Analysis of differential lipofection efficiency in primary and established myoblasts

Polylysine for skin regeneration: A review of recent advances and future perspectives

There have been several attempts to find promising biomaterials for skin regeneration, among which polylysine (a homopolypeptide) has shown benefits in the regeneration and treatment of skin disorders. This class of biomaterials has shown exceptional abilities due to their macromolecular structure. Polylysine-based biomaterials can be used as tissue engineering scaffolds for skin regeneration, and as drug carriers or even gene delivery vectors for the treatment of skin diseases. In addition, polylysine can play a preservative role in extending the lifetime of skin tissue by minimizing the appearance of photodamaged skin. Research on polylysine is growing today, opening new scenarios that expand the potential of these biomaterials from traditional treatments to a new era of tissue regeneration. This review aims to address the basic concepts, recent trends, and prospects of polylysine-based biomaterials for skin regeneration. Undoubtedly, this class of biomaterials needs further evaluations and explorations, and many critical questions have yet to be answered.

Improved CRISPR/Cas9 gene editing in primary human myoblasts using low confluency cultures on Matrigel

Background

CRISPR/Cas9 is an invaluable tool for studying cell biology and the development of molecular therapies. However, delivery of CRISPR/Cas9 components into some cell types remains a major hurdle. Primary human myoblasts are a valuable cell model for muscle studies, but are notoriously difficult to transfect. There are currently no commercial lipofection protocols tailored for primary myoblasts, and most generic guidelines simply recommend transfecting healthy cells at high confluency. This study aimed to maximize CRISPR/Cas9 transfection and editing in primary human myoblasts.

Methods

Since increased cell proliferation is associated with increased transfection efficiency, we investigated two factors known to influence myoblast proliferation: cell confluency, and a basement membrane matrix, Matrigel. CRISPR/Cas9 editing was performed by delivering Cas9 ribonucleoprotein complexes via lipofection into primary human myoblasts, cultured in wells with or without a Matrigel coating, at low (~ 40%) or high (~ 80%) confluency.

Results

Cells transfected at low confluency on Matrigel-coated wells had the highest levels of transfection, and were most effectively edited across three different target loci, achieving a maximum editing efficiency of 93.8%. On average, editing under these conditions was >4-fold higher compared to commercial recommendations (high confluency, uncoated wells).

Conclusion

This study presents a simple, effective and economical method of maximizing CRISPR/Cas9-mediated gene editing in primary human myoblasts. This protocol could be a valuable tool for improving the genetic manipulation of cultured human skeletal muscle cells, and potentially be adapted for use in other cell types.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13395-021-00278-1.

Gene transfer to skeletal muscle using hydrodynamic limb vein injection: current applications, hurdles and possible optimizations

Hydrodynamic limb vein injection is an in vivo locoregional gene delivery method. It consists of administrating a large volume of solution containing nucleic acid constructs in a limb with both blood inflow and outflow temporarily blocked using a tourniquet. The fast, high pressure delivery allows the musculature of the whole limb to be reached. The skeletal muscle is a tissue of choice for a variety of gene transfer applications, including gene therapy for Duchenne muscular dystrophy or other myopathies, as well as for the production of antibodies or other proteins with broad therapeutic effects. Hydrodynamic limb vein delivery has been evaluated with success in a large range of animal models. It has also proven to be safe and well-tolerated in muscular dystrophy patients, thus supporting its translation to the clinic. However, some possible limitations may occur at different steps of the delivery process. Here, we have highlighted the interests, bottlenecks and potential improvements that could further optimize non-viral gene transfer following hydrodynamic limb vein injection.

