Ultrasound with microbubbles enhances gene expression of plasmid DNA in the liver via intraportal delivery

Ultrasound-mediated gene delivery specifically targets liver sinusoidal endothelial cells for sustained FVIII expression in hemophilia A mice

The ability to target the native production site of factor VIII (FVIII)-liver sinusoidal endothelial cells (LSECs)-can improve the outcome of hemophilia A (HA) gene therapy. By testing a matrix of ultrasound-mediated gene delivery (UMGD) parameters for delivering a GFP plasmid into the livers of HA mice, we were able to define specific conditions for targeted gene delivery to different cell types in the liver. Subsequently, two conditions were selected for experiments to treat HA mice via UMGD of an endothelial-specific human FVIII plasmid: low energy (LE; 50 W/cm2, 150 μs pulse duration) to predominantly target endothelial cells or high energy (HE; 110 W/cm2, 150 μs pulse duration) to predominantly target hepatocytes. Both groups of UMGD-treated mice achieved persistent FVIII activity levels of ∼10% over 84 days post treatment; however, half of the HE-treated mice developed low-titer inhibitors while none of the LE mice did. Plasma transaminase levels and histological liver examinations revealed minimal transient liver damage that was lower in the LE group than in the HE group. These results indicate that UMGD can safely target LSECs with a lower-energy condition to achieve persistent FVIII gene expression, demonstrating that this novel technology is highly promising for therapeutic correction of HA.

Major Strategies for Spatial Control of Ultrasound-Driven Gene Expression to Enhance Therapeutic Specificity

A major challenge of gene therapy is to achieve highly specific transgene expression in tissues of interest with minimized off-target expression. Ultrasound in combination with microbubbles can transiently increase permeability of desired cells or tissues and thereby facilitate gene transfer. This kind of ultrasound-driven transgene expression has gained increasing attention due to its deep tissue penetration and high spatiotemporal resolution. However, successful genetic manipulation in vivo with ultrasound need to well optimize various aspects involved in this process. Ultrasound parameters, microbubble dose, and gene vectors need to be optimized for highly increased transgene expression in the cells of interest. Conversely, the potential off-target transgene expression and toxicities need to be reduced by modification of gene vectors and/or promoter sequence. This review will discuss some major strategies for enhanced specificity of the ultrasound-mediated gene transfer in vivo. Five major strategies will be discussed, including the integration of real-time imaging methods, local injection, targeted microbubbles loaded with nucleic acids, stealth nanocarriers, and cell-specific promoter. The advantages and limitations of each strategy were outlined, hoping to provide a guideline for researchers in achieving high specific ultrasound-driven gene expression.

Silencing TLR4 using an ultrasound-targeted microbubble destruction-based shRNA system reduces ischemia-induced seizures in hyperglycemic rats

The toll-like receptor 4 (TLR4) pathway is involved in seizures. We investigated whether ultrasound-targeted microbubble destruction (UTMD)-mediated delivery of short hairpin RNA (shRNA) targeting the TLR4 gene (shRNA-TLR4) can reduce ischemia-induced seizures in rats with hyperglycemia. A total of 100 male Wistar rats were randomly assigned to five groups: (1) Sham; (2) normal saline (NS); (3) shRNA-TLR4, where rats were injected with shRNA-TLR4; (4) shRNA-TLR4 + US, where rats were injected with shRNA-TLR4 followed by ultrasound (US) irradiation; and (5) shRNA-TLR4 + microbubbles (MBs) + US, where rats were injected with shRNA-TLR4 mixed with MBs followed by US irradiation. Western blot and immunohistochemical staining were used to measure TLR4-positive cells. Half of the rats in the NS group developed tonic-clonic seizures, and TLR4 expression in the CA3 region of the hippocampus was increased in these rats. In addition, the NS group showed an increased number of TLR4-positive cells compared with the Sham group, while there was a decreased number of TLR4-positive cells in the shRNA, shRNA + US, and shRNA + MBs + US groups. Our findings indicate that the TLR4 pathway is involved in the pathogenesis of ischemia-induced seizures in hyperglycemic rats and that UTMD technology may be a promising strategy to treat brain diseases.

Ultrasound-mediated gene delivery of factor VIII plasmids for hemophilia A gene therapy in mice

Gene therapy offers great promises for a cure of hemophilia A resulting from factor VIII (FVIII) gene deficiency. We have developed and optimized a non-viral ultrasound-mediated gene delivery (UMGD) strategy. UMGD of reporter plasmids targeting mice livers achieved high levels of transgene expression predominantly in hepatocytes. Following UMGD of a plasmid encoding human FVIII driven by a hepatocyte-specific promoter/enhancer (pHP-hF8/N6) into the livers of hemophilia A mice, a partial phenotypic correction was achieved in treated mice. In order to achieve persistent and therapeutic FVIII gene expression, we adopted a plasmid (pHP-hF8-X10) encoding an FVIII variant with significantly increased FVIII secretion. By employing an optimized pulse-train ultrasound condition and immunomodulation, the treated hemophilia A mice achieved 25%–150% of FVIII gene expression on days 1–7 with very mild transient liver damage, as indicated by a small increase of transaminase levels that returned to normal within 3 days. Therapeutic levels of FVIII can be maintained persistently without the generation of inhibitors in mice. These results indicate that UMGD can significantly enhance the efficiency of plasmid DNA transfer into the liver. They also demonstrate the potential of this novel technology to safely and effectively treat hemophilia A.

Ultrasonic particles: An approach for targeted gene delivery

Gene therapy has been widely investigated for the treatment of genetic, acquired, and infectious diseases. Pioneering work utilized viral vectors; however, these are suspected of causing serious adverse events, resulting in the termination of several clinical trials. Non-viral vectors, such as lipid nanoparticles, have attracted significant interest, mainly due to their successful use in vaccines in the current COVID-19 pandemic. Although they allow safe delivery, they come with the disadvantage of off-target delivery. The application of ultrasound to ultrasound-sensitive particles allows for a direct, site-specific transfer of genetic materials into the organ/site of interest. This process, termed ultrasound-targeted gene delivery (UTGD), also increases cell membrane permeability and enhances gene uptake. This review focuses on the advances in ultrasound and the development of ultrasonic particles for UTGD across a range of diseases. Furthermore, we discuss the limitations and future perspectives of UTGD.

Regeneration of testis tissue after ectopic implantation of porcine testis cell aggregates in mice: improved consistency of outcomes and in situ monitoring

Ectopic implantation of donor testis cell aggregates in recipient mice results in de novo formation or regeneration of testis tissue and, as such, provides a unique invivo model for the study of testis development. However, currently the results are inconsistent and the efficiency of the model remains low. This study was designed to: (1) examine several factors that can potentially improve the consistency and efficiency of this model and (2) explore the use of ultrasound biomicroscopy (UBM) for the non-invasive invivo evaluation of implants. Testis cell aggregates, containing ~40% gonocytes, from 1-week-old donor piglets were implanted under the back skin of immunodeficient mice through skin incisions using gel matrices or through subcutaneous injection without using gel matrices. The addition of gel matrices led to inconsistent tissue development; gelatin had the greatest development, followed by collagen, whereas agarose resulted in poor development. The results also depended on the implanted cell numbers since implants with 100×106 cells were larger than those with 50×106 cells. The injection approach for cell implantation was less invasive and resulted in more consistent and efficient testis tissue development. UBM provided promising results as a means of non-invasive monitoring of implants.

