Gene expression following direct injection of DNA into liver

Safe Procedure for Efficient Hydrodynamic Gene Transfer to Isolated Porcine Liver in Transplantation

Although calcineurin inhibitors are very effective as immunosuppressants in organ transplantation, complete graft acceptance remains as a challenge. Transfer of genes with immunosuppressant functions could contribute to improving the clinical evolution of transplantation. In this sense, hydrodynamic injection has proven very efficacious for liver gene transfer. In the present work, the hIL-10 gene was hydrofected 'ex vivo' to pig livers during the bench surgery stage, to circumvent the cardiovascular limitations of the procedure, in a model of porcine orthotopic transplantation with a 10-day follow-up. We used IL-10 because human and porcine proteins can be differentially quantified and for its immunomodulatory pleiotropic functions. Safety (biochemical parameters and histology), expression efficacy (RNA transcription and blood protein expression), and acute inflammatory response (cytokines panel) of the procedure were evaluated. The procedure proved safe as no change in biochemical parameters was observed in treated animals, and human IL-10 was efficaciously expressed, with stationary plasma protein levels over 20 pg/mL during the follow-up. Most studied cytokines showed increments (interferon-α, IFN-α; interleukin-1β, IL-1β; tumor necrosis factor α, TNFα; interleukin-6, IL-6; interleukin-8, IL-8; interleukin-4, IL-4; and transforming growth factor-β, TGF-β) in treated animals, without deleterious effects on tissue. Collectively, the results support the potential clinical interest in this gene therapy model that would require further longer-term dose-response studies to be confirmed.

Mfap4: a promising target for enhanced liver regeneration and chronic liver disease treatment

The liver has a remarkable regenerative capacity. Nevertheless, under chronic liver-damaging conditions, this capacity becomes exhausted, allowing the accumulation of fibrotic tissue and leading to end-stage liver disease. Enhancing the endogenous regenerative capacity by targeting regeneration breaks is an innovative therapeutic approach. We set up an in vivo functional genetic screen to identify such regeneration breaks. As the top hit, we identified Microfibril associated protein 4 (Mfap4). Knockdown of Mfap4 in hepatocytes enhances cell proliferation, accelerates liver regeneration, and attenuates chronic liver disease by reducing liver fibrosis. Targeting Mfap4 modulates several liver regeneration-related pathways including mTOR. Our research opens the way to siRNA-based therapeutics to enhance hepatocyte-based liver regeneration.

Virally induced CRISPR/Cas9-based knock-in of fluorescent albumin allows long-term visualization of cerebral circulation in infant and adult mice

Albumin, a protein produced by liver hepatocytes, represents the most abundant protein in blood plasma. We have previously engineered a liver-targeting adeno-associated viral vector (AAV) that expresses fluorescent protein-tagged albumin to visualize blood plasma in mice. While this approach is versatile for imaging in adult mice, transgene expression vanishes when AAV is administered in neonates due to dilution of the episomal AAV genome in the rapidly growing liver. Here, we use CRISPR/Cas9 genome editing to insert the fluorescent protein mNeonGreen (mNG) gene into the albumin (Alb) locus of hepatocytes to produce fluorescently labeled albumin (Alb-mNG). We constructed a CRISPR AAV that includes ∼1 kb homologous arms around Alb exon 14 to express Alb-mNG. Subcutaneous injection of this AAV with AAV-CMV-Cas9 in postnatal day 3 mice resulted in two-photon visualization of the cerebral cortex vasculature within ten days. The expression levels of Alb-mNG were persistent for at least three months and were so robust that vasomotion and capillary blood flow could be assessed transcranially in early postnatal mice. This knock-in approach provides powerful means for micro- and macroscopic imaging of cerebral vascular dynamics in postnatal and adult mice.

In Vivo Tissue-Specific DNA Demethylation in Mouse Liver Through a Hydrodynamic Tail Vein Injection

A new technique called the dCas9-SunTag and scFv-TET1CD epigenome editing system has recently been developed to edit the DNA methylation status of specific genes. The transfection of an all-in-one vector containing this system into cells is feasible and induces the DNA demethylation of specific genes; however, due to the large size of the vector, difficulties are associated with its introduction into mice. We herein used a hydrodynamic tail vein injection (HTVi) to introduce the all-in-one vector into mice for in vivo epigenome editing. HTVi needs to be considered for inducing the targeted DNA demethylation of particular genes in the mouse liver.

Extracellular vesicle expansion of PMIS-miR-210 expression inhibits colorectal tumour growth via apoptosis and an XIST/NME1 regulatory mechanism

BACKGROUND

Colorectal cancer (CRC) has a high mortality rate, and therapeutic approaches to treat these cancers are varied and depend on the metabolic state of the tumour. Profiles of CRC tumours have identified several biomarkers, including microRNAs. microRNA-210 (miR-210) levels are directly correlated with CRC survival. miR-210 expression is higher in metastatic colon cancer cells versus non-metastatic and normal colon epithelium. Therefore, efficient methods to inhibit miR-210 expression in CRC may provide new advances in treatments.

METHODS

Expression of miRs was determined in several metastatic and non-metastatic cell lines. miR-210 expression was inhibited using PMIS-miR-210 in transduced cells, which were transplanted into xenograft mice. In separate experiments, CRC tumours were allowed to grow in xenograft mice and treated with therapeutic injections of PMIS-miR-210. Molecular and biochemical experiments identified several new pathways targeted by miR-210 inhibition.

RESULTS

miR-210 inhibition can significantly reduce tumour growth of implanted colon cancer cells in xenograft mouse models. The direct administration of PMIS-miR-210 to existing tumours can inhibit tumour growth in both NSG and Foxn1nu/j mouse models and is more efficacious than capecitabine treatments. Tumour cells further transfer the PMIS-miR-210 inhibitor to neighbouring cells by extracellular vesicles to inhibit miR-210 throughout the tumour. miR-210 inhibition activates the cleaved caspase 3 apoptotic pathway to reduce tumour formation. We demonstrate that the long non-coding transcript XIST is regulated by miR-210 correlating with decreased XIST expression in CRC tumours. XIST acts as a competing endogenous RNA for miR-210, which reduces XIST levels and miR-210 inhibition increases XIST transcripts in the nucleus and cytoplasm. The increased expression of NME1 is associated with H3K4me3 and H3K27ac modifications in the NME1 proximal promoter by XIST.

CONCLUSION

Direct application of the PMIS-miR-210 inhibitor to growing tumours may be an effective colorectal cancer therapeutic.