Uptake and intracellular distribution of different types of nanoparticles in primary human myoblasts and myotubes

The use of nanoparticles as drug carriers in the field of skeletal muscle diseases has been poorly addressed and the interaction of nanoparticles with skeletal muscle cells has been investigated almost exclusively on C2C12 murine myoblasts. In this study we investigated the effects poly(lactide-co-glycolide) nanoparticles, mesoporous silica nanoparticles and liposomes, on the viability of primary human myoblasts and analyzed their cellular uptake and intracellular distribution in both primary human myoblasts and myotubes. Our data demonstrate that poly(lactide-co-glycolide) nanoparticles do not negatively affect myoblasts viability, contrarily to mesoporous silica nanoparticles and liposomes that induce a decrease in cell viability at the highest doses and longest incubation time. Poly(lactide-co-glycolide) nanoparticles and mesoporous silica nanoparticles are internalized by endocytosis, poly(lactide-co-glycolide) nanoparticles undergo endosomal escape whereas mesoporous silica nanoparticles always occur within vacuoles. Liposomes were rarely observed within the cells. The uptake of all tested nanoparticles was less prominent in primary human myotubes as compared to myoblasts. Our findings represent the first step toward the characterization of the interaction between nanoparticles and primary human muscle cells and suggest that poly(lactide-co-glycolide) nanoparticles might find an application for drug delivery to skeletal muscle.

A mechanistic investigation exploring the differential transfection efficiencies between the easy-to-transfect SK-BR3 and difficult-to-transfect CT26 cell lines

Background

Gold–polyamidoamine (AuPAMAM) has previously been shown to successfully transfect cells with high efficiency. However, we have observed that certain cell types are more amenable to Au–PAMAM transfection than others. Here we utilized two representative cell lines—a “difficult to transfect” CT26 cell line and an “easy to transfect” SK-BR3 cell line—and attempted to determine the underlying mechanism for differential transfection in both cell types. Using a commonly established poly-cationic polymer similar to PAMAM (polyethyleneimine, or PEI), we additionally sought to quantify the relative transfection efficiencies of each vector in CT26 and SK-BR3 cells, in the hopes of elucidating any mechanistic differences that may exist between the two transfection vectors.

Results

A comparative time course analysis of green fluorescent protein reporter-gene expression and DNA uptake was conducted to quantitatively compare PEI- and AuPAMAM-mediated transfection in CT26 and SK-BR3, while flow cytometry and confocal microscopy were used to determine the contribution of cellular uptake, endosomal escape, and cytoplasmic transport to the overall gene delivery process. Results from the time course analysis and flow cytometry studies revealed that initial complex uptake and cytoplasmic trafficking to the nucleus are likely the two main factors limiting CT26 transfectability.

Conclusions

The cell type-dependent uptake and intracellular transport mechanisms impacting gene therapy remain largely unexplored and present a major hurdle in the application-specific design and efficiency of gene delivery vectors. This systematic investigation offers insights into the intracellular mechanistic processes that may account for cell-to-cell differences, as well as vector-to-vector differences, in gene transfectability.

Electronic supplementary material

The online version of this article (doi:10.1186/s12951-017-0271-8) contains supplementary material, which is available to authorized users.

Microporation is an efficient method for siRNA-induced knockdown of PEX5 in HepG2 cells: evaluation of the transfection efficiency, the PEX5 mRNA and protein levels and induction of peroxisomal deficiency

The pathomechanism of peroxisomal biogenesis disorders (PBDs), a group of inherited autosomal recessive diseases with mutations of peroxin (PEX) genes, is not yet fully understood. Therefore, several knockout models, e.g., the PEX5 knockout mouse, have been generated exhibiting a complete loss of peroxisomal function. In this study, we wanted to knockdown PEX5 using the siRNA technology (1) to mimic milder forms of PBDs in which the mutated peroxin has some residual function and (2) to analyze the cellular consequences of a reduction of the PEX5 protein without adaption during the development as it is the case in a knockout animal. First, we tried to optimize the transfection of the hepatoma cell line HepG2 with PEX5 siRNA using different commercially available liposomal and non-liposomal transfection reagents (Lipofectamine(®) 2000, FuGENE 6, HiPerFect(®), INTERFERin™, RiboJuice™) as well as microporation using the Neon™ Transfection system. Microporation was found to be superior to the transfection reagents with respect to the transfection efficiency (100 vs. 0-70%), to the reduction of PEX5 mRNA (by 90 vs. 0-50%) and PEX5 protein levels (by 70 vs. 0-50%). Interestingly, we detected that a part of the cleaved PEX5 mRNA still existed as 3' fragment (15%) 24 h after microporation. Using microporation, we further analyzed whether the reduced PEX5 protein level impaired peroxisomal function. We indeed detected a reduced targeting of SKL-tagged proteins into peroxisomes as well as an increased oxidative stress as found in PBD patients and respective knockout mouse models. Knockdown of the PEX5 protein and functional consequences were at a maximum 48 h after microporation. Thereafter, the PEX5 protein was resynthesized, which may allow the temporal analysis of the loss as well as the reconstitution of peroxisomes in the future. In conclusion, we propose microporation as an efficient and reproducible method to transfect HepG2 cells with PEX5 siRNA. We succeeded to transiently knockdown PEX5 mRNA and its protein level leading to functional consequences similar as observed in peroxisome deficiencies.

