[Development of an ultrasound-mediated nucleic acid delivery system for treating muscular dystrophies]

Muscular dystrophies are a group of heterogeneous diseases that are characterized by progressive muscle weakness, wasting and degeneration. These muscular deficiencies are often caused by the loss of the protein dystrophin, a crucial element of the dystrophin-glycoprotein complex of muscle fibers. Duchenne muscular dystrophy (DMD) is a fatal, X-linked muscular disease that occurs in 1 out of every 3500 males. Therefore, feasible strategies for replacing or repairing the defective gene are required; however, to date, no effective therapeutic strategies for muscular dystrophies have been established. In this review, we first introduce gene therapies mediated by adeno-associated viruses (AAVs) including a functional dystrophin cDNA or antisense oligonucleotide (AO)-induced exon-skipping therapies, which are designed to exclude the mutated or additional exon(s) in the defective gene and thereby correct the translational reading frame. Recently, we developed "Bubble liposomes" (BLs), which are polyethylene glycol (PEG)-modified liposomes entrapping echo-contrast gas that is known as ultrasound (US) imaging gas. BL application combined with US exposure can function as a novel gene delivery tool, and we demonstrate that the US-mediated eruption of BLs is a feasible and efficient technique to deliver plasmid DNA or AOs for the treatment of muscular dystrophies.

Alkylimidazolium end-modified poly(ethylene glycol) to form the mono-ion complex with plasmid DNA for in vivo gene delivery

In this study, we consider that the decrease in the transfection activity of polycations in vivo, compared with that in vitro, results from their polyion complex formation. Namely, owing to cross-linking between polycations and plasmid DNAs (pDNAs), the disadvantage of in vivo gene delivery mainly stems from the difficulty in controlling the properties of the resulting polyion complex at the nanoscale size. To avoid the cross-linking by polycations, we have establish the concept of "mono-ion complex" formation between pDNA and a monocationic biocompatible polymer. Here we have synthesized alkylimidazolium end-modified poly(ethylene glycol), that is, R-Im-PEG, and have tuned the electrostatic interaction between the resulting alkylimidazolium group and the phosphate group of pDNA by the length of the alkyl chain to achieve "mono-ion complex" formation with pDNA for in vivo gene delivery. Instead of a polyion complex, our original concept of the "mono-ion complex" consisting of the Bu-Im-PEG and pDNA is expected to offer unique tools to break through the barriers of in vivo gene delivery. As well as the field of gene delivery, this study is considered to have exploded the common sense that it is impossible to form not a polyion complex but a "mono-ion complex" under aqueous conditions for all fields of the modification of biomacromolecules.

Bubble liposomes and ultrasound exposure improve localized morpholino oligomer delivery into the skeletal muscles of dystrophic mdx mice

Duchenne muscular dystrophy (DMD) is a genetic disorder that is caused by mutations in the DMD gene that lead to an absence of functional protein. The mdx dystrophic mouse contains a nonsense mutation in exon 23 of the dystrophin gene; a phosphorodiamidate morpholino oligomer (PMO) designed to skip this mutated exon in the mRNA induces dystrophin expression. However, an efficient PMO delivery method is needed to improve treatment strategies for DMD. We previously developed polyethylene glycol (PEG)-modified liposomes (Bubble liposomes) that entrap ultrasound contrast gas and demonstrated that the combination of Bubble liposomes with ultrasound exposure is an effective gene delivery tool in vitro and in vivo. In this study, to evaluate the ability of Bubble liposomes as a PMO delivery tool, we tested the potency of the Bubble liposomes combined with ultrasound exposure to boost the delivery of PMO and increase the skipping of the mutated exon in the mdx mouse. The results indicated that the combination of Bubble liposomes and ultrasound exposure increased the uptake of the PMO targeting a nonsense mutation in exon 23 of the dystrophin gene and consequently increased the PMO-mediated exon-skipping efficiency compared with PMO injection alone, leading to significantly enhanced dystrophin expression. This increased efficiency indicated the potential of the combination of Bubble liposomes with ultrasound exposure to enhance PMO delivery for treating DMD. Thus, this ultrasound-mediated Bubble liposome technique may provide an effective, noninvasive, nonviral method for PMO therapy for DMD muscle as well as for other muscular dystrophies.

