Long-term expression of human alpha1-antitrypsin gene in mouse liver achieved by intravenous administration of plasmid DNA using a hydrodynamics-based procedure

Potency of siRNA versus shRNA mediated knockdown in vivo

The intracellular delivery of small interfering RNA (siRNA) is a therapeutic strategy to transiently block gene expression. Two silencing RNA strategies utilize either synthetic double stranded RNA or plasmid DNA encoding a short hairpin RNA (shRNA). In the present study, we have quantitatively compared the potency of siRNA (siLuc1) and shRNA (pShagLuc) mediated knockdown of luciferase expression in vivo using hydrodynamic dosing and bioluminescence imaging (BLI). Following hydrodynamic coadministration of siLuc1 or pShagLuc with a plasmid encoding luciferase (pGL3), mice were analyzed for transgene expression by BLI. The knockdown of luciferase expression by siLuc1 or pShagLuc was observed at 3 h and persisted for 3 days. The potency of siLuc1 and pShagLuc was equivalent with maximal effect at 10 microg coadministered with 1 microg of pGL3 resulting in >80% knockdown. Combined dosing of siLuc1 and pShagluc (5 microg each) with 1 microg of pGL3 resulted in >99% knockdown. Analysis of the data established that shRNA was significantly more potent than siRNA at mediating knockdown when compared on a mole basis. The combination of hydrodynamic dosing and BLI to measure siRNA or shRNA mediated knockdown of luciferase provide an attractive in vivo quantitative method to test formulations that target the liver.

Hydrodynamic gene delivery: its principles and applications

Efficient and safe methods for delivering genetic materials into cells must be developed before the clinical potential of gene therapy can be fully realized. Recently, hydrodynamic gene delivery using a rapid injection of a relatively large volume of DNA solution has opened up a new avenue for gene therapy studies in vivo. This method is superior to the existing delivery systems because of its simplicity, efficiency, and versatility. Wide success in applying hydrodynamic principles to delivery of DNA, RNA, proteins, and synthetic compounds, into the cells in various tissues of small animals, has inspired the recent attempts at establishing a hydrodynamic procedure for clinical use. In this review, we provide an overview of the theory and practice of hydrodynamic gene delivery so as to aid researchers for the use of this method in their pre-clinical and translational gene therapy studies.

Establishment and primary application of a mouse model with hepatitis B virus replication

AIM: To establish a rapid and convenient animal model with hepatitis B virus (HBV) replication.

METHODS: A naked DNA solution of HBV-replication-competent plasmid was transferred to BALB/C mice via the tail vein, using a hydrodynamic in vivo transfection procedure. After injection, these mice were sacrificed on d 1, 3, 4, 5, 7 and 10. HBV DNA replication intermediates in the liver were analyzed by Southern blot hybridization. The expression of hepatitis B core antigen (HBcAg) and hepatitis B surface antigen (HBsAg) in the liver was checked by immunohistochemistry. Serum HBsAg and hepatitis B e antigen (HBeAg) was detected by enzyme-linked immunosorbent assay (ELISA). Inhibition of HBV replication was compared in HBV replication model mice treated intraperitoneally with polyinosinic-polytidylin acid (polyIC) or phosphate-buffered saline (PBS).

RESULTS: After hydrodynamic in vivo transfection, HBV DNA replication intermediates in the mouse liver were detectable on d 1 and abundant on d 3 and 4, the levels were slightly decreased and remained relatively stable between d 5 and 7, and were almost undetectable on d 10. The expression patterns of HBcAg and HBsAg were similar to that of HBV replication intermediate DNA, except that they reached a peak on d 1 after injection. No obvious differences in HBV DNA replication intermediates were observed in the left, right and middle lobes of the liver. After treatment with polyIC, the level of HBV intermediate DNA in the liver was lower than that in the control mice injected with PBS.

CONCLUSION: A rapid and convenient mouse model with a high level of HBV replication was developed and used to investigate the inhibitory effect of polyIC on HBV replication, which provides a useful tool for future functional studies of the HBV genome.

Delivery and long-term expression of a 135 kb LDLR genomic DNA locus in vivo by hydrodynamic tail vein injection

BACKGROUND

The delivery of a complete genomic DNA locus in vivo may prove advantageous for complementation gene therapy, especially when physiological regulation of gene expression is desirable. Hydrodynamic tail vein injection has been shown to be a highly efficient means of non-viral delivery of plasmid DNA to the liver. Here, we apply hydrodynamic tail vein injection to deliver and express large genomic DNA inserts > 100 kb in vivo.

METHODS

Firstly, a size series (12-172 kb) of bacterial artificial chromosome (BAC) plasmids, carrying human genomic DNA inserts, episomal retention elements, and the enhanced green fluorescent protein (EGFP) reporter gene, was delivered to mice by hydrodynamic tail vein injection. Secondly, an episomal BAC vector carrying the whole genomic DNA locus of the human low-density lipoprotein receptor (LDLR) gene, and an expression cassette for the LacZ reporter gene, was delivered by the same method.

RESULTS

We show that the efficiency of delivery is independent of vector size, when an equal number of plasmid molecules are used. We also show, by LacZ reporter gene analysis, that BAC delivery within the liver is widespread. Finally, BAC-end PCR, RT-PCR and immunohistochemistry demonstrate plasmid retention and long-term expression (4 months) of human LDLR in transfected hepatocytes.

CONCLUSION

This is the first demonstration of somatic delivery and long-term expression of a genomic DNA transgene > 100 kb in vivo and shows that hydrodynamic tail vein injection can be used to deliver and express large genomic DNA transgenes in the liver.

Nonviral gene delivery: what we know and what is next

Gene delivery using nonviral approaches has been extensively studied as a basic tool for intracellular gene transfer and gene therapy. In the past, the primary focus has been on application of physical, chemical, and biological principles to development of a safe and efficient method that delivers a transgene into target cells for appropriate expression. This review summarizes the current status of the most commonly used nonviral methods, with an emphasis on their mechanism of action for gene delivery, and their advantages and limitations for gene therapy applications. The technical aspects of each delivery system are also reviewed, with a focus on how to achieve optimal delivery efficiency. A brief discussion of future development and further improvement of the current systems is intended to stimulate new ideas and encourage rapid advancement in this new and promising field.

The use of tissue inhibitors of matrix metalloproteinases to increase the efficacy of a tumor necrosis factor/interferonγ antitumor therapy

Owing to its impressive ability to kill tumor cells, especially in combination with interferon-gamma (IFNgamma), tumor necrosis factor (TNF) is widely appreciated as being a potential systemic therapeutic for the treatment of cancer. On the other hand, owing to its proinflammatory activities, administration of TNF leads to many systemic side effects and eventually to a potentially lethal systemic inflammatory response syndrome (SIRS). However, systemic treatment of tumor-bearing mice with TNF/IFNgamma in combination with BB-94 (a broad-spectrum metalloproteinase inhibitor) confers protection against TNF/IFNgamma-induced mortality, whereas preserving the antitumor activity. In this study, we investigated the effect of the adenoviral delivery of human tissue inhibitors of matrix metalloproteinase (hTIMP)-1 and hTIMP-2 genes on the outcome of TNF/IFNgamma antitumor therapy. The dose of adenovirus was limited to 10(8) PFU per mouse owing to the additive toxicity of combining it with TNF/IFNgamma therapy. Nevertheless, this dose was sufficient to achieve highly efficient adenoviral transfer and expression of hTIMP-1 and hTIMP-2 in the liver, but not the tumor. Treatment with this low dose of AdhTIMP-1 or AdhTIMP-2 was not enough to protect the host against the toxic effects of TNF/IFNgamma. However, it was sufficient to show a synergistic effect of hTIMPs with TNF/IFNgamma such that tumors regressed significantly faster. Interestingly, only AdTIMP-2 was able to prevent relapses after treatment.

