cell. Indeed, we reproducibly found that OKSM expression from four AAV vectors – each encoding a single factor under the strong and ubiquitous SFFV promoter, and pseudotyped with the potent chimeric AAV-DJ capsid – resulted in reprogramming of murine embryonic fibroblasts. Notably, the up to 0.2% reprogramming efficiency obtained with our AAV vectors is comparable to the best lentiviral system. Curiously, and defying our original prediction, we observed by PCR that the AAV vector DNA persisted in the reprogrammed cells even after extended cultivation for up to 21 passages. Using a combination of LAM-PCR and SureSelect technologies, we were then able to identify a variety of OKSM vector integration sites in the mouse genome, including a previously reported hot spot for AAV vector insertion. We speculate that the unusual high frequency of genomic AAV integration in iPSC is either related to mutational inactivation of genes that inhibit reprogramming, or merely a by-product of the relaxation of the chromatin structure triggered by OKSM expression. Based on the robust ex vivo efficiency, we next asked whether our OKSM vectors could also mediate reprogramming in vivo, and therefore applied different doses of AAV8-pseudotyped variants to adult mice via tail vein injection. Strikingly, four to eight weeks later, we found various small and large teratomas in their livers that we identified through histological analysis and isolation of residual iPSC. Moreover, by week eight, one mouse showed signs of extra-hepatic reprogramming in the pancreas and the thoracic cavity, congruent with the in vivo tropism of AAV serotype 8. These features make our novel AAV vector-mediated in vivo reprogramming strategy comparable to our previously published OKSM-transgenic mice (Nature 2013, 502:340-5), with the added benefits that AAV vectors can be applied in any mouse strain or other animals, and can be re-targeted to specific tissues, which opens up entirely novel avenues for stem cell research.

Improved gene transfer efficiency of a DNA-lipid-apatite composite layer by controlling the layer molecular composition

Surface-mediated nonviral gene transfer systems using biocompatible apatite-based composite layers have potential use in tissue engineering applications. Herein, we investigated a relatively efficient system based on a DNA-lipid-apatite composite layer (DLp-Ap layer): an apatite (Ap) layer with immobilized DNA and lipid (Lp) complexes (DLp complexes). DLp-Ap layers were fabricated on substrates using supersaturated calcium phosphate coprecipitation solutions supplemented with DLp complexes, and the molecular compositions of the DLp-Ap layers were controlled by varying the net DNA concentrations and Lp/DNA ratios in the coprecipitation solutions. Increases in both the DNA concentration and Lp/DNA ratio in the coprecipitation solution increased the DLp complex content of the resulting DLp-Ap layer. However, a higher DLp complex content did not always provide increased gene transfer efficiency to the CHO-K1 cells, because there was a threshold content of approximately 10μg/cm2. In addition, DLp-Ap layers with similar DLp complex contents exhibited different gene transfer efficiencies, most likely due to the different Lp/DNA ratios in the layers. Notably, the optimized Lp/DNA ratios in the coprecipitation solutions for maximizing the gene transfer efficiency were lower than those of the conventional particle-mediated lipofection systems. These findings will serve as a useful design guide for the preparation of DLp-Ap layers with high gene transfer efficiency.

A novel peptide‐modified and gene‐activated biomimetic bone matrix accelerating bone regeneration

The osteogenic differentiation of bone marrow stromal cells (BMSCs) can be regulated by systemic or local growth factor, especially by transforming growth factor beta 1 (TGF-β1). However, how to maintain the bioactivity of exogenous TGF-β1 is a great challenge due to its short half-life time. The most promising solution is to transfer TGF-β1 gene into seed cells through transgenic technology and then transgenic cells to continuously secret endogenous TGF-β1 protein via gene expression. In this study, a novel non-viral vector (K)16GRGDSPC was chemically linked to bioactive bone matrices PLGA-[ASP-PEG]n using cross-linker to construct a novel non-viral gene transfer system. TGF-β1 gene was incubated with this system and subsequently rabbit-derived BMSCs were co-cultured with this gene-activated PLGA-[ASP-PEG]n, while co-cultured with PLGA-[ASP-PEG]n modified with (K)16GRGDSPC only and original PLGA-[ASP-PEG]n as control. Thus we fabricated three kinds of composites: Group A (BMSCs-TGF-β1DNA-(K)16GRGDSPC-PLGA-[ASP-PEG]n composite); Group B (BMSCs-(K)16GRGDSPC-PLGA-[ASP-PEG]n composite); and Group C (BMSCs-PLGA-[ASP-PEG]n composite). TGF-β1 and other osteogenic phenotype markers of alkaline phosphatase, osteocalcin, osteopontin and type I collagen in Group A were all significantly higher than the other two groups ex vivo. In vivo, 15-mm long segmental rabbit bone defects were created and randomly implanted the aforementioned composites separately, and then fixed with plate-screws. The results demonstrated that the implants in Group A significantly accelerated bone regeneration compared with the other implants based on X-rays, histological and biomechanical examinations. Therefore, we conclude this novel peptide-modified and gene-activated biomimetic bone matrix of TGF-β1DNA-(K)16GRGDSPC-PLGA-[ASP-PEG]n is a very promising scaffold biomaterial for accelerating bone regeneration.

