Increased level and duration of expression in muscle by co-expression of a transactivator using plasmid systems

CORP: Gene delivery into murine skeletal muscle using in vivo electroporation

The strategy of gene delivery into skeletal muscles has provided exciting avenues in identifying new potential therapeutics towards muscular disorders and addressing basic research questions in muscle physiology through overexpression and knockdown studies. In vivo electroporation methodology offers a simple, rapidly effective technique for the delivery of plasmid DNA into post-mitotic skeletal muscle fibers and the ability to easily explore the molecular mechanisms of skeletal muscle plasticity. The purpose of this review is to describe how to robustly electroporate plasmid DNA into different hindlimb muscles of rodent models. Further, key parameters (e.g., voltage, hyaluronidase, plasmid concentration) which contribute to the successful introduction of plasmid DNA into skeletal muscle fibers will be discussed. In addition, details on processing tissue for immunohistochemistry and fiber cross-sectional area (CSA) analysis will be outlined. The overall goal of this review is to provide the basic and necessary information needed for successful implementation of in vivo electroporation of plasmid DNA and thus open new avenues of discovery research in skeletal muscle physiology.

Scaling-up recombinant plasmid DNA for clinical trial: current concern, solution and status

Gene therapy and vaccines are rapidly developing field in which recombinant nucleic acids are introduced in mammalian cells for enhancement, restoration, initiation or silencing biochemical function. Beside simplicity in manipulation and rapid manufacture process, plasmid DNA-based vaccines have inherent features that make them promising vaccine candidates in a variety of diseases. This present review focuses on the safety concern of the genetic elements of plasmid such as propagation and expression units as well as their host genome for the production of recombinant plasmid DNA. The highlighted issues will be beneficial in characterizing and manufacturing plasmid DNA for save clinical use. Manipulation of regulatory units of plasmid will have impact towards addressing the safety concerns raised in human vaccine applications. The gene revolution with plasmid DNA by alteration of their plasmid and production host genetics will be promising for safe delivery and obtaining efficient outcomes.

Polymeric nanoparticles containing conjugated phospholipase A2 for nonviral gene delivery

Polyethylenimine (PEI) was conjugated to phospholipase A(2) (PLA(2)) in an effort to improve transfection efficiency. PLA(2) was conjugated to PEI using EDC as a coupling reagent. The activity of enzyme in the conjugate was measured. DNA condensation ability of the conjugate to polymer was determined. The resultant nanoparticles were characterized by dynamic and electrophoretic light scattering. Two reporter genes were used to evaluate transfection efficiency in human embryonic kidney (HEK293) and human hepatoma (HepG2) cell lines. Conjugate was shown to retain PLA(2) activity and its ability to condense plasmid DNA, resulting in nanoparticles of a similar size to native PEI. The results demonstrated at N/P ratios of 15 and 20 showed 13- and 8-fold increase in transfection efficiency, respectively, compared to the maximum transfection efficiency of PEI (N/P ratio of 5) in the whole range of N/P ratios tested, from 5 to 60 in HepG2 cells. Toxicity studies in HepG2 cells showed uncomplexed conjugate had similar toxicity as PEI, and when complexed with DNA the conjugate had a significantly reduced toxicity. The results clearly indicate the potential for this approach to improve efficiencies of nonviral gene delivery vectors.

Cre-loxP system as a versatile tool for conferring increased levels of tissue-specific gene expression from a weak promoter