Transcutaneous Ultrasound-Mediated Nonviral Gene Delivery to the Liver in a Porcine Model

Ultrasound (US)-mediated gene delivery (UMGD) of nonviral vectors was demonstrated in this study to be an effective method to transfer genes into the livers of large animals via a minimally invasive approach. We developed a transhepatic venous nonviral gene delivery protocol in combination with transcutaneous, therapeutic US (tUS) to facilitate significant gene transfer in pig livers. A balloon catheter was inserted into the pig hepatic veins of the target liver lobes via jugular vein access under fluoroscopic guidance. tUS exposure was continuously applied to the lobe with simultaneous infusion of pGL4 plasmid (encoding a luciferase reporter gene) and microbubbles. tUS was delivered via an unfocused, two-element disc transducer (H105) or a novel focused, single-element transducer (H114). We found applying transcutaneous US using H114 and H105 with longer pulses and reduced acoustic pressures resulted in an over 100-fold increase in luciferase activity relative to untreated lobes. We also showed effective UMGD by achieving focal regions of >10⁵ relative light units (RLUs)/mg protein with minimal tissue damage, demonstrating the feasibility for clinical translation of this technique to treat patients with genetic diseases.

Applications of Ultrasound to Stimulate Therapeutic Revascularization

Many pathological conditions are characterized or caused by the presence of an insufficient or aberrant local vasculature. Thus, therapeutic approaches aimed at modulating the caliber and/or density of the vasculature by controlling angiogenesis and arteriogenesis have been under development for many years. As our understanding of the underlying cellular and molecular mechanisms of these vascular growth processes continues to grow, so too do the available targets for therapeutic intervention. Nonetheless, the tools needed to implement such therapies have often had inherent weaknesses (i.e., invasiveness, expense, poor targeting, and control) that preclude successful outcomes. Approximately 20 years ago, the potential for using ultrasound as a new tool for therapeutically manipulating angiogenesis and arteriogenesis began to emerge. Indeed, the ability of ultrasound, especially when used in combination with contrast agent microbubbles, to mechanically manipulate the microvasculature has opened several doors for exploration. In turn, multiple studies on the influence of ultrasound-mediated bioeffects on vascular growth and the use of ultrasound for the targeted stimulation of blood vessel growth via drug and gene delivery have been performed and published over the years. In this review article, we first discuss the basic principles of therapeutic ultrasound for stimulating angiogenesis and arteriogenesis. We then follow this with a comprehensive cataloging of studies that have used ultrasound for stimulating revascularization to date. Finally, we offer a brief perspective on the future of such approaches, in the context of both further research development and possible clinical translation.

High frequency acoustic permeabilisation of drugs through tissue for localised mucosal delivery

The majority of infectious diseases enter the body through mucosal membranes that line the ocular, nasal, oral, vaginal and rectal surfaces. As infections can be effectively prevented by instigating a local immune response in the immunocyte-rich regions of the mucosa, an efficacious route of vaccine administration is to directly target their delivery to these surfaces. It is nevertheless challenging to provide sufficient driving force to penetrate both the mucus lining as well as the epithelial barrier of the mucosal surfaces, which are designed to effectively keep foreign entities out, but not excessively such that the therapeutic agent penetrates deeper into the vascularised submucosal regions where they are mostly taken up by the systemic circulation, thus resulting in a far weaker immune response. In this work, we demonstrate the possibility of controllably localising and hence maximising the delivery of both small and large molecule model therapeutic agents in the mucosa of a porcine buccal model using high frequency acoustics. Unlike their low (kHz order) frequency bulk ultrasonic counterpart, these high frequency (>10 MHz) surface waves do not generate cavitation, which leads to large molecular penetration depths beyond the 100 μm order thick mucosal layer, and which has been known to cause considerable cellular/tissue damage and hence scarring. Through system parameters such as the acoustic irradiation frequency, power and exposure duration, we show that it is possible to tune the penetration depth such that over 95% of the delivered drug are localised within the mucosal layer, whilst preserving their structural integrity.

Prolonging pulse duration in ultrasound-mediated gene delivery lowers acoustic pressure threshold for efficient gene transfer to cells and small animals

While ultrasound-mediated gene delivery (UMGD) has been accomplished using high peak negative pressures (PNPs) of 2 MPa or above, emerging research showed that this may not be a requirement for microbubble (MB) cavitation. Thus, we investigated lower-pressure conditions close to the MB inertial cavitation threshold and focused towards further increasing gene transfer efficiency and reducing associated cell damage. We created a matrix of 21 conditions (n = 3/cond.) to test in HEK293T cells using pulse durations spanning 18 μs-36 ms and PNPs spanning 0.5-2.5 MPa. Longer pulse duration conditions yielded significant increase in transgene expression relative to sham with local maxima between 20 J and 100 J energy curves. A similar set of 17 conditions (n = 4/cond.) was tested in mice using pulse durations spanning 18 μs-22 ms and PNPs spanning 0.5-2.5 MPa. We observed local maxima located between 1 J and 10 J energy curves in treated mice. Of these, several low pressure conditions showed a decrease in ALT and AST levels while maintaining better or comparable expression to our positive control, indicating a clear benefit to allow for effective transfection with minimized tissue damage versus the high-intensity control. Our data indicates that it is possible to eliminate the requirement of high PNPs by prolonging pulse durations for effective UMGD in vitro and in vivo, circumventing the peak power density limitations imposed by piezo-materials used in US transducers. Overall, these results demonstrate the advancement of UMGD technology for achieving efficient gene transfer and potential scalability to larger animal models and human application.

The present and future role of ultrasound targeted microbubble destruction in preclinical studies of cardiac gene therapy

Multiple limitations for cardiac pharmacologic therapies like intolerance, individual variation in effectiveness, side effects, and high cost still remain, despite the recent progress in diagnosis and health support. Gene therapy is poised to be an attractive alternative in various ways for the future, refractory cardiac diseases being one aspect of it. As a novel therapy to deliver the objective gene to organs of living animals, ultrasound targeted microbubble destruction (UTMD) has therapeutic potential in cardiovascular disorders. UTMD, which binds microbubbles with DNA or RNA carriers into the shell and destroys the located microbubbles with low frequency and high mechanical index ultrasound can release target agents to specific organs. UTMD has the ability to transfect markedly through sonoporation, cavitation and other effects by way of intravenous injection that is minimally invasive and highly specific for gene deliverance. Here, we have summarized the present role of UTMD in pre-clinical studies of cardiac gene therapy which covers myocardial infarction, regeneration, ischaemia/reperfusion injury, hypertension, diabetic cardiomyopathy, adriamycin cardiomyopathy and some discussion for further studies.