Systemic delivery of miR-126 by miRNA-loaded Bubble liposomes for the treatment of hindlimb ischemia

Currently, micro RNA (miRNA) is considered an attractive target for therapeutic intervention. A significant obstacle to the miRNA-based treatments is the efficient delivery of miRNA to the target tissue. We have developed polyethylene glycol-modified liposomes (Bubble liposomes (BLs)) that entrap ultrasound (US) contrast gas and can serve as both plasmid DNA (pDNA) or small interfering RNA (siRNA) carriers and US contrast agents. In this study, we investigated the usability of miRNA-loaded BLs (mi-BLs) using a hindlimb ischemia model and miR-126. It has been reported that miR-126 promotes angiogenesis via the inhibition of negative regulators of VEGF signaling. We demonstrated that mi-BLs could be detected using diagnostic US and that mi-BLs with therapeutic US could deliver miR-126 to an ischemic hindlimb, leading to the induction of angiogenic factors and the improvement of blood flow. These results suggest that combining mi-BLs with US may be useful for US imaging and miRNA delivery.

[Novel dianostics and therapeutics with ultrasound technologies and nanotechnologies]

Ultrasound is a good tool for theranostics due to have multi-potency both of diagnostics with sonography and therapeutics with high intensity focused ultrasound (HIFU). In addition, microbubbles and nanobubbles are utilized as not only contrast imaging agent but also enhancer of drug and gene delivery by combination of ultrasound. Recently, we developed novel liposomal nanobubbles (Bubble liposomes) which were containing perfluoropropane. Bubble liposomes induced jet stream by low intensity ultrasound exposure and resulted in enhancing permeability of cell membrane. This phenomenon has been utilized as driving force for drug and gene delivery. On the other hand, the combination of Bubble liposomes and high intensity ultrasound induces strong jet stream and increase temperature. This condition can directly damage to tumor cells, we are applying this for cancer therapy. Therefore, their combination has potency for various cancer therapies such as gene therapy, immunotherapy and hyperthermia. In this review, we discuss about cancer therapy by the combination of Bubble liposomes and ultrasound.

Paraneoplastic cerebellar degeneration caused by ovarian clear-cell carcinoma

Paraneoplastic cerebellar degeneration is a paraneoplastic neurological syndrome caused by the remote effect of certain systemic cancers and is characterized by subacute cerebellar symptoms. A 62-year-old woman suffering from unidentified cerebellar symptoms was admitted to our hospital. Paraneoplastic cerebellar degeneration was suspected and ovarian cancer was detected after the systemic examination for malignancy. The symptoms of vertigo and dysarthria were improved a little after surgical operation and treatments of γ-globulin, steroid pulse and tacrolimus hydrate. The cerebellar symptoms of paraneoplastic cerebellar degeneration are often evident prior to detection of malignancy. It is important to perform systemic examination for malignancy in case of unidentified cerebellar symptoms.

Gene delivery to periodontal tissue using Bubble liposomes and ultrasound

BACKGROUND AND OBJECTIVE

Periodontitis is the most common inflammatory disease caused by oral biofilm infection. For efficient periodontal treatment, it is important to enhance the outcome of existing regenerative therapies. The physical action of an ultrasound may be able to deliver a therapeutic gene or drugs into the local area of the periodontium being treated for periodontal regeneration. Previously, we developed "Bubble liposomes" as a useful carrier for gene or drug delivery, and reported that delivery efficiency was increased with high-frequency ultrasound in vitro and in vivo. Hence, the aim of the present study was to examine the possibility of delivering genes into gingival tissues using Bubble liposomes and ultrasound.

MATERIAL AND METHODS

We attempted to deliver naked plasmid DNA encoding luciferase or enhanced green fluorescent protein (EGFP) into the lower labial gingiva of Wistar rats using Bubble liposomes, with or without ultrasound exposure. Ultrasound parameters were optimized for intensity (0-4.0 W/cm(2) ) and exposure time (0-120 s) to establish the most efficient conditions for exposure. The efficacy and duration of gene expression in the gingiva were investigated using a luciferase assay and fluorescence microscopy.

RESULTS

The strongest relative luciferase activity was observed when rats were treated under the following ultrasound conditions: 2.0 W/cm(2) intensity and 30 s of exposure time. Relative luciferase activity, 1 d after gene delivery, was significantly higher in gingiva treated using Bubble liposomes and ultrasound than in gingiva of the other treatment groups. Histological analysis also showed that distinct EGFP-expressing cells were observed in transfected gingiva when rats were treated under optimized conditions.

CONCLUSION

From these results, the combination of Bubble liposomes and ultrasound provides an efficient technique for delivering plasmid DNA into the gingiva. This technique can be applied for the delivery of a variety of therapeutic molecules into target tissue, and may serve as a useful treatment strategy for periodontitis.