Attempts to image reporter gene expression driven by weak promoters are often hampered by the poor transcriptional activity of such promoters. Most tissue-specific promoters are weak compared with stronger but constitutively expressing viral promoters. In this study, we validated methods of enhancing the transcriptional activity of weak promoters using a Cre-loxP system in vitro and in vivo. We constructed a tester vector, pCTL, which carries a strong systemic cytomegalovirus enhancer/chicken beta-actin promoter (CAG), loxP-flanked CAT, and firefly luciferase (luc) cDNAs. Herpes simplex virus-thymidine kinase (HSV-tk) promoter was used as a weak and systemic promoter and ligated to Cre for construction of pTC. Luc activity was higher (about 10-fold enhancement) in co-transfected (with pCTL and pTC) than in singly (with HSV-tk promoter-driven luc expression vector pTL) transfected NIH3T3 cells. In vivo electroporation-mediated gene delivery of both pCTL and pTC into murine oviductal epithelium yielded results (about 16-fold enhancement) similar to those obtained with in vitro-transfected NIH3T3 cells. To evaluate tissue-specific enhancement of gene expression, podocyte (glomerular visceral epithelial cell)-specific nephrin promoter was ligated to the Cre gene or luc cDNA to create pNC and pNL, respectively. We achieved 2.4-fold improvement of luc gene expression in the mouse kidney in vivo when pCTL and pNC were co-transfected via the tail vein via the lipoplex method. The combination of a weak tissue-specific promoter with the Cre-loxP system could thus be used to enhance the strength of tissue-specific promoters in vitro and in vivo.

Development of peptide-targeted lipoplexes to CXCR4-expressing rat glioma cells and rat proliferating endothelial cells

A peptide analog, 4-fluorobenzoyl-RR-(L-3-(2-naphthyl)alanine)-CYEK-(L-citrulline)-PYR-(L-citrulline)-CR, covalently linked to a phospholipid, was used for targeting a lipid-based gene delivery vehicle to CXCR4(+)-cells. Characterization of transfection activity was done in vitro using a transformed rat glioma cell line (RG2) that expresses CXCR4. The substitution of the targeting lipid at increasing mole percentages in the place of helper lipids yielded a progressive increase in reporter gene expression, reaching a maximum of 2.5 times the control value at 20 mol% of ligand. The substitution of helper lipids with cysteine-derivatized phospholipid analog or phosphatidylethanolamine resulted in a progressive decrease in transfection activity, with complete inactivation of the complex occurring at 20 mol%. A DNA dose-response with 10 mol% of lipopeptide reduced the effective DNA dose at least fivefold with regard to the number of transfected cells and >20-fold with regard to the amount of gene expression. Gene transfer to rat endothelial cells was studied in the context of an arterial organ culture. Mesenteric arteries were cannulated and maintained in culture for up to 4 days. CXCR4 cell-surface expression on endothelial cells was induced after overnight incubation with vascular endothelial growth factor (VEGF). Gene transfer studies showed that only the peptide-targeted lipoplexes transfected the endothelium, and only after CXCR4 had been induced with VEGF. These results demonstrate that non-viral transfection complexes can be targeted to cells expressing CXCR4, and that gene transfer is dependent upon cell surface receptor expression levels.

Gene therapy with anabolic growth factors to prevent muscle atrophy

PURPOSE OF REVIEW

Many situations cause muscle atrophy. When severe, muscle atrophy is associated with an increase in morbidity and mortality. This loss of muscle mass is thought to be due to an imbalance between catabolic and anabolic pathways, resulting in an increase of muscle protein proteolysis and in a decrease in protein synthesis. Changes in muscle levels of muscle growth factors are thought to play a major role in this imbalance. Despite recent better understanding of the metabolic and molecular derangements leading to muscle wasting, therapy of muscle atrophy still has a poor success rate.

RECENT FINDINGS

The recent demonstration that changes in local growth factors, such as insulin-like growth factor-I and myostatin, occur during muscle atrophy has stimulated research interest to prevent muscle mass loss by delivering these growth factors or their inhibitors into the muscle. During the last few years, several advances in the field of muscle gene transfer, using electroporation or recombinant adeno-associated viral vectors, have opened novel therapeutic ways to deliver growth factors able to counteract the loss of muscle mass.

SUMMARY

Preventing decrease of insulin-like growth factor-I muscle, or inhibiting myostatin action by local genes over-expression, may provide a clinically relevant avenue for the preservation, attenuation or reversal of disease-related muscle loss.