Engineered factor IX variants bypass FVIII and correct hemophilia A phenotype in mice

The complex of the serine protease factor IX (FIX) and its cofactor, factor VIII (FVIII), is crucial for propagation of the intrinsic coagulation cascade. Absence of either factor leads to hemophilia, a disabling disorder marked by excessive hemorrhage after minor trauma. FVIII is the more commonly affected protein, either by X-chromosomal gene mutations or in autoimmune-mediated acquired hemophilia. Whereas substitution of FVIII is the mainstay of hemophilia A therapy, treatment of patients with inhibitory Abs remains challenging. In the present study, we report the development of FIX variants that can propagate the intrinsic coagulation cascade in the absence of FVIII. FIX variants were expressed in FVIII-knockout (FVIII-KO) mice using a nonviral gene-transfer system. Expression of the variants shortened clotting times, reduced blood loss after tail-clip assay, and reinstalled clot formation, as tested by in vivo imaging of laser-induced vessel injury. In addition, we confirmed the therapeutic efficacy of FIX variants in mice with inhibitory Abs against FVIII. Further, mice tolerant to wild-type human FIX did not develop immune responses against the protein variants. Our results therefore indicate the feasibility of using variants of FIX to bypass FVIII as a novel treatment approach in hemophilia with and without neutralizing FVIII Abs.

Manipulating piggyBac Transposon Chromosomal Integration Site Selection in Human Cells

The ability to direct gene delivery to a user-defined chromosomal location would greatly improve gene transfer applications. The piggyBac transposon system is a nonviral gene transfer system proven effective in a variety of cells and tissues, including human cells. We fused a highly site-specific synthetic zinc-finger DNA-binding domain (ZFP) to the N-terminus of the piggyBac transposase and evaluated site-directed genomic integration in human cells. Chimeric ZFP-piggyBac transposase exhibited robust gene transfer activity, targeted binding to a cognate endogenous chromosomal ZFP site in the human genome, and site-directed transposon integration into an episomal plasmid target containing a single ZFP site in human cells. We evaluated the ability of ZFP-piggyBac to direct gene integration into an engineered chromosomal ZFP target site in the human genome and consistently observed a higher degree of ZFP-piggyBac site-directed genomic integration when compared to native piggyBac. Chromatin immunoprecipitation (ChIP) experiments revealed binding of native piggyBac to our engineered TTAA-containing chromosomal target which supported integration, but not a TTAA-deficient chromosomal target which lacked integration. Our results offer insight into the requirements for using a chimeric zinc finger-piggyBac transposase to direct integration into a user-defined chromosomal location.

A novel nanometer non-viral gene transfer system for cartilage defects

Objective To develop a clinically applicable approach to enhance repair of cartilage defects by constructing an in vivo non-viral gene transfer system targeting chondrocytes. Methods High molecular weight chitosan (HMWC) was degraded to produce low molecular weight chitosan (LM-WC) that was combined with transforming growth factor-β1 (TGF-β1) plasmid to form stable nano-sizc complexes. After being tested in vitro firstly, these nano-size complexes were injected into the knee joint of New Zealand white rabbit models with full-thickness cartilage defects to detect their feasibility of delive-ring the growth factor gent in vivo. Results The results showed that LMWC/DNA nano-sizc comple-xes could deliver the gone into the cultured chondroeytes and cartilage tissue efficiently in vitro. When used in vivo, LMWC/TGF-β1 gene nano-size complexes could enhance the transfection efficiency and prolong the expression of TGF-β1 gone. In the animal models of articular osteechondral defect of rabbits, better healing and gentler degeneration could be observed in comparison with the control. Conclusion In vivo transfection of LMWC/TGF-β1 nano-size complexe is a safe and effective method to early promote the repair of osteochondral defects. Key words: Cartilage, articular; Wounds and injuries; Gene; Nanometer