In vivo HSC transduction in rhesus macaques with an HDAd5/3+ vector targeting desmoglein 2 and transiently over-expressing cxcr4

We developed a new in vivo hematopoietic stem cell (HSC) gene therapy approach that involves only intravenous injections and does not require myeloablation/conditioning and HSC transplantation. In this approach, HSCs are mobilized from the bone marrow into the peripheral blood stream and transduced with intravenously injected helper-dependent adenovirus (HDAd) vectors. A fraction of transduced HSCs returns to the bone marrow and persists there long-term. Here, we report desmoglein 2 (DSG2) as a new receptor that can be employed for in in vivo HSC transduction. We developed HDAd5/3+ vectors that use DSG2 as a high-affinity attachment receptor and studied in vivo HSC transduction and safety after intravenous injection of an HDAd5/3+GFP vector in G-CSF/AMD3100(Plerixafor)-mobilized rhesus macaques. Unlike previously used CD46-targeting HDAd5/35++ vectors, HDAd5/3+ virions were not sequestered by rhesus erythrocytes and therefore mediated ~10-fold higher GFP marking rates in primitive HSCs (CD34+/CD45RA-/CD90+ cells) in the bone marrow at day 7 after vector injection. To further increase the return of in vivo transduced, mobilized HSCs to the bone marrow, we transiently expressed CXC motif chemokine receptor 4 (cxcr4) in mobilized HSCs from the HDAd5/3+ vector. In vivo transduction with a HDAd5/3+GFP/cxcr4 vector at a low dose of 0.4x1012vp/kg resulted in up to 7% of GFP-positive CD34+/CD45RA-/CD90+ cells in the bone marrow. This transduction rate is a solid basis for in vivo base or prime editing in combination with natural or drug-induced expansion of edited HSCs. Furthermore, our study provides new insights into HSC biology and trafficking after mobilization in non-human primates.

Somatic Tissue Engineering in Mouse Models Reveals an Actionable Role for WNT Pathway Alterations in Prostate Cancer Metastasis

To study genetic factors influencing the progression and therapeutic responses of advanced prostate cancer, we developed a fast and flexible system that introduces genetic alterations relevant to human disease directly into the prostate glands of mice using tissue electroporation. These electroporation-based genetically engineered mouse models (EPO-GEMM) recapitulate features of traditional germline models and, by modeling genetic factors linked to late-stage human disease, can produce tumors that are metastatic and castration-resistant. A subset of tumors with Trp53 alterations acquired spontaneous WNT pathway alterations, which are also associated with metastatic prostate cancer in humans. Using the EPO-GEMM approach and an orthogonal organoid-based model, we show that WNT pathway activation drives metastatic disease that is sensitive to pharmacologic WNT pathway inhibition. Thus, by leveraging EPO-GEMMs, we reveal a functional role for WNT signaling in driving prostate cancer metastasis and validate the WNT pathway as therapeutic target in metastatic prostate cancer. SIGNIFICANCE: Our understanding of the factors driving metastatic prostate cancer is limited by the paucity of models of late-stage disease. Here, we develop EPO-GEMMs of prostate cancer and use them to identify and validate the WNT pathway as an actionable driver of aggressive metastatic disease.This article is highlighted in the In This Issue feature, p. 890.

Targeted DNA demethylation of the Fgf21 promoter by CRISPR/dCas9-mediated epigenome editing

Recently, we reported PPARα-dependent DNA demethylation of the Fgf21 promoter in the postnatal mouse liver, where reduced DNA methylation is associated with enhanced gene expression after PPARα activation. However, there is no direct evidence for the effect of site-specific DNA methylation on gene expression. We employed the dCas9-SunTag and single-chain variable fragment (scFv)-TET1 catalytic domain (TET1CD) system to induce targeted DNA methylation of the Fgf21 promoter both in vitro and in vivo. We succeeded in targeted DNA demethylation of the Fgf 21 promoter both in Hepa1-6 cells and PPARα-deficient mice, with increased gene expression response to PPARα synthetic ligand administration and fasting, respectively. This study provides direct evidence that the DNA methylation status of a particular gene may determine the magnitude of the gene expression response to activation cues.

Plasma proteomic analysis of autoimmune hepatitis in an improved AIH mouse model

Background

The prevalence of autoimmune hepatitis (AIH) is increasing, and its early clinical diagnosis is difficult. The pathogenesis of AIH remains unclear, and AIH-related studies are largely limited because of lack of suitable mouse models.

Methods

To obtain a good tool for research on AIH, we first established an improved immune-mediated mouse model that can mimic the pathological process of AIH as in the human body, through repeated injections of human cytochrome P450 2D6 (CYP2D6) plasmid. Next, a proteomic analysis based on isobaric tag (IBT) technology was performed to detect the differentially expressed proteins (DEPs), and related biological functions and pathways in the plasma of AIH and normal mice. Finally, we performed enzyme-linked immunosorbent assay (ELISA) to further confirm the most abundant DEP in the plasma of patients with AIH.

Results

Autoantibodies and the characteristic pathology of AIH were observed in our mouse model. Inflammatory infiltration also increased in the livers of AIH mice over time and plateaued by day 42 post the first injection. Chronic hepatitis was most severe on day 35 with the development of fibrosis as well, and the plasma of AIH mice were collected for proteomic analysis. A total of 176 DEPs were found in this experiment, of which 148 DEPs were up-regulated and 28 DEPs were down-regulated. Thirty significant Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways (P < 0.05) were detected. Arginine biosynthesis was found to be the most significant pathway involved in the AIH process. During the Gene Ontology (GO) analysis, most DEPs were found to be involved in the binding, cellular, and metabolic processes. Using ELISA, the most overexpressed DEP, serum amyloid A 1 (SAA1), was confirmed to be increased specifically in the plasma of patients with AIH compared to other chronic hepatitis. Different plasma levels of SAA1 were also found related to different grades of inflammation and stages of fibrosis in the liver of patients with AIH.

Conclusions

Our study is the first to describe the proteomics analysis of a true sense of AIH mouse model, which is beneficial for a better understanding of AIH pathogenesis and identifying potential biomarkers for its clinical diagnosis.

Genetic Modification of the Lung Directed Toward Treatment of Human Disease

Genetic modification therapy is a promising therapeutic strategy for many diseases of the lung intractable to other treatments. Lung gene therapy has been the subject of numerous preclinical animal experiments and human clinical trials, for targets including genetic diseases such as cystic fibrosis and α1-antitrypsin deficiency, complex disorders such as asthma, allergy, and lung cancer, infections such as respiratory syncytial virus (RSV) and Pseudomonas, as well as pulmonary arterial hypertension, transplant rejection, and lung injury. A variety of viral and non-viral vectors have been employed to overcome the many physical barriers to gene transfer imposed by lung anatomy and natural defenses. Beyond the treatment of lung diseases, the lung has the potential to be used as a metabolic factory for generating proteins for delivery to the circulation for treatment of systemic diseases. Although much has been learned through a myriad of experiments about the development of genetic modification of the lung, more work is still needed to improve the delivery vehicles and to overcome challenges such as entry barriers, persistent expression, specific cell targeting, and circumventing host anti-vector responses.