Epidermal growth factor receptor-targeted sonoporation with microbubbles enhances therapeutic efficacy in a squamous cell carcinoma model

Sonoporation is a drug and gene delivery system using ultrasonication that allows the intracellular delivery of foreign molecules that cannot enter cells under normal conditions. We previously reported that sonoporation with microbubbles (MBs) could achieve effective intracellular drug delivery to human gingival squamous carcinoma Ca9-22 cells. In this study, we developed anti-epidermal growth factor receptor (EGFR) antibody-conjugated MBs (EGFR-MBs) and evaluated their capacity to enhance anti-cancer drug toxicity in vitro and in vivo. We first assessed the effect of sonoporation with EGFR-MBs on Ca9-22 cells by the WST-8 assay, flow cytometry and Hoechst's staining in vitro. Sonoporation and EGFR-MB had a strong cytotoxic effect on Ca9-22 cells with low-dose bleomycin. Furthermore, bleomycin delivery using sonoporation with EGFR-MBs remarkably increased the number of apoptotic cells. We next examined the effect of EGFR-MBs in a murine squamous cell carcinoma model. Bleomycin delivery by sonoporation with EGFR-MBs exhibited remarkable antitumor activity. Together, our results show that EGFR-MBs and ultrasound treatment increases the efficacy and specificity of intracellular drug uptake, suggesting this could be a novel drug-targeting modality for oral squamous cell carcinoma chemotherapy treatment.

Anti-microRNA-21/221 and microRNA-199a transfected by ultrasound microbubbles induces the apoptosis of human hepatoma HepG2 cells

Gene therapy, particularly microRNA (miRNA), is a promising candidate in the treatment of cancer; however, it is challenging to develop gene delivery systems. Ultrasound microbubbles have been used for gene delivery with excellent results. The present study aimed to investigate the transfection efficiency of HepG2 cells using ultrasound microbubbles. The effects of three miRNAs (miR-21, miR-221 and miR-199a) on HepG2 cells were also determined by performing ultrasound microbubble-mediated gene transfection. Three recombinant plasmids containing anti-miR-21, anti-miR-221 and miR-199a were fused with enhanced green fluorescent protein. For the transfection of genes, the type of contrast agent, the concentration of microbubble contrast agent and the exposure intensity of ultrasound were optimized. The expression of miRNAs was detected using reverse transcription-polymerase chain reaction. To determine the effect of anti-miR-21, anti-miR-221 and miR-199a on HepG2 cells, MTT, cell cycle analysis and Annexin V-PE/7-ADD apoptosis assays were performed. The optimal condition was 10% sulfur hexafluoride microbubbles at an ultrasound frequency of 2.0 MHz and mechanical index of 0.28. When cells were transfected with three recombinant plasmids using ultrasound microbubbles, there was significant downregulation of miR-21 and miR-221 and upregulation of miR-199a (P<0.05). All three treatments inhibited cell proliferation and promoted the apoptosis of cells. The present data indicated that the delivery of anti-miR-21, anti-miR-221 and miR-199a may be mediated by ultrasound microbubble contrast agents. With this approach, cell proliferation may be effectively inhibited and cell apoptosis may be induced. These are novel cancer therapy targets.

Microvascular Injury and Perfusion Changes Induced by Ultrasound and Microbubbles in a Machine-Perfused Pig Liver

Localized drug delivery and uptake can benefit from the combined action of ultrasound and microbubbles at a specific site. Some of the possible mechanisms suggested are vessel poration and/or cell poration, but the exact acoustic parameters that trigger those phenomena remain unknown. Ex vivo machine perfusion of human-sized organs is a technique that provides an ideal environment for pre-clinical investigations with high physiologic relevance not possible with in vitro experiments. In this work, ex vivo machine-perfused pig livers were combined with an image-guided therapy system to investigate microvascular flow changes caused by the interaction of ultrasound-driven microbubbles with the vasculature. The effects of acoustic pressure (1.7-4 MPa peak negative pressures) and number of cycles (1000 or 20 cycles) were examined. Perfusion changes caused by the action of ultrasound on microbubbles in the microcirculation were qualitatively and quantitatively assessed with contrast-enhanced ultrasound and used as a metric of the extent of vessel perforation, thus, extravasation. Areas that were exposed to peak negative pressures above 1.7 MPa underwent a detectable and irreversible perfusion change. Complete devascularization of the area exposed to ultrasound was observed at much larger acoustic pressures (∼4 MPa). Shorter acoustic pulses (20 cycles) produced markedly fewer perfusion changes than longer pulses (1000 cycles) under the same acoustic amplitude exposure.

Gene therapy based on interleukin-12 loaded chitosan nanoparticles in a mouse model of fibrosarcoma

OBJECTIVES

Interleukin-12 (IL-12) as a cytokine has been proved to have a critical role in stimulating the immune system and has been used as immunotherapeutic agents in cancer gene therapy. Chitosan as a polymer, with high ability of binding to nucleic acids is a good candidate for gene delivery since it is biodegradable, biocompatible and non-allergenic polysaccharide. The objective of the present study was to investigate the effects of cells transfected with IL-12 loaded chitosan nanoparticles on the regression of fibrosarcoma tumor cells (WEHI-164) in vivo.

MATERIALS AND METHODS

WEHI-164 tumor cells were transfected with IL-12 loaded chitosan nanoparticles and then were injected subcutaneously to inoculate tumor in BALB/c mice. Tumor volumes were determined and subsequently extracted after mice sacrifice. The immunohistochemistry staining was performed for analysis of Ki-67 expression (a tumor proliferation marker) in tumor masses. The expression of IL-12 and IFN-γ were studied using real-time polymerase chain reaction and immunoblotting.

RESULTS

The group treated with IL-12 loaded chitosan nanoparticles indicated decreasing of tumor mass[r1] volume (P<0.001). The results of western blotting and real-time PCR showed that the IL-12 expression was increased in the group. Immunohistochemistry staining indicated that the Ki-67expression was reduced in the group treated with IL-12 loaded chitosan nanoparticles.

CONCLUSION

IL-12 gene therapy using chitosan nanoparticles has therapeutic effects on the regression of tumor masses in fibrosarcoma mouse model.

Enhanced therapeutic effect of Adriamycin on multidrug resistant breast cancer by the ABCG2-siRNA loaded polymeric nanoparticles assisted with ultrasound

The overexpression of the breast cancer resistance protein (ABCG2) confers resistance to Adriamycin (ADR) in breast cancer. The silencing of ABCG2 using small interfering RNA (siRNA) could be a promising approach to overcome multidrug resistance (MDR) in cancer cells. To deliver ABCG2-siRNA effectively into breast cancer cells, we used mPEG-PLGA-PLL (PEAL) nanoparticles (NPs) with ultrasound-targeted microbubble destruction (UTMD). PEAL NPs were prepared with an emulsion-solvent evaporation method. The NPs size was about 131.5 ± 6.5 nm. The siRNA stability in serum was enhanced. The intracellular ADR concentration increased after the introduction of siRNA-loaded NPs. After intravenous injection of PEAL NPs in tumor-bearing mice, the ABCG2-siRNA-loaded NPs with UTMD efficiently silenced the ABCG2 gene and enhanced the ADR susceptibility of MCF-7/ADR (ADR resistant human breast cancer cells). The siRNA-loaded NPs with UTMD + ADR showed better tumor inhibition effect and good safety in vivo. These results indicate that ADR-chemotherapy in combination with ABCG2-siRNA is an attractive strategy to treat breast cancer.