Inhibition of hepatocarcinoma and tumor metastasis to liver by gene therapy with recombinant CBD-HepII polypeptide of fibronectin

Unlike the intact fibronectin (FN) molecule, some proteolytic or recombinant fragments of FN possess inhibitory activities on tumor, providing potential strategies in tumor therapeutics. Using the hydrodynamics-based gene delivery technique, we demonstrated that the treatment by in vivo expression of a recombinant CBD-HepII polypeptide of FN, designated as CH50, strongly inhibited the tumor growth, tumor invasion and angiogenesis. Such inhibitory effects of CH50 on tumor were partly ascribed to its influence on the activities of MMP-9 and alphavbeta3 integrin. The in vivo expressed CH50 decreased both the production and the activity of MMP-9 in tumor tissues. CH50 also down-regulated alphavbeta3 expression in tumor cells and endothelial cells in vitro. The decreased activity of alphavbeta3 integrin was proved by its reduced binding ability to fibrinogen and the down-regulation of cdc2 expression. The gene therapy with CH50 not only prolonged the survival of mice bearing hepatocarcinoma in the liver, but also suppressed the growth and invasive ability of tumor in spleen and its metastasis to liver. Taken together, these findings suggest a prospective utility of CH50 in the gene therapy of liver cancer.

Structural impact of hydrodynamic injection on mouse liver

The impact of hydrodynamic injection on liver structure was evaluated in mice using various microscopic techniques. Upon hydrodynamic injection of approximately 9% of body weight by volume, the liver rapidly expanded, reaching maximal size at the end of the injection and returned to its original size in 30 min. Histological analysis revealed a swollen appearance in the peri-central region of the liver where delivery of genes and fluorescence-labeled markers was observed. Scanning and transmission electron microscopy showed enlargement and rupture of endothelium that in about 24-48 h regains its morphology and normal function as a barrier against infection by adenovirus viral particles. At the cellular level in hydrodynamically treated animals, four types of hepatocytes were seen: cells with normal appearance; cells with enriched vesicles in the cytoplasm; cells with lightly stained cytosol; and cells with significant dilution of the cytoplasm. In addition, red blood cells and platelets were observed in the space of Disse and even inside hepatocytes. Vesicle formation is triggered by hydrodynamic injection and resembles the process of macropinocytosis. These results, whereas confirming the physical nature of hydrodynamic delivery, are important for a better understanding of this efficient method for intrahepatic gene and small interfering RNA delivery.

Ex vivo lentivirus transduction and immediate transplantation of uncultured hepatocytes for treating hyperbilirubinemic Gunn rat

BACKGROUND

Ex vivo liver gene therapy provides an attractive alternative to orthotopic liver transplantation for the treatment of liver diseases. We previously reported a protocol in which human primary hepatocytes are highly transduced in Suspension with Lentiviral vectors and Immediately Transplanted (SLIT). Here, we evaluated the SLIT approach in Gunn rats, the animal model for Crigler-Najjar syndrome type 1, a defect in bilirubin UDP-glucuronosyltransferase (BUGT).

METHODS

We constructed lentiviral vectors coding for BUGT under control of an ubiquitous promoter. Control vectors contained Green Fluorescent Protein (GFP) under control of the same promoter. Hepatocytes were isolated from jaundiced Gunn rats and transduced in suspension for four hr. After washing, 2x10 hepatocytes were immediately transplanted into syngeneic rats. Bilirubinemia and bile pigments were regularly assessed after cell transplantation. The percentage and presence of transduced hepatocytes was analyzed by immunohistochemistry in GFP-transplanted animals.

RESULTS

In rats receiving BUGT-transduced hepatocytes, bilirubinemia decreased by about 30%. The level of correction remained stable for up to 240 days. Bilirubin glucuronides were present in the bile of treated animals, indicating the metabolic activity of engrafted hepatocytes. In contrast, bilirubinemia in GFP-transplanted rats did not decline but rather increased. GFP-positive hepatocytes amounted to 0.5-1% of the liver, which is in agreement with the number of transplanted and genetically-modified hepatocytes (6x10).

CONCLUSIONS

This work reports the first demonstration of long-term metabolic benefit after rapid transplantation of ex vivo lentivirally tranduced hepatocytes. Therefore, this study demonstrates the therapeutic proof-of-principle and potential of the SLIT approach for treating inherited metabolic liver diseases.

Pig liver gene therapy by noninvasive interventionist catheterism

The efficacy of noninvasive interventionist catheterism in large animals as an alternative to the hydrodynamic procedure, described for small animals, is evaluated. Basically, gene transfer is performed by implantation and fixation of a balloon catheter within the suprahepatic vein of anesthetized pigs, through the femoral vein. The catheter tip is identified by fluoroscopy, injecting a contrast solution that marks large or small hepatic territories. Animals were injected with a 100 ml pTG7101 plasmid solution (40 microg/ml), which contains the human alpha-1 antitrypsin gene, perfused at a rate of 7.5 ml/s and efficacy and toxicity of the procedure were evaluated. The results show: (i) the highest efficacy in protein production is reached when perfusion is limited to small areas of the liver; (ii) no relevant hepatic toxicity was observed; (iii) gene transfer is mainly located in the areas around the central vein, as seen in the immunohistochemical studies; (iv) the electron microscopy studies indicate that the areas with good transfection efficacy show the presence of abundant endocytic vesicles that may even fuse among themselves. These data suggest that retrovenous injection by noninvasive interventionist catheterism could become an efficient procedure for hepatic gene transfer with potential clinical applications.

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Direct Assessment of Promoter Activity of Human Cytochrome P450 Genes Using Optimized Transfection in Vitro and in Vivo

Although transcription regulation of human cytochrome P450 enzymes (CYP) is known to play an important role in drug metabolism and homeostasis, factors influencing the expression of various CYP genes in humans remain largely undefined. We used three cell lines and CD-1 mice to assess the activity of genomic promoter sequences of human CYP2D6, 1A2, 3A4, 2C9, 2C18, and 2E1 genes. CYP promoter sequences were amplified by PCR using human liver genomic DNA as the template and cloned into pGL3-Basic vectors that contain a luciferase reporter gene but lack promoter or enhancer sequences. Each plasmid construct was transfected into cells in vitro using polyethylenimine (PEI) as the transfection reagent and into mice using the recently developed hydrodynamics-based procedure. Relative promoter strength was determined by the level of luciferase expression in transfected cells. All six human CYP promoters are active in driving reporter gene expression in cultured hepatic HepG2 cells and non-hepatic cells such as human embryonic kidney fibroblasts (293 cells) and murine melanoma cells (BL-16) as well as cells in intact mouse liver, lung, heart, kidney and spleen. The order of strength among CYP promoters examined was found to be 2D6 > 1A2 > 3A4 > 2C9 > 2C18 > 2E1.