YAP determines the cell fate of injured mouse hepatocytes in vivo

The presence of senescent, transformed or damaged cells can impair tissue function or lead to tumorigenesis; therefore, organisms have evolved quality control mechanisms to eliminate them. Here, we show that YAP activation induced by inactivation of the Hippo pathway specifically in damaged hepatocytes promotes their selective elimination by using in vivo mosaic analysis in mouse liver. These damaged hepatocytes migrate into the hepatic sinusoids, undergo apoptosis and are engulfed by Kupffer cells. In contrast, YAP activation in undamaged hepatocytes leads to proliferation. Cellular stresses such as ethanol that damage both liver sinusoidal endothelial cells and hepatocytes switch cell fate from proliferation to migration/apoptosis in the presence of activated YAP. This involves the activation of CDC42 and Rac that regulate cell migration. Thus, we suggest that YAP acts as a stress sensor that induces elimination of injured cells to maintain tissue and organ homeostasis.

Senescent and injured cells affect tissue functions and can drive tumorigenesis. Thus, efficient elimination of these cells is pivotal for tissue integrity. Here Miyamura et al. show that YAP acts as a cellular stress sensor and promotes the elimination of damaged cells to maintain tissue homeostasis.

Gene Therapy for Alpha-1 Antitrypsin Deficiency Lung Disease

Alpha-1 antitrypsin (AAT) deficiency, characterized by low plasma levels of the serine protease inhibitor AAT, is associated with emphysema secondary to insufficient protection of the lung from neutrophil proteases. Although AAT augmentation therapy with purified AAT protein is efficacious, it requires weekly to monthly intravenous infusion of AAT purified from pooled human plasma, has the risk of viral contamination and allergic reactions, and is costly. As an alternative, gene therapy offers the advantage of single administration, eliminating the burden of protein infusion, and reduced risks and costs. The focus of this review is to describe the various strategies for AAT gene therapy for the pulmonary manifestations of AAT deficiency and the state of the art in bringing AAT gene therapy to the bedside.

Non-viral nucleic acid containing nanoparticles as cancer therapeutics

INTRODUCTION

The delivery of nucleic acids such as DNA and short interfering RNA (siRNA) is promising for the treatment of many diseases, including cancer, by enabling novel biological mechanisms of action. Non-viral nanoparticles are a promising class of nucleic acid carriers that can be designed to be safer and more versatile than traditional viral vectors.

AREAS COVERED

In this review, recent advances in the intracellular delivery of DNA and siRNA are described with a focus on non-viral nanoparticle-based delivery methods. Material properties that have enabled successful delivery are discussed as well as applications that have directly been applied to cancer therapy. Strategies to co-deliver different nucleic acids are highlighted, as are novel targets for nucleic acid co-delivery.

EXPERT OPINION

The treatment of complex genetically-based diseases such as cancer can be enabled by safe and effective intracellular delivery of multiple nucleic acids. Non-viral nanoparticles can be fabricated to deliver multiple nucleic acids to the same cell simultaneously to prevent tumor cells from easily compensating for the knockdown or overexpression of one genetic target. The continued innovation of new therapeutic modalities and non-viral nanotechnologies to provide target-specific and personalized forms of gene therapy hold promise for genetic medicine to treat diseases like cancer in the clinic.

Gene delivery using calcium phosphate nanoparticles: Optimization of the transfection process and the effects of citrate and poly(l-lysine) as additives

Despite the long history of nanoparticulate calcium phosphate (CaP) as a non-viral transfection agent, there has been limited success in attempts to optimize its properties for transfection comparable in efficiency to that of viral vectors. Here we focus on the optimization of: (a) CaP nanoparticle precipitation conditions, predominantly supersaturation and Ca/P molar ratios; (b) transfection conditions, mainly the concentrations of the carrier and plasmid DNA; (c) the presence of surface additives, including citrate anion and cationic poly(l-lysine) (PLL). CaP nanoparticles significantly improved transfection with plasmid DNA encoding enhanced green fluorescent protein (eGFP) in pre-osteoblastic MC3T3-E1 cells compared to a commercial non-viral carrier. At the same time they elicited significantly lesser cytotoxicity than the commercial carrier. Plasmid DNA acted as a nucleation promoter, decreasing the nucleation lag time of metastable CaP solutions and leading to a higher rate of nucleation and a lower size of the precipitated particles. The degree of supersaturation (DS) of 15 was found to be more optimal for transfection than that of 12.5 or 17.5 and higher. Because CaP particles precipitated at DS 15 were spherical, while DS 17.5 and 21 yielded acicular particles, it was concluded that spherical particle morphologies were more conducive to transfection than the anisotropic ones. Even though the yield at DS 15 was 10 and 100 times lower than that at DS 17.5 and 21, respectively, transfection rates were higher using CaP nanoparticle colloids prepared at DS 15 than using those made at higher or lower DS, indicating that the right particle morphology can outweigh the difference in the amount of the carrier, even when this difference is close to 100×. In contrast to the commercial carrier, the concentration of CaP-pDNA delivered to the cells was directly proportional to the transfection rate. Osteosarcoma K7M2 cells were four times more easily transfectable with CaP nanoparticles than the MC3T3-E1 cells. The addition of citrate increased the transfection rate at lower concentrations; however, a complete redispersal of CaP-pDNA nanoparticles at higher concentrations of citrate coincided with a complete diminishment of transfection, implying the benefits of partial aggregation of CaP nanoparticles carrying pDNA. In contrast, PLL delayed transfection initially, but enhanced it at longer time points (⩾96h), leading to the conclusion that both citrate and PLL could exert positive effects on transfection: citrate if added at low concentrations and PLL to extend transfection over longer periods of time.