Polyplex-induced cytosolic nuclease activation leads to differential transgene expression

Cytosolic nucleases have been proposed to play an important role in limiting the effectiveness of polyplex-based gene delivery agents. In order to explore the effect of cell membrane disruption on nuclease activation, nuclease activity upon polyplex uptake and localization, and nuclease activity upon gene expression, we employed an oligonucleotide molecular beacon (MB). The MB was incorporated as an integral part of the polymer/DNA polyplex, and two-color flow cytometry experiments were performed to explore the relationship of MB cleavage with propidium iodide (PI) uptake, protein expression, and polyplex uptake. In addition, confocal fluorescence microcopy was performed to examine both polyplex and cleaved MB localization. The impact of cell membrane disruption was also probed using whole-cell patch clamp measurement of the plasma membrane's electrical conductance. Differential activation of cytosolic nuclease was observed with substantial activity for B-PEI and G5 PAMAM dendrimer (G5), less cleavage for jetPEI, and little activity for L-PEI. jetPEI and L-PEI exhibited substantially greater transgene expression, consistent with the lower amounts of MB oligonucleotide cleavage observed. Cytosolic nuclease activity, although dependent on the choice of polymer employed, was not related to the degree of cell plasma membrane disruption that occurred as measured by PI uptake or whole-cell patch clamp.

Genetic manipulation of myoblasts and a novel primary myosatellite cell culture system: comparing and optimizing approaches

The genetic manipulation of skeletal muscle cells in vitro is notoriously difficult, especially when using undifferentiated muscle cell lines (myoblasts) or primary muscle stem cells (myosatellites). We therefore optimized methods of gene transfer by overexpressing green fluorescent protein (GFP) in mouse C2C12 cells and in a novel system, primary rainbow trout myosatellite cells. A common lipid-based transfection reagent was used (Lipofectamine 2000) along with three different viral vectors: adeno-associated virus serotype 2 (AAV2), baculovirus (BAC) and lentivirus. Maximal transfection efficiencies of 49% were obtained in C2C12 cells after optimizing cell density and reagent : DNA ratio, although the GFP signal rapidly dissipated with proliferation and was not maintained with differentiation. The transduction efficiency of AAV2 was optimized to 65% by extending incubation time and decreasing cell density, although only 30% of cells retained expression after passing. A viral comparison revealed that lentivirus was most efficient at transducing C2C12 myoblasts as 97% of cells were transduced with only 10(6) viral genomes (vg) compared to 54% with 10(8) vg AAV2 and 23% with 10(9) vg BAC. Lentivirus also transduced 90% of primary trout myosatellites compared to 1-10% with AAV2 and BAC. The phosphoglycerate kinase 1 (pgk) promoter was 10-fold more active than the cytomegalovirus immediate-early promoter in C2C12 cells and both were effective in trout myosatellites. Maximal transduction of C2C12 myotubes was achieved by differentiating myoblasts previously transduced with lentivirus and the pgk promoter. Thus, our optimized protocol proved highly effective in diverse muscle cell systems and could therefore help overcome a common technological barrier.