Expression of non-signaling membrane-anchored death receptors protects murine livers in different models of hepatitis

Fas and tumor necrosis factor receptor 1 (TNFR1) are death receptors involved in various diseases such as hepatitis, sepsis, or graft rejection. Neutralizing antibodies to death ligands or soluble death receptors can inhibit cell death; however, they induce side effects because of their systemic actions. To specifically block death signaling to target cells, we created death domain-deficient (DeltaDD) membrane-anchored receptors, delivered to the liver by either recombinant adenovirus or hydrodynamic pressure of nonviral recombinant plasmids. In anti-Fas antibody-induced fulminant hepatitis, mice expressing recombinant Fas-decoy receptors (FasDeltaDD) in their livers were completely protected against apoptosis and survived fulminant hepatitis. In T-cell-dependent concanavalin A-induced autoimmune hepatitis, FasDeltaDD antagonist expression prevented hepatocyte damage and mouse death. Finally, TNFR1DeltaDD effectively protected mice against LPS-induced septic shock. In conclusion, such DeltaDD-decoy receptors act as dominant-negative receptors exerting local inhibition, while avoiding systemic neutralization of apoptosis ligands, and might have therapeutic potential in hepatitis.

Hydrodynmics-based delivery of human interleukin-10 gene in rats

AIM: To study hydrodynmics-based delivery of human interleukin-10 (hIL-10) transferred with Sleeping Beauty (SB) transposon system in rats.

METHODS: All the rats were injected with 20 mL Rinegers solution within 10-12 s via the tail vein. The rats were divided into the following groups according to different treatments: Ringers control; 100 μg empty liposome DOTAP; 100 μg liposome DOTAP + 50 μg pT-hIL-10; 50 μg pT-hIL-10 + 5 μg pCMV-SB (n = 6, in each group). The levels of alanine aminotransferase (ALT) were measured in each group, and the concentrations of hIL-10 in the serum were examined by enzyme-linked immunosorbent assay (ELISA) on postoperative day 1, 4, 7, 14 in transferred gene groups, respectively. The expression of hIL-10 mRNA was detected by reverse transcription polymerase chain reaction (RT-PCR).

RESULTS: The levels of alanine aminotransferase were as follows: 4339 ± 602, 13 516 ± 535, 6576 ± 347, 4451 ± 465; 984 ± 125, 4087 ± 600, 2117 ± 243, 1158 ± 130; 592 ± 85, 2339 ± 300, 1384 ± 165, 667 ± 90 nkat/L on postoperative day 1, 4, 7 in the group of Ringers control, empty liposome DOTAP, liposome DOTAP + pT-hIL-10 and pT-hIL-10 + pCMV-SB, respectively. The concentrations of hIL-10 in the serum were 818.3 ± 24.9, 640.7 ± 20.6, 441.3 ± 25.4, 322.3 ± 15.4 and 1008.3 ± 65.8, 820.8 ± 20.9, 675.8 ± 31.6, 438.2 ± 26.0 μg/L on postoperative day 1, 4, 7, 14 in the latter two groups, respectively, and there were significantly differences between the two groups (P < 0.01). In pT-hIL-10 + pCMV-SB transferred gene group, hIL-10 mRNA expression was still detected on postoperative day 14.

CONCLUSION: High level of hIL-10 gene can be expressed by hydrodynmics-based delivery in rats, and the transfection rate efficacy can be improved with combination of SB transposon system.

Conditional gene modification in mouse liver using hydrodynamic delivery of plasmid DNA encoding Cre recombinase

The success of Cre-mediated conditional gene targeting in liver of mice has until now depended on the generation of Cre recombinase transgenic mice or on viral-mediated transduction. Here, we sought to establish the feasibility of using hydrodynamic gene delivery of Cre recombinase into liver, using a ROSA26 EGFP mouse. The expression of EGFP and beta-galactosidase was exclusively detected in the liver of mice treated with hydrodynamic gene delivery of Cre recombinase, as assessed with fluorescence microscopy and X-Gal staining, respectively; Southern blotting also showed that Cre mediated recombination occurred specifically in the liver and not in other organs. The Cre mediated recombination reached about 61% of hepatocytes of mouse after repeated injection, as analyzed by flow cytometry. These results demonstrate that Cre recombinase can be transferred to the liver of mice through a simple hydrodynamic gene-delivery approach and can mediate efficient recombination in hepatocytes. Thus, hydrodynamic gene delivery of the Cre recombinase provides a valuable approach for Cre-loxP-mediated conditional gene modification in the liver of mice.

Hydrodynamics-based gene delivery of naked DNA encoding fetal liver kinase-1 gene effectively suppresses the growth of pre-existing tumors

Antiangiogenic gene therapy is a promising strategy for cancer treatment, which generally requires highly efficient delivery systems. To date, success of this strategy has depended almost exclusively on the delivery of high titers of viral vectors, which can result in effective transgene expression. However, their cytotoxicity and immunogenicity are a major concern for clinical applications. Recent advances in delivery efficiency of naked DNA could potentially meet the requirement for both high transgene expression and minimal side effects. To investigate whether naked DNA can be used for antiangiogenic cancer therapy, an expression plasmid was generated that encodes a soluble form of fetal liver kinase-1 (Flk-1) gene, a receptor for vascular endothelial growth factor (VEGF). Hydrodynamic injection of this plasmid resulted in close to 0.1 mg/ml of soluble Flk-1 protein in mouse serum and blocked VEGF-driven angiogenesis in matrigel in vivo. The same delivery significantly suppressed the growth of two different pre-existing subcutaneous tumors, Renca renal cell carcinoma and 3LL lung carcinoma. CD31 immunohistochemistry revealed that the tumor-associated angiogenesis was also highly attenuated in soluble Flk-1-treated mice. Thus, expression of genes by hydrodynamics-based gene delivery of naked DNA appears to be a promising approach for antiangiogenic cancer gene therapy.

Expression of recombination human anti-HBsAg Fab in murine liver

AIM: To evaluate the expression of recombinant and soluble human anti-HBsAg Fab in murine liver.

METHODS: The 5-40 μg recombinant plasmid pXXUF1-HBs-Fab was transfected by hydrodynamics-based administration via tail vein into C57BL/6 mice within 5 s. Meanwhile the empty plasmid transfection group and non-transfection group were established. The serum and tissue samples from liver, kidney and spleen of these mice were collected 3 d after transfection. The expression of genetically engineered Fab antibody in vivo was identified by reverse transcription-polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry both at mRNA and protein level.

