mRNA-mediated gene delivery into human progenitor cells promotes highly efficient protein expression

Gene transfer into human CD34+ haematopoietic progenitor cells (HPC) and multi-potent mesenchymal stromal cells (MSC) is an essential tool for numerous in vitro and in vivo applications including therapeutic strategies, such as tissue engineering and gene therapy. Virus based methods may be efficient, but bear risks like tumorigenesis and activation of immune responses. A safer alternative is non-viral gene transfer, which is considered to be less efficient and accomplished with high cell toxicity. The truncated low affinity nerve growth factor receptor (ALNGFR) is a marker gene approved for human in vivo application. Human CD34+ HPC and human MSC were transfected with in vitro-transcribed mRNA for DeltaLNGFR using the method of nucleofection. Transfection efficiency and cell viability were compared to plasmid-based nucleofection. Protein expression was assessed using flow cytometry over a time period of 10 days. Nucleofection of CD34+ HPC and MSC with mRNA resulted in significantly higher transfection efficiencies compared to plasmid transfection. Cell differentiation assays were performed after selecting DeltaLNGFR positive cells using a fluorescent activating cell sorter. Neither cell differentiation of MSC into chondrocytes, adipocytes and osteoblasts, nor differentiation of HPC into burst forming unit erythroid (BFU-E) colony forming unit-granulocyte, erythrocyte, macrophage and megakaryocyte (CFU-GEMM), and CFU-granulocyte-macrophage (GM) was reduced. mRNA based nucleofection is a powerful, highly efficient and non-toxic approach for transient labelling of human progenitor cells or, via transfection of selective proteins, for transient manipulation of stem cell function. It may be useful to transiently manipulate stem cell characteristics and thus combine principles of gene therapy and tissue engineering.     

An effective method for adenoviral-mediated delivery of small interfering RNA into mesenchymal stem cells

Mesenchymal stem cells (MSCs) promise as a main actor of cell-based therapeutic strategies, due to their intrinsic ability to differentiate along different mesenchymal cell lineages, able to repair the diseased or injured tissue in which they are localized. The application of MSCs in therapies requires an in depth knowledge of their biology and of the molecular mechanisms leading to MSC multilineage differentiation. The knockdown of target genes through small interfering RNA (siRNA) carried by adenoviruses (Ad) represents a valid tool for the study of the role of specific molecules in cell biology. Unfortunately, MSCs are poorly transfected by conventional Ad serotype 5 (Ad5) vectors. We set up a method to obtain a very efficient transduction of rat MSCs with low doses of unmodified Ad5, carrying the siRNA targeted against the mRNA coding for Rb2/p130 (Ad-siRNA-Rb2), which plays a fundamental role in cell differentiation. This method allowed a 95% transduction rate of Ad-siRNA in MSC, along with a siRNA-mediated 85% decrease of Rb2/p130 mRNA and a 70% decrease of Rb2/p130 protein 48 h after transduction with 50 multiplicities of infection (MOIs) of Ad5. The effect on Rb2/p130 protein persisted 15 days after transduction. Finally, Ad-siRNA did not compromise the viability of transduced MSCs neither induced any cell cycle modification. The effective Ad-siRNA-Rb2 we constructed, together with the efficient method of delivery in MSCs we set up, will allow an in depth analysis of the role of Rb2/p130 in MSC biology and multilineage differentiation.     

