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Overcoming intracellular barriers in non-viral gene delivery : chromatin targeting, messenger RNA and non-coding DNA

Nathalie Symens (UGent)
(2012)
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(UGent) , (UGent) and (UGent)
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Abstract
In principle, gene therapy could increase or restore the expression of virtually any protein in a cell. This in consequence could bring a cure for various inherited or acquired genetic diseases. In spite of years of extensive research, gene delivery by non-viral carriers has not met with these expectations. None of numerous polymeric and lipidic nucleic acid carriers has received approval from the Food and Drug Administration (FDA) and the European Medicines Agency (EMA), which indicates that existing carriers do not possess suitable properties to ensure safe and effective in vivo delivery of nucleic acids. One of the reasons is the low frequency at which plasmid DNA (pDNA) reaches its target, the nucleus. This is mostly due to the presence of multiple extracellular and intracellular barriers which have to be overcome before pDNA can be transcribed. For example, when particles carrying pDNA are administered systemically, they should be stable in the blood stream and be able to reach the target organ. Moreover, these particles should evade clearance by the immune system. Once the particles reach the organ of interest, they should be taken up only by desired cell subpopulations. The internalized particles should then timely escape the endosomal compartment. pDNA in the cytosol should be protected against degradation by nucleases and should be transported toward the nucleus. The nuclear envelope (NE) is one of the most difficult intracellular barriers to overcome. In non-dividing cells the only way for pDNA to enter the nucleus is via the nuclear pore complexes (NPCs). This process is very inefficient due to the size limit of the pores. In dividing cells, the NE is timely disassembled during mitosis allowing pDNA enclosure in the newly formed daughter nuclei. To ensure transfection, intranuclearly located pDNA should be able to reach transcription-active sites. The research presented in this thesis focused on overcoming the intracellular barriers that limit non-viral delivery of pDNA. The first chapter provides a detailed overview on intracellular partitioning of cell organelles, foreign macromolecules and nanoparticles during mitosis. Moreover, it highlights how viruses take advantage of cell division to transfer or segregate their genetic information into the daughter nuclei. It also proposes strategies to enhance non-viral gene delivery in dividing cells. Chapter 2 reports on one of these strategies. Specifically, the nuclear inclusion of fluorescent polystyrene nanospheres and pDNA-containing nanoparticles modified with chromatin-binding peptides was studied. Initially, the nuclear inclusion was followed in the cell-free Xenopus nuclear envelope reassembly (XNER) model in which artificial nuclei are formed. The same particles were also injected and followed in living cells. In chapter 3, the effect of non-coding DNA co-delivered with coding pDNA on transfection efficiency mediated by lipoplexes was studied. Non-coding pDNA in supercoiled and linear form as well as non-coding salmon DNA were evaluated for their influence on transfection efficiency. It was further investigated at which level(s) of the transfection pathway the presence of non-coding DNA becomes essential. In chapter 4, polycationic amphiphilic cyclodextrins (paCDs) were assessed as nucleic acids carriers. mRNA-based transfection was presented as an alternative to pDNAbased transfection in slowly dividing cells. The specific uptake of complexes of galactosylated paCDs and mRNA via asialoglycoprotein receptors (ASGPr) on the surface of hepatocytes was also evaluated.
Keywords
gene therapy, nuclear membrane, plasmid DNA

