High-efficiency adenovirus-mediated in vivo gene transfer into neonatal and adult rodent skeletal muscle

PPARβ/δ Agonism Upregulates Forkhead Box A2 to Reduce Inflammation in C2C12 Myoblasts and in Skeletal Muscle

Daily activities expose muscles to innumerable impacts, causing accumulated tissue damage and inflammation that impairs muscle recovery and function, yet the mechanism modulating the inflammatory response in muscles remains unclear. Our study suggests that Forkhead box A2 (FoxA2), a pioneer transcription factor, has a predominant role in the inflammatory response during skeletal muscle injury. FoxA2 expression in skeletal muscle is upregulated by fatty acids and peroxisome proliferator-activated receptors (PPARs) but is refractory to insulin and glucocorticoids. Using PPARβ/δ agonist GW501516 upregulates FoxA2, which in turn, attenuates the production of proinflammatory cytokines and reduces the infiltration of CD45+ immune cells in two mouse models of muscle inflammation, systemic LPS and intramuscular injection of carrageenan, which mimic localized exercise-induced inflammation. This reduced local inflammatory response limits tissue damage and restores muscle tetanic contraction. In line with these results, a deficiency in either PPARβ/δ or FoxA2 diminishes the action of the PPARβ/δ agonist GW501516 to suppress an aggravated inflammatory response. Our study suggests that FoxA2 in skeletal muscle helps maintain homeostasis, acting as a gatekeeper to maintain key inflammation parameters at the desired level upon injury. Therefore, it is conceivable that certain myositis disorders or other forms of painful musculoskeletal diseases may benefit from approaches that increase FoxA2 activity in skeletal muscle.

Synthesis and evaluation of L-arabinose-based cationic glycolipids as effective vectors for pDNA and siRNA in vitro

Glycolipids might become a new type of promising non-viral gene delivery systems because of their low cytotoxicity, structural diversity, controllable aqua- and lipo-solubility, appropriate density and distribution of positive charges, high transfer efficiency and potential targeting function. In this study, four kinds of L-arabinose-based cationic glycolipids (Ara-DiC12MA, Ara-DiC14MA, Ara-DiC16MA and Ara-DiC18MA) containing quaternary ammonium as hydrophilic headgroup and two alkane chains as hydrophobic domain were synthesized and characterized. They were observed to have strong affinities for plasmid DNA (pDNA) and siRNA, the pDNA can be completely condensed at N/P ratio less than 2, and the siRNA can be completely retarded at N/P ratio less than 3. The dynamic light scattering (DLS) experiment and atomic force microscopy (AFM) experiment demonstrated that cationic lipids and their lipoplexes possessed suitable particle sizes with near-spherical shape and proper ζ-potentials for cell transfection. The Ara-DiC16MA liposome was found to have good transfection efficacy in HEK293, PC-3 and Mat cells compared with other three kinds of liposomes, and also maintain low cytotoxicity and better uptake capability in vitro. Furthermore, the gene silencing assay showed that Ara-DiC14MA and Ara-DiC16MA liposomes have demonstrated effective delivery and higher gene knockdown activity (>80%) in the above mentioned cells than Lipofectamine 2000. These results indicated Ara-DiC16MA can be developed for efficient and low toxic gene delivery.

Preparation, Physicochemical Properties, and Transfection Activities of Tartaric Acid-Based Cationic Lipids as Effective Nonviral Gene Delivery Vectors

In this work two novel cationic lipids using natural tartaric acid as linking backbone were synthesized. These cationic lipids were simply constructed by tartaric acid backbone using head group 6-aminocaproic acid and saturated hydrocarbon chains dodecanol (T-C12-AH) or hexadecanol (T-C16-AH). The physicochemical properties, gel electrophoresis, transfection activities, and cytotoxicity of cationic liposomes were tested. The optimum formulation for T-C12-AH and T-C16-AH was at cationic lipid/dioleoylphosphatidylethanolamine (DOPE) molar ratio of 1 : 0.5 and 1 : 2, respectively, and N/P charge molar ratio of 1 : 1 and 1 : 1, respectively. Under optimized conditions, T-C12-AH and T-C16-AH showed effective gene transfection capabilities, superior or comparable to that of commercially available transfecting reagent 3β-[N-(N',N'-dimethylaminoethyl)carbamoyl]cholesterol (DC-Chol) and N-[2,3-dioleoyloxypropyl]-N,N,N-trimethylammonium chloride (DOTAP). The results demonstrated that the two novel tartaric acid-based cationic lipids exhibited low toxicity and efficient transfection performance, offering an excellent prospect as nonviral vectors for gene delivery.

