Ultrasound enhances reporter gene expression after transfection of vascular cells in vitro

Therapeutic Ultrasound for Topical Corneal Delivery of Macromolecules

Purpose

The objective of this study was to utilize therapeutic ultrasound in enhancing delivery of topical macromolecules into the cornea.

Methods

Rabbit corneas were dissected and placed in a diffusion cell with a small ultra-red fluorescent protein (smURFP; molecular weight of 32,000 Da) as a macromolecule solution. The corneas were treated with continuous ultrasound application at frequencies of 400 or 600 kHz and intensities of 0.8 to 1.0 W/cm2 for 5 minutes, or sham-treated. Fluorescence imaging of the cornea sections was used to observe the delivery of macromolecules into individual epithelial cells. Spectrophotometric analysis at smURFP maximal absorbance of 640 nm was done to determine the presence of macromolecules in the receiver compartment. Safety of ultrasound application was studied through histology analysis.

Results

Ultrasound-treated corneas showed smURFP delivery into epithelial cells by fluorescence in the cytoplasm, whereas sham-treated corneas lacked any appreciable fluorescence in the individual cells. The sham group showed 0% of subcellular penetration, whereas the 400 kHz ultrasound-treated group and 600 kHz ultrasound-treated group showed 31% and 57% of subcellular penetration, respectively. Spectrophotometry measurements indicated negligible presence of smURFP macromolecules in the receiver compartment solution in both the sham and ultrasound treatment groups, and these macromolecules did not cross the entire depth of the cornea. Histological studies showed no significant corneal damage due to ultrasound application.

Conclusions

Therapeutic ultrasound application was shown to increase the delivery of smURFP macromolecules into the cornea.

Translational Relevance

Our study offers a clinical potential for a minimally invasive macromolecular treatment of corneal diseases.

Development and application of ultrasound contrast agents in biomedicine

With the rapid development of molecular imaging, ultrasound (US) medicine has evolved from traditional imaging diagnosis to integrated diagnosis and treatment at the molecular level. Ultrasound contrast agents (UCAs) play a crucial role in the integration of US diagnosis and treatment. As the micro-bubbles (MBs) in UCAs can enhance the cavitation effect and promote the biological effect of US, UCAs have also been studied in the fields of US thrombolysis, mediated gene transfer, drug delivery, and high intensity focused US. The application range of UCAs is expanding, and the value of their applications is improving. This paper reviews the development and application of UCAs in biomedicine in recent years, and the existing problems and prospects are pointed out.

Ultrasonic microbubble VEGF gene delivery improves angiogenesis of senescent endothelial progenitor cells

The therapeutic effects of ultrasonic microbubble transfection (UMT)-based vascular endothelial growth factor 165 (VEGF165) gene delivery on young and senescent endothelial progenitor cells (EPCs) were investigated. By UMT, plasmid DNA (pDNA) can be delivered into both young EPCs and senescent EPCs. In the UMT groups, higher pDNA-derived protein expression was found in senescent EPCs than in young EPCs. Consistent with this finding, a higher intracellular level of pDNA copy number was detected in senescent EPCs, with a peak at the 