Quantitative evaluation of DNA dissociation from liposome carriers and DNA escape from endosomes during lipid-mediated gene delivery

Defining the EM-signature of successful cell-transfection

In this report, we describe the architecture of Lipofectamine 2000 and 3000 transfection- reagents, as they appear inside of transfected cells, using classical transmission electron microscopy (EM). We also demonstrate that they provoke consistent structural changes after they have entered cells, changes that not only provide new insights into the mechanism of action of these particular transfection-reagents, but also provide a convenient and robust method for identifying by EM which cells in any culture have been successfully transfected. This also provides clues to the mechanism(s) of their toxic effects, when they are applied in excess. We demonstrate that after being bulk-endocytosed by cells, the cationic spheroids of Lipofectamine remain intact throughout the entire time of culturing, but escape from their endosomes and penetrate directly into the cytoplasm of the cell. In so doing, they provoke a stereotypical recruitment and rearrangement of endoplasmic reticulum (ER), and they ultimately end up escaping into the cytoplasm and forming unique 'inclusion-bodies.' Once free in the cytoplasm, they also invariably develop dense and uniform coatings of cytoplasmic ribosomes on their surfaces, and finally, they become surrounded by 'annulate' lamellae' of the ER. In the end, these annulate-lamellar enclosures become the ultrastructural 'signatures' of these inclusion-bodies, and serve to positively and definitively identify all cells that have been effectively transfected. Importantly, these new EM-observations define several new and unique properties of these classical Lipofectamines, and allow them to be discriminated from other lipoidal or particulate transfection-reagents, which we find do not physically break out of endosomes or end up in inclusion bodies, and in fact, provoke absolutely none of these 'signature' cytoplasmic reactions.

Transcriptomic analysis of the innate immune response to in vitro transfection of plasmid DNA

The innate immune response to cytosolic DNA is intended to protect the host from viral infections, but it can also inhibit the delivery and expression of therapeutic transgenes in gene and cell therapies. The goal of this work was to use mRNA sequencing to identify genes that may influence transfection efficiency in four different cell types (PC-3, Jurkat, HEK-293T, and primary T cells). The highest transfection efficiency was observed in HEK-293T cells, which upregulated only 142 genes with no known antiviral functions after transfection with lipofectamine. Lipofection upregulated 1,057 cytokine-stimulated genes (CSGs) in PC-3 cells, which exhibited a significantly lower transfection efficiency. However, when PC-3 cells were transfected in serum-containing media or electroporated, the observed transfection efficiencies were significantly higher while the expression levels of cytokines and CSGs decreased. In contrast, lipofection of Jurkat and primary T cells only upregulated a few genes, but several of the antiviral CSGs that were absent in HEK-293T cells and upregulated in PC-3 cells were observed to be constitutively expressed in T cells, which may explain the relatively low Lipofection efficiencies observed with T cells (8%-21% GFP⁺). Indeed, overexpression of one CSG (IFI16) significantly decreased transfection efficiency in HEK-293T cells.

Encapsulation of a CpG oligonucleotide in cationic liposomes enhances its local antitumor activity following pulmonary delivery in a murine model of metastatic lung cancer

Immunotherapy brings new hope to the fight against lung cancer. General immunostimulatory agents represent an immunotherapy strategy that has demonstrated efficacy with limited toxicity when delivered intratumorally. The goal of this study was to enhance the antitumor efficacy of unmethylated oligodeoxynucleotides containing CpG motifs (CpG) and polyinosinic-polycytidylic acid (poly I:C) double-stranded RNA following their local delivery in lung cancer by encapsulating them in liposomes. Liposomes encapsulation of nucleic acids could increase their uptake by lung phagocytes and thereby the activation of toll-like receptors within endosomes. Liposomes were prepared using a cationic lipid, dioleoyltrimethylammoniumpropane (DOTAP), and dipalmitoylphosphatidylcholine (DPPC), the main phospholipid in lung surfactant. The liposomes permanently entrapped CpG but could not efficiently withhold poly I:C. Both poly I:C and CpG delayed tumor growth in the murine B16F10 model of metastatic lung cancer. However, only CpG increased IFN-γ levels in the lungs. Pulmonary administration of CpG was superior to its intraperitoneal injection to slow the growth of lung metastases and to induce the production of granzyme B, a pro-apoptotic protein, and IFNγ, MIG and RANTES, T helper type 1 cytokines and chemokines, in the lungs. These antitumor activities of CpG were strongly enhanced by CpG encapsulation in DOTAP/DPPC liposomes. Delivery of low CpG doses to the lungs induced increased inflammation markers in the airspaces but the inflammation did not reach the systemic compartment in a significant manner. These data support the use of a delivery carrier to strengthen CpG antitumor activity following its pulmonary delivery in lung cancer.

