Pressure-Mediated Transfection of Murine Spleen and Liver

Effects of Tissue Pressure on Transgene Expression Characteristics via Renal Local Administration Routes from Ureter or Renal Artery in the Rat Kidney

We previously developed a renal pressure-mediated transfection method (renal pressure method) as a kidney-specific in vivo gene delivery system. However, additional information on selecting other injection routes and applicable animals remains unclear. In this study, we selected renal arterial and ureteral injections as local administration routes and evaluated the characteristics of gene delivery such as efficacy, safety, and distribution in pressured kidney of rat. Immediately after the naked pDNA injection, via renal artery or ureter, the left kidney of the rat was pressured using a pressure controlling device. Transfection efficiency of the pressured kidney was about 100-fold higher than that of the injection only group in both administration routes. The optimal pressure intensity in the rat kidney was 1.2 N/cm² for renal arterial injection and 0.9 N/cm² for ureteral injection. We found that transgene expression site differs according to administration route: cortical fibroblasts and renal tubule in renal arterial injection and cortical and medullary tubule and medullary collecting duct in ureteral injection. This is the first report to demonstrate that the renal pressure method can also be effective, after renal arterial and ureteral injections, in rat kidney.

Determining Transgene Expression Characteristics Using a Suction Device with Multiple Hole Adjusting a Left Lateral Lobe of the Mouse Liver

We developed a tissue suction-mediated transfection method (suction method) as a relatively reliable and less invasive technique for in vivo transfection. In this study, we determined hepatic transgene expression characteristics in the mouse liver, using a suction device, collecting information relevant to gene therapy and gene functional analysis by the liver suction method. To achieve high transgene expression levels, we developed a suction device with four holes (multiple hole device) and applied it to the larger portion of the left lateral lobe of the mouse liver. Hepatic transfection with physical stimuli was potentially controlled by activator protein-1 (AP-1) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). We examined the spatial distribution of transgene expression in the suctioned lobe by 2-dimensional imaging with histochemical staining and 3-dimensional multicolor deep imaging with tissue clearing methods. Through monitoring spatial distribution of transgene expression, the liver suction method was used to efficiently transfect extravascular hepatocytes in the suction-deformable upper lobe of the liver. Moreover, long-term transgene expression, at least 14 d, was achieved with the liver suction method when cytosine-phosphate-guanine (CpG)-free plasmid DNA was applied.

Multistep, effective drug distribution within solid tumors

The distribution of drugs within solid tumors presents a long-standing barrier for efficient cancer therapies. Tumors are highly resistant to diffusion, and the lack of blood and lymphatic flows suppresses convection. Prolonged, continuous intratumoral drug delivery from a miniature drug source offers an alternative to both systemic delivery and intratumoral injection. Presented here is a model of drug distribution from such a source, in a multistep process. At delivery onset the drug mainly affects the closest surroundings. Such 'priming' enables drug penetration to successive cell layers. Tumor 'void volume' (volume not occupied by cells) increases, facilitating lymphatic perfusion. The drug is then transported by hydraulic convection downstream along interstitial fluid pressure (IFP) gradients, away from the tumor core. After a week tumor cell death occurs throughout the entire tumor and IFP gradients are flattened. Then, the drug is transported mainly by 'mixing', powered by physiological bulk body movements. Steady state is achieved and the drug covers the entire tumor over several months. Supporting measurements are provided from the LODER system, releasing siRNA against mutated KRAS over months in pancreatic cancer in-vivo models. LODER was also successfully employed in a recent Phase 1/2 clinical trial with pancreatic cancer patients.

Optimization of renal transfection using a renal suction-mediated transfection method in mice

BACKGROUND

We previously developed a suction-mediated transfection method in mice.

PURPOSE

The purpose of this study was to optimize the suction-mediated transfection conditions using a pressure-controlled computer system for efficient and safe kidney-targeted gene delivery in mice.

METHODS

Naked pCMV-Luc was injected into the tail vein in mice, and then the right kidney was suctioned by a device of the suction pressure-controlled system. The effects of renal transfection conditions, such as the suction pressure degree, suction pressure waveform and device area were evaluated by measuring luciferase expression. In addition, renal injury was examined.

RESULTS

The renal suction-mediated transfection method at -30 kPa showed high transgene expression. The renal suction waveform did not affect the transfection activity. Under the optimized conditions, the high transgene expression was mostly observed at the renal suctioned site. The transfection conditions used did not induce histological defects or increases in two renal injury biomarkers (Kidney injury molecule-1 mRNA and Clusterin mRNA).

DISCUSSION AND CONCLUSION

We have clarified the transfection conditions for efficient and safe transfection in the kidney using the suction-mediated transfection method in mice.

In vivo site-specific transfection of naked plasmid DNA and siRNAs in mice by using a tissue suction device

We have developed an in vivo transfection method for naked plasmid DNA (pDNA) and siRNA in mice by using a tissue suction device. The target tissue was suctioned by a device made of polydimethylsiloxane (PDMS) following the intravenous injection of naked pDNA or siRNA. Transfection of pDNA encoding luciferase was achieved by the suction of the kidney, liver, spleen, and heart, but not the duodenum, skeletal muscle, or stomach. Luciferase expression was specifically observed at the suctioned region of the tissue, and the highest luciferase expression was detected at the surface of the tissue (0.12±0.03 ng/mg protein in mice liver). Luciferase expression levels in the whole liver increased linearly with an increase in the number of times the liver was suctioned. Transfection of siRNA targeting glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene significantly suppressed the expression of GAPDH mRNA in the liver. Histological analysis shows that severe damage was not observed in the suctioned livers. Since the suction device can be mounted onto the head of the endoscope, this method is a minimally invasive. These results indicate that the in vivo transfection method developed in this study will be a viable approach for biological research and therapies using nucleic acids.