RESULTS: After transfection with different doses (5, 10, 20 and 40 μg) of pXXUF1-HBs-Fab, the plasma expression of anti-HBsAg Fab was 201.3 ± 13.7, 213.1 ± 13.5, 513.6 ± 12.8 and 954.1 ± 12.7 μg/L, respectively, with specific binding activities to HBsAg protein. There was a postive correlation between the expression of the protein and plasmid dose(r = 0.912, P < 0.01). Meanwhile, the mRNA of Fd and κ chain were detected in liver tissues by RT-PCR. Immunohistochemistry showed brown positive granules in the cytoplasm of liver cells and Fab protein cohered on the inner walls of glomerular capillary lumen and collectors, but the parenchyma cells of the kidney and spleen had no expression of Fd, κ chain and the target protein. The expression of target protein was not observed in both empty plasmid transfection and non-transfection group.

CONCLUSION: The recombinant and soluble human anti-HBsAg Fab can be successfully expressed in mice, and the expression level is increased with the increase of plasmid dose. The above study also shows the Fab protein can be filtrated through glomerular.

A 16bp Rep Binding Element is Sufficient for Mediating Rep-dependent Integration into AAVS1

Adeno-associated virus (AAV) is a non-pathogenic virus and the only known eukaryotic virus capable of targeting human chromosome 19 for integration at a well-characterized AAVS1 site. Its site-specific integration is mediated by Rep68 and Rep78, viral proteins that bind to both the viral genome and AAVS1 site on ch19 through a specific Rep-binding element (RBE) located in both the viral genome and AAVS1. There are three RBEs in the AAV genome: two identical ones in both inverted terminal repeats (ITR) and another one in a recently discovered region termed the P5 integration efficiency element (P5IEE) that encompasses the viral P5 promoter. In order to identify the viral cis-acting sequence essential for Rep-mediated integration, we tested a series of constructs containing various lengths of P5IEE and compared the two RBEs from ITR (RBE(itr)) and P5IEE (RBE(p5)) in terms of their efficiency in Rep-dependent integration. Methods employed included a colony-forming assay, a PCR-based assay and Southern blotting analysis. We found that 16bp of the RBE cis-element was sufficient for mediating Rep-dependent site-specific integration. Furthermore, RBE(itr) was both more effective and specific than the RBE(p5) in Rep-dependent integration at the AAVS1 site. These findings added new information on the mechanism of Rep-dependent AAV genome insertion at the AAVS1 site and may be helpful in developing new high efficiency vectors for site-specific transgene integration.

Transthoracic direct current shock facilitates intramyocardial transfection of naked plasmid DNA infused via coronary vessels in canines

Catheter-mediated, percutaneous, transluminal delivery of naked plasmid DNA (pDNA) into myocardium may offer a valuable strategy to heart diseases. Here, we examined whether clinically available transthoracic direct current (DC) shock improves intracoronary naked DNA transfection into myocardium. Plasmid vector encoding the GL3 luciferase was infused retrogradely into the coronary veins of beagle dogs, whereas another pDNA solution was infused into the left coronary artery. During and after these procedures, the coronary venous sinus was occluded by balloon, and transthoracic DC shock of 200 J was applied immediately after the infusions. Without DC shock, no remarkable increase in luciferase activity was demonstrated in any part of the left ventricular myocardium. In the presence of DC pulsation, significant luciferase expression was detected in the regions that were supplied by left anterior descending coronary artery (LAD), whereas the gene expression in the right coronary artery (RCA) regions was much less drastic. X-gal (5-bromo-4-chloro-3-indolyl-beta-D-galactoside) staining of cardiac cross-sections also revealed regional expression of beta-galactosidase. Immunohistochemical examinations of heart cryosections revealed that cardiomyocytes in LAD regions successfully expressed transgene product. The present system may enable a new strategy for myocardial gene therapy, without any special device or technique other than cardiac catheterization and DC cardioversion that are generally performed in ordinary hospitals.

Expression of foreign genes in chicks by hydrodynamics-based naked plasmid transfer in vivo

The study of gene function in vivo is considered one of the top achievements of modern biology, inasmuch as it provides tools to study gene function in the context of the whole animal. In chickens, techniques of DNA-mediated gene transfer are less advanced than in other animal or livestock models, and remain a significant challenge. The study presented here is the first to show that a hydrodynamics-based gene-transfer technique, originally developed for naked DNA transfer in mice, can be applied to chickens. Rapid injection of naked plasmids containing expression cassettes into the jugular vein of 6- to 10-day-old chicks resulted in specific expression of the transgenes. A CMV promoter-driven luciferase reporter gene was expressed at significant levels in the liver during the first 3 days post-injection with lower levels also detected in the kidney. Significantly, all injected birds showed detectable levels of luciferase expression. Similarly, injection of a plasmid containing the secreted human coagulation factor IX (hFIX) gene under the control of human alpha-1-anti-trypsin promoter resulted in detectable levels of the hFIX in the plasma during the first 2 days post-injection. The method described herein has the potential for a quick and simple route for gain and loss-of function experiments in chicken liver and kidney, as well as for studying systemic effects of secreted proteins and hormones.

Attenuation of mouse acute colitis by naked hepatocyte growth factor gene transfer into the liver

BACKGROUND

Hepatocyte growth factor (HGF) has multiple biological effects on a wide variety of cells. It modulates intestinal epithelial proliferation and migration, and critically regulates intestinal wound healing.

AIMS

To investigate the therapeutic effect of HGF gene transfer, we introduced the HGF gene into the liver of mice with acute colitis.

METHODS

The rat HGF expression plasmid vector, pCAGGS-HGF, was injected via the tail vein into C57BL/6 mice, followed by dosing with dextran sulfate sodium in distilled water. Firstly, the HGF gene was injected once on day 0. Secondly, the HGF gene was injected on day 0 and again on day 2.

RESULTS

Injection of the HGF gene ameliorated colitis with inhibition of both loss of body weight and shortening of colon length. It protected the colon from epithelial erosions and cellular infiltration. Expression of mRNAs for IFN-gamma, IL18, and TNF-alpha was reduced in the colon. In contrast, expression of mRNA for IL-10 was increased. The numbers of BrdU-positive intestinal epithelial cells were increased, and the numbers of TUNEL-positive apoptotic cells were decreased. Furthermore, a second injection prolonged the elevation of serum HGF levels, and ameliorated the symptoms better than a single injection. The empty pCAGGS plasmid did not ameliorate acute colitis.

CONCLUSIONS

HGF gene transfer attenuated acute colitis by facilitating intestinal wound repair as well as inhibiting inflammation, suggesting a new strategy for treatment of IBD.