Hydrophilic Hyperbranched Polymer-Coated siRNA/Polyamidoamine Dendron-Bearing Lipid Complexes Preparation for High Colloidal Stability and Efficient RNAi

RNA interference (RNAi) using siRNA has gained much attention for use in therapies for cancer and genetic disorders. To establish RNAi-based therapeutics, the development of efficient siRNA nanocarriers is desired. Earlier, we developed polyamidoamine dendron-bearing lipids able to form complexes with nucleic acids as gene vectors. Especially, dendron lipids with unsaturated alkyl chains (DL-G1-U2) induced efficient endosomal escape by membrane fusion, leading to efficient transfection in vitro. For this study, dendron lipids having oleyl/linoleyl groups (DL-G1-U3) were designed to increase membrane fusogenic activity further. Indeed, DL-G1-U3/siRNA complexes achieved higher membrane fusogenic activity and knockdown of the target gene more efficiently than conventional DL-G1-U2/siRNA complexes did. A hydrophilic polymer, hyperbranched polyglycidol lauryl ester (HPG-Lau), was modified further on the surface of DL-G1-U3/siRNA complexes to provide colloidal stability. Surface modification of HPG-Lau increased the colloidal stability in a physiological condition more than complexes without HPG-Lau. Importantly, HPG-Lau-coated DL/siRNA complexes showed identical RNAi effects to those of parental DL/siRNA complexes, whereas the RNAi activity of poly(ethylene glycol)-bearing lipid (PEG-PE)-modified DL/siRNA complexes was hindered completely. Introduction of unsaturated bonds into dendron lipids and selection of suitable hydrophilic polymers for nanocarrier modification are important for obtaining efficient siRNA vectors toward in vivo siRNA delivery.

Cationic lipid/pDNA complex formation as potential generic method to generate specific IRF pathway stimulators

Cationic liposome - CpG DNA complexes (lipoplexes) are known as stimulators of innate immunity via Toll-like receptor 9 (TLR9)-triggered activation of the nuclear factor kappa B (NF-κB) pathway. More recent reports suggest that DNA lipoplexes also engage DNA sensors in the cytosol leading to the stimulation of the interferon response factor (IRF) pathway. In this study a range of lipoplexes were formulated by using an invariable helper lipid, three different cationic lipids (DOTAP, DOTMA and DDA) and three different CpG-containing plasmids of different sizes. These lipoplexes exhibited similar hydrodynamic diameters, zeta-potentials and plasmid loading rates, despite the different lipid blends and CpG-containing plasmids. Binding and uptake of liposomal lipids by J774.A1 macrophages and JAWSII dendritic cells increased significantly (up to 4-fold) upon lipoplex formation. Cellular plasmid DNA uptake via lipoplexes compared to naked DNA was increased up to 18-fold. Analysis of signal transduction pathway activation in J774-DUAL™ reporter cells by liposomes or naked CpG plasmid DNA compared to their derived lipoplexes showed only minor activation of the NF-κB pathway, while the IRF pathway displayed massive activation factors of up to 46-fold. DOTAP- and DOTMA lipoplexes also led to massive interferon-alpha and -beta secretion of J774A.1 macrophages and JAWSII dendritic cells, which is a hallmark of IRF pathway activation. Cellular distribution studies on DOTAP lipoplexes suggest delivery of plasmid DNA via vesicular compartments into the cytosol. Taken together, the CpG plasmid DNA lipoplexes generated in this study appear to selectively stimulate DNA receptors activating the IRF pathway, while bypassing TLR9 and NF-κB activation.

The Multifaceted Uses and Therapeutic Advantages of Nanoparticles for Atherosclerosis Research

Nanoparticles are uniquely suited for the study and development of potential therapies against atherosclerosis by virtue of their size, fine-tunable properties, and ability to incorporate therapies and/or imaging modalities. Furthermore, nanoparticles can be specifically targeted to the atherosclerotic plaque, evading off-target effects and/or associated cytotoxicity. There has been a wealth of knowledge available concerning the use of nanotechnologies in cardiovascular disease and atherosclerosis, in particular in animal models, but with a major focus on imaging agents. In fact, roughly 60% of articles from an initial search for this review included examples of imaging applications of nanoparticles. Thus, this review focuses on experimental therapy interventions applied to and observed in animal models. Particular emphasis is placed on how nanoparticle materials and properties allow researchers to learn a great deal about atherosclerosis. The objective of this review was to provide an update for nanoparticle use in imaging and drug delivery studies and to illustrate how nanoparticles can be used for sensing and modelling, for studying fundamental biological mechanisms, and for the delivery of biotherapeutics such as proteins, peptides, nucleic acids, and even cells all with the goal of attenuating atherosclerosis. Furthermore, the various atherosclerosis processes targeted mainly for imaging studies have been summarized in the hopes of inspiring new and exciting targeted therapeutic and/or imaging strategies.