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Citation

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Chicago
Symens, Nathalie. 2012. “Overcoming Intracellular Barriers in Non-viral Gene Delivery : Chromatin Targeting, Messenger RNA and Non-coding DNA”. Ghent, Belgium: Ghent University. Faculty of Pharmaceutical Sciences.
APA
Symens, N. (2012). Overcoming intracellular barriers in non-viral gene delivery : chromatin targeting, messenger RNA and non-coding DNA. Ghent University. Faculty of Pharmaceutical Sciences, Ghent, Belgium.
Vancouver
1.
Symens N. Overcoming intracellular barriers in non-viral gene delivery : chromatin targeting, messenger RNA and non-coding DNA. [Ghent, Belgium]: Ghent University. Faculty of Pharmaceutical Sciences; 2012.
MLA
Symens, Nathalie. “Overcoming Intracellular Barriers in Non-viral Gene Delivery : Chromatin Targeting, Messenger RNA and Non-coding DNA.” 2012 : n. pag. Print.
@phdthesis{2983079,
  abstract     = {In principle, gene therapy could increase or restore the expression of virtually any protein in a cell. This in consequence could bring a cure for various inherited or acquired genetic diseases. In spite of years of extensive research, gene delivery by non-viral carriers has not met with these expectations. None of numerous polymeric and lipidic nucleic acid carriers has received approval from the Food and Drug Administration (FDA) and the European Medicines Agency (EMA), which indicates that existing carriers do not possess suitable properties to ensure safe and effective in vivo delivery of nucleic acids. One of the reasons is the low frequency at which plasmid DNA (pDNA) reaches its target, the nucleus. This is mostly due to the presence of multiple extracellular and intracellular barriers which have to be overcome before pDNA can be transcribed. For example, when particles carrying pDNA are administered systemically, they should be stable in the blood stream and be able to reach the target organ. Moreover, these particles should evade clearance by the immune system. Once the particles reach the organ of interest, they should be taken up only by desired cell subpopulations. The internalized particles should then timely escape the endosomal compartment. pDNA in the cytosol should be protected against degradation by nucleases and should be transported toward the nucleus. The nuclear envelope (NE) is one of the most difficult intracellular barriers to overcome. In non-dividing cells the only way for pDNA to enter the nucleus is via the nuclear pore complexes (NPCs). This process is very inefficient due to the size limit of the pores. In dividing cells, the NE is timely disassembled during mitosis allowing pDNA enclosure in the newly formed daughter nuclei. To ensure transfection, intranuclearly located pDNA should be able to reach transcription-active sites.
The research presented in this thesis focused on overcoming the intracellular barriers that limit non-viral delivery of pDNA. The first chapter provides a detailed overview on intracellular partitioning of cell organelles, foreign macromolecules and nanoparticles during mitosis. Moreover, it highlights how viruses take advantage of cell division to transfer or segregate their genetic information into the daughter nuclei. It also proposes strategies to enhance non-viral gene delivery in dividing cells.
Chapter 2 reports on one of these strategies. Specifically, the nuclear inclusion of fluorescent polystyrene nanospheres and pDNA-containing nanoparticles modified with chromatin-binding peptides was studied. Initially, the nuclear inclusion was followed in the cell-free Xenopus nuclear envelope reassembly (XNER) model in which artificial nuclei are formed. The same particles were also injected and followed in living cells. In chapter 3, the effect of non-coding DNA co-delivered with coding pDNA on transfection efficiency mediated by lipoplexes was studied. Non-coding pDNA in supercoiled and linear form as well as non-coding salmon DNA were evaluated for their influence on transfection efficiency. It was further investigated at which level(s) of the transfection pathway the presence of non-coding DNA becomes essential. In chapter 4, polycationic amphiphilic cyclodextrins (paCDs) were assessed as nucleic acids carriers. mRNA-based transfection was presented as an alternative to pDNAbased transfection in slowly dividing cells. The specific uptake of complexes of galactosylated paCDs and mRNA via asialoglycoprotein receptors (ASGPr) on the surface of hepatocytes was also evaluated.},
  author       = {Symens, Nathalie},
  keywords     = {gene therapy,nuclear membrane,plasmid DNA},
  language     = {eng},
  pages        = {205},
  publisher    = {Ghent University. Faculty of Pharmaceutical Sciences},
  school       = {Ghent University},
  title        = {Overcoming intracellular barriers in non-viral gene delivery : chromatin targeting, messenger RNA and non-coding DNA},
  year         = {2012},
}