Optimizing splinted ligation of highly structured small RNAs

The synthesis of highly structured small RNAs containing nonstandard nucleotides is of high interest for structural and functional investigations. A general approach is the joining, by T4 DNA ligase-mediated splinted ligation, of two or more RNA fragments, each of which may contain its own set of modified nucleotides. The RNA fragments hybridize with a complementary DNA splint to form a ternary ligation-competent-complex (LCC), which is then turned over by the DNA ligase. We studied the formation of the LCC and its precursors using size exclusion chromatography combined with a fluorescence detector. The spatial proximity of two cyanine-dye-labeled RNA fragments in LCCs was detected by monitoring FRET. An observed correlation of LCC formation and ligation yields suggests the use of long splints to stabilize LCCs. Splint oligos of increasing length, which in general appear to reduce the number of different hybridization intermediate species found in a reaction mixture, were applied to the synthesis by T4-DNA-ligation of two highly structured target molecules, one a 73 mer tRNA, the other a 49 mer synthetic ribozyme. A stable LCC could be isolated and turned over with>95% ligation efficiency. In conclusion, the use of long splints presents a generally applicable means to overcome the low propensity of highly structured RNAs for hybridization, and thus to significantly improve ligation efficiencies.     

Improved methods for the delivery of liposome-sequestered RNA into eucaryotic cells

RNA sequestered by negatively charged liposomes becomes cell-associated following interaction between eucaryotic cells and the liposomes. This paper provides evidence that cell-associated RNA is internalized by the cells. In fact, (a) when Escherichia coli and mammalian RNA are entrapped within the same liposome population and delivered into cultured cells, one can observe degradation of the procaryotic but not the eucaryotic RNA. Such an event cannot happen extracellularly. (b) Scanning electron microscopy reveals no more than 10 liposomes adhering to each cell upon liposome-cell interaction under conditions in which the RNA entrapped by 140 liposomes becomes associated with each cell. The ability of liposomes prepared by (a) the cochleate process, (b) the reverse-phase evaporation technique, and (c) the ether infusion technique, to sequester and deliver RNA into cells was investigated. Reverse-phase evaporated liposomes were most efficient in sequestering RNA (20–40%), however, all types of liposomes delivered RNA with comparable efficiency. The rate of liposome-mediated RNA delivery into mammalian cells could be substantially improved when: (a) liposome-cell interaction was carried out at pH 6.5 (twofold increase over pH 7.5), (b) a basic protein (methylated albumin) was present (two- to threefold increase), (c) liposome-cell cultures were treated with polyethylene glycol 6000 (four- to eight-fold increase), and (d) DEAE-dextran was added during interaction of liposomes with cell monolayers (four- to eight-fold increase).     

In vivo delivery of small interfering RNA targeting brain capillary endothelial cells

Brain capillary endothelial cells (BCECs) play an important role in blood-brain barrier (BBB) functions and pathophysiologic mechanisms in brain ischemia and inflammation. We try to suppress gene expression in BCECs by intravenous application of small interfering RNA (siRNA). After injection of large dose siRNA with hydrodynamic technique to mouse, suppression of endogenous protein and the BBB function of BCECs was investigated. The brain-to-blood transport function of organic anion transporter 3 (OAT3) that expressed in BCECs was evaluated by Brain Efflux Index method in mouse. The siRNA could be delivered to BCECs and efficiently inhibited endogenously expressed protein of BCECs. The suppression effect of siRNA to OAT3 is enough to reduce the brain-to-blood transport of OAT3 substrate, benzylpenicillin at BBB. The in vivo siRNA-silencing method with hydrodynamic technique may be useful for the study of BBB function and gene therapy targeting BCECs.     

Microfluidic delivery of small molecules into mammalian cells based on hydrodynamic focusing

Microfluidics-based cell assays offer high levels of automation and integration, and allow multiple assays to be run in parallel, based on reduced sample volumes. These characteristics make them attractive for studies associated with drug discovery. Controlled delivery of drug molecules or other exogenous materials into cells is a critical issue that needs to be addressed before microfluidics can serve as a viable platform for drug screening and studies. In this study, we report the application of hydrodynamic focusing for controlled delivery of small molecules into cells immobilized on the substrate of a microfluidic device. We delivered calcein AM which was permeant to the cell membrane into cells, and monitored its enzymatic conversion into fluorescent calcein during and after the delivery. Different ratios of the sample flow to the side flow were tested to determine how the conditions of hydrodynamic focusing affected the delivery. A 3D numerical model was developed to help understand the fluid flow, molecular diffusion due to hydrodynamic focusing in the microfluidic channel. The results from the simulation indicated that the calcein AM concentration on the outer surface of a cell was determined by the conditions of hydrodynamic focusing. By comparing the results from the simulation with those from the experiment, we found that the calcein AM concentration on the cell outer surface correlated very well with the amount of the molecules delivered into the cell. This suggests that hydrodynamic focusing provides an effective way for potentially quantitative delivery of exogenous molecules into cells at the single cell or subcellular level. We expect that our technique will pave the way to high-throughput drug screening and delivery on a microfluidic platform.     