Inhibition of monocyte chemoattractant protein-1 prevents diaphragmatic inflammation and maintains contractile function during endotoxemia

Introduction

Respiratory muscle weakness is common in sepsis patients. Proinflammatory mediators produced during sepsis have been implicated in diaphragmatic contractile dysfunction, but the role of chemokines has not been explored. This study addressed the role of monocyte chemoattractant protein-1 (MCP-1, also known as CCL2), in the pathogenesis of diaphragmatic inflammation and weakness during endotoxemia.

Methods

Mice were treated as follows (n = 6 per group): (a) saline, (b) endotoxin (25 μg/g IP), (c) endotoxin + anti-MCP-1 antibody, and (d) endotoxin + isotype control antibody. Muscles were also exposed to recombinant MCP-1 in vivo and in vitro. Measurements were made of diaphragmatic force generation, leukocyte infiltration, and proinflammatory mediator (MCP-1, IL-1α, IL-1β, IL-6, NF-κB) expression/activity.

Results

In vivo, endotoxin-treated mice showed a large decrease in diaphragmatic force, together with upregulation of MCP-1 and other cytokines, but without an increase in intramuscular leukocytes. Antibody neutralization of MCP-1 prevented the endotoxin-induced force loss and reduced expression of MCP-1, IL-1α, IL-1β, and IL-6 in the diaphragm. MCP-1 treatment of nonseptic muscles also led to contractile weakness, and MCP-1 stimulated its own transcription independent of NF-κB activation in vitro.

Conclusions

These results suggest that MCP-1 plays an important role in the pathogenesis of diaphragmatic weakness during sepsis by both direct and indirect mechanisms. We speculate that its immunomodulatory properties and ability to modify skeletal muscle function make MCP-1 a potential therapeutic target in critically ill patients with sepsis and associated respiratory muscle weakness.

Efficient transfection of mouse-derived C2C12 myoblasts using a matrigel basement membrane matrix

Myogenic cell lines have been used widely in the study of myogenic differentiation, muscle regeneration and homeostasis, but, myoblasts and myotubes are difficult to transfect using conventional techniques. We have used liposome-based transfection method to introduce a green fluorescence protein (GFP)-expressing plasmid into Matrigel basement membrane matrix-coated C2C12 mouse myoblast cells. Myoblasts adhered and proliferated more rapidly on a Matrigel; thus, a dramatic increase in transfection efficiency can be obtained compared to Matrigel-untreated cells. Transfection efficiency was determined by counting fluorescent and total cells from six random fields for each condition. This protocol results in efficient (up to 60-70%) transfection of C2C12 myoblasts, high levels of GFP expression and low rate of cell death (10%). This technique is rapid, reliable, uses a lipid-based transfection reagent, and yields high transfection rates in a previously hard-to-transfect cell type.

Chemokine receptor and ligand upregulation in the diaphragm during endotoxemia and Pseudomonas lung infection

Sepsis-induced diaphragmatic inflammation has been associated with respiratory failure, but the role of chemokines in this process has not been evaluated. Here we sought to study the local expression and molecular regulation of the chemokines, regulated upon activation normal T cell expressed and secreted (RANTES) and macrophage inflammatory protein (MIP)-1α, in the murine diaphragm during sepsis. Constitutive expression levels of RANTES and MIP-1α, as well as their receptors, CCR1 and CCR5, were significantly higher in diaphragm than limb muscle. Sepsis was induced by acute lipopolysaccharide (LPS) delivery or subacutely by intratracheal administration of live Pseudomonas aeruginosa bacteria. Both sepsis models triggered a marked upregulation of RANTES and MIP-1α in the diaphragm. In vitro, stimulation of diaphragmatic muscle cells with LPS also led to RANTES upregulation. Inhibition of the NF-kB pathway using pharmacologic or dominant negative genetic approaches blocked the LPS-induced RANTES upregulation, while free radical scavengers had no effect. We conclude that sepsis leads to greatly increased expression of RANTES, MIP-1α and their cognate receptors in the diaphragm. Manipulation of the NF-kB pathway and other regulators of chemokine expression in the diaphragm could represent a novel method for mitigating the skeletal muscle inflammatory response associated with sepsis-induced diaphragmatic dysfunction.