AG73-modified Bubble liposomes for targeted ultrasound imaging of tumor neovasculature

Ultrasound imaging is a widely used imaging technique. The use of contrast agents has become an indispensible part of clinical ultrasound imaging, and molecular imaging via ultrasound has recently attracted significant attention. We recently reported that "Bubble liposomes" (BLs) encapsulating US imaging gas liposomes were suitable for ultrasound imaging and gene delivery. The 12 amino acid AG73 peptide derived from the laminin α1 chain is a ligand for syndecans, and syndecan-2 is highly expressed in blood vessels. In this study, we prepared AG73 peptide-modified BLs (AG73-BLs) and assessed their specific attachment and ultrasound imaging ability for blood vessels in vitro and in vivo. First, we assessed the specific attachment of AG73-BLs in vitro, using flow cytometry and microscopy. AG73-BLs showed specific attachment compared with non-labeled or control peptide-modified BLs. Next, we examined ultrasound imaging in tumor-bearing mice. When BLs were administered, contrast imaging of AG73-BLs was sustainable for up to 4 min, while contrast imaging of non-labeled BLs was not observed. Thus, it is suggested that AG73-BLs may become useful ultrasound contrast agents in the clinic for diagnosis based on ultrasound imaging.

CXCL17 expression by tumor cells recruits CD11b+Gr1 high F4/80- cells and promotes tumor progression

Background

Chemokines are involved in multiple aspects of pathogenesis and cellular trafficking in tumorigenesis. In this study, we report that the latest member of the C-X-C-type chemokines, CXCL17 (DMC/VCC-1), recruits immature myeloid-derived cells and enhances early tumor progression.

Methodology/Principal Findings

CXCL17 was preferentially expressed in some aggressive types of gastrointestinal, breast, and lung cancer cells. CXCL17 expression did not impart NIH3T3 cells with oncogenic potential in vitro, but CXCL17-expressing NIH3T3 cells could form vasculature-rich tumors in immunodeficient mice. Our data showed that CXCL17-expressing tumor cells increased immature CD11b⁺Gr1⁺ myeloid-derived cells at tumor sites in mice and promoted CD31⁺ tumor angiogenesis. Extensive chemotactic assays proved that CXCL17-responding cells were CD11b⁺Gr1^highF4/80⁻ cells (∼90%) with a neutrophil-like morphology in vitro. Although CXCL17 expression could not increase the number of CD11b⁺Gr1⁺ cells in tumor-burdened SCID mice or promote metastases of low metastatic colon cancer cells, the existence of CXCL17-responding myeloid-derived cells caused a striking enhancement of xenograft tumor formation.

Conclusions/Significance

These results suggest that aberrant expression of CXCL17 in tumor cells recruits immature myeloid-derived cells and promotes tumor progression through angiogenesis.

Involvement of Ca²⁺ and ATP in enhanced gene delivery by bubble liposomes and ultrasound exposure

Recently, we reported the accelerated gene transfection efficiency of laminin-derived AG73-peptide-labeled polyethylene glycol-modified liposomes (AG73-PEG liposomes) and cell penetrating TAT-peptide labeled PEG liposomes using PEG-modified liposomes, which trap echo-contrast gas, "Bubble liposomes" (BLs), and ultrasound (US) exposure. BLs and US exposure were reported to enhance the endosomal escape of AG73-PEG liposomes, thereby leading to increased gene expression. However, the mechanism behind the effect of BLs and US exposure on endosomes is not well understood. US exposure was reported to induce an influx of calcium ions (Ca²⁺) by enhancing permeability of the cell membrane. Therefore, we examined the effect of Ca²⁺ on the endosomal escape and transfection efficiency of AG73-PEG liposomes, which were previously enhanced by BLs and US exposure. For cells treated with EGTA, the endosomal escape and gene expression of AG73-PEG liposomes were not enhanced by BLs and US exposure. Similarly, transfection efficiency of the AG73-PEG liposomes in ATP-depleted cells was not enhanced. Our results suggest that Ca²⁺ and ATP are necessary for the enhanced endosomal escape and gene expression of AG73-PEG liposomes by BLs and US exposure. These findings may contribute to the development of useful techniques to improve endosomal escape and achieve efficient gene transfection.

Involvement of actin cytoskeleton in macrophage apoptosis induced by cationic liposomes

We clarified whether actin cytoskeleton is involved in the macrophage apoptosis induced by cationic liposomes composed of stearylamine (SA-liposomes). Externalization of phosphatidylserine induced by SA-liposomes was suppressed by cytochalasin D, a specific inhibitor of polymerization of F-actin. Furthermore, activation of PKCδ and reactive oxygen species (ROS) generation, which could be involved in the macrophage apoptosis, were inhibited by cytochalasin D. Microscopical observation revealed the co-localization of 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI)-labeled SA-liposomes and fluorescein-labeled phalloidin, which specifically binds to F-actin, and this co-localization was also inhibited by cytochalasin D. Co-localization of SA-liposomes and F-actin was also inhibited by the pre-treatment of cells with chondroitinase ABC. These findings could be the first observation concerning the contribution of the proteoglycan-actin cytoskeleton-ROS generation pathway to apoptosis induced by SA-liposomes in macrophages.