Interleukin-6 receptor specific RNA aptamers for cargo delivery into target cells

Aptamers represent an emerging strategy to deliver cargo molecules, including dyes, drugs, proteins or even genes, into specific target cells. Upon binding to specific cell surface receptors aptamers can be internalized, for example by macropinocytosis or receptor mediated endocytosis. Here we report the in vitro selection and characterization of RNA aptamers with high affinity (Kd = 20 nM) and specificity for the human IL-6 receptor (IL-6R). Importantly, these aptamers trigger uptake without compromising the interaction of IL-6R with its natural ligands the cytokine IL-6 and glycoprotein 130 (gp130). We further optimized the aptamers to obtain a shortened, only 19-nt RNA oligonucleotide retaining all necessary characteristics for high affinity and selective recognition of IL-6R on cell surfaces. Upon incubation with IL-6R presenting cells this aptamer was rapidly internalized. Importantly, we could use our aptamer, to deliver bulky cargos, exemplified by fluorescently labeled streptavidin, into IL-6R presenting cells, thereby setting the stage for an aptamer-mediated escort of drug molecules to diseased cell populations or tissues.     

TAT-mediated delivery of human glutamate dehydrogenase into PC12 cells

Human glutamate dehydrogenase (GDH) gene was fused with a gene fragment encoding the nine amino acid (RKKRRQRRR) protein transduction domain of human immunodeficiency virus TAT protein in bacterial expression vector to produce genetic in-frame TAT-GDH fusion protein. The TAT-GDH protein can enter PC12 cells efficiently when added exogenously in culture media as determined by Western blot analysis and enzyme activities. Once inside the cells, the transduced denatured TAT-GDH protein showed a full activity of GDH indicating that the TAT-GDH fusion protein was correctly refolded after delivery into cells and the activities of GDH in the TAT-GDH fusion protein was not affected by the addition of the TAT sequence. TAT-GDH fusion protein and TAT itself showed no cytotoxicity in PC12 cells. Although the exact mechanism of transduction across a membrane remains unclear, the transduction activity of TAT-GDH into PC12 cells may suggest new possibilities for direct delivery of GDH into the patients with the GDH-deficient disorders.     

Conversion of human urine-derived cells into neuron-like cells by small molecules

Molecular Biology Reports - Neural cell transplantation is an effective way for treatment of neurological diseases. However, the absence of transplantable human neurons remains a barrier for...     

The paradoxical behavior of a highly structured misfolded intermediate in RNA folding

Like many structured RNAs, the Tetrahymena group I ribozyme is prone to misfolding. Here we probe a long-lived misfolded species, referred to as M, and uncover paradoxical aspects of its structure and folding. Previous work indicated that a non-native local secondary structure, termed alt P3, led to formation of M during folding in vitro. Surprisingly, hydroxyl radical footprinting, fluorescence measurements with site-specifically incorporated 2-aminopurine, and functional assays indicate that the native P3, not alt P3, is present in the M state. The paradoxical behavior of alt P3 presumably arises because alt P3 biases folding toward M, but, after commitment to this folding pathway and before formation of M, alt P3 is replaced by P3. Further, structural and functional probes demonstrate that the misfolded ribozyme contains extensive native structure, with only local differences between the two states, and the misfolded structure even possesses partial catalytic activity. Despite the similarity of these structures, re-folding of M to the native state is very slow and is strongly accelerated by urea, Na+, and increased temperature and strongly impeded by Mg2+ and the presence of native peripheral contacts. The paradoxical observations of extensive native structure within the misfolded species but slow conversion of this species to the native state are readily reconciled by a model in which the misfolded state is a topological isomer of the native state, and computational results support the feasibility of this model. We speculate that the complex topology of RNA secondary structures and the inherent rigidity of RNA helices render kinetic traps due to topological isomers considerably more common for RNA than for proteins.     