Inhibitory effects of shRNA on expression of JNK1 and migration and invasion in mouse hepatocellular carcinoma cell lines mediated by ultrasound-targeted microbubble destruction

AIM

The inhibitory effects on expression of JNK1 in mouse hepatocellular carcinoma cell lines and cell migration and invasion were mediated by ultrasound-targeted microbubble destruction (UTMD).

MATERIALS AND METHODS

The best shRNA vector was built and screened. The hepatocellular carcinoma cell lines were cultured in vitro and divided into five groups: the group of normal Hca-F cells, the group of shRNA plasmid (already selected from the above procedure), the group of Lipofectamine, the group of UTMD (ultrasound microbubbles combined with ultrasound exposure) and the group of Lipofectamine and UTMD. The transfection rate was observed by inverted fluorescence microscope. The expression levels of JNK1 mRNA and protein were evaluated by fluorescence quantitative PCR and Western Blot respectively. The cell proliferation was detected by CCK-8. The ability of migration and invasion in vitro was detected by transwell assay.

RESULTS

The best shRNA vector was established. The comparison of the transfection rate: The group of Lipofectamine and UTMD was larger than that of the groups of shRNA plasmid, Lipofectamine lipofection and UTMD (all P<0.05). There was no significant difference between the group of Lipofectamine and the group of UTMD (P>0.05). The comparison of the expression levels of JNK1 mRNA and protein: Both of the mRNA and protein expression levels were lowest in the group of Lipofectamine and UTMD (all P<0.05). CCK-8 showed that cell viability decreased most in the group of Lipofectamine and UTMD (all P<0.05); Transwell assay showed that the abilities of migration and invasion decreased most in the group of Lipofectamine and UTMD (all P<0.05).

CONCLUSION

The transfection rate of JNK1 shRNA can be improved through the combination of lipofection and UTMD in mouse hepatocellular carcinoma cell lines, therefore enhancing the inhibitory effects of gene expression. The inhibitory effects of cell proliferation, migration and invasion can also be enhanced.

Targeted gene delivery to the synovial pannus in antigen-induced arthritis by ultrasound-targeted microbubble destruction in vivo

The purpose of this study was to optimize an ultrasound-targeted microbubble destruction (UTMD) technique to improve the in vivo transfection efficiency of the gene encoding enhanced green fluorescent protein (EGFP) in the synovial pannus in an antigen-induced arthritis rabbit model. A mixture of microbubbles and plasmids was locally injected into the knee joints of an antigen-induced arthritis (AIA) rabbits. The plasmid concentrations and ultrasound conditions were varied in the experiments. We also tested local articular and intravenous injections. The rabbits were divided into five groups: (1) ultrasound+microbubbles+plasmid; (2) ultrasound+plasmid; (3) microbubble+plasmid; (4) plasmid only; (5) untreated controls. EGFP expression was observed by fluorescent microscope and immunohistochemical staining in the synovial pannus of each group. The optimal plasmid dosage and ultrasound parameter were determined based on the results of EGFP expression and the present and absent of tissue damage under light microscopy. The irradiation procedure was performed to observe the duration of the EGFP expression in the synovial pannus and other tissues and organs, as well as the damage to the normal cells. The optimal condition was determined to be a 1-MHz ultrasound pulse applied for 5 min with a power output of 2 W/cm(2) and a 20% duty cycle along with 300 μg of plasmid. Under these conditions, the synovial pannus showed significant EGFP expression without significant damage to the surrounding normal tissue. The EGFP expression induced by the local intra-articular injection was significantly more increased than that induced by the intravenous injection. The EGFP expression in the synovial pannus of the ultrasound+microbubbles+plasmid group was significantly higher than that of the other four groups (P<0.05). The expression peaked on day 5, remained detectable on day 40 and disappeared on day 60. No EGFP expression was detected in the other tissues and organs. The UTMD technique can significantly enhance the in vivo gene transfection efficiency without significant tissue damage in the synovial pannus of an AIA model. Thus, this could become a safe and effective non-viral gene transfection procedure for arthritis therapy.

Gene therapy with IL-12 induced enhanced anti-tumor activity in fibrosarcoma mouse model

Context Immunotherapy is among the most promising modalities for treatment of cancer. Recently, interleukin 12 (IL-12) has been used as an immunotherapeutic agent in cancer gene therapy. IL-12 can activate dendritic cells (DCs) and boost anti-tumor immune responses. Objective In the current study, we have investigated if IL-12 gene therapy can lead to the regression of tumor mass in a mouse model of fibrosarcoma. Material and methods To investigate the therapeutic efficacy of IL-12, WEHI-164 tumor cells were transfected with murine-IL12 plasmids using Lipofectamine. Enzyme linked immunosorbent assay (ELISA) was used to confirm IL-12 expression in transfected cells. The fibrosarcoma mouse model was established by subcutaneous injection of transfected cells to Balb/C mice. Mice were sacrificed and the tumors were extracted. Tumor sizes were measured by caliper. The expression of IL-12 and IFN-γ was studied with real-time PCR and western blotting. The expression of Ki-67(a tumor proliferation marker) in tumor mass was studied by immunohistochemistry staining. Results and discussion The group treated with IL-12 showed a significant decrease in tumor mass volume (P: 0.000). The results of real-time PCR and western blotting showed that IL-12 and IFN-γ expression increased in the group treated with IL-12 (relative expression of IL-12: 1.9 and relative expression of IFN-γ: 1.766). Immunohistochemistry staining showed that Ki-67 expression was reduced in the group treated with IL-12. Conclusion IL-12 gene therapy successfully led to regress of tumor mass in the fibrosarcoma mouse model. This may serve as a candidate therapeutic approach for treatment of cancer.

Patient-Specific Therapy via Cell-Reprogramming Technology: a Curative Potential for Patients with Diabetes

Gene therapeutics provides great opportunities for curing diabetes. Numerous attempts have been made to establish a safe and high-efficiency gene delivery strategy, but all of them are unsuccessful. To achieve an ideal transfection, a novel gene delivery strategy was presented in this research. The novel system proposed was transfection mediated by the combination of ultrasound with microbubbles and cross-linked polyethylenimines (PEIs). Ultrasound with microbubbles enhances the permeability of target cells; moreover, cross-linked PEIs enabled DNA to escape from endosomes into the cytoplasm. If the proposed method is feasible and effective, the endogenous secretion system of insulin would be re-established in patients with diabetes.

Therapeutic potential of ultrasound microbubbles in gastrointestinal oncology: recent advances and future prospects

Microbubbles were initially invented as contrast agents for ultrasound imaging. However, lately more and more therapeutic applications of microbubbles are emerging, mostly related to drug and gene delivery. Ultrasound is a safe and noninvasive therapeutic modality which has the unique ability to interact with microbubbles and release their payload in situ in addition to permeabilizing the target tissues. The combination of drug-loaded microbubbles and ultrasound has been used in preclinical studies on blood-brain barrier opening, drug and gene delivery to solid tumors, and ablation of blood vessels. This review covers the basic principles of ultrasound-microbubble interaction, the types of microbubbles and the effect they have on tissue, and the preclinical and clinical experience with this approach to date in the field of gastrointestinal oncology.