In Vitro Synthesis, Delivery, and Bioavailability of Exogenous mRNA in Gene Transfer Mediated by PiggyBac Transposition

Nowadays, nonviral gene transfer is currently of great importance for introducing exogenous genes into genomes and for ensuring that transgene expression is suitable for therapeutic and bioproduction purposes. The piggyBac transposon-based system is particularly interesting since it is easy to engineer and has a large cargo capacity, up to 100 kb. In its setup, the system requires only the piggyBac transposase protein and the transgene delineated by the two piggyBac-specific inverted terminal repeats. Usually the source of transposase is carried by a DNA plasmid. However, the principal drawback of this method is the lasting presence of the transposase, due to episomal persistence or possible integration of the transposase gene vector into the cell's genome. This can lead to genotoxic effects such as multiple genomic integration events and remobilization of the transposon vector once it has been integrated. One alternative to improve the safety of the system is to deliver the transposase as in vitro-synthesized messenger RNA in order to define a very narrow expression window during which a one-shot transposition process would occur. Issues that can be encountered when working on mRNA cell transfer are related to the quality of the synthetic mRNA, the system used to introduce mRNA into the cells and the bioavailability of the mRNA molecules. Here we describe a method to produce mRNA, verify its quality, determine which transfecting reagents can be used and how this mRNA is available to promote the transposition process in HeLa cells. Additionally, we illustrate this method in stromal mesenchymal cell lines in order to support hematopoiesis.

Flow cytometric sex sorting affects CD4 membrane distribution and binding of exogenous DNA on bovine sperm cells

Bovine sex-sorted sperm have been commercialized and successfully used for the production of transgenic embryos of the desired sex through the sperm-mediated gene transfer (SMGT) technique. However, sex-sorted sperm show a reduced ability to internalize exogenous DNA. The interaction between sperm cells and the exogenous DNA has been reported in other species to be a CD4-like molecule-dependent process. The flow cytometry-based sex-sorting process subjects the spermatozoa to different stresses causing changes in the cell membrane. The aim of this study was to elucidate the relationship between the redistribution of CD4-like molecules and binding of exogenous DNA to sex-sorted bovine sperm. In the first set of experiments, the membrane phospholipid disorder and the redistribution of the CD4 were evaluated. The second set of experiments was conducted to investigate the effect of CD4 redistribution on the mechanism of binding of exogenous DNA to sperm cells and the efficiency of lipofection in sex-sorted bovine sperm. Sex-sorting procedure increased the membrane phospholipid disorder and induced the redistribution of CD4-like molecules. Both X-sorted and Y-sorted sperm had decreased DNA bound to membrane in comparison with the unsorted sperm; however, the binding of the exogenous DNA was significantly increased with the addition of liposomes. Moreover, we demonstrated that the number of sperm-bound exogenous DNA was decreased when these cells were preincubated with anti-bovine CD4 monoclonal antibody, supporting our hypothesis that CD4-like molecules indeed play a crucial role in the process of exogenous DNA/bovine sperm cells interaction.

Characterization of exogenous DNA mobility in live cells through fluctuation correlation spectroscopy

The spatial-temporal dynamics of delivered DNA is a critical aspect influencing successful gene delivery. A comprehensive model of DNA lipoplex trafficking through live cells has yet to be demonstrated. Here the bioimaging approaches Raster Image Correlation Spectroscopy (RICS) and image-Means Square Displacement (iMSD) were applied to quantify DNA mechanical dynamics in live cells. DNA lipoplexes formed from DNA with a range of 21 bp to 5.5 kbp exhibited a similar range of motion within the cytoplasm of myoblast cells regardless of size. However, the rate of motion was dictated by the intracellular location, and DNA cluster size. This analysis demonstrated that the different transport mechanisms either had a size dependent mobility, including random diffusion, whereas other mechanisms were not influenced by the DNA size such as active transport. The transport mechanisms identified followed a spatial dependence comparable to viral trafficking of non-active transport mechanism upon cellular entry, active transport within the cytoplasm and further inactive transportation along the peri-nuclear region. This study provides the first real-time insight into the trafficking of DNA delivered through lipofection using image-based fluctuation correlation spectroscopy approaches. Thereby, gaining information with single particle sensitivity to develop a deeper understanding of DNA lipoplex delivery through the cell.