Gene therapy and intracytoplasmatic sperm injection (ICSI) - a review

Human gene therapy (HGT), the treatment or prevention of disease by gene transfer is, regarded by many, as a potential revolution in medicine, because gene therapies target the causes of disease, whereas most current drugs treat the symptoms. Micro-assisted fertilization in the form of intracytoplasmatic sperm injection (ICSI) has truly revolutionized the treatment options for couples with impaired semen quality, and those with both obstructive and non-obstructive azoospermia. ICSI involves the injection of a single sperm directly into the cytoplasm of a mature egg (oocyte) using a glass needle (pipette). Fertilization with this technique occurs in 50%-80% of injected oocytes, but may damage a small percentage of them. With gene therapy, there are new and varied strategies for gene transfer and genome sequence manipulation with improved methodologies that use the technique of microinjection such as the intracytoplasmatic sperm injection-mediated transgenesis (ICSI-Tr), active transgenesis or the pronuclear microinjection technique. This review will look at these methods as well as their potential applications and limitations.

Analysis of novel nonviral gene transfer systems for gene delivery to cells of the musculoskeletal system

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

Nucleocytoplasmic transport of DNA: enhancing non-viral gene transfer

Gene therapy, the correction of dysfunctional or deleted genes by supplying the lacking component, has long been awaited as a means to permanently treat or reverse many genetic disorders. To achieve this, therapeutic DNA must be delivered to the nucleus of cells using a safe and efficient delivery vector. Although viral-based vectors have been utilized extensively due to their innate ability to deliver DNA to intact cells, safety considerations, such as pathogenicity, oncogenicity and the stimulation of an immunological response in the host, remain problematical. There has, however, been much progress in the development of safe non-viral gene-delivery vectors, although they remain less efficient than the viral counterparts. The major limitations of non-viral gene transfer reside in the fact that it must be tailored to overcome the intracellular barriers to DNA delivery that viruses already master, including the cellular and nuclear membranes. In particular, nuclear transport of the therapeutic DNA is known to be the rate-limiting step in the gene-delivery process. Despite this, much progress had been made in recent years in developing novel means to overcome these barriers and efficiently deliver DNA to the nuclei of intact cells. This review focuses on the nucleocytoplasmic delivery of DNA and mechanisms to enhance to non-viral-mediated gene transfer.

Flow-cytometric analysis of mouse embryonic stem cell lipofection using small and large DNA constructs

Using the lipofection reagent LipofectAMINE 2000 we have examined the delivery of plasmid DNA (5-200 kb) to mouse embryonic stem (mES) cells by flow cytometry. To follow the physical uptake of lipoplexes we labeled DNA molecules with the fluorescent dye TOTO-1. In parallel, expression of an EGFP reporter cassette in constructs of different sizes was used as a measure of nuclear delivery. The cellular uptake of DNA lipoplexes is dependent on the uptake competence of mES cells, but it is largely independent of DNA size. In contrast, nuclear delivery was reduced with increasing plasmid size. In addition, linear DNA is transfected with lower efficiency than circular DNA. Inefficient cytoplasmic trafficking appears to be the main limitation in the nonviral delivery of large DNA constructs to the nucleus of mES cells. Overcoming this limitation should greatly facilitate functional studies with large genomic fragments in embryonic stem cells.

Multiple strategies for gene transfer, expression, knockdown, and chromatin influence in mammalian cell lines and transgenic animals

Manipulation of the eukaryotic genome has contributed to the progress in our knowledge of multicellular organisms but has also ameliorated our experimental strategies. Biological questions can now be addressed with more efficiency and reproducibility. There are new and varied strategies for gene transfer and sequence manipulation with improved methodologies that facilitate the acquisition of results. Cellular systems and transgenic animals have demonstrated their invaluable benefits. In this review, I present an overview of the methods of gene transfer with particular attention to cultured cell lines and large-scale sequence vectors, like artificial chromosomes, with the possibility of their manipulation based on homologous recombination strategies. Alternative strategies of gene transfer, including retroviral vectors, are also described and the applications of such methods are discussed. Finally, several comments are made about the influence of chromatin structure on gene expression. Recent experimental data have shown that for convenient stable transgene expression, the influence of chromatin structure should be seriously taken into account. Novel chromatin regulatory and structural elements are proposed as an alternative for proper and sustained gene expression. These chromatin elements are facing a new era in transgenesis and we are probably beginning a new generation of gene and cancer therapy vectors.