Magnetofection Enhances Adenoviral Vector-based Gene Delivery in Skeletal Muscle Cells

The goal of magnetic field-assisted gene transfer is to enhance internalization of exogenous nucleic acids by association with magnetic nanoparticles (MNPs). This technique named magnetofection is particularly useful in difficult-to-transfect cells. It is well known that human, mouse, and rat skeletal muscle cells suffer a maturation-dependent loss of susceptibility to Recombinant Adenoviral vector (RAd) uptake. In postnatal, fully differentiated myofibers, the expression of the primary Coxsackie and Adenoviral membrane receptor (CAR) is severely downregulated representing a main hurdle for the use of these vectors in gene transfer/therapy. Here we demonstrate that assembling of Recombinant Adenoviral vectors with suitable iron oxide MNPs into magneto-adenovectors (RAd-MNP) and further exposure to a gradient magnetic field enables to efficiently overcome transduction resistance in skeletal muscle cells. Expression of Green Fluorescent Protein and Insulin-like Growth Factor 1 was significantly enhanced after magnetofection with RAd-MNPs complexes in C2C12 myotubes in vitro and mouse skeletal muscle in vivo when compared to transduction with naked virus. These results provide evidence that magnetofection, mainly due to its membrane-receptor independent mechanism, constitutes a simple and effective alternative to current methods for gene transfer into traditionally hard-to-transfect biological models.

A new role for sterol regulatory element binding protein 1 transcription factors in the regulation of muscle mass and muscle cell differentiation

The role of the transcription factors sterol regulatory element binding protein 1a (SREBP-1a) and SREBP-1c in the regulation of cholesterol and fatty acid metabolism has been well studied; however, little is known about their specific function in muscle. In the present study, analysis of recent microarray data from muscle cells overexpressing SREBP1 suggested that they may play a role in the regulation of myogenesis. We then demonstrated that SREBP-1a and -1c inhibit myoblast-to-myotube differentiation and also induce in vivo and in vitro muscle atrophy. Furthermore, we have identified the transcriptional repressors BHLHB2 and BHLHB3 as mediators of these effects of SREBP-1a and -1c in muscle. Both repressors are SREBP-1 target genes, and they affect the expression of numerous genes involved in the myogenic program. Our findings identify a new role for SREBP-1 transcription factors in muscle, thus linking the control of muscle mass to metabolic pathways.

PEG-conjugated PAMAM dendrimers mediate efficient intramuscular gene expression

Generations 5 and 6 (G5 and G6) poly(amidoamine) (PAMAM) dendrimers have been shown to be highly efficient nonviral carriers in in vitro gene delivery. However, their high toxicity and unsatisfied in vivo efficacy limit their applications. In this study, to improve their characteristics as gene delivery carriers, polyethylene glycol (PEG, molecular weight 5,000) was conjugated to G5 and G6 PAMAM dendrimers (PEG-PAMAM) at three different molar ratios of 4%, 8%, and 15% (PEG to surface amine per PAMAM dendrimer molecular). Compared with unconjugated PAMAM dendrimers, PEG conjugation significantly decreased the in vitro and in vivo cytotoxicities and hemolysis of G5 and G6 dendrimers, especially at higher PEG molar ratios. Among all of the PEG-PAMAM dendrimers, 8% PEG-conjugated G5 and G6 dendrimers (G5-8% PEG, G6-8% PEG) resulted in the most efficient muscular gene expression when polyplexes were injected intramuscularly to the quadriceps of neonatal mice. Consistent with the in vivo results, these two 8% PEG-conjugated PAMAM dendrimers could also mediate the highest in vitro transfection in 293A cells. Therefore, G5-8% PEG and G6-8% PEG possess a great potential for gene delivery both in vivo and in vitro.