Novel ultrasound-targeted microbubble destruction mediated short hairpin RNA plasmid transfection targeting survivin inhibits gene expression and induces apoptosis of HeLa cells

Survivin is an attractive target for tumor growth inhibition and represents a significant approach to anticancer therapy. RNA interference is an important tool for specifically down-regulating the expression of cellular genes. However, the efficiency of short hairpin RNA (shRNA) on the expression of survivin gene and the influence on the cell apoptosis transfected by the non-viral gene transfer system of ultrasound-targeted microbubble destruction was not explored. In this work, recombinant expression plasmid of shRNA targeting survivin gene was constructed and added to cultured cervical cancer cells followed by ultrasound exposure and SonoVue((R)) microbubble. Expression of survivin mRNA and protein were assessed by RT-PCR and western blot analysis. Apoptosis ratio was quantified by flow cytometry marked with annexin V and 7-AAD. After transfected for 48 h, the expression of survivin mRNA and protein were (16.67 +/- 2.73)% and (21.33 +/- 3.55)%, respectively. The apoptosis rate was (45.41 +/- 1.47)%. The differences were significant as compared with other groups (P < 0.01). In conclusion, we suggested that survivin could be regarded as an ideal anticancer target of cervical cancer. Recombinant expression plasmid of shRNA targeting survivin gene mediated by ultrasound-targeted microbubble destruction technique could effectively inhibit the expression of target gene and induce cell apoptosis. This novel method for RNA interference represents a powerful, promising non-viral technology that can be used in the tumor gene therapy and research.

An Epidermal Growth Factor-like Repeat of Del1 Protein Increases the Efficiency of Gene Transfer In Vitro

In this paper, we found that Del1, an extracellular matrix protein secreted by embryonic endothelial cells, increases the efficiency of transfection in vitro. Conditioned medium containing Del1 increased transfection by the LacZ gene using several non-viral gene transfer systems, including lipoplex and polyplex methods. Experiments using deletion mutants and fragments of Del1 revealed that the third epidermal growth factor-like repeat (E3) of Del1 mediates the enhancement of gene transfer and, furthermore, that the motif CXDXXXFXCXC is essential. Incubation of Pro5 cells, a yolk sac-derived cell line, with as low as 16 pM recombinant E3 was sufficient to enhance transfection, and 1 nM recombinant E3 enhanced the transfection 12-fold. Inhibitors of endocytosis suppressed this activity of the recombinant E3. These results suggest that the E3 fragment of Del1 can be used as a general biological enhancer of non-viral gene transfer.

Analysis of Novel Nonviral Gene Transfer Systems for Gene Delivery to Cells of the Musculoskeletal System

The aim of the present study was to evaluate the efficacy of novel nonviral gene delivery systems in cells of musculoskeletal origin. Primary cultures of lapine skeletal muscle cells, lapine articular chondrocytes, human cells from fibrous dysplasia and cell lines established from human osteosarcoma (SAOS-2), chondrosarcoma (CS-1), murine skeletal myoblasts (L8) and fibroblasts (NIH 3T3) were transfected with the P. pyralis luc or the E. coli lacZ genes using Nanofectin 1 and 2, Superfect, JetPEI, GeneJammer, Effectene, TransPass D2, FuGENE 6, Lipofectamine 2000, Dreamfect, Metafectene, Escort III, and calcium phosphate. Maximal transfection efficiency in lapine skeletal muscle cells was of 60.8 +/- 21.2% using Dreamfect, 38.9 +/- 5.0% in articular chondrocytes using Gene Jammer, 5.2 +/- 8.0% in human cells from fibrous dysplasia using Lipofectamine 2000, 12.7 +/- 16.2% in SAOS-2 cells using FuGENE 6, 29.9 +/- 3.5% in CS-1 cells using Lipofectamine 2000, 70.7 +/- 8.6% in L8 cells using FuGENE 6, and 48.9 +/- 13.0% in NIH 3T3 cells using Metafectene. When the cells were transfected with a human IGF-I gene, significant amounts of the IGF-I protein were secreted. These results indicate that relatively high levels of transfection can be achieved using novel nonviral gene transfer methods.