Nucleocytoplasmic transport of plasmid DNA: a perilous journey from the cytoplasm to the nucleus

Nonviral vectors represent a promising approach for the safe delivery of therapeutic DNA in genetic and acquired human diseases. Before synthetic vector systems can be used for clinical applications, their limited efficacy must be addressed. At the cellular level, successful gene transfer is dependent on several additional factors including DNA uptake, release from the DNA-vector complex, and nucleocytoplasmic transport. This paper reviews the major metabolic and physical impediments that plasmid DNA vectorized by synthetic vectors encounters between the cytosol and the nucleus. Plasmid DNA that escapes the endolysosomal compartment encounters the diffusional and metabolic barriers of the cytoplasm, reducing the number of intact plasmids that reach the nuclear envelope. Nuclear translocation of DNA requires either the disassembly of the nuclear envelope during cell division or active nuclear transport via the nuclear pore complex. In the nucleus, plasmid DNA is relatively stable, but its transcription and its fate during cell division are still debated. A better understanding of the cellular and molecular basis of nonviral gene transfer during nucleocytoplasmic trafficking may provide strategies to overcome those obstacles that limit the efficiency of nonviral gene delivery. We review some of the current methods of gene transfer mediated by synthetic vectors, highlighting systems that exploit our actual knowledge of the nucleocytoplasmic transport of plasmid DNA.

Comparing reagents for efficient transfection of human primary myoblasts: FuGENE 6, Effectene and ExGen 500

This study compared three different synthetic reagents (FuGENE 6, Effectene and ExGen 500) for the transfection of human primary myoblasts. We examined the efficiency, cytotoxicity and size of the complexes formed in the presence of different amounts of vector and DNA and with variable amounts of serum. Transfection rates were relatively high for primary cells, especially with FuGENE 6 (20%), which appeared to be the best transfection reagent for these cells, even in the presence of 10% serum. Cultured human myoblasts are an interesting tool for studying neuromuscular diseases and are potentially useful for myoblast transfer therapy studies. Moreover, the efficiency of these transfection reagents in a medium containing 10% serum is promising for possible gene therapy protocols for muscle diseases.

Endotoxin triggers nuclear factor-kappaB-dependent up-regulation of multiple proinflammatory genes in the diaphragm

BACKGROUND

Sepsis-induced diaphragmatic force loss and failure are associated with an increased exposure of the muscle to proinflammatory mediators.

OBJECTIVES

Our objectives were to test the hypothesis that force-inhibiting mediators may arise in large part from the diaphragm itself and to evaluate the roles of mechanical stress, free radicals, and the nuclear factor (NF)-kappaB transcription factor pathway in endotoxin (LPS)-induced proinflammatory responses of the diaphragm.

METHODS

Murine diaphragm and limb muscle cells were exposed to LPS in vitro and in vivo. Proinflammatory gene expression was measured using RNase protection assays (tumor necrosis factor [TNF]-alpha, TNF-alpha receptor p55, interleukin [IL]-1alpha, IL-1beta, IL-6, macrophage inflammatory peptide-2, intercellular adhesion molecule-1, Fas ligand, and inducible nitric oxide synthase) and ELISAs (TNF-alpha, IL-6, and macrophage inflammatory peptide-2). Cyclical muscle cell stretch and free-radical scavengers (N-acetylcysteine and catalase) were used to alter mechanical and oxidative stress levels, respectively. Pharmacologic (pyrrolidinedithiocarbamate) and dominant-negative transfection strategies were used to inhibit the NF-kappaB pathway.

RESULTS

In primary diaphragm muscle cell cultures, modulation of mechanical stress levels or free-radical exposure did not alter responses to LPS stimulation. However, pharmacologic blockade of the NF-kappaB pathway and dominant-negative molecular inhibition of IKB kinase-beta strongly suppressed LPS-induced proinflammatory gene expression. In vivo, acute endotoxemia induced significantly greater mRNA and protein levels for proinflammatory mediators in the diaphragm as compared with limb muscle. Basal expression levels of proinflammatory genes were significantly higher in the diaphragm.