Sleeping Beauty-mediated transposition and long-term expression in vivo: use of the LoxP/Cre recombinase system to distinguish transposition-specific expression

The Sleeping Beauty transposon system (SB) has been shown to mediate nonviral integration of expression constructs resulting in long-term gene expression in several mammalian targets. Often, however, it is difficult to discern long-term expression resulting from transposition vs nonhomologous chromosomal recombination or maintenance of plasmid DNA in an extrachromosomal form. We have designed a system to silence expression from nontransposed sequences, making it possible to determine more specifically the amount of expression resulting from transposition. A transposon plasmid, pT2F/Cage (carrying a murine erythropoietin (Epo) gene transcriptionally regulated by the ubiquitously expressed CAGS promoter), was engineered to contain LoxP sites positioned so as to interrupt expression upon Cre-mediated recombination. Upon transposition these sites become segregated, thus protecting the expression construct from Cre-mediated recombination and subsequent silencing. Interferon-inducible Mx1Cre mice were administered pT2F/Cage with or without transposase-encoding plasmid. At 2 to 4 weeks postinjection, in the absence of SB transposase, Cre induction reduced Epo expression to about 1% of that seen in the group that was administered transposase-encoding plasmid, which maintained Epo levels near those of the uninduced groups. Southern hybridization analysis and plasmid rescue of transfected tissue supported the efficient Cre-mediated silencing of nontransposed sequences. These results indicate a substantial level of DNA-mediated expression not associated with transposition, but which can be quantitatively distinguished from transposition by its sensitivity to Cre recombinase. The results also provide additional evidence for the effectiveness of the Sleeping Beauty transposon system as an in vivo DNA-mediated gene transfer strategy for achieving long-term expression.

Nonviral Jet-Injection Gene Transfer for Efficient in Vivo Cytosine Deaminase Suicide Gene Therapy of Colon Carcinoma

Jet-injection technology has developed into an efficient gene delivery system for nonviral in vivo gene transfer. In this study the jet-injector system was used for the intratumoral gene transfer of small volumes of naked DNA encoding the Escherichia coli cytosine deaminase (CD) suicide gene. In our in vivo studies human colon carcinoma (patient-derived tumor model Colo5734 and SW480 colon carcinoma)-bearing NMRI-nu/nu male mice received four jet injections (10 microl per injection) of the CD-gene-carrying plasmid, representing 40 microg plasmid DNA per animal. Forty-eight hours after jet-injection, treatment of tumors with 5-fluorocytosine (5-FC; 500 mg/kg ip) was started and during treatment tumor volumes were measured. Starting from day 5 of 5-FC treatment inhibition of tumor growth was seen in the CD-gene-transduced tumors compared to the respective control groups, which lasted for the entire observation time. Expression analysis at the mRNA and protein levels revealed efficient expression of the CD gene in the jet-injected tumors. Therefore, in this in vivo study jet-injection gene transfer of 40 microg CD-expressing naked plasmid DNA leads to a significant tumor growth inhibition. This study demonstrates the applicability of the jet-injection technology for in vivo gene transfer into tumors to achieve efficient tumor gene therapy.

Dynamic Gene Expression After Systemic Delivery of Plasmid DNA as Determined by In Vivo Bioluminescence Imaging

Nonviral gene therapy approaches face the challenge of achieving stable gene expression in target organs and tissues. We used fluorescence microscopy and in vivo imaging after rapid, high-volume delivery of plasmid DNA (pDNA) encoding DsRed and luciferase as products of the same mRNA to detect localized gene expression in liver. Plasmids encoding the luciferase gene transcriptionally regulated by cellular and viral promoters were injected under similar conditions to test for potency and stability of gene expression in the liver of adult mice. Animals were imaged at 3, 6, 12, 24, and 48 hr and followed up at 1- to 2-week intervals over 2 months to identify maximum and persistent luciferase expression after injection of equimolar amounts of each plasmid. Emitted light representing luciferase expression was detected as early as 3 hr after pDNA infusion, reaching maximum levels at 12 hr for promoters containing viral sequences and at 24 hr for elements from human genes. Viral elements displayed 10- to 20-fold higher peak levels of expression but also yielded the most dramatic decline in expression over 8 weeks. In contrast, only a moderate decrease was observed for the cellular ubiquitin C promoter during that same period of time. Both promoter-deleted and phosphoglycerate kinase (PGK)-containing plasmids failed to maintain luciferase expression at levels above the limit of detection. These results demonstrate fine temporal analyses of reporter gene activity using promoters of various strength, suggesting an effective and reproducible method for studying gene therapy vectors in vivo.

Hydrodynamic liver gene transfer mechanism involves transient sinusoidal blood stasis and massive hepatocyte endocytic vesicles

The present study contributes to clarify the mechanism underlying the high efficacy of hepatocyte gene transfer mediated by hydrodynamic injection. Gene transfer experiments were performed employing the hAAT gene, and the efficacy and differential identification in mouse plasma of human transgene versus mouse gene was assessed by ELISA and proteomic procedures, respectively. By applying different experimental strategies such as cumulative dose-response efficacy, hemodynamic changes reflected by venous pressures, intravital microscopy, and morphological changes established by transmission electron microscopy, we found that: (a) cumulative multiple doses of transgene by hydrodynamic injection are efficient and well tolerated, resulting in therapeutic plasma levels of hAAT; (b) hydrodynamic injection mediates a transient inversion of intrahepatic blood flow, with circulatory stasis for a few minutes mainly in pericentral vein sinusoids; (c) transmission electron microscopy shows hydrodynamic injection to promote massive megafluid endocytic vesicles among hepatocytes around the central vein but not in hepatocytes around the periportal vein. We suggest that the mechanism of hydrodynamic liver gene transfer involves transient inversion of intrahepatic flow, sinusoidal blood stasis, and massive fluid endocytic vesicles in pericentral vein hepatocytes.

Parenchymal expression of CD86/B7.2 contributes to hepatitis C virus-related liver injury

Hepatitis C virus (HCV) infection is a major global health problem. Hepatic expression of immune costimulatory signaling molecules (e.g., B7) is known to be associated with ongoing liver injury in hepatitis C patients. However, due to the general lack of viral culture systems and adequate animal models, the function of these molecules in disease pathogenesis is poorly understood. To investigate the role of CD86 in HCV-related liver injury, we developed two transgenic mouse lineages with inducible expression of HCV structural proteins and constitutive expression of the costimulatory molecule CD86/B7.2 in the liver. Using a hydrodynamic-based, nonviral delivery protocol, we induced HCV transgene expression in the livers of HCV and CD86 single- and double-transgenic mice. We found that hepatic CD86 expression resulted in increased activation of and cytokine production (e.g., interleukin-2 and gamma interferon) by CD4+ T cells and that the retention of these cells was associated with more pronounced necroinflammatory lesions in the liver. Taken together, these data suggest that augmented, parenchymal antigen presentation conferred by hepatocyte CD86 expression alters homeostasis and effector functions of CD4+ T cells and contributes to liver injury. This study provides an additional rationale for exploring immunomodulation-based therapies that could reduce disease progression in individuals with chronic HCV infection.