TGF-beta 1 gene-activated matrices regulated the osteogenic differentiation of BMSCs

Poly (lactic acid/glycolic acid/asparagic acid-co-polyethylene glycol)(PLGA-[ASP-PEG]) scaffold materials were linked with a novel nonviral vector (K)16GRGDSPC through cross linker Sulfo-LC-SPDP to construct a new type of nonviral gene transfer system. Eukaryotic expressing vector containing transforming growth factor beta 1 (pcDNA3-TGFβ1) was encapsulated by the system. Bone marrow stromal cells (BMSCs) obtained from rabbit were cultured on PLGA-[ASP-PEG] modified by (K)16GRGDSPC and TGF-β1 gene and PLGA-[ASP-PEG] modified by (K)16GRGDSPC and empty vector pcDNA3 as control. The expressions of osteogenic makers of the BMSCs cultured on the TGF-β1 gene-activated scaffold materials were found significantly higher than those of the control group (P<0.05). A brand-new way was provided for regulating seed cells to directionally differentiate into osteoblasts for bone defect restoration in bone tissue engineering.

Electro-gene therapy in a human oral tongue cancer cell by intratumoral injection of pcDNA3.1-p27&lt;sup&gt;Kip1&lt;/sup&gt; wt

Oral tongue cancers are characterized by a high degree of local invasion and a high rate of metastases to the cervical lymph nodes. Also, treatment options for this cancer are limited. However, a new strategy for refractory cancer, gene therapy is watched with keen interest. Recently, a novel method for high-efficiency and region-controlled in vivo gene transfer was developed by combining in vivo electro-gene therapy and intratumoral plasmid DNA injection. In the present study, a nonviral gene transfer system, in vivo electrogene therapy in human oral tongue cancer cell, SP-C1 xenograft was examined. The aim of the study is to examine the efficiency of transfection of exogenous p27Kip1 gene by electroporation and the antitumor activity of p27Kip1 gene therapy in human oral tongue cancer xenografts using pcDNA3.1-p27Kip1 wild type (wt) and pcDNA3.1 empty vector with the local application of electric pulses. To evaluate this in vivo gene transfer method, the enhanced green fluorescence protein (EGFP) gene was transfected into xenografts by electroporation. The efficiency of transfection of exogenous p27Kip1 gene by electroporation was confirmed by Western blotting analysis. To estimate the reduction of oral tongue cancer xenografts by this method, the size of SP-C1 xenografts in nude mice after electroporation with wild type p27Kip1 gene was measured. The growth of tumors was markedly suppressed by wild type p27Kip1 gene transfection by electroporation compared with transfection of empty vector only. Moreover, histological specimens revealed apoptotic cell death was increased in wild type p27Kip1-transfected tumors than empty vector. These results suggest that it is possible to transfer wild type p27Kip1 into human oral tongue cancer xenografts using electroporation. Wild type p27Kip1 has a high-potencially to suppress the growth of tumors. Finally, combination system of pcDNA3.1-p27Kip1 wt-injected tumor and electroporationmight be used for human oral cancer.

Serum-resistant lipopolyplexes for gene delivery to liver tumour cells

In this study, an efficient non-viral gene transfer system has been developed by employing polyethylenimine (PEI 800, 25 and 22 kDa) and DOTAP and cholesterol (Chol) as lipids (lipopolyplex), at three different lipid/DNA molar ratios (2/1, 5/1 and 17/1) by using five different protocols of formulation. Condensation assays revealed that PEI of 800, 25 and 22 kDa were very effective in condensing plasmid DNA, leading to a complete condensation at N/P ratios above 4. Addition of DOTAP/Chol liposomes did not further condense DNA. Increasing the molar ratio lipid/DNA in the complex resulted in higher positive values of the ζ-potential, while the particle size increased in some protocols, but not in others. High molecular weight PEI (800 kDa) used in the formulation of lipopolyplexes lead to a bigger particle size, compared to that obtained with smaller PEI species, whether branched (25 kDa) or linear (22 kDa). These vectors were also highly effective in protecting DNA from attack by DNAse I. Transfection activity was maximal by using protocols 3 and 4 and a lipid/DNA molar ratio of 17/1. These complexes showed high efficiency in gene delivery of DNA to liver cancer cells, even in the presence of high concentration of serum (60% FBS). On the other hand, complexes formed with linear PEI (22 kDa) were more effective than lipopolyplexes containing branched PEI (800 or 25 kDa). The complexes resulted to be much more efficient than conventional lipoplexes (cationic lipid and DNA) and polyplexes (cationic polymer and DNA). The same behaviour was observed for complexes prepared in the presence of the therapeutic gene pCMVIL-12. Toxicity assays revealed a viability higher than 80% in all cases, independently of the protocol, molar ratio (lipid/DNA), molecular weight and type of PEI.