Plasmid Biopharmaceuticals

Plasmids are currently an indispensable molecular tool in life science research and a central asset for the modern biotechnology industry, supporting its mission to produce pharmaceutical proteins, antibodies, vaccines, industrial enzymes, and molecular diagnostics, to name a few key products. Furthermore, plasmids have gradually stepped up in the past 20 years as useful biopharmaceuticals in the context of gene therapy and DNA vaccination interventions. This review provides a concise coverage of the scientific progress that has been made since the emergence of what are called today plasmid biopharmaceuticals. The most relevant topics are discussed to provide researchers with an updated overview of the field. A brief outline of the initial breakthroughs and innovations is followed by a discussion of the motivation behind the medical uses of plasmids in the context of therapeutic and prophylactic interventions. The molecular characteristics and rationale underlying the design of plasmid vectors as gene transfer agents are described and a description of the most important methods used to deliver plasmid biopharmaceuticals in vivo (gene gun, electroporation, cationic lipids and polymers, and micro- and nanoparticles) is provided. The major safety issues (integration and autoimmunity) surrounding the use of plasmid biopharmaceuticals is discussed next. Aspects related to the large-scale manufacturing are also covered, and reference is made to the plasmid products that have received marketing authorization as of today.

Gelatin-based nanoparticles as DNA delivery systems: Synthesis, physicochemical and biocompatible characterization

The rapidly rising demand for therapeutic grade DNA molecules requires associated improvements in encapsulation and delivery technologies. One of the challenges for the efficient intracellular delivery of therapeutic biomolecules after their cell internalization by endocytosis is to manipulate the non-productive trafficking from endosomes to lysosomes, where degradation may occur. The combination of the endosomal acidity with the endosomolytic capability of the nanocarrier can increase the intracellular delivery of many drugs, genes and proteins, which, therefore, might enhance their therapeutic efficacy. Among the suitable compounds, the gelification properties of gelatin as well as the strong dependence of gelatin ionization with pH makes this compound an interesting candidate to be used to the effective intracellular delivery of active biomacromolecules. In the present work, gelatin (either high or low gel strength) and protamine sulfate has been selected to form particles by interaction of oppositely charged compounds. Particles in the absence of DNA (binary system) and in the presence of DNA (ternary system) have been prepared. The physicochemical characterization (particle size, polydispersity index and degree of DNA entrapment) have been evaluated. Cytotoxicity experiments have shown that the isolated systems and the resulting gelatin-based nanoparticles are essentially non-toxic. The pH-dependent hemolysis assay and the response of the nanoparticles co-incubated in buffers at defined pHs that mimic extracellular, early endosomal and late endo-lysosomal environments demonstrated that the nanoparticles tend to destabilize and DNA can be successfully released. It was found that, in addition to the imposed compositions, the gel strength of gelatin is a controlling parameter of the final properties of these nanoparticles. The results indicate that these gelatin-based nanoparticles have excellent properties as highly potent and non-toxic intracellular delivery systems, rendering them promising DNA vehicles to be used as non-viral gene delivery systems.

Spatiotemporal control of gene expression in mammalian cells and in mice using the LightOn system

A light-switchable transgene system could be a powerful optogenetic tool for the precise manipulation of spatiotemporal gene expression in multicellular organisms. We have developed the LightOn system, which consists of a single chimeric protein (GAVPO) that can homodimerize and bind to promoters upon exposure to blue light, activating transcription of a target gene. This article describes protocols for precise control of gene expression in mammalian cells and mice using the LightOn system. These protocols can be carried out in an ordinary laboratory, as both liposome-mediated transfection and hydrodynamic tail vein injection are routine methods that can easily transfer the LightOn system to mammalian cells and mouse liver, respectively. The illumination equipment can also be easily obtained. The LightOn system can provide a robust, convenient means to control the expression of a gene of interest, with unprecedented temporal and spatial accuracy in manipulating an extremely broad range of biological processes.

Physical methods for gene transfer

The key impediment to the successful application of gene therapy in clinics is not the paucity of therapeutic genes. It is rather the lack of nontoxic and efficient strategies to transfer therapeutic genes into target cells. Over the past few decades, considerable progress has been made in gene transfer technologies, and thus far, three different delivery systems have been developed with merits and demerits characterizing each system. Viral and chemical methods of gene transfer utilize specialized carrier to overcome membrane barrier and facilitate gene transfer into cells. Physical methods, on the other hand, utilize various forms of mechanical forces to enforce gene entry into cells. Starting in 1980s, physical methods have been introduced as alternatives to viral and chemical methods to overcome various extra- and intracellular barriers that limit the amount of DNA reaching the intended cells. Accumulating evidence suggests that it is quite feasible to directly translocate genes into cytoplasm or even nuclei of target cells by means of mechanical force, bypassing endocytosis, a common pathway for viral and nonviral vectors. Indeed, several methods have been developed, and the majority of them share the same underlying mechanism of gene transfer, i.e., physically created transient pores in cell membrane through which genes get into cells. Here, we provide an overview of the current status and future research directions in the field of physical methods of gene transfer.

Novel adeno-associated viruses derived from pig tissues transduce most major organs in mice

Recently, development of Adeno-associated virus (AAV) vectors has been focusing on expanding the genetic diversity of vectors from existing sequences via directed evolution or epitope remapping. Apart from intelligent design, AAV isolation from natural sources remains an important source of new AAVs with unique biological features. In this study, several new AAV sequences were isolated from porcine tissues (AAVpo2.1, -po4, -po5, and -po6), which aligned in divergent new clades. Viral particles generated from these sequences displayed tissue tropism and transduction efficiency profile specific to each porcine-derived AAV. When delivered systemically, AAVpo2.1 targeted the heart, kidney, and muscle, AAVpo5 performed poorly but was able to transduce muscle fibers when injected intramuscularly, whereas AAVpo4 and -po6 efficiently transduced all the major organs sampled, contending with ‘gold-standard’ AAVs. When delivered systemically, AAVpo4 and -po6 were detected by polymerase chain reaction (PCR) and histochemical staining of the transgene product in adult mouse brain, suggesting that these vectors can pass through the blood-brain barrier with efficiencies that may be useful for the development of therapeutic approaches. Porcine tissues are antigenically similar to human tissues and by inference, porcine AAVs may provide fresh tools to contribute to the development of gene therapy-based solutions to human diseases.

Recent trends of polymer mediated liposomal gene delivery system

Advancement in the gene delivery system have resulted in clinical successes in gene therapy for patients with several genetic diseases, such as immunodeficiency diseases, X-linked adrenoleukodystrophy (X-ALD) blindness, thalassemia, and many more. Among various delivery systems, liposomal mediated gene delivery route is offering great promises for gene therapy. This review is an attempt to depict a portrait about the polymer based liposomal gene delivery systems and their future applications. Herein, we have discussed in detail the characteristics of liposome, importance of polymer for liposome formulation, gene delivery, and future direction of liposome based gene delivery as a whole.