Nonviral gene transfer into liver and muscle for treatment of hyperbilirubinemia in the gunn rat

We evaluated naked plasmid DNA (pDNA)-mediated expression of human hepatic bilirubin UDP-glucuronosyltransferase (hUGT1A1) in skeletal muscle to correct hyperbilirubinemia in the UGT1A1-deficient Gunn rat, an animal model of Crigler-Najjar syndrome type I (CN-I). After delivery of pDNA encoding hUGT1A1 via hepatic vein or femoral artery, in vitro bilirubin glucuronidation activity was detectable in Gunn rat liver and muscle extracts. Expression of hUGT1A1 in Gunn rat liver or muscle resulted in excretion of bilirubin glucuronides in bile. Total biliary bilirubin concentrations increased from a pretreatment average of 10.5 +/- 2.1 microM to 29.2 +/- 4.2 microM after gene transfer into the liver, and to 28.6 +/- 3.8 microM after gene transfer into muscle. Total serum bilirubin decreased by up to 31.2 +/- 6.9 and 29.2 +/- 3.7% and remained significantly lower for at least 1 and 2 weeks, respectively. Tissue damage associated with the procedure was minimal and reversible. Our results demonstrate that muscle can be genetically modified to glucuronidate bilirubin, leading to elimination in bile. A 30% decrease in serum bilirubin, if sustained, would provide meaningful clinical benefit for CN-I patients. However, to be clinically useful, this method needs further optimization and stable gene expression must be achieved.

The hydrodynamics-based procedure for controlling the pharmacokinetics of gene medicines at whole body, organ and cellular levels

Hydrodynamics-based gene delivery, involving a large-volume and high-speed intravenous injection of naked plasmid DNA (pDNA), gives a significantly high level of transgene expression in vivo. This has attracted a lot of attention and has been used very frequently as an efficient, simple and convenient transfection method for laboratory animals. Until recently, however, little information has been published on the pharmacokinetics of the injected DNA molecules and of the detailed mechanisms underlying the efficient gene transfer. We and other groups have very recently demonstrated that the mechanism for the hydrodynamics-based gene transfer would involve, in part, the direct cytosolic delivery of pDNA through the cell membrane due to transiently enhanced permeability. Along with the findings in our series of studies, this article reviews the cumulative reports and other intriguing information on the controlled pharmacokinetics of naked pDNA in the hydrodynamics-based gene delivery. In addition, we describe various applications reported so far, as well as the current attempts and proposals to develop novel gene medicines for future gene therapy using the concept of the hydrodynamics-based procedure. Furthermore, the issues associated with the clinical feasibility of its seemingly invasive nature, which is probably the most common concern about this hydrodynamics-based procedure, are discussed along with its future prospects and challenges.

A novel gene expression system: non-viral gene transfer for hemophilia as model systems

It is highly desirable to generate tissue-specific and persistently high-level transgene expression per genomic copy from gene therapy vectors. Such vectors can reduce the cost and preparation of the vectors and reduce possible host immune responses to the vector and potential toxicity. Many gene therapy vectors have failed to produce therapeutic levels of transgene because of inefficient promoters, loss of vector or gene expression from episomal vectors, or a silencing effect of integration sites on integrating vectors. Using in vivo screening of vectors incorporating many different combinations of gene regulatory sequences, liver-specific, high-expressing vectors to accommodate factor IX, factor VIII, and other genes for effective gene transfer have been established. Persistent and high levels of factor IX and factor VIII gene expression for treating hemophilia B and A, respectively, were achieved in mouse livers using hydrodynamics-based gene transfer of naked plasmid DNA incorporating these novel gene expression systems. Some other systems to prolong or stabilize the gene expression following gene transfer are also discussed.

Hydrodynamic Delivery

Hydrodynamic delivery has emerged as a near-perfect method for intracellular DNA delivery in vivo. For gene delivery to parenchymal cells, only essential DNA sequences need to be injected via a selected blood vessel, eliminating safety concerns associated with current viral and synthetic vectors. When injected into the bloodstream, DNA is capable of reaching cells in the different tissues accessible to the blood. Hydrodynamic delivery employs the force generated by the rapid injection of a large volume of solution into the incompressible blood in the circulation to overcome the physical barriers of endothelium and cell membranes that prevent large and membrane-impermeable compounds from entering parenchymal cells. In addition to the delivery of DNA, this method is useful for the efficient intracellular delivery of RNA, proteins, and other small compounds in vivo. This review discusses the development, current application, and clinical potential of hydrodynamic delivery.

Sleeping Beauty Transposon‐Mediated Gene Therapy for Prolonged Expression

The Sleeping Beauty (SB) transposon system represents a new vector for non-viral gene transfer that melds advantages of viruses and other forms of naked DNA transfer. The transposon itself is comprised of two inverted terminal repeats of about 340 base pairs each. The SB system directs precise transfer of specific constructs from a donor plasmid into a mammalian chromosome. The excision of the transposon from a donor plasmid and integration into a chromosomal site is mediated by Sleeping Beauty transposase, which can be delivered to cells vita its gene or its mRNA. As a result of its integration in chromosomes, and its lack of viral sequences that are often detected by poorly understood cellular defense mechanisms, a gene in a chromosomally integrated transposon can be expressed over the lifetime of a cell. SB transposons integrate nearly randomly into chromosomes at TA-dinucleotide base pairs although the sequences flanking the TAs can influence the probability of integration at a given site. Although random integration of vectors into human genomes is often thought to raise significant safety issues, evidence to date does not indicate that random insertions of SB transposons represent risks that are equal to those of viral vectors. Here we review the activities of the SB system in mice used as a model for human gene therapy, methods of delivery of the SB system, and its efficacy in ameliorating disorders that model human disease.

Conditions affecting hydrodynamics-based gene delivery into mouse liver in vivo

1. It has been demonstrated that the hydrodynamics-based procedure has high efficiency to deliver foreign genes into the liver. The widespread use of this procedure in gene function studies and as a treatment option for liver and other organ diseases puts considerable importance on the investigation of various conditions that affect hydrodynamics-based gene delivery into mouse liver in vivo. 2. Various conditions, including the volume, speed and solution of the injection and the state, gender and strain of the animal were manipulated to evaluate their effect on the expression levels in mice of human factor IX (hFIX) 8 h after tail vein injection of the plasmid pCMV-hFIX. 3. It was found that an injection volume of 2-2.5 mL and an injection speed of 5-7 s were very effective in delivering DNA into the mouse liver. Using Ringer's solution as an injection fluid increased the efficiency of hFIX expression. 4. Anaesthetized mice expressed higher hFIX than conscious mice. Males expressed higher hFIX than females. The ICR mouse strain demonstrated higher expression of the foreign gene than did the C57 strain. 5. The effects of these specific factors on hFIX expression may be caused by variations in hydrostatic pressure, the degree of liver damage and liver size. 6. It can be concluded that there are optimal conditions for hFIX expression in the liver. This information may be helpful for the application of hydrodynamics-based procedures in the investigation of gene expression and gene therapy.

Use of siRNAs to prevent and treat influenza virus infection

Influenza virus causes one of the most prevalent infections in humans. In a typical year, 10-20% of the population in the United States are infected by influenza virus, resulting in up to 40,000 deaths. Current vaccines can prevent illness in approximately 70-80% of healthy individuals under age 65, but the protection rate is much lower in those most susceptible to infection, namely infants, the elderly, and immunocompromised individuals. Although four antiviral drugs have been approved in the United States for treatment and/or prophylaxis of influenza, their use is limited because of concerns about side effects, compliance, and the possible emergence of resistant virus. We found that short interfering RNAs (siRNAs) specific for conserved regions of the influenza virus genome are potent inhibitors of influenza virus replication in both cell lines and embryonated chicken eggs. In this review, we discuss the potential value of siRNAs for preventing and treating influenza virus infections in humans and the challenges that have to be overcome to realize their potential.