Cell mechanics in biomedical cavitation

Studies on the deformation behaviours of cellular entities, such as coated microbubbles and liposomes subject to a cavitation flow, become increasingly important for the advancement of ultrasonic imaging and drug delivery. Numerical simulations for bubble dynamics of ultrasound contrast agents based on the boundary integral method are presented in this work. The effects of the encapsulating shell are estimated by adapting Hoff's model used for thin-shell contrast agents. The viscosity effects are estimated by including the normal viscous stress in the boundary condition. In parallel, mechanical models of cell membranes and liposomes as well as state-of-the-art techniques for quantitative measurement of viscoelasticity for a single cell or coated microbubbles are reviewed. The future developments regarding modelling and measurement of the material properties of the cellular entities for cutting-edge biomedical applications are also discussed.

Ultrasound-Targeted Microbubble Destruction Enhances Gene Expression of microRNA-21 in Swine Heart via Intracoronary Delivery

BACKGROUND

Ultrasound-targeted microbubble destruction (UTMD) has proved to be a promising method for gene delivery. However, the feasibility and efficacy of UTMD-mediated gene delivery to the heart of large animals remain unclear. The present study was to explore the probability of increasing the transfection of microRNA-21 (miR-21) in swine heart by UTMD, and to search for the most suitable transfection conditions.

METHODS

We first optimized ultrasound intensity for successful miR-21 delivery. After intravenous injection of miR-21/microbubble mixture (miR-21/MB), transthoracic ultrasound irradiation (US) was applied from the left anterior chest using different intensities (1, 2, and 3 W/cm(2)). Then the efficacy of UTMD-mediated miR-21 delivery into myocardium via intracoronary injection was explored. Solution of miR-21/MB was infused intravenously or intracoronarily with US over the heart. Swine undergoing phosphate-buffered saline (PBS) injection, miR-21/MB injection via ear vein or coronary artery without US served as the control. The dynamic changes of left ventricular ejection fraction (LVEF) and serum troponin I (cTnI) after UTMD were detected, then the left ventricular myocardium was harvested for hematoxylin and eosin (H&E) staining 4 days later; the expression levels of miR-21 and programmed cell death 4 (PDCD4) were detected by quantitative real time polymerase chain reaction (qRT-PCR) and Western blot, respectively.

RESULTS

Results showed that pulse ultrasound at an intensity of 2 W/cm(2) and a 50% duty ratio for 20 minutes, there was no increase in serum cTnI, no histological sign of myocardial damage, and no noted cardiac dysfunction with relatively higher miR-21 expression (P < 0.05). Compared to miR-21/MB alone, UTMD significantly increased gene expression in myocardium regardless of the delivery routes (P < 0.05). Interestingly, the transfection efficiency was found to be a little bit higher with intracoronary injection than that with intravenous injection, though the dose for intracoronary injection was half of the intravenous injection (P < 0.05).

CONCLUSION

Under suitable conditions, UTMD can efficiently enhance gene expression in swine heart regardless of the delivery routes. The intravenous injection might be superior to intracoronary injection with less invasiveness and lower requirement of the technique. And for those undergoing percutaneous coronary intervention, intracoronary injection seems to be another alternative.

Physical methods for gene transfer

The key impediment to the successful application of gene therapy in clinics is not the paucity of therapeutic genes. It is rather the lack of nontoxic and efficient strategies to transfer therapeutic genes into target cells. Over the past few decades, considerable progress has been made in gene transfer technologies, and thus far, three different delivery systems have been developed with merits and demerits characterizing each system. Viral and chemical methods of gene transfer utilize specialized carrier to overcome membrane barrier and facilitate gene transfer into cells. Physical methods, on the other hand, utilize various forms of mechanical forces to enforce gene entry into cells. Starting in 1980s, physical methods have been introduced as alternatives to viral and chemical methods to overcome various extra- and intracellular barriers that limit the amount of DNA reaching the intended cells. Accumulating evidence suggests that it is quite feasible to directly translocate genes into cytoplasm or even nuclei of target cells by means of mechanical force, bypassing endocytosis, a common pathway for viral and nonviral vectors. Indeed, several methods have been developed, and the majority of them share the same underlying mechanism of gene transfer, i.e., physically created transient pores in cell membrane through which genes get into cells. Here, we provide an overview of the current status and future research directions in the field of physical methods of gene transfer.

Nucleic acid delivery with microbubbles and ultrasound

Nucleic acid-based therapy is a growing field of drug delivery research. Although ultrasound has been suggested to enhance transfection decades ago, it took a combination of ultrasound with nucleic acid carrier systems (microbubbles, liposomes, polyplexes, and viral carriers) to achieve reasonable nucleic acid delivery efficacy. Microbubbles serve as foci for local deposition of ultrasound energy near the target cell, and greatly enhance sonoporation. The major advantage of this approach is in the minimal transfection in the non-insonated non-target tissues. Microbubbles can be simply co-administered with the nucleic acid carrier or can be modified to carry nucleic acid themselves. Liposomes with embedded gas or gas precursor particles can also be used to carry nucleic acid, release and deliver it by the ultrasound trigger. Successful testing in a wide variety of animal models (myocardium, solid tumors, skeletal muscle, and pancreas) proves the potential usefulness of this technique for nucleic acid drug delivery.

Cell-penetrating peptides: A tool for effective delivery in gene-targeted therapies

The current landscapes of novel therapeutic approaches rely mostly on gene-targeted technologies, enabling to fight rare genomic diseases, from infections to cancer and hereditary diseases. Although, reaching the action-site for this novel treatments requires to deliver nucleic acids, or other macromolecules into cells, which may pose difficult tasks to pharmaceutical companies. To overcome this technological limitation, a wide variety of vectors have been developed in the past decades and have proven to be successful in delivering various therapeutics. Cell-penetrating peptides (CPP) have been one of the technologies widely studied and have been increasingly used to transport small RNA/DNA, plasmids, antibodies, and nanoparticles into cells. Despite the already proved huge potential that these peptide-based approaches may suggest, few advances have been put to pharmacological or clinical use. This review will describe the origin, development, and usage of CPP to deliver therapeutic agents into cells, with special emphasis on their current application to gene-therapies. Specifically, we will describe the current trials being conducted to treat cancer, gene disorders, and autoimmune diseases using CPP-based therapies. © 2014 IUBMB Life, 66(3):182-194, 2014.

Ultrasound-enhanced delivery of morpholino with Bubble liposomes ameliorates the myotonia of myotonic dystrophy model mice

Phosphorodiamidate morpholino oligonucleotide (PMO)-mediated control of the alternative splicing of the chloride channel 1 (CLCN1) gene is a promising treatment for myotonic dystrophy type 1 (DM1) because the abnormal splicing of this gene causes myotonia in patients with DM1. In this study, we optimised a PMO sequence to correct Clcn1 alternative splicing and successfully remedied the myotonic phenotype of a DM1 mouse model, the HSALR mouse. To enhance the efficiency of delivery of PMO into HSALR mouse muscles, Bubble liposomes, which have been used as a gene delivery tool, were applied with ultrasound exposure. Effective delivery of PMO led to increased expression of Clcn1 protein in skeletal muscle and the amelioration of myotonia. Thus, PMO-mediated control of the alternative splicing of the Clcn1 gene must be important target of antisense therapy of DM1.