Postmitotic nuclear retention of episomal plasmids is altered by DNA labeling and detection methods

One often overlooked aspect of nonviral gene therapy is the maintenance and localization of plasmids within a transfected cell. In this study we have quantified the nuclear retention of plasmids within microinjected cells after a single round of cell division. We employed several commercially available reagents to label plasmids with fluorophores for our microinjection tracking experiments. Interestingly, plasmids labeled with different techniques produced drastically different results. Naked plasmids microinjected directly into nuclei and later detected by in situ hybridization were found almost exclusively within the nuclei of the daughter cells after mitosis and were partitioned between the daughter nuclei with a normal, Gaussian distribution. Identical results were obtained with plasmids labeled with a fluorescent peptide nucleic acid. However, when plasmids were labeled with several commercially available fluorescent DNA labeling kits that randomly attach fluorophores to the entire plasmid and injected into HeLa cell nuclei, the modified plasmids were excluded from daughter nuclei after cell division. Taken together, these results suggest that naked, unmodified plasmids are retained in the nucleus following cell division and likely continue to express in the daughter cells. Our results demonstrate the significant alterations in episome localization that the labeling technique itself can have on plasmid trafficking.

Ghrelin and truncated ghrelin variant plasmid vectors administration into skeletal muscle augments long-term growth in rats

Ghrelin is an acylated peptide recently identified as an endogenous ligand for the growth hormone (GH) secretagogues (GHSs) receptor (GHS-R) and is involved in a novel system for regulating GH release. To study the biological activities of ghrelin using plasmid vector administration, we constructed myogenic expression vectors containing the full length cDNA of swine ghrelin-28 (pGEM-wt-sGhln) and truncated variant (pGEM-tmt-sGhln) consisting of the first seven residues of ghrelin (including Ser3 substituted with Trp3) with addition of a basic amino acid, Lys (K) at the C-terminus. After intramuscular injection of pGEM-wt-sGhln and pGEM-tmt-sGhln, RT-PCR analysis demonstrated that the ectopic expressions of ghrelin and its variant were observed 30 days post-injection. The level of GH increased in rat serum, and was significantly higher than that of the control group 20 days post-injection with pGEM-tmt-sGhln (P < 0.05). Administration of 150 microg of pGEM-wt-sGhln and pGEM-tmt-sGhln enhanced growth in rats over 30 days and great stimulatory responses were observed at day 10 and 20 post-injection respectively, whose body weight gains were on average 15% (P < 0.05) and 21% P < 0.033 significantly heavier than controls. These results suggested that skeletal muscle might have the potential to perform post-translational acylation for ghrelin, and short ghrelin variant might have the biological effects as wild type ghrelin.

Preferential expression of hPGFS in primary SCCHN and tumour cell lines derived from respiratory and digestive organs

Identifying overexpressed genes in tumours is a critical step for tumour diagnosis, prognosis, and treatment. Using differential display polymerase chain reaction, sequence analysis, and gene Blast searches, we discovered that human prostaglandin F synthase (hPGFS) was upregulated in squamous cell carcinoma of the head and neck (SCCHN). Northern blot analysis indicated that up to a 16-fold increase in the level of hPGFS expression was detected in 40.5% (15 out of 37) of SCCHN primary tumours. The increased expression of hPGFS in SCCHN was primarily detected in SCC of larynx and hypopharynx (59%, P<0.05). Using the same primary tissue samples, increased levels of epidermal growth factor receptor (EGFR) expression were detected in only 32% of tumour tissues, suggesting hPGFS may have the potential to become a drug target or molecular marker for SCCHN. To determine if the increased level of hPGFS expression came from tumour cells, we determined the level of hPGFS expression in SCCHN tumour cell lines. A high level of hPGFS expression was detected in four out of five tumour SCCHN cell lines. To determine if upregulation of hPGFS is SCCHN-specific, hPGFS expression was analysed in 59 tumour cell lines derived from different types of tumours. The expression of hPGFS was increased from two- to 500-fold in a large portion of cell lines derived from lung (five out of nine), colon (five out of seven) as well as head and neck cancer (four out of five). These data link hPGFS expression to tumours located in the respiratory and digestive organs.