Involvement of activated transcriptional process in efficient gene transfection using unmodified and mannose-modified bubble lipoplexes with ultrasound exposure

Recently, our group developed ultrasound (US)-responsive and mannose-modified gene carriers (Man-PEG(2000) bubble lipoplexes), and successfully obtained a high level of gene expression in mannose receptor-expressing cells following gene transfection using Man-PEG(2000) bubble lipoplexes and US exposure. We also reported that large amounts of plasmid DNA (pDNA) were transferred into the cytoplasm of the targeted cells in the gene transfection using this method. In the present study, we investigated the involvement of transcriptional processes on enhanced gene expression obtained by unmodified and Man-PEG(2000) bubble lipoplexes with US exposure. The transcriptional process related to activator protein-1 (AP-1) and nuclear factor-κB (NFκB) was activated by US exposure, and was founded to be involved in enhanced gene expression obtained by gene transfection using unmodified and Man-PEG(2000) bubble lipoplexes with US exposure. On the other hand, activation of AP-1 and NFκB pathways followed by US exposure was hardly involved in the inflammatory responses in the gene transfection using this method. These findings suggest that activation of AP-1 and NFκB followed by US exposure is involved in the enhanced gene expression using unmodified and Man-PEG(2000) bubble lipoplexes with US exposure, and the selection of pDNAs activated by US exposure is important in this gene transfection method.

[Development of tissue pressure-mediated transfection method aimed at organ-specific gene expression control]

A mechanism-based logical approach is a mainstream of current novel drug therapy development in the context of these trends and, therefore, the elucidation of gene function and the molecular level mechanism analysis of diseases at an individual level in mammals are essential in addition to that in cultured cells. In vivo gene transfection techniques are also indispensable for these purposes as well as the evaluation of gene therapy and nucleic acid-based therapy approaches and clinical applications during the process of development of novel drug therapies. Various recombinant virus and synthetic carrier-mediated transfection methods have been reported, however, above all, naked plasmid DNA transfection without virus vectors, synthetic carriers and special physical devices has attracted much attention, because of its advantages including convenience of preparation and handling and lack of toxicity associated with the transfection agents. In this review, I collect the information of these naked plasmid DNA transfection methods involving tissue pressure-mediated transfection from the comprehensive view point including side effects. Additively, the key physiological phenomena affecting transgene expression, especially activation of transcriptional factors, are reviewed. Combined with conventional approach based with biodistribution control, regulation of physiological change in transfected cells will provide spatial- and temporal-controlled transgene expression at various organs, which leads us to elucidate mechanism of diseases and to develop novel drug therapy in near future.

Strategies for in vivo delivery of siRNAs: recent progress

RNA interference (RNAi) is a post-transcriptional gene-silencing mechanism that involves the degradation of messenger RNA in a highly sequence-specific manner. Double-stranded small interfering RNA (siRNA), consisting of 21-25 nucleotides, can induce RNAi and inhibit the expression of target proteins. Therefore, siRNA is considered a promising therapeutic for treatment of a variety of diseases, including genetic and viral diseases, and cancer. Clinical trials of siRNA are ongoing or have been planned, although some issues need to be addressed. For example, cellular uptake of naked siRNA is extremely low due to its polyanionic nature. Furthermore, siRNA is easily degraded by enzymes in blood, tissues, and cells. Several types of chemically modified siRNA have been produced and investigated to improve stability; these have involved modification of the siRNA backbone, the sugar moiety, and the nucleotide bases of antisense and/or sense strands. Because the accumulation at the target site after administration is extremely low, even if stability is improved, an effective delivery system is required to induce RNAi at the site of action. Delivery strategies can be categorized into physical methods, conjugation methods, and drug delivery system carrier-mediated methods. Physical techniques can enhance siRNA uptake at a specific tissue site using electroporation, pressure, mechanical massage, etc. Terminal modification of siRNAs can enhance their resistance to degradation by exonucleases in serum and tissue. Moreover, modification with a suitable ligand can achieve targeted delivery. Several types of carrier for drug delivery have been developed for siRNA in addition to traditional cationic liposome and cationic polymer systems. Ultrasound and microbubbles or liposomal bubbles have also been used in combination with a carrier for siRNA delivery. New materials with unique characteristics such as carbon nanotubes, gold nanoparticles, and gold nanorods have attracted attention as innovative carriers for siRNA.

piggyBac transposon-mediated long-term gene expression in mice

Transposons are promising systems for somatic gene integration because they can not only integrate exogenous genes efficiently, but also be delivered to a variety of organs using a range of transfection methods. piggyBac (PB) transposon has a high transposability in mammalian cells in vitro, and has been used for genetic and preclinical studies. However, the transposability of PB in mammalian somatic cells in vivo has not been demonstrated yet. Here, we demonstrated PB-mediated sustained gene expression in adult mice. We constructed PB-based plasmid DNA (pDNA) containing reporter [firefly and Gaussia luciferase (Gluc)] genes. Mice were transfected by injection of these pDNAs using a hydrodynamics-based procedure, and the conditions for high-level sustained gene expression were examined. Consequently, gene expressions were sustained over 2 months. Our results suggest that PB is useful for organ-selective somatic integration and sustained gene expression in mammals, and will contribute to basic genetic studies and gene therapies.