The effect of interleukin 36 gene therapy in the regression of tumor

BACKGROUND

Cancer immunotherapy attempts to stimulate the immune system to reject and destroy tumors and is one of the cancer treatment strategies. Recently, interluekin36 (IL36) has been used as immunotherapeutic agents in cancer gene therapy. Present study investigated that the IL36 gene therapy effects on the regression of tumor masses in mouse model. Aim of this study is determination of the gene therapy effects by IL36 in the regression of tumor masses in mouse model.

METHODS

To study the therapeutic efficacy of this cytokine, WEHI-164 tumor cells were transected with mIL36 plasmids. ELISA test was used to check cytokine production by transected cells. To establish fibro sarcoma mouse model, Tumoral transfected cells were injected subcutaneously to inoculate tumor in BALB/C mice. Tumor volumes were measured by caliper. Mice were sacrificed and tumors were extracted. The expression of IL36 and IFN-γ was studied with Real-time PCR and immunoblotting. The expression of Ki-67 (a tumor proliferation marker) in tumor masses was studied by immunohistochemistry staining. In this study we had 2 groups which are treated with IL-36 and Untreated with IL-36 as a blank.

RESULTS

The group treated with IL36 indicated decrease of tumor mass volume (p<0.001). The results of western blotting and real-time PCR showed the IL36 expression increased in the group treated with IL36 (with relative expression of 1.9).

CONCLUSION

Immunohistochemistry staining indicated that the Ki-67expression has been reduced in the group interfered with IL36. IL36 gene therapy has therapeutic effects on the regression of tumor masses in fibro sarcoma mouse model.

Ultrasound directs a transposase system for durable hepatic gene delivery in mice

Our aim was to evaluate the delivery of transposase-based vectors by ultrasound targeted microbubble destruction (UTMD) in mice. DNA vectors were attached to cationic lipid microbubbles (1-3 μm in diameter), injected intravenously and delivered to the liver by destruction of the carrier bubbles with ultrasound in burst mode at 1.0 MHz, 20-μs pulse duration, 10-Hz pulse repetition frequency and ∼1.3-MPa acoustic peak negative pressure. We evaluated the expression and genomic integration of conventional (pcDNA3) and piggyBac transposase-based (pmGENIE) reporter vectors. In vivo, we observed UTMD-mediated liver-specific expression of pmGENIE for an average of 24 d, compared with 4 d with pcDNA3. Reporter expression was located predominately near blood vessels initially, whereas expression after 3 d was more evenly distributed through the parenchyma of the liver. We confirmed random genomic integration for pmGENIE in vitro; however, integration events for pmGENIE in vivo were targeted to specific areas of chromosome 14. Our results suggest that a combination of UTMD and non-viral DNA transposase vectors can mediate weeks of hepatic-specific gene transfer in vivo, and analyses performed by non-restrictive linear amplification-mediated (nrLAM) polymerase chain reaction, cloning and sequencing identify an unexpected tropism for integration within a specific sequence on chromosome 14 in mice. UTMD delivery of transgenes may be useful for the treatment of hepatic gene deficiency disorders.

Ultrasound-targeted microbubble destruction-mediated gene delivery into canine livers

Ultrasound (US) was applied to a targeted canine liver lobe simultaneously with injection of plasmid DNA (pDNA)/microbubble (MB) complexes into a portal vein (PV) segmental branch and occlusion of the inferior vena cava (IVC) to facilitate DNA uptake. By using a 1.1 MHz, 13 mm diameter transducer, a fivefold increase in luciferase activity was obtained at 3.3 MPa peak negative pressure (PNP) in the treated lobe. For more effective treatment of large tissue volumes in canines, a planar unfocused transducer with a large effective beam diameter (52 mm) was specifically constructed. Its apodized dual element configuration greatly reduced the near-field transaxial pressure variations, resulting in a remarkably uniform field of US exposure for the treated tissues. Together with a 15 kW capacity US amplifier, a 692-fold increase of gene expression was achieved at 2.7 MPa. Transaminase and histology analysis indicated minimal tissue damage. These experiments represent an important developmental step toward US-mediated gene delivery in large animals and clinics.

Kidney-targeted transplantation of mesenchymal stem cells by ultrasound-targeted microbubble destruction promotes kidney repair in diabetic nephropathy rats

We test the hypothesis that ultrasound-targeted microbubble destruction (UTMD) technique increases the renoprotective effect of kidney-targeted transplantation of bone-marrow-derived mesenchymal stem cells (BM-MSCs) in diabetic nephropathy (DN) rats. Diabetes was induced by streptozotocin injection (60 mg/Kg, intraperitoneally) in Sprague-Dawley rats. MSCs were administered alone or in combination with UTMD to DN rats at 4 weeks after diabetes onset. Random blood glucose concentrations were measured at 1, 2, 4, and 8 weeks, and plasma insulin levels, urinary albumin excretion rate (UAER) values, the structures of pancreas and kidney, the expressions of TGF- β 1, synaptopodin, and IL-10 were assessed at 8 weeks after MSCs transplantation. MSCs transplantation decreased blood glucose concentrations and attenuated pancreatic islets/ β cells damage. The permeability of renal interstitial capillaries and VCAM-1 expression increased after UTMD, which enhanced homing and retention of MSCs to kidneys. MSCs transplantation together with UTMD prevented renal damage and decreased UAER values by inhibiting TGF- β 1 expression and upregulating synaptopodin and IL-10 expression. We conclude that MSCs transplantation reverts hyperglycemia; UTMD technique noninvasively increases the homing of MSCs to kidneys and promotes renal repair in DN rats. This noninvasive cell delivery method may be feasible and efficient as a novel approach for personal MSCs therapy to diabetic nephropathy.

Sonoporation: mechanistic insights and ongoing challenges for gene transfer

Microbubbles first developed as ultrasound contrast agents have been used to assist ultrasound for cellular drug and gene delivery. Their oscillation behavior during ultrasound exposure leads to transient membrane permeability of surrounding cells, facilitating targeted local delivery. The increased cell uptake of extracellular compounds by ultrasound in the presence of microbubbles is attributed to a phenomenon called sonoporation. In this review, we summarize current state of the art concerning microbubble-cell interactions and cellular effects leading to sonoporation and its application for gene delivery. Optimization of sonoporation protocol and composition of microbubbles for gene delivery are discussed.

Cavitation-enhanced delivery of a replicating oncolytic adenovirus to tumors using focused ultrasound

Oncolytic viruses (OV) and ultrasound-enhanced drug delivery are powerful novel technologies. OV selectively self-amplify and kill cancer cells but their clinical use has been restricted by limited delivery from the bloodstream into the tumor. Ultrasound has been previously exploited for targeted release of OV in vivo, but its use to induce cavitation, microbubble oscillations, for enhanced OV tumor extravasation and delivery has not been previously reported. By identifying and optimizing the underlying physical mechanism, this work demonstrates that focused ultrasound significantly enhances the delivery and biodistribution of systemically administered OV co-injected with microbubbles. Up to a fiftyfold increase in tumor transgene expression was achieved, without any observable tissue damage. Ultrasound exposure parameters were optimized as a function of tumor reperfusion time to sustain inertial cavitation, a type of microbubble activity, throughout the exposure. Passive detection of acoustic emissions during treatment confirmed inertial cavitation as the mechanism responsible for enhanced delivery and enabled real-time monitoring of successful viral delivery.