Advanced Materials for Gene Delivery

Gene therapy is a widespread and promising treatment of many diseases resulting from genetic disorders, infections and cancer. The feasibility of the gene therapy is mainly depends on the development of appropriate method and suitable vectors. For an efficient gene delivery, it is very important to use a carrier that is easy to produce, stable, non-oncogenic and non-immunogenic. Currently most of the vectors actually suffer from many problems. Therefore, the ideal gene therapy delivery system should be developed that can be easily used for highly efficient delivery and able to maintain long-term gene expression, and can be applicable to basic research as well as clinical settings. This article provides a brief over view on the concept and aim of gene delivery, the different gene delivery systems and use of different materials as a carrier in the area of gene therapy.

Immortalized human fetal bone marrow-derived mesenchymal stromal cell expressing suicide gene for anti-tumor therapy in vitro and in vivo

BACKGROUND AIMS

Cancer is one of the greatest health challenges facing the world today with >10 million new cases of cancer every year. The self-renewal, tumor-homing ability and low immunogenicity of mesenchymal stromal cells (MSCs) make them potential delivery candidates for suicide genes for anti-tumor therapy. However, unstable supply and short life span of adult MSCs in vitro have limited this therapeutic potential. In this study, we aimed to evaluate if immortalization of human fetal bone marrow-derived mesenchymal stromal cells by simian virus 40 (SV40-hfBMSCs) could be a stable source of MSCs for clinical application of suicide gene therapy.

METHODS AND RESULTS

Transduction of SV40 and herpes simplex virus thymidine kinase-IRES-green fluorescent protein (TK-GFP) did not cause significant change in the stem cell properties of hfBMSCs. The anti-tumor effect of SV40-TK-hfBMSCs in the presence of the prodrug ganciclovir was demonstrated in vitro and in nude mice bearing human prostate cancer cells, DU145 and PC3, which had been transduced with luciferase and GFP for imaging evaluation by an in vivo live imaging system (IVIS 200 imaging system; Caliper Life Sciences). Repeated injection of low doses (1 × 10(6) cells/kg) of SV40-TK-hfBMSCs was as effective as previously reported and did not cause observable harmful side effects in multiple organs. Mixed lymphocyte reaction showed that SV40-TK-hfBMSCs did not induce significant proliferation of lymphocytes isolated from healthy adults.

CONCLUSIONS

Taken together, immortalized hfBMSCs represent a reliable and safe source of MSCs for further clinical translational study.

A Direct in vivo RNAi screen identifies MKK4 as a key regulator of liver regeneration

The liver harbors a distinct capacity for endogenous regeneration; however, liver regeneration is often impaired in disease and therefore insufficient to compensate for the loss of hepatocytes and organ function. Here we describe a functional genetic approach for the identification of gene targets that can be exploited to increase the regenerative capacity of hepatocytes. Pools of small hairpin RNAs (shRNAs) were directly and stably delivered into mouse livers to screen for genes modulating liver regeneration. Our studies identify the dual-specific kinase MKK4 as a master regulator of liver regeneration. MKK4 silencing robustly increased the regenerative capacity of hepatocytes in mouse models of liver regeneration and acute and chronic liver failure. Mechanistically, induction of MKK7 and a JNK1-dependent activation of the AP1 transcription factor ATF2 and the Ets factor ELK1 are crucial for increased regeneration of hepatocytes with MKK4 silencing.

Proteinuria decreases tissue lipoprotein receptor levels resulting in altered lipoprotein structure and increasing lipid levels

Rats with nephrotic syndrome (NS) have a fivefold increase in lipids and a similar decrease in triglyceride-rich lipoprotein (TRL) clearance. Lipoprotein lipase (LPL) is reduced both in NS and in the Nagase analbuminemic rat. These rats have nearly normal triglyceride levels and TRL clearance, suggesting that reduction in LPL alone is insufficient to cause increased TRL levels. Apolipoprotein E (apoE) was decreased in lipoprotein fractions in NS, but not in analbuminemia. Here we tested whether decreased apoE binding to lipoproteins in NS contributes to hyperlipidemia by decreasing their affinity for lipoprotein receptors. Plasma apoE was increased 60% in both NS and analbuminemia compared with control (CTRL) as a result of a 60% decreased apoE clearance. Very-low-density lipoprotein and high-density lipoprotein in NS had significantly less apoE per mole of phospholipid compared with analbuminemia or CTRL and significantly greater lipid content; however, apoE binding did not differ by lipoprotein class or group. There was a significant reduction of receptors for lipoproteins in nearly all tissues in NS compared with CTRL and analbuminemia. Thus, apoE within lipoprotein fractions was reduced by dilution resulting from expansion of the lipid fraction due to decreased lipolysis and not to differing affinity for apoE. Decreased lipoprotein receptors result from proteinuria and contribute to hyperlipidemia in NS.

Pretreatment with epidermal growth factor enhances naked plasmid DNA transfer onto gastric serosal surface in mice

We have developed a simple administration method, which is gastric serosal surface instillation of naked plasmid DNA (pDNA) in experimental animals. The purpose of this study was to improve gastric gene transfer efficiency by pre-treatment with a macropinocytosis enhancer, such as fetuin or epidermal growth factor (EGF), in mice. A series of concentrations of fetuin were instilled onto gastric serosal surface prior to instillation of naked pDNA in mice; however, fetuin did not improve transgene expression in the stomach 6 h after administration of pDNA. EGF also did not affect transgene expression in the stomach when pDNA was instilled immediately after EGF instillation. On the other hand, when pDNA was instilled onto gastric serosal surface 24 h after EGF treatment, transgene expression in the stomach was significantly improved by 2.6-fold. In addition, transgene-positive cells were increased 5.3-fold by EGF pre-treatment. High transgene expression in the stomach lasted for 48 h in the EGF pre-treatment group in comparison with that in the no pre-treatment group. These findings are valuable to develop an effective method of in vivo gene transfer to the stomach.

Vector systems for prenatal gene therapy: principles of non-viral vector design and production

Gene therapy vectors based on viruses are the most effective gene delivery systems in use today and although efficient at gene transfer their potential toxicity (Hacein-Bey-Abina et al., Science 302:415-419, 2003) provides impetus for the development of safer non-viral alternatives. An ideal vector for human gene therapy should deliver sustainable therapeutic levels of gene expression without affecting the viability of the host at either the cellular or somatic level. Vectors, which comprise entirely human elements, may provide the most suitable method of achieving this. Non-viral vectors are attractive alternatives to viral gene delivery systems because of their low toxicity, relatively easy production, and great versatility. The development of more efficient, economically prepared, and safer gene delivery vectors is a crucial prerequisite for their successful clinical application and remains a primary strategic task of gene therapy research.