Rat liver-targeted naked plasmid DNA transfer by tail vein injection

High levels of foreign gene expression in mouse hepatocytes can be achieved by "hydrodynamics-based transfection," the rapid injection of a large volume of a naked deoxyribonucleic acid (DNA) solution into the tail vein. Rats are more tolerant of the frequent phlebotomies required for monitoring blood parameters than mice and, thus, are more suitable for some biomedical research. Recently, we demonstrated that hydrodynamics-based transfection can also be used to deliver naked plasmid DNA into the normal rat, which is more than 10 times larger than the mouse. We performed the tail vein injection using a syringe with a winged needle equipped with an external tube. Injection of a lac Z expression plasmid, pCAGGS-lac Z by this technique resulted in the exclusive detection of beta-galactosidase in the liver. We also injected a rat erythropoietin (Epo) expression plasmid, pCAGGS-Epo (800 microg). Maximal Epo gene expression was achieved when a 25-mL injection volume (approx 100 mL/kg body wt) was transferred within 15 s.

Long-term Transgene Expression from Plasmid DNA Gene Therapy Vectors Is Negatively Affected by CpG Dinucleotides

CpG-reduced, CMV-based plasmid DNA constructs encoding human alpha-galactosidase A and factor IX were injected into C57Bl/6, BALB/c, and CD1 mice using hydrodynamics-based delivery of plasmid DNA (pDNA), and gene expression was monitored for 6 months. Linearized and supercoiled pDNAs were compared for their abilities to support long-term expression and to generate immune responses to the transgene product. In all mouse strains supercoiled CpG-reduced pDNA encoding alpha-galactosidase A and factor IX generated higher and more sustained levels of circulating gene product than their supercoiled CpG-replete analogs. Linearizing supercoiled CpG-reduced pDNA did not significantly increase levels of circulating gene product beyond levels supercoiled CpG-reduced pDNA could achieve. Linearizing supercoiled CpG-replete pDNA vectors significantly increased expression compared to their supercoiled CpG-replete analogs, but the increase was short-lived or subtherapeutic. Regardless of vector, liver depot expression did not elicit significant antibody responses to human alpha-galactosidase A or factor IX. Taken together, these data suggest that a clinically acceptable hydrodynamics-based approach targeting the liver combined with CpG-reduced pDNA vectors may represent a viable option for individuals with hemophilia, a lysosomal storage disease, or other disease in which prolonged depot expression of a therapeutic protein from the liver is desirable.

Prolonged liver-specific transgene expression by a non-primate lentiviral vector

Liver-directed gene therapy has the potential for treatment of numerous inherited diseases affecting metabolic functions. The aim of this study was to evaluate gene expression in hepatocytes using feline immunodeficiency virus-based lentiviral vectors, which may be potentially safer than those based on human immunodeficiency virus. In vitro studies revealed that gene expression was stable for up to 24 days post-transduction and integration into the host cell genome was suggested by Alu PCR and Southern blot analyses. Systemic in vivo administration of viral particles by the hydrodynamics method resulted in high levels of gene expression exclusively in the liver for over 7 months whereas injection of plasmid DNA by the same method led to transient expression levels. Our studies suggest that feline immunodeficiency-based lentiviral vectors specifically transduce liver cells and may be used as a novel vehicle of gene delivery for treatment of metabolic disease.

Hydroporation as the mechanism of hydrodynamic delivery

We have reported that a rapid tail vein injection of a large volume of plasmid DNA solution into a mouse results in high level of transgene expression in the liver. Gene transfer efficiency of this hydrodynamics-based procedure is determined by the combined effect of a large volume and high injection speed. Here, we show that the hydrodynamic injection induces a transient irregularity of heart function, a sharp increase in venous pressure, an enlargement of liver fenestrae, and enhancement of membrane permeability of the hepatocytes. At the cellular level, our results suggest that hepatic delivery by the hydrodynamic injection is accomplished by the generation of membrane pores in the hepatocytes.

Low-Density Lipoprotein (LDL) Receptor/Transferrin Fusion Protein:In VivoProduction and Functional Evaluation as a Potential Therapeutic Tool for Lowering Plasma LDL Cholesterol

A soluble form of human low-density lipoprotein receptor (LDL-R) fused in frame with rabbit transferrin (LDL-Rs(hu)/Tf(rab)) is assessed in vivo as a therapeutic tool for lowering plasma LDL cholesterol. The cDNA encoding LDL-Rs(hu)/Tf(rab) is expressed in mice, using a hydrodynamics-based gene transfer procedure. The transgene is transcribed in the liver of transduced animals and the corresponding protein is secreted into the bloodstream. Circulating LDL-Rs(hu)/Tf(rab) binds LDL specifically, thus indicating that it is correctly processed through the cellular compartments in vivo. More importantly, the expression of LDL-Rs(hu)/Tf(rab) allows the removal of injected human (125)I-labeled LDL ((123)I-LDL) from the bloodstream of transduced CD1 mice, which show faster LDL plasma clearance, anticipating by approximately 90 min the same clearance value observed in control animals. A similar effect is observed in transduced LDL-R(-/-) mice, in which the clearance of injected human LDL depends solely on the presence of circulating LDL-Rs(hu) /Tf(rab). In these animals the extent of plasma LDL clearance is directly related to the concentration of LDL-Rs(hu)/Tf(rab) in the blood. Finally, LDL-Rs(hu)/Tf(rab) does not alter the pattern of LDL organ distribution: in transduced animals, as well as in control animals, liver and bladder are the predominantly labeled organs after (123)I-LDL injection. However, LDL-Rs(hu)/Tf(rab) has a quantitative effect on LDL tissue deposition: in treated animals LDL-Rs(hu)/Tf(rab) determines an increase in radioactivity in the liver at early times after (123)I-LDL injection and a progressive labeling of the bladder, starting 20 min after injection.

GENE THERAPY FOR ORGAN GRAFTS USING RAPID INJECTION OF NAKED DNA: APPLICATION TO THE RAT LIVER

BACKGROUND

We developed a nonviral gene transfer method using rapid injection of naked DNA targeting the liver and applied it in a rat model of liver transplantation.

METHODS

Inbred Dark Agouti and Lewis rats were used. To test the efficacy and adverse effects of systemic or local (catheter-based) injection, different volumes of phosphate-buffered saline containing naked DNA encoding beta-galactosidase (lacZ) were injected. Luciferase expression was followed by non-invasive imaging, and a cytotoxic T-lymphocyte antigen 4-immunoglobulin (CTLA4Ig) protein was tested functionally by allogenic heart transplantation. Gene transfer was then tested in rat auxiliary liver transplantation (ALT) and orthotopic liver transplantation (OLT). The timing of gene transfer was evaluated in the auxiliary liver transplantation model, and OLT was performed using a liver graft to which luciferase or the CTLA4Ig gene was transferred 2 days before.