CONCLUSIONS

Constitutive and LPS-induced proinflammatory gene expression are exaggerated in the diaphragm compared with limb muscles and are critically dependent on the NF-kappaB pathway. We suggest the diaphragm may be relatively predisposed to proinflammatory responses.

Highly efficient molecular delivery into mammalian cells using carbon nanotube spearing

Introduction of exogenous DNA into mammalian cells represents a powerful approach for manipulating signal transduction. The available techniques, however, are limited by low transduction efficiency and low cell viability after transduction. Here we report a highly efficient molecular delivery technique, named nanotube spearing, based on the penetration of nickel-embedded nanotubes into cell membranes by magnetic field driving. DNA plasmids containing the enhanced green fluorescent protein (EGFP) sequence were immobilized onto the nanotubes, and subsequently speared into targeted cells. We have achieved an unprecedented high transduction efficiency in Bal17 B-lymphoma, ex vivo B cells and primary neurons with high viability after transduction. This technique may provide a powerful tool for highly efficient gene transfer into a variety of cells, especially the hard-to-transfect cells.

Polyfection as Nonviral Gene Transfer Method —Design of Novel Nonviral Vector Using α-Cyclodextrin—

Due to the growing concerns over the toxicity and immunogenicity of viral DNA delivery systems, DNA delivery via nonviral routes has become more desirable and advantageous. In particular, polycation complexes with DNA (polyplex) are attractive nonviral vectors. To design novel polycationic vectors, we prepared polyamidoamine starburst dendrimer (dendrimer) conjugates with three cyclodextrins (CDE conjugates) and three generations (G2, G3, and G4) of dendrimers. Of seven CDE conjugates, an alpha-CDE conjugate (G3) with an average degree of substitution (DS) of alpha-CyD of 2.4 [alpha-CDE conjugate (G3, DS 2.4)] showed greater gene transfer activity than dendrimers and other alpha-CDE conjugates with less cytotoxicity. These results suggest the potential use of alpha-CDE conjugate (G3, DS 2.4) as a polycationic vector in vitro and in vivo. Herein, I review a recent polyfection method, with special focus on alpha-CDE conjugate (G3, DS 2.4).

Quantitative Three-Dimensional Analysis of the Intracellular Trafficking of Plasmid DNA Transfected by a Nonviral Gene Delivery System Using Confocal Laser Scanning Microscopy

Since endosomal escape and the nuclear delivery of plasmid DNA (pDNA) constitute major barriers for transgene expression, a quantitative evaluation of intracellular trafficking of pDNA would be highly desirable in terms of optimizing a nonviral gene delivery system. In the present study, a novel strategy is proposed for the quantification of rhodamine-labeled pDNA in endosomes/lysosomes, cytosol, and nucleus. Endosomes/lysosomes and nucleus were stained with LysoSensor DND-189 and Hoechst 33258, respectively, to distinguish them from the cytosol. The pixel areas of the clusters derived from the rhodamine were used as an index for the amount of pDNA. This approach was applied to the analysis of the intracellular trafficking of pDNA transfected by LipofectAMINE PLUS, stearylated octaarginine (STR-R8), and octaarginine (R8). In the case of R8, most of the pDNA was trapped by endosomes/lysosomes. STR-R8 exhibited endosomal escape followed by nuclear translocation in a time-dependent manner. LipofectAMINE PLUS was the most effective in rapidly delivering pDNA to the nucleus as well as the cytosol. These differences in the intracellular trafficking of pDNA correlated well with the transgene expression. Therefore, this method enables the quantitative analysis of the intracellular pharmacokinetics of pDNA and promises to provide useful information for optimizing nonviral gene delivery systems.