Sustained, high transgene expression in liver with plasmid vectors using optimized promoter-enhancer combinations

BACKGROUND

Plasmid-based gene therapy approaches often lack long-term transgene expression in vivo as a result of silencing or loss of the vector. One way to overcome these limitations is to combine nonsilenced promoters with strong enhancers.

METHODS

In the present study, we combine murine or human cytomegalovirus (CMV)-derived enhancer elements with the human elongation factor 1α (EF1α) promoter in a plasmid backbone devoid of potentially immunostimulating cytosine-guanine repeat sequences. Luciferase transgene activity was monitored in mouse liver after hydrodynamic plasmid delivery.

RESULTS

Luciferase activity of a CMV-promoter driven plasmid rapidly declined within days, whereas the activity of the EF1α driven plasmid remained high for 2 weeks (murine enhancer) and detectable for > 80 days (human enhancer). Expression levels clearly correlated with higher plasmid copy number found in the liver at 2 months after gene delivery. Furthermore, we developed a novel synthetic CMV-EF1α hybrid promoter (SCEP) combining the high activity of CMV and sustained activity of EF1α promoter. The SCEP led to a constitutive three-fold increase in expression levels compared to the EF1α promoter in vivo.

CONCLUSIONS

This novel combination of enhancer and promoter element with optimized plasmid backbones will pave the way for more efficient nonviral approaches in gene therapy.

Senescence surveillance of pre-malignant hepatocytes limits liver cancer development

Upon the aberrant activation of oncogenes, normal cells can enter the cellular senescence program, a state of stable cell-cycle arrest, which represents an important barrier against tumour development in vivo. Senescent cells communicate with their environment by secreting various cytokines and growth factors, and it was reported that this 'secretory phenotype' can have pro- as well as anti-tumorigenic effects. Here we show that oncogene-induced senescence occurs in otherwise normal murine hepatocytes in vivo. Pre-malignant senescent hepatocytes secrete chemo- and cytokines and are subject to immune-mediated clearance (designated as 'senescence surveillance'), which depends on an intact CD4(+) T-cell-mediated adaptive immune response. Impaired immune surveillance of pre-malignant senescent hepatocytes results in the development of murine hepatocellular carcinomas (HCCs), thus showing that senescence surveillance is important for tumour suppression in vivo. In accordance with these observations, ras-specific Th1 lymphocytes could be detected in mice, in which oncogene-induced senescence had been triggered by hepatic expression of Nras(G12V). We also found that CD4(+) T cells require monocytes/macrophages to execute the clearance of senescent hepatocytes. Our study indicates that senescence surveillance represents an important extrinsic component of the senescence anti-tumour barrier, and illustrates how the cellular senescence program is involved in tumour immune surveillance by mounting specific immune responses against antigens expressed in pre-malignant senescent cells.

Intracellular trafficking pathways involved in the gene transfer of nano-structured calcium phosphate-DNA particles

Nano-structured calcium phosphate (NanoCaP) particles have been proven to be a powerful means of non-viral gene delivery. In order to better understand the mechanisms through which NanoCaPs-mediated mammalian cell transfection is achieved, we have sought to define the intracellular trafficking pathways involved in the cellular uptake and intracellular processing of these particles. Previous work has indicated that NanoCaP-DNA complexes are most likely internalized via endocytosis, however the subsequent pathways involved have not been determined. Through the use of specific inhibitors, we show that endocytosis of NanoCaP particles is both clathrin- and caveolae-dependent, and suggest that the caveolaer mechanism is the major contributor. We demonstrate colocalization of NanoCaP-pDNA complexes with known markers of both clathrin-coated and caveolar vesicles. Furthermore, through the use of quantitative flow cytometry, we present the first work in which the percent internalization of CaP-DNA complexes into cells is quantified. The overall goal of this research is to foster the continued improvement of NanoCaP-based gene delivery strategies.

Administration of naked plasmid encoding hepatic stimulator substance by hydrodynamic tail vein injection protects mice from hepatic failure by suppressing the mitochondrial permeability transition

Acute liver failure is a devastating illness of various causes with considerable mortality. Hepatic stimulator substance (HSS) has been suggested for use as a protective agent against acute hepatic injury induced by chemical poisons because it has a variety of biological activities. However, the mechanism whereby HSS protects against hepatotoxins is poorly understood. In this study, we established a hepatic gene transfer system via hydrodynamic tail vein injection to deliver a naked plasmid containing the human HSS gene (hHSS) and analyzed HSS-mediated protection of the liver during fulminant hepatic failure (FHF) induced by D-galactosamine (D-gal) and lipopolysaccharide (LPS). The results showed that the reporter gene, enhanced green fluorescent protein, was efficiently expressed in the liver of BALB/c mice. Hydrodynamic-based transfection of hHSS yielded a 70% survival rate compared with 36.7% for the control group at 24 h after D-gal/LPS treatment. In addition, hHSS expression preserved liver morphology and function. It is noteworthy that hHSS hydrodynamic-based transfer ameliorated indices of the mitochondrial permeability transition (MPT) resulting from the toxic effects of d-gal/LPS on the liver such as mitochondrial swelling, mitochondrial transmembrane potential disruption, and cytochrome c translocation. Furthermore, mitochondrial morphology and ATP levels were maintained in hHSS-administered mice. HSS-mediated protection was similar to that observed with the MPT inhibitor N-methyl-4-isoleucine-cyclosporin (NIM811), indicating a possible role for HSS in the regulation of MPT. In conclusion, a single dose of hHSS plasmid protected mice from FHF, and this hepatoprotective effect seemed to correlate with the inhibition of MPT.

[Development of tissue pressure-mediated transfection method aimed at organ-specific gene expression control]

A mechanism-based logical approach is a mainstream of current novel drug therapy development in the context of these trends and, therefore, the elucidation of gene function and the molecular level mechanism analysis of diseases at an individual level in mammals are essential in addition to that in cultured cells. In vivo gene transfection techniques are also indispensable for these purposes as well as the evaluation of gene therapy and nucleic acid-based therapy approaches and clinical applications during the process of development of novel drug therapies. Various recombinant virus and synthetic carrier-mediated transfection methods have been reported, however, above all, naked plasmid DNA transfection without virus vectors, synthetic carriers and special physical devices has attracted much attention, because of its advantages including convenience of preparation and handling and lack of toxicity associated with the transfection agents. In this review, I collect the information of these naked plasmid DNA transfection methods involving tissue pressure-mediated transfection from the comprehensive view point including side effects. Additively, the key physiological phenomena affecting transgene expression, especially activation of transcriptional factors, are reviewed. Combined with conventional approach based with biodistribution control, regulation of physiological change in transfected cells will provide spatial- and temporal-controlled transgene expression at various organs, which leads us to elucidate mechanism of diseases and to develop novel drug therapy in near future.