Enhanced gene expression of systemically administered plasmid DNA in the liver with therapeutic ultrasound and microbubbles

Ultrasound-mediated delivery (USMD) of novel therapeutic agents in the presence of microbubbles is a potentially safe and effective method for gene therapy offering many desired characteristics, such as low toxicity, potential for repeated treatment, and organ specificity. In this study, we tested the capability of USMD to improve gene expression in mice livers using glycogen storage disease Type Ia as a model disease under systemic administration of naked plasmid DNA. Image-guided therapeutic ultrasound was used in two studies to provide therapeutic ultrasound to mice livers. In the first study, involving wild-type mice, control animals received naked plasmid DNA (pG6Pase 150 μg) via the tail vein, followed by an infusion of microbubbles; the treated animals additionally received therapeutic ultrasound (1 MHz). Following the procedure, the animals were left to recover and were subsequently euthanized after 2 d and liver samples were extracted. Reverse transcription polymerase chain reaction (RT-PCR) assays were performed on the samples to quantify mRNA expression. In addition, Western blot assays of FLAG-tagged glucose-6-phosphatase (G6Pase) were performed to evaluate protein expression. Ultrasound-exposed animals showed a 4-fold increase in G6Pase RNA in the liver, in comparison with control animals. Furthermore, results from Western blot analysis demonstrated a 2-fold increased protein expression in ultrasound-exposed animals after two days ( p < 0.05). A second pilot study was performed with G6Pase knockout mice, and the animals were monitored for correction of hypoglycemia over a period of 3 weeks before tissue analysis. The RT-PCR assays of samples from these animals demonstrated increased G6Pase RNA in the liver following ultrasound treatment. These results demonstrate that USMD can increase gene expression of systemically injected naked pDNA in the liver and also provide insight into the development of realistic approaches that can be translated into clinical practice.

Effects of diagnostic ultrasound-targeted microbubble destruction on permeability of normal liver in rats

This work investigated the effect of diagnostic ultrasound-targeted microbubble destruction (UTMD) on the permeability of normal liver tissue and the safety of this technique. One hundred and four rats were divided into four groups: the control group, the microbubble-only (MB) group, the ultrasound-only (US) group, and the ultrasound-targeted microbubble destruction group (UTMD). The permeabilities of capillaries and cell membranes were determined using Evans blue and lanthanum nitrate as tracers, respectively. The amount of Evans blue was approximately fourfold higher in the UTMD group than in the control, MB-only, and US-only groups (all P<0.01). Evans blue extravasation, visualized as red fluorescence, was detectable by laser confocal scanning microscopy in the parenchyma only in the UTMD group. Lanthanum nitrate-tracing transmission electron microscopy examination indicated that intracellular lanthanum was detectable in the cytoplasm only in the UTMD group. Blood chemical analysis indicated that the effect of diagnostic ultrasound-targeted microbubble destruction on the rats' serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels was transient and recoverable and that this technique had no obvious effect on renal function. Cellular swelling was observed in liver cells in the UTMD group at 0.5 h, but this swelling was no longer apparent after 1 week. These results suggest that diagnostic ultrasound-targeted microbubble destruction can increase the capillary and cell membrane permeabilities in normal liver tissue without a significant increase in hepatic and renal toxicity.

Optimization of transfection parameters for ultrasound/SonoVue microbubble-mediated hAng-1 gene delivery in vitro

This study aimed to explore the effects of microbubble concentration, gene dosage, cell-microbubble mixing mode and fetal bovine serum (FBS) on gene delivery. 293T cells were transfected with Sonovue microbubbles carrying the hAng-1 gene via ultrasound irradiation. Various ultrasound exposure parameters and microbubble and DNA concentrations were investigated. In addition, FBS and the cell suspension or adherent mode was explored. Transfection efficiency and cell viability were used to determine the optimal transfection parameters. hAng-1 gene transfection efficiency gradually increased with elongation of ultrasound exposure and increasing microbubble concentration. However, if ultrasound irradiation exceeded 1.5 W/cm² and 30 sec or the microbubble concentration was over 20%, hAng-1 gene expression was significantly decreased, coupled with extensive cell death. Gene transfection levels were low under DNA concentrations less than 15 µg/ml. Furthermore, the gene transfer rate was significantly increased under cell suspension mode; FBS had no effect on hAng-1 gene transfection. The integrity of hAng-1 DNA was not affected by ultrasonic irradiation under optimal conditions. The optimal transfection parameters for the hAng-1 gene and Sonovue microbubble were ultrasound exposure of 1.5 W/cm² and 30 sec, 20% microbubbles, 15 µg/ml of DNA and under cell suspension mode.

Efficient microbubble- and ultrasound-mediated plasmid DNA delivery into a specific rat liver lobe via a targeted injection and acoustic exposure using a novel ultrasound system

To develop efficient gene delivery in larger animals, based on a previous mouse study, we explored the luciferase reporter gene transfer in rats by establishing a novel unfocused ultrasound system with simultaneous targeted injection of a plasmid and microbubble mixture into a specific liver lobe through a portal vein branch. Luciferase expression was significantly enhanced over 0-30 vol % of the Definity microbubbles, with a plateau between 0.5 and 30 vol %. The increase of gene delivery efficiency also depended on the acoustic peak negative pressure, achieving over 100-fold enhancement at 2.5 MPa compared with plasmid only controls. Transient, modest liver damage following treatment was assessed by transaminase assays and histology, both of which correlated with gene expression induced by acoustic cavitation. In addition, pulse-train ultrasound exposures (i.e., with relatively long quiescent periods between groups of pulses to allow tissue refill with microbubbles) produced gene expression levels comparable to the standard US exposure but reduced the extent of liver damage. These results indicated that unfocused high intensity therapeutic ultrasound exposure with microbubbles is highly promising for safe and efficient gene delivery into the liver of rats or larger animals.

Neuroepithelial transforming protein 1 short interfering RNA-mediated gene silencing with microbubble and ultrasound exposure inhibits the proliferation of hepatic carcinoma cells in vitro

OBJECTIVES

Short interfering RNA (siRNA) has been used to knock down the expression of targeted genes in a process known as RNA interference. However, the key to RNA interference is the efficient intracellular delivery of the siRNA. In this study, we sought to enhance the efficiency of transduction and find a novel therapy for hepatic carcinoma.