Robust in vivo transduction of a genetically stable Epstein-Barr virus episome to hepatocytes in mice by a hybrid viral vector

To make a safe, long-lasting gene delivery vehicle, we developed a hybrid vector that leverages the relative strengths of adenovirus and Epstein-Barr virus (EBV). A fully gene-deleted helper-dependent adenovirus (HDAd) is used as the delivery vehicle for its scalability and high transduction efficiency. Upon delivery, a portion of the HDAd vector is recombined to form a circular plasmid. This episome includes two elements from EBV: an EBV nuclear antigen 1 (EBNA1) expression cassette and an EBNA1 binding region. Along with a human replication origin, these elements provide considerable genetic stability to the episome in replicating cells while avoiding insertional mutagenesis. Here, we demonstrate that this hybrid approach is highly efficient at delivering EBV episomes to target cells in vivo. We achieved nearly 100% transduction of hepatocytes after a single intravenous injection in mice. This is a substantial improvement over the transduction efficiency of previously available physical and viral methods. Bioluminescent imaging of vector-transduced mice demonstrated that luciferase transgene expression from the hybrid was robust and compared well to a traditional HDAd vector. Quantitative PCR analysis confirmed that the EBV episome was stable at approximately 30 copies per cell for up to 50 weeks and that it remained circular and extrachromosomal. Approaches for adapting the HDAd-EBV hybrid to a variety of disease targets and the potential benefits of this approach are discussed.

Imaging of human sodium-iodide symporter gene expression mediated by recombinant adenovirus in skeletal muscle of living rats

PURPOSE

We evaluated the feasibility of non-invasive imaging of recombinant adenovirus-mediated human sodium-iodide symporter (hNIS) gene expression by (99m)TcO(4)(-) scintigraphy in skeletal muscle of rats.

METHODS

Replication-defective recombinant adenovirus encoding hNIS gene [Rad-CMV-hNIS 5x10(7), 2x10(8) or 1x10(9) plaque forming units (pfu)] or beta-galactosidase gene (Rad-CMV-LacZ 1x10(9) pfu) was injected into the right biceps femoris muscle of rats ( n=5-6 for each group). Three days after gene transfer, scintigraphy was performed using a gamma camera 30 min after injection of (99m)TcO(4)(-) (1.85 MBq). An additional two rats injected with 1x10(9) pfu of Rad-CMV-hNIS underwent (99m)TcO(4)(-) scintigraphy with sodium perchlorate. After the imaging studies, rats were sacrificed for assessment of the biodistribution of (99m)TcO(4)(-) and measurement of hNIS mRNA expression.

RESULTS

In all the rats injected with 1x10(9) pfu of Rad-CMV-hNIS, hNIS expression was successfully imaged by (99m)TcO(4)(-) scintigraphy, while rats injected with Rad-CMV-LacZ or lower doses of Rad-CMV-hNIS failed to show uptake. The biodistribution studies indicated that a significantly different amount of (99m)TcO(4)(-) was retained in the liver ( p<0.001) and the right muscle ( p<0.05), with the highest uptake in rats injected with 1x10(9) pfu of Rad-CMV-hNIS. The muscular hNIS mRNA level quantified by real-time reverse transcription-polymerase chain reaction was significantly higher in rats injected with 1x10(9) pfu of Rad-CMV-hNIS ( p<0.05), with a positive correlation with the imaging counts ( r=0.810, p<0.05) and the biodistribution ( r=0.847, p<0.001). Hot spots in rats injected with 1x10(9) pfu of Rad-CMV-hNIS were specifically inhibited by sodium perchlorate.

CONCLUSION

This study illustrated that (99m)TcO(4)(-) scintigraphy can monitor Rad-CMV-hNIS-mediated gene expression in skeletal muscle of rats, non-invasively and quantitatively.

Electrotransfer in differentiated myotubes: a novel, efficient procedure for functional gene transfer

Development of reliable techniques for experimental manipulation of gene expression in multinucleated skeletal muscle fibers is critical for understanding molecular mechanisms involved in both physiology and pathophysiology. At present, viral vectors represent the only method to obtain efficient gene transfer in terminally differentiated myotubes. Here we present an in vitro procedure that relies on the application of a pulsed electric field for transferring naked DNA into differentiated myotubes seeded on coverslips. Compared with standard transfection methods, electroporation was at least 1000 times more efficient, as judged by quantitative determination of luciferase content. Percentage of transfected myotubes averaged around 45%. Moreover, we were successful in transfecting a dominant-negative ADP ribosylation factor 1 (ARF1) mutant, i.e., ARF1N126I, in myotubes, thus interfering with endoplasmic reticulum-Golgi traffic, as indicated by alterations of subcellular distribution of GM130, a cis/medial-Golgi marker. Co-transfection experiments with beta-galactosidase also showed that the ARF1 mutant appeared to inhibit myoblast fusion and could not be used before myotube formation. The present work validates the use of electroporation as a highly efficient approach for gene transfer in fully differentiated myotubes.