High volume naked DNA tail-vein injection restores liver function in Fah-knock out mice

BACKGROUND

Despite pharmaceutical treatment with NTBC (2-2-nitro-4-fluoromethylbenzoyl-1,3-cyclohexanedione), a high incidence of liver malignancies occur in humans and mice suffering from hereditary tyrosinemia type 1 (HT1) caused by mutation of the fumarylacetoacetate hydrolase (fah) gene.

METHODS

To evaluate the efficacy of a definitive treatment for HT1, we transfected fah knockout mice with naked plasmid DNA using high volume tail-vein injection. This approach was chosen to reduce the occurrence of insertional mutagenesis that is frequently observed when using other (retro-)viral vectors. To prolong gene expression, the fah gene was cloned between adeno-associated virus (AAV)-specific inverted terminal repeats (ITRs).

RESULTS

All animals treated with high volume plasmid DNA injections could be successfully weaned off NTBC and survived in the long term without any further pharmacological support. Up to 50% fah positive hepatocytes were detected in livers of naked plasmid DNA-treated animals and serum liver function tests approximated those of wild-type controls.

CONCLUSIONS

Naked plasmid DNA transfection offers a promising alternative treatment for HT1. Minimizing side-effects makes this approach especially appealing.

DNA-based nano-sized systems for pharmaceutical and biomedical applications

DNA is one of the most important components for all living organisms and many species, including humans, use DNA to store and transmit genetic information to new generations. Recent advances in the handling of DNA have made it possible to use DNA as a building block of nano-sized materials with precisely designed architectures. Although various approaches have been proposed to obtain DNA assemblies with designed architecture in the nano- to micrometer range, there is little information about their interaction with biological components, including target molecules. Understanding the interaction between DNA assemblies and the body is highly important for successful pharmaceutical and biomedical applications. Here, we first review the basic aspects of externally administered DNA molecules, including the stability, permeability and delivery issues. Then, we discuss the unique responses observed in the interaction of structured DNA assemblies and cells expressing Toll-like receptor-9, the receptor responsible for the recognition of unmethylated CpG dinucleotides that are abundant in the DNA of invading pathogens, such as bacteria and viruses.

[Organ-, region- and cell-selective gene transfer using non-viral vectors]

Safety in gene therapy is an important issue since both viral and non-viral vectors have toxic side effects. Not only vectors themselves, but also distributions of produced proteins affect safety in gene therapy; thus, development of target-selective gene transfer methods is rational. We have developed organ-, region- and cell-selective gene transfer methods using non-viral vectors. To deliver foreign gene to liver parenchymal cells (hepatocytes), galactosylation of cationic liposome/plasmid DNA complex is useful strategy. Based on analyses for intrahepatic disposition characteristics and interaction with blood components, we formulated novel galactosylated lipoplex with regulated salt concentration to reduce particle size of lipoplex and to stabilize lipoplex simultaneously; as a consequence, we succeeded in improvement of hepatocyte-selective gene transfer after intraportal injection of the lipoplex in mice. On the other hand, administration routes are important for target-selective gene transfer. We discovered that simple instillation of naked plasmid DNA onto organ surface (the liver, kidney, spleen, stomach and lung) in mice and rats could result in effective and region-selective transgene expression. Neither physical force nor carriers are necessary for gene transfer onto organ surface mesothelial cells. To rationally improve transfection efficiency, mechanism of gene transfer should be elucidated. We clarified that Rac-mediated macropinocytosis was required for naked plasmid DNA transfer in gastric mesothelial cells.

Liver- and lobe-specific gene transfer following the continuous microinstillation of Plasmid DNA onto the liver surface in mice: effect of instillation speed

Development of technology to deliver foreign gene(s) to a specific organ/tissue is one of the major challenges in gene therapy. Here, we show liver- and lobe-specific gene transfer following the continuous microinstillation of plasmid DNA (pDNA) onto the liver surface in mice. Naked pDNA was continuously instilled onto the right medial liver lobe using syringe pump in male ddY mice. Our previous studies showed liver- and lobe-selective gene expression after instillation of 30 mul of pDNA solution onto the liver surface, but gene expression was also found in the other liver lobe, kidney and spleen. To improve target site selectivity of gene expression, the instillation volume was decreased; however, non-specific gene expression in the other liver lobe and diaphragm was still detected. To prevent immediate diffusion of the pDNA solution, we performed continuous microinstillation of pDNA using a syringe pump; as a result, target site selectivity was greatly improved. As for instillation speed, 5 min infusion was enough to prevent diffusion of pDNA solution. Furthermore, transfection efficiency in the target site was maintained when instillation speed was slowed. Wiping off residual pDNA solution from the applied liver lobe resulted in a further improvement in selectivity, suggesting not only immediate diffusion, but also gradual diffusion, are important factors for successful target site-specific gene transfer. Information in this study will be useful for further development of an effective gene delivery system targeted to a specific organ/tissue by use of other non-viral or viral vectors.

Low-amplitude ultrasound enhances hydrodynamic-based gene delivery to rat kidney

The synergistic combination of hydrodynamic-based gene delivery and ultrasound was investigated to achieve improved gene transfer to the kidney. Plasmids encoding firefly luciferase and Erythropoietin (EPO) gene were delivered into the left kidney of rats by single or combinative application of renal vein hydrodynamic injection and ultrasound treatment with or without the addition of ultrasound contrast agents (UCA). Ultrasound exposure was found to enhance the efficiency of hydrodynamic-based gene delivery for both luciferase and EPO expression. An ultrasound exposure intensity of 2 W/cm2 at 10% duty cycle for 15 min, produced a maximal gene expression 4.5 times higher than hydrodynamic delivery alone. Duration, location, and tissue-specificity of gene expression were not changed by ultrasound exposure. Application of UCA reduced the intensity and exposure duration of ultrasound treatment needed for optimal expression. Appropriate application of ultrasound and UCA did not alter histological structure or impair physiological function of the treated kidney.

Highly stomach-selective gene transfer following gastric serosal surface instillation of naked plasmid DNA in rats

BACKGROUND

The purpose of this study was to achieve stomach-selective gene transfer in rats by our simple and novel administration method, which is gastric serosal surface instillation of naked plasmid DNA (pDNA).

METHODS

Naked pDNA encoding firefly luciferase as a reporter gene was instilled onto the gastric serosal surface in male Wistar rats. As controls, we performed intraperitoneal, intragastric and intravenous administration of naked pDNA. At appropriate time intervals, we measured luciferase activities in the stomach and other tissues.