Deoxyribonuclease II is a lysosomal barrier to transfection

DNA delivered in nonviral vectors or as naked DNA must overcome a number of extracellular and intracellular barriers to transfection. Since many vectors deliver DNA into cells by the endocytic route, DNA degradation by lysosomal nucleases has been proposed as a significant barrier to transfection, despite the fact that this has not yet been formally demonstrated to occur. To test this hypothesis, we have investigated the role of deoxyribonuclease II (DNase II), the primary acidic endonuclease active in the lysosome, in transfection. Two genetic systems were engineered in which mammalian cells either overexpressed DNase II or were knocked out for the enzyme. In both models, higher levels of DNase II correlated with decreased transfection efficiency by nonviral DNA delivery vectors. These data provide direct evidence implicating lysosomal DNase II as a barrier to transfection.

Transfection of normal primary human skeletal myoblasts with p21 and p57 antisense oligonucleotides to improve their proliferation: a first step towards an alternative molecular therapy approach of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD), caused by the absence of dystrophin, is associated with decreased muscle cell proliferation. An increased p21 mRNA level in DMD patients may be involved in the process. In this context we are interested to improve the proliferation of primary human skeletal muscle cells (SkMC) by a reduction in the cell cycle proteins p21 and p57 using the appropriate antisense oligonucleotides (ASO). Therefore a transfection procedure needs to be optimized in which the oligonucleotide enters the SkMC with a minimal loss of cell vitality and high efficiency. Three different formulations, Effectene, DAC40, and SuperFect, were compared. Proliferation was analyzed comparing cells transfected with p21 and/or p57 ASO vs. cells transfected with scrambled ASO using a bromodeoxyuridine assay. Under optimal conditions (a mixture of 0.25 microg ASO, 5 microl Effectene, 0.8 microl enhancer) SkMC transfected with p21 ASO reveal an average increase in cell proliferation of 32.5+/-11% after 24 h. p57 ASO shows the same effect, but concomitant transfection of p21 and p57 does not enhance it. A cell vitality of 78+/-14% after 24 h was determined by the MTT test. SkMC transfected with DAC40 reveal a maximal increase in proliferation of 38+/-7% after 48 h and show a vitality of 65+/-8%. In contrast to both these formulations, SuperFect was found to be highly toxic for SkMC, with more than 70% dead cells after 24 h. The increase in proliferation, the functional biological effect of p21 ASO, is well correlated with a decrease in p21 detected by western blot analysis of 31.6% for Effectene. Transfection efficiency was measured directly by FACS analysis using FITC-labeled ASO and data showing ASO internalization in 75.8+/-11.2% of the cell population for Effectene and 74.4+/-6.6% cells for DAC40. Taken together transient transfection of p21 or p57 ASO into primary human SkMC using Effectene significantly improves their proliferation compared to transfection with scrambled ASO without a major loss of cell vitality. This represents a basis for the transfer of this technique to dystrophin-deficient SkMC cultures and the introduction of the short interference-RNA technique which might enhance the effect on cell proliferation.

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.

Gene delivery by a steroid-peptide nucleic acid conjugate

We previously introduced a method called steroid-mediated gene delivery (SMGD), which uses steroid receptors as shuttles to facilitate the nuclear uptake of transfected DNA. Here, we describe a SMGD strategy with peptide nucleic acids (PNAs) that allowed linkage of a steroid molecule to a defined position in a plasmid without disturbing its gene expression. We synthesized and tested several bifunctional steroid derivatives [patent in process of nationalization] and finally selected the compound named DEX-bisPNA, a molecule consisting of a dexamethasone moiety linked to a PNA clamp (bisPNA) through a 30-atom chemical spacer. Dex-bisPNA binds to the glucocorticoid receptor (GR) as well as to reporter plasmids containing the corresponding PNA binding sites, translocates the GR from the cytoplasm into the nucleus, and increases the delivery of plasmid to the nucleus, resulting in enhanced GR-dependent expression of the reporter gene. The SMGD effect was more pronounced in growth-arrested cells than in proliferating cells. The specificity for the GR was shown by the reversion of the SMGD effect in the presence of dexamethasone as well as an enhanced expression in GR-positive cells but not in GR-negative cells. Thus, SMGD with PNA is a promising strategy for nonviral gene delivery into target tissues expressing specific steroid receptors.