Effects of doxorubicin-encapsulating AG73 peptide-modified liposomes on tumor selectivity and cytotoxicity

Doxorubicin-encapsulating liposomal formulations, known as Doxil, have been used for the treatment of Kaposi's sarcoma and ovarian cancer. However, there is still a need for a drug delivery system for doxorubicin that limits the treatment's side effects, namely, mucositis and hand-and-foot syndrome. The AG73 peptide derived from the laminin α1 chain is a ligand for syndecans, and syndecan-2 is highly expressed in some cancer cells. In this study, to develop a safer and more selective liposomal formulation, we prepared doxorubicin-encapsulating AG73 peptide-modified liposomes (AG73-Dox). First, we assessed the selectivity of AG73-Dox for cancer cells, including syndecan-2 over-expressing cells, using flow cytometry and confocal microscopy. AG73-Dox showed selective cellular uptake on cancer cells and enhancement of the intracellular uptake. Next, we examined the cytotoxicity of AG73-Dox using a WST assay. AG73-Dox exhibited a higher cytotoxicity against cancer cells than other control liposomes. In addition, we showed that the antitumor efficacy of AG73-Dox in vivo was better than that of free Dox. When we examined the biodistribution of liposomes, AG73 peptide-modified liposomes (AG73-L) tended to bind to intratumoral vessels and extravasated in the tumor tissue. Thus, further optimization of AG73-L toward tumor targeting may lead to a development of a useful tool for cancer therapy.

Involvement of lipid rafts in macrophage apoptosis induced by cationic liposomes

We have demonstrated that protein kinase Cδ (PKCδ) could be involved in macrophage apoptosis induced by cationic liposomes composed of stearylamine (SA-liposomes), but the detailed mechanism of how SA-liposomes activate PKCδ has remained unclear. In this paper, we clarified whether lipid rafts are involved in the PKCδ activation induced by SA-liposomes. Co-localization of SA-liposomes and Cholera toxin B subunit (CBT), which specifically binds to ganglioside GM1 on lipid rafts, was found by microscopic observation. The incorporation of SA-liposomes into lipid rafts was clearly inhibited by the pretreatment of cells with an agent, 2,6-di-O-methyl-α-cyclodextrin (DM-α-CD) which disrupts lipid rafts. Activation of PKCδ and externalization of phosphatidylserine induced by SA-liposomes were also suppressed by DM-α-CD, which extracts sphingolipids and proteins from lipid rafts. Reactive oxygen species (ROS) generation, which could be involved in the macrophage apoptosis, was also inhibited by DM-α-CD. Furthermore, apoptosis induced by SA-liposomes was clearly inhibited when the cells were pre-treated with DM-α-CD, but not nystatin, a cholesterol-sequestering agent that disrupt lipid rafts. These findings suggest that sphingolipids in lipid rafts are involved in the activation of PKCδ which leads to apoptosis induced by cationic liposomes, SA-liposomes.

An RNA G-quadruplex is essential for cap-independent translation initiation in human VEGF IRES

RNA G-quadruplexes located within the 5'-UTR of mRNA are almost always known to be associated with repression of cap-dependent translation. However, in this report we present functional as well as structural evidence that sequence redundancy in a G-rich segment within the 5'-UTR of human VEGF mRNA supports a 'switchable' RNA G-quadruplex structure that is essential for IRES-mediated translation initiation. Additionally, utilization of a specific combination of G-tracts within this segment allows for the conformational switch that implies a tunable regulatory role of the quadruplex structure in translation initiation. A sequence engineered from a functionally handicapped mutant moderately rescued the activity, further indicating the importance of G-quadruplex structure for VEGF IRES-A function. This to our knowledge is the first report of a conformationally flexible RNA G-quadruplex which is essential for IRES-mediated translation initiation.

Cancer cell specific gene delivery by laminin-derived peptide AG73-labeled liposomes

We developed laminin-derived AG73 peptide labeled liposomes for cancer specific gene therapy. AG73 peptide is well known as a ligand for syndecan-2 which is highly expressed in various cancer cells. Liposomes labeled with AG73 showed high efficient transfection efficiency in syndecan-2 overexpressing cells, and found that AG73 could be a superior molecule in the development of non-viral vector using liposomes for the gene delivery to syndecan-2 overexpressing cancer cells.