RESULTS

Gene expression in the stomach 6 h after gastric serosal surface instillation of naked pDNA (5 microg) was significantly higher than that after using other administration methods. The present study is the first report on stomach-selective gene transfer following instillation of naked pDNA onto the gastric serosal surface in rats. Also, the gene expression level in the stomach 6 h after gastric serosal surface instillation of naked pDNA was markedly higher than that in other tissues. In a dose-dependent study, the gene expression level was saturated over 5 microg. Gene expression in the stomach was detected 3 h after gastric serosal surface instillation of naked pDNA. The gene expression level peaked 12-24 h after instillation of naked pDNA, then decreased to a level similar to 3 h at 48 h.

CONCLUSIONS

Gastric serosal surface in stillation of naked pDNA can be a highly stomach-selective gene transfer method in rats.

Novel jet-injection technology for nonviral intratumoral gene transfer in patients with melanoma and breast cancer

PURPOSE

This phase I clinical trial evaluated safety, feasibility, and efficiency of nonviral intratumoral jet-injection gene transfer in patients with skin metastases from melanoma and breast cancer.

EXPERIMENTAL DESIGN

Seventeen patients were enrolled. The patients received five jet injections with a total dose of 0.05 mg beta-galactosidase (LacZ)-expressing plasmid DNA (pCMVbeta) into a single cutaneous lesion. Clinical and laboratory safety monitoring were done. Systemic plasmid clearance was monitored by quantitative real-time PCR of blood samples throughout the study. All lesions were resected after 2 to 6 days. Intratumoral plasmid DNA load, DNA distribution, and LacZ expression was analyzed by quantitative real-time PCR, quantitative reverse transcription-PCR, Western blot, immunohistochemistry, and 5-bromo-4-chloro-3-indolyl-beta-D-galactoside staining.

RESULTS

Jet injection of plasmid DNA was safely done in all patients. No serious side effects were observed. Thirty minutes after jet injection, peak plasmid DNA levels were detected in the blood followed by rapid decline and clearance. Plasmid DNA and LacZ mRNA and protein expression were detected in all treated lesions. Quantitative analysis revealed a correlation of plasmid DNA load and LacZ-mRNA expression confirmed by Western blot. Immunohistochemistry and 5-bromo-4-chloro-3-indolyl-beta-D-galactoside staining showed LacZ-protein throughout the tumor. Transfected tumor areas were found close and distant to the jet-injection site with varying levels of DNA load and transgene expression.

CONCLUSION

Intratumoral jet injection of plasmid DNA led to efficient LacZ reporter gene expression in all patients. No side effects were experienced, supporting safety and applicability of this novel nonviral approach. A next step with a therapeutic gene product should determine antitumor efficacy of jet-injection gene transfer.

Plasma yolk precursor dynamics during egg production by female greater scaup (Aythya marila): Characterization and indices of reproductive state

We characterized dynamics of the plasma yolk precursors vitellogenin (VTG), very-low-density lipoprotein (total VLDL-TG), and VLDL particle size distribution during egg production by female greater scaup (order: Anseriformes, Aythya marila). We also evaluated VTG and total VLDL-TG as physiological indices of reproductive state. Mean (+/-1 SE) plasma concentrations of VTG and total VLDL-TG for females with nondeveloped ovaries were 0.58 +/- 0.05 microg Zn mL(-1) and 3.75 +/- 0.29 mmol TG L(-1), respectively. Yolk precursor concentrations increased rapidly to maximum levels in association with small increases in ovary mass during rapid follicle growth. Mean concentrations of VTG and total VLDL-TG for females with a full ovarian follicle hierarchy were 3.38 +/- 0.40 microg Zn mL(-1) and 7.31 +/- 2.56 mmol TG L(-1), respectively. Concentrations of VTG and total VLDL remained elevated throughout the laying cycle and decreased markedly by 3 d into incubation. Individual reproductive state (non-egg producing vs. egg producing) was more accurately identified by plasma profiles of VTG (90%) than by those of total VLDL-TG (74%). Greater scaup VLDL particle sizes during egg production were within the range for predicted yolk-targeted VLDL size (25-44 nm). We conclude that plasma profiles of VTG and total VLDL-TG can be used as nonlethal, physiological indices of reproductive state in greater scaup and should be of great utility to a variety of evolutionary, ecological, and applied conservation studies of reproduction in waterfowl.

Physical approaches for nucleic acid delivery to liver

The liver is a key organ for numerous metabolic pathways and involves many inherited diseases that, although being different in their pathology, are often caused by lack or overproduction of a critical gene product in the diseased cells. In principle, a straightforward method to fix such problem is to introduce into these cells with a gene-coding sequence to provide the missing gene product or with the nucleic acid sequence to inhibit production of the excessive gene product. Practically, however, success of nucleic acid-based pharmaceutics is dependent on the availability of a method capable of delivering nucleic acid sequence in the form of DNA or RNA to liver cells. In this review, we will summarize the progress toward the development of physical methods for nucleic acid delivery to the liver. Emphasis is placed on the mechanism of action, pros, and cons of each method developed so far. We hope the information provided will encourage new endeavor to improve the current methodologies or develop new strategies that will lead to safe and effective delivery of nucleic acids to the liver.

Reduction of fibrosis in a rat model of non-alcoholic steatohepatitis cirrhosis by human HGF gene transfection using electroporation

BACKGROUND AND AIM

To study the histological changes caused by transfection of the hepatocyte growth factor (HGF) gene using electroporation (EP) in a non-alcoholic steatohepatitis (NASH) cirrhotic liver model.

METHODS

NASH cirrhotic livers were prepared by administering a choline-deficient diet to 5-week-old male Wister rats for 12 weeks. Three groups of rats were used: rats in the G(+) group were transfected with the GFP gene using EP, rats in the H(+) group were transfected with the HGF gene using EP, and rats in the H(-) group were only injected with the HGF gene. Rats were sacrificed 2 days after gene transfection, and the Azan positive rate (APR) and Sudan positive rate (SPR) were calculated to evaluate fibrosis and fatty changes.

RESULTS

The APR of the NASH cirrhotic livers was significantly higher than that in the normal livers. The APR did not decrease in the G(+) group and the H(-) group, but decreased significantly in the nonelectroporated as well as electroporated areas of the H(+) group. For SPR, there were no significant differences between the G(+), H(-), and H(+) groups.

CONCLUSION

The improvement of fibrosis was not significant when a direct injection of the HGF gene was used alone, but it was enhanced by the concomitant use of EP. However, no efficacy was observed in fat components. These findings suggest that transfection of the HGF gene by EP may lead to an improvement of irreversible cirrhotic livers to reversible fatty livers.