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      Small Poly- L-Lysines Improve Cationic Lipid-Mediated Gene Transfer in Vascular Cells in vitro and in vivo


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          The potential of two small poly- L-lysines (sPLLs), low molecular weight sPLL (LMW-L) containing 7–30 lysine residues and L18 with 18 lysine repeats, to enhance the efficiency of liposome-mediated gene transfer (GT) with cationic lipid DOCSPER [1,3-dioleoyloxy-2-(N<sup>5</sup>-carbamoyl-spermine)-propane] in vascular smooth muscle cells (SMCs) was investigated. Dynamic light scattering was used for determination of particle size. Confocal microscopy was applied for colocalization studies of sPLLs and plasmid DNA inside cells. GT was performed in proliferating and quiescent primary porcine SMCs in vitro and in vivo in porcine femoral arteries. At low ionic strength, sPLLs formed small complexes with DNA (50–100 nm). At high ionic strength, large complexes (>1 µm) were observed without any significant differences in particle size between lipoplexes (DOCSPER/DNA) and lipopolyplexes (DOCSPER/sPLL/DNA). Both sPLLs were colocalized with DNA inside cells 24 h after transfection, protecting DNA against degradation. DOCSPER/sPLL/DNA formulations enhanced GT in vitro up to 5-fold, in a porcine model using local periadventitial application up to 1.5-fold. Both sPLLs significantly increased liposome-mediated GT. Poly- L-lysine L18 was superior to LMW-L since it enabled maximal GT at a 10-fold lower concentration. Thus, sPLLs may serve as enhancers for GT applications in SMCs in vitro and in vivo using local delivery.

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          Most cited references 20

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          Uptake pathways and subsequent intracellular trafficking in nonviral gene delivery.

          The successful delivery of therapeutic genes to the designated target cells and their availability at the intracellular site of action are crucial requirements for successful gene therapy. Nonviral gene delivery is currently a subject of increasing attention because of its relative safety and simplicity of use; however, its use is still far from being ideal because of its comparatively low efficiency. Most of the currently available nonviral gene vectors rely on two main components, cationic lipids and cationic polymers, and a variety of functional devices can be added to further optimize the systems. The design of these functional devices depends mainly on our understanding of the mechanisms involved in the cellular uptake and intracellular disposition of the therapeutic genes as well as their carriers. Macromolecules are internalized into cells by a variety of mechanisms, and their intracellular fate is usually linked to the entry mechanism. Therefore, the successful design of a nonviral gene delivery system requires a deep understanding of gene/carrier interactions as well as the mechanisms involved in the interaction of the systems with the target cells. In this article, we review the different uptake pathways that are involved in nonviral gene delivery from a gene delivery point of view. In addition, available knowledge concerning cellular entry and the intracellular trafficking of cationic lipid-DNA complexes (lipoplexes) and cationic polymer-DNA complexes (polyplexes) is summarized.
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            The size of DNA/transferrin-PEI complexes is an important factor for gene expression in cultured cells.

            Under physiological salt concentration, plasmid DNA complexed with transferrin-conjugated or unmodified polyethylenimine (PEI, 800 kDa) forms huge (up to > 1000 nm) aggregates, unless the individual components are mixed at a highly positive nitrogen/phosphate (N/P) charge ratio. At low ionic strengths, however, small particles with an average size of 40 nm are formed over a broad range of N/P ratios. Interestingly, in transfection experiments these small particles result in a 10-fold (B16F10 cells) to more than 100-fold (Neuro2A cells, K562 cells) reduced luciferase gene expression efficiency in comparison to the large complexes formed in physiological salt solutions. Limited transport of the small particles to the cell surfaces is one possible reason for this effect. Application of the small particles in more concentrated form and over extended periods of time improves transfection activity. Reduced intracellular release may be another explanation for the decreased transfection efficiency; incubation with chloroquine or incorporation of the endosomolytic peptide INF5 into the small complexes enhances gene expression approximately 10-fold. Analysis of gene expression at the cellular level using a green fluorescence protein reporter gene and flow cytometry revealed that the differences in overall gene expression largely result from different intensities per expressing cell, while the difference in the percentage of expressing cells is less substantial.
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              Protamine sulfate enhances lipid-mediated gene transfer.

              A polycationic peptide, protamine sulfate, USP, has been shown to be able to condense plasmid DNA efficiently for delivery into several different types of cells in vitro by several different types of cationic liposomes. The monovalent cationic liposomal formulations (DC-Chol and lipofectin) exhibited increased transfection activities comparable to that seen with the multivalent cationic liposome formulation, lipofectamine. This suggests that lipofectamine's superior in vitro activity arises from its ability to condense DNA efficiently and that protamine's primary role is that of a condensation agent, although it also possesses several amino acid sequences resembling that of a nuclear localization signal. While the use of polycations to condense DNA has been previously reported, the of protamine sulfate, USP as a condensation agent was found to be superior to poly-L-lysine as well as to various other types of protamine. These differences among various salt forms of protamine appear to be attributable to structural differences between the protamines and not due to differences in the net charge of the molecule. The appearance of lysine residues within the protamine molecule correlate with a reduction in binding affinity to plasmid DNA as well as an observed loss in transfection enhancing activity. This finding sheds light on the structural requirements of condensation agents for use in gene transfer protocols. Furthermore, protamine sulfate, USP is an FDA-approved compound with a documented safety profile and could be readily used as an adjuvant to a human gene therapy protocol.

                Author and article information

                J Vasc Res
                Journal of Vascular Research
                S. Karger AG
                June 2007
                30 March 2007
                : 44
                : 4
                : 273-282
                aDepartment of Cardiology and Angiology, University Hospital, Westfaelische Wilhelms University, Muenster, bMedical Department I, University Hospital, Grosshadern Ludwig Maximilian University, and cDepartment of Vascular Surgery, Klinikum rechts der Isar, Technical University Munich, Munich, Germany; dLaboratory of Hemodynamics and Cardiovascular Mechanics, School of Medicine, Mediterranean University, Marseille, France
                101449 J Vasc Res 2007;44:273–282
                © 2007 S. Karger AG, Basel

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                Page count
                Figures: 5, Tables: 3, References: 30, Pages: 10
                Research Paper


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