Non-viral gene delivery in skeletal muscle: a protein factory

Ever since the publication of the first reports in 1990 using skeletal muscle as a direct target for expressing foreign transgenes, an avalanche of papers has identified a variety of proteins that can be synthesized and correctly processed by skeletal muscle. The impetus to the development of such applications is not only amelioration of muscle diseases, but also a range of therapeutic applications, from immunization to delivery of therapeutic proteins, such as clotting factors and hormones. Although the most efficient way of introducing transgenes into muscle fibres has been by a variety of recombinant viral vectors, there are potential benefits in the use of non-viral vectors. In this review we assess the recent advances in construction and delivery of naked plasmid DNA to skeletal muscle and highlight the options available for further improvements to raise efficiency to therapeutic levels.

Regression of tumors by IFN-alpha electroporation gene therapy and analysis of the responsible genes by cDNA array

The key to success with nonviral gene therapy as a treatment for cancer is to discover effective therapeutic genes and gene delivery methods and to understand how tumors are eradicated. We discovered that electroporation of IFN-alpha DNA into tumors in the SCCVII tumor-bearing mice led to tumor eradication in 50% of the mice and a more than two-fold increase in survival time when compared with controls (P = 0.0012). Analyses using cDNA array and Northern blot indicated that the genes responsible for the therapeutic effect of electro-IFN-alpha gene therapy included IRF-7, Granzyme A, Granzyme C, Gjb2, Krt14, Mig, IP-10 and MCP3. Because most of these genes have been known to either inhibit angiogenesis (Mig, IP-10), inhibit tumor growth (Gjb2, MCP3), kill tumor cells (Granzyme A and C), or induce expression of antitumor gene (IRF-7), they may become promising therapeutic gene candidates for a combination gene therapy approach to cancer treatment.

Muscle-specific enhancement of gene expression by incorporation of SV40 enhancer in the expression plasmid

Skeletal muscle is established as an ideal tissue for gene delivery to treat systemic diseases. However, the relatively low levels of gene expression obtained from using naturally occurring promoters, including the strong cytomegalovirus (CMV) enhancer/promoter (E/P), have limited the use of muscle as a target tissue. The relatively weak simian virus 40 (SV40) enhancer is known to have dual functions promoting localization of DNA to the nucleus and activating transcription. An SV40 enhancer incorporated either at the 5' end of CMV E/P or the 3' end of the polyadenylation site gave as much as a 20-fold increase in the level of exogenous gene expression in muscle in vivo, compared with expression observed with CMV E/P alone. The minimum requirement for this enhancement is a single copy of a 72-bp element of the SV40 enhancer, in combination with either the CMV E/P or skeletal actin (SkA) promoter. Enhancement of gene expression in muscle by this SV40 enhancer was also observed by using the powerful electroporation delivery. However, the SV40 enhancer does not increase the level of CMV E/P driven reporter gene expression in dividing tumor cells in vivo and in the dividing myoblast cell C2C12 in vitro. The data suggest that including this enhancer in the plasmid will enhance the level of gene production for muscle-based gene therapy.

Gene therapy and molecular approaches to the treatment of hereditary muscular disorders

Gene therapy for inherited muscle disease is an active area of research and development. Initial emphasis has been on gene replacement but alternative approaches are increasingly being considered in order to overcome difficulties, such as the immune rejection of transduced cells, the need for appropriate and tissue-specific control of expression, and the requirement for systemic spread in some conditions. However, the most significant obstacles to the clinical success of gene therapy are still the lack of efficiency and accuracy of gene medicine delivery.