Vectors for airway gene delivery.

Delivery of genes to the airway epithelium for therapeutic purposes seemed easy at first, because the epithelial cells interface with the environment and are therefore accessible. However, problems encountered were more substantial than were originally expected. Nonviral systems may be preferred for long-term gene expression, for they can be dosed repeatedly. Two nonviral gene transfer systems have been in clinical trials, lipid-mediated gene transfer and DNA nanoparticles. Both have sufficient efficiency to be candidates for correction of the cystic fibrosis defect, and both can be dosed repeatedly. However, lipid-mediated gene transfer in the first generation provokes significant inflammatory toxicity, which may be engineered out by adjustments of the lipids, the plasmid CpG content, or both. Both lipid-mediated gene transfer and DNA nanoparticles in the first generation have short duration of expression, but reengineering of the plasmid DNA to contain mostly eukaryotic sequences may address this problem. Considerable advances in the understanding of the cellular uptake and expression of these agents and in their practical utility have occurred in the last few years; these advances are reviewed here.

Sleeping Beauty‐based gene therapy with indoleamine 2,3‐dioxygenase inhibits lung allograft fibrosis

Sleeping Beauty (SB) transposon is a natural nonviral gene transfer system that can mediate long-term transgene expression. Its potential utility in treating organ transplantation-associated long-term complications has not yet been explored. In the present study we generated an improved SB transposon encoding the human gene indoleamine-2,3-dioxygenase (hIDO), an enzyme that possesses both T cell-suppressive and antioxidant properties and selectively delivered the SB transposon in combination with a hyperactive transposase plasmid to donor lung using the cationic polymer polyethylenimine (PEI) as transfection reagent. This nonviral gene therapeutic approach led to persistent and uniform transgene expression in the rat lung tissue without noticeable toxicity and inflammation. Importantly, IDO activity produced by hIDO transgene showed a remarkable therapeutic response, as evident by near normal pulmonary function (peak airway pressure and oxygenation), histological appearance, and reduced collagen content in lung allografts. In addition, we established a hIDO-overexpressing type II cell line using the SB-based gene transfer system and found that hIDO-overexpressing lung cells effectively inhibited transforming growth factor-beta-stimulated fibroblast proliferation in vitro. In summary, the SB-based gene therapy with hIDO represents a new strategy for treating lung transplantation-associated chronic complications, e.g., obliterative bronchiolitis.

Intraarterial Gene Delivery in Rabbit Hepatic Tumors: Transfection with Nonviral Vector by Using Iodized Oil Emulsion

To evaluate the feasibility of an iodized oil emulsion that is used for the chemoembolization of hepatocellular carcinoma as a modifier of a nonviral gene transfer system for intraarterial gene delivery in experimentally induced hepatic tumors. Experiments were performed in accordance with National Institutes of Health guidelines for the care and use of laboratory animals and were approved by the animal research committee at Seoul National University Hospital. VX2 carcinoma was implanted into the liver of 26 rabbits. Four nonviral gene transfer systems were prepared by using pCMV-luc+ as a reporter gene. The first system consisted of a DNA and polyethylenimine (PEI) complex (n = 7); the second, of a DNA and PEI complex mixed with iopamidol and iodized oil (n = 7); the third, of a DNA and PEI complex mixed with iopamidol (n = 7); and the fourth, of a DNA and PEI complex mixed with iodized oil (n = 5). For the DNA and PEI complex that was mixed with iopamidol and iodized oil, iopamidol was used to stabilize the emulsion. Twenty days after tumor implantation, intraarterial gene delivery was performed by selective catheterization of the hepatic artery. Rabbits were euthanized 24 hours after gene delivery. Luciferase activity was assayed in the tumor, left hepatic lobe, right hepatic lobe, and other organs and was statistically analyzed for comparison between complexes by using the Kruskal-Wallis test. Luciferase activity in the tumor was significantly higher for the group that received DNA, PEI, iopamidol, and iodized oil than for any other group (Kruskal-Wallis test, P < .05). Luciferase activity in the left hepatic lobe, right hepatic lobe, and other organs was not significantly different between complexes. Selective gene expression in tumor cells was confirmed by means of immunohistochemical analysis for luciferase. It is feasible to use an iodized oil emulsion system for the intratumoral transfection of nonviral vectors in experimentally induced hypervascular hepatic tumors.