RESULTS

LacZ was expressed extensively in a volume-dependent manner; however, a large volume often induced recipient death. After local delivery of CTLA4Ig cDNA to the liver, survival of Dark Agouti heart grafts lengthened with increased CTLA4Ig serum levels. Liver grafts injected with naked DNA at the time of donation did not survive, but livers grafted 2 days after gene transfer survived. Successful expression of luciferase and production of CTLA4Ig were finally confirmed in the rat that underwent OLT.

CONCLUSIONS

We successfully applied a nonviral hydrodynamic gene transfer method to the rat liver and showed its potential in liver grafting. The high incidence of graft failure when this procedure is performed on the day of organ donation is a potential limitation that needs to be overcome in clinical application.

Interleukin-12 genetic administration suppressed metastatic liver tumor unsusceptible to CTL

A cytokine gene therapy approach was conducted against metastatic lesions of cytotoxic T lymphocyte (CTL)-unsusceptible tumor in mice. The EBV-based and conventional plasmid vectors that encode murine interleukin-12 (IL-12) gene (pGEG.mIL-12 and pG.mIL-12, respectively) were intravenously transfected into the mice that had received a subcutaneous inoculation of M5076 sarcoma cells. The pGEG.mIL-12 transfection drastically suppressed the subcutaneous as well as hepatic metastatic tumors, resulting in significant prolongation of survival period of the animals. Although single administration with pG.mIL-12 was not effective, repetitive transfection with the plasmid significantly prolonged the longevity of the mice-bearing the metastatic liver tumors. Multiple transfection with either pGEG.mIL-12 or pG.mIL-12 also suppressed peritoneal carcinomatosis in mice that had been injected with M5076 cells into the peritoneal cavity. It was suggested that a high level IL-12 production elicited by the intravenous delivery of the cytokine gene may be quite effective in inhibiting metastatic and CTL-unsusceptible neoplasms.

Hydrodynamics-based transfer of PCR-amplified DNA fragments into rat liver

A high level of plasmid DNA expression in rat liver can be achieved by the rapid injection of a large volume of a naked DNA solution into the tail vein, called the 'hydrodynamics-based procedure.' The preparation of PCR-amplified DNA fragments is easier than that of naked DNA. In this paper we evaluated the effects of expressing the erythropoietin (Epo) gene in the rat liver by injecting fCAGGS-Epo, an Epo-expressing PCR-amplified DNA fragment, via the tail vein. After injection of 5 pmol fCAGGS-Epo (10 microg) or pCAGGS-Epo (18.4 microg), plasmid DNA, the serum Epo levels peaked at week 1, then persisted for at least 12 weeks. Transgene-derived Epo secretion resulted in significant erythropoiesis. These results demonstrated that transfer of PCR-amplified DNA fragments into the rat liver via rapid tail vein injection can be achieved. This method may provide a useful means for studying the physiologic function of a putative gene.

The role of inducible nitric oxide synthase in a murine acute hepatitis B virus (HBV) infection model induced by hydrodynamics-based in vivo transfection of HBV-DNA

BACKGROUND/AIMS

Inducible nitric oxide synthase (iNOS) is found to have antiviral activity. Its role is evaluated using a murine acute hepatitis B virus (HBV) infection model.

METHODS

pHBV3.6 plasmid containing HBV genome was injected into mice by hydrodynamics-based in vivo transfection. HBV antigenemia and serum HBV-DNA were detected by enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction, respectively. HBV replication in liver was analyzed by Northern and Southern blot. Intrahepatic leukocytes were isolated and analyzed with flow cytometry.

RESULTS

After hydrodynamics injection of pHBV3.6, HBV genome was synthesized in the liver and HBV-DNA, as well as hepatitis B surface antigen and hepatitis B e antigen were secreted into the blood. Anti-HBV antibody responses developed afterward. A murine acute HBV infection model was established with hydrodynamics injection of non-transponase based HBV-DNA. Using this protocol in iNOS deficient or wild type B6 mice, the level of HBV transcript, replicative intermediate, and antigenemia were higher in iNOS(-/-) than in B6 mice. The intrahepatic leukocytes in iNOS(-/-) mice were also affected after transfection.

CONCLUSIONS

Our data suggests that the iNOS expression not only affects the HBV clearance, but also modulates the infiltrating leukocytes response to HBV antigens.

Hydrodynamic delivery of DNA

Hydrodynamic delivery is an efficient and inexpensive procedure to deliver a wide range of nucleic acids to hepatic tissues and other organs in vivo. The successful application of hydrodynamic delivery is dependent on the rapid injection of a large aqueous volume containing DNA, RNA or other molecules into the vasculature of the liver. In this review, the development of the procedures for hydrodynamic delivery will be described and the parameters necessary for attaining maximal gene expression will be highlighted. A review of the mechanisms for transfecting hepatocytes, as well as potential uses of this approach in various research and clinical applications, will also be discussed.

Long-term therapeutic levels of human alpha-1 antitrypsin in plasma after hydrodynamic injection of nonviral DNA

The transfection efficacy of several vectors containing the full genomic hAAT gene with its natural promoter (pTG7101) and others containing the cDNA of hAAT gene driven by cytomegalovirus immediate-early promoter or the 0.5 kb upstream of hAAT gene sequence has been studied by hydrodynamic tail-vein injection (20 microg/mouse). pTG7101 (but not the other plasmids) results in therapeutic and stable concentration of hAAT in plasma. A dose-response study with this plasmid (0.3-320 microg/mouse) confirms that hAAT remains long-term stable in plasma, with therapeutic concentrations of hAAT (>0.9 mg/ml). The parameters of the dose-response curve were: R: 0.98, E(max) 3449.0+/- 279.7 microg/ml and EC(50) 1.2 x 10(12) plasmid-gene units. In addition, 4 months after transfection, the intrinsic efficacy of transgenic expression (amount of RNA/DNA) in mouse liver was 50-80% that normally expressed by the mouse gene. The important efficacy of nonviral genomic DNA opens a new avenue in the safety applications of human gene therapy.

Reproductive tract gene transfer

OBJECTIVE

Gene therapy is a rapidly evolving novel treatment for human disease. This review discusses the latest development in gene transfer technology and its potential use in the female reproductive tract.

METHODS

A comprehensive search using the MEDLINE database was performed to review current, innovative trends in gene transfer technology. In addition, articles on reproductive tract gene transfer were reviewed.

CONCLUSION(S)

Recent developments, such as the Human Genome Project, have generated great interest in the genetic basis of human health and disease. Gene therapy is a rapidly evolving field that uses gene transfer to treat disease. Ongoing research in the field focuses on improving vector technology to enable efficient in vivo gene transfer. Although multiple techniques for gene transfer have been described, no single technique can be used in all instances. The human female reproductive tract is easily accessible and can be readily transfected. In vivo gene transfer has resulted in successful alteration of implantation rates and has demonstrated potential for use in treatment of ovarian cancer.