METHODS

Three types of neuroepithelial transforming protein 1 (NET-1) siRNAs (labeled fluorescent) were designed and transduced into HepG2 cells. Then the most effective one in silencing NET-1 was determined. The HepG2 cells were divided into 5 groups: untreated control; delivery of siRNA; delivery of siRNA using Lipofectamine 2000 (Invitrogen, Carlsbad, CA; group L); delivery of siRNA using ultrasound exposure and microbubbles (group US); and delivery of siRNA using Lipofectamine, ultrasound exposure, and microbubbles (group LUS). The efficiency of siRNA transfer was determined by detection of luciferase activity on microscopy; NET-1 expression was assayed by reverse transcription-polymerase chain reaction and western blotting; and proliferation investigations of the HepG2 cells were performed. RESULTS- The transfection efficiency of microbubbles combined with ultrasound exposure was nearly equal to Lipofectamine-mediated transfection (P = .609). More importantly, the combination of Lipofectamine, microbubbles, and ultrasound exposure effectively reduced NET-1 expression compared with the other groups (P < .01). Furthermore, the proliferation of cells in groups L, US, and LUS was visibly inhibited between 24 and 72 hours.

CONCLUSIONS

The use of a microbubble contrast agent combined with ultrasound exposure could be a potent physical method for increasing gene delivery efficiency. This technique is a promising nonviral approach that can be used in liver cancer.

Investigation of microbubble response to long pulses used in ultrasound-enhanced drug delivery

In current drug delivery approaches, microbubbles and drugs can be co-administered while ultrasound is applied. The mechanism of microbubble interaction with ultrasound, the drug and the cells is not fully understood. The aim of this study was to investigate microbubble response to long ultrasonic pulses used in drug delivery approaches. Two different in vitro set-ups were considered: with the microbubbles diluted in an enclosure and with the microbubbles flowing in a capillary tube. Acoustic streaming, which influences the observed bubble response, was observed in "typical" drug delivery conditions in the first set-up. With the capillary set-up, streaming effects were avoided and accurate bubble responses were recorded. The diffraction pattern of the source greatly influences the bubble response and in different locations of the field different bubble responses are observed. At low nondestructive pressures, microbubbles can oscillate for thousands of cycles repeatedly. At high acoustic pressures (at 1 MHz), most bubble activity disappeared within about 100 μs despite the length of the pulse, mainly due to violent bubble destruction and subsequent accelerated diffusion.

Engineering and identifying supercharged proteins for macromolecule delivery into mammalian cells

Supercharged proteins are a class of engineered or naturally occurring proteins with unusually high positive or negative net theoretical charge. Both supernegatively and superpositively charged proteins exhibit a remarkable ability to withstand thermally or chemically induced aggregation. Superpositively charged proteins are also able to penetrate mammalian cells. Associating cargo with these proteins, such as plasmid DNA, siRNA, or other proteins, can enable the functional delivery of these macromolecules into mammalian cells both in vitro and in vivo. The potency of functional delivery in some cases can exceed that of other current methods for macromolecule delivery, including the use of cell-penetrating peptides such as Tat and adenoviral delivery vectors. This chapter summarizes methods for engineering supercharged proteins, optimizing cell penetration, identifying naturally occurring supercharged proteins, and using these proteins for macromolecule delivery into mammalian cells.

Sonoporation-mediated anti-angiogenic gene transfer into muscle effectively regresses distant orthotopic tumors

Ultrasound (US) is an effective tool for local delivery of genes into target tumors or organs. In combination with microbubbles, US can temporarily change the permeability of cell membranes by cavitation and facilitate entry of plasmid DNA into cells. Here, we demonstrate that repeated US-mediated delivery of anti-angiogenic genes, endostatin or calreticulin, into muscle significantly inhibits the growth of orthotopic tumors in the liver, brain or lung. US-mediated anti-angiogenic gene therapy also seems to function as an adjuvant therapy that significantly enhances the antitumor effects of the chemotherapeutic drug doxorubicin and adenovirus-mediated cytokine gene therapy. Significantly higher levels of tumor apoptosis or tumor-infiltrating lymphocytes were observed after combined therapy consisting of either anti-angiogenic therapy and chemotherapy, or anti-angiogenic therapy and immunotherapy. Taken together, our experiments demonstrate that intramuscular delivery of anti-angiogenic genes by US exposure can effectively treat distant orthotopic tumors, and thus has great therapeutic potential in terms of clinical treatment.

Ultrasound biomicroscopy in small animal research: applications in molecular and preclinical imaging

Ultrasound biomicroscopy (UBM) is a noninvasive multimodality technique that allows high-resolution imaging in mice. It is affordable, widely available, and portable. When it is coupled to Doppler ultrasound with color and power Doppler, it can be used to quantify blood flow and to image microcirculation as well as the response of tumor blood supply to cancer therapy. Target contrast ultrasound combines ultrasound with novel molecular targeted contrast agent to assess biological processes at molecular level. UBM is useful to investigate the growth and differentiation of tumors as well as to detect early molecular expression of cancer-related biomarkers in vivo and to monitor the effects of cancer therapies. It can be also used to visualize the embryological development of mice in uterus or to examine their cardiovascular development. The availability of real-time imaging of mice anatomy allows performing aspiration procedures under ultrasound guidance as well as the microinjection of cells, viruses, or other agents into precise locations. This paper will describe some basic principles of high-resolution imaging equipment, and the most important applications in molecular and preclinical imaging in small animal research.

Acoustic accessibility investigation for ultrasound mediated treatment of glycogen storage disease type Ia patients

Glycogen storage disease type Ia (GSDIa) is caused by an inherited defect in the glucose-6-phosphatase gene. The recent advent of targeted ultrasound-mediated delivery (USMD) of plasmid DNA (pDNA) to the liver in conjunction with microbubbles may provide an alternative treatment option. This study focuses on determining the acoustically accessible liver volume in GSDIa patients using transducer models of various geometries with an image-based geometry-driven approach. Results show that transducers with longer focal lengths and smaller apertures (up to an f/number of 2) are able to access larger liver volumes in GSDIa patients while still being capable of delivering the required ultrasound dose in situ (2.5 MPa peak negative pressure at the focus). With sufficiently large acoustic windows and the ability to use glucose to easily assess efficacy, GSD appears to be a good model for testing USMD as proof of principle as a potential therapy for liver applications in general.

Explorations of high-intensity therapeutic ultrasound and microbubble-mediated gene delivery in mouse liver

Ultrasound (US) combined with microbubbles (MBs) is a promising technology for non-viral gene delivery. Significant enhancements of gene expression have been obtained in our previous studies. To optimize and prepare for application to larger animal models, the luciferase reporter gene transfer efficacy of lipid-based Definity MBs of various concentrations, pressure amplitudes and a novel unfocused high-intensity therapeutic US (HITU) system were explored. Luciferase expression exhibited a dependence on MB dose over the range of 0-25 vol%, and a strong dependence on acoustic peak negative pressure at over the range of 0-3.2 MPa. Gene expression reached an apparent plateau at MB concentration ≥2.5 vol% or at negative pressures >1.8 MPa. Maximum gene expression in treated animals was 700-fold greater than in negative controls. Pulse train US exposure protocols produced an upward trend of gene expression with increasing quiescent time. The hyperbolic correlation of gene expression and transaminase levels suggested that an optimum gene delivery effect can be achieved by maximizing acoustic cavitation-induced enhancement of DNA uptake and minimizing unproductive tissue damage. This study validated the new HITU system equipped with an unfocused transducer with a larger footprint capable of scanning large tissue areas to effectively enhance gene transfer efficiencies.