The highly structured encapsidation signal of MuLV RNA is involved in the nuclear export of its unspliced RNA

p27Kip1 (p27) influences cell division by regulating nuclear cyclin-dependent kinases. Before binding, p27 is at least partially disordered and folds upon binding its Cdk/cyclin targets. 30-40% of human proteins, including p27, are predicted to contain disordered segments, and have been termed intrinsically unstructured proteins (IUPs). Unfortunately, the inherent dynamics of IUPs hamper detailed analysis of their structure/function relationships. Here, we describe the use of molecular dynamics (MD) computations and solution NMR spectroscopy to reveal that several segments of the p27 kinase inhibitory domain (p27-KID), in addition to the previously characterized helical segment, exist as highly populated, intrinsically folded structural units (IFSUs). Several IFSUs resemble structural features of bound p27-KID, while another exhibits alternative conformations. Interestingly, the highly conserved, specificity determining segment of p27 is shown to be highly disordered. Elucidation of IFSUs within p27-KID allows consideration of their influences on the thermodynamics and kinetics of Cdk/cyclin binding. The degree to which IFSUs are populated within p27-KID is surprising and suggests that other putative IUPs contain IFSUs that may be studied using similar techniques.     

siRNA delivery using amphipathic cell-penetrating peptides into human hepatoma cells

Cell-penetrating peptides (CPPs) are an attractive tool for delivering membrane-impermeable compounds, including anionic biomacromolecules such as DNA and RNA, into living cells. Amphipathic helical peptides composed of hydrophobic amino acids and cationic amino acids are typical CPPs. In the current study, we designed amphipathic helical 12-mer peptides containing α,α-disubstituted α-amino acids (dAAs), which are known to stabilize peptide secondary structures. The dominant secondary structures of peptides in aqueous solution differed according to the introduced dAAs. Peptides containing hydrophobic dAAs and adopting a helical structure exhibited a good cell-penetrating ability. As an application of amphipathic helical peptides, small interfering RNA (siRNA) delivery into living human hepatoma cells was investigated. One of the peptides containing dAAs dipropylglycine formed stable complexes with siRNA at appropriate zeta-potential and size for intracellular siRNA delivery. This peptide showed effective RNA interference efficiency at short peptide length and low concentrations of peptide and siRNA. These findings will be helpful for the design of amphipathic helical CPPs as intracellular siRNA delivery.     

Types of non-viral delivery systems of small interfering RNA

To date, RNA interference remains the most powerful and promising tool for gene-targeted therapy. Several problems still have to be solved for its successful use in clinics. One of the main issues is the siRNA's efficient delivery. This review covers various types of nonviral siRNA delivery systems.     

Conjugate for efficient delivery of short interfering RNA (siRNA) into mammalian cells

Cholesterol enrichment of rat liver mitochondria (CHM) impairs atractyloside-induced mitochondrial permeability transition (MPT) due to decreased membrane fluidity. In this study we addressed the effect of cholesterol enrichment on MPT induced by reactive oxygen species (ROS). Superoxide anion generated by xanthine plus xanthine oxidase triggered mitochondrial swelling and cytochrome c release in CHM, which was prevented by butylated hydroxytoluene, an anti-voltage-dependent anion channel antibody, or cyclosporin A. Furthermore, hydrogen peroxide generated by the combination of ganglioside GD3 and mitochondrial GSH depletion elicited mitochondrial swelling and release of cytochrome c, Smac/Diablo and apoptosis-inducing factor in control mitochondria and CHM. Thus, ROS induce MPT and apoptosome activation regardless of decreased mitochondrial membrane dynamics due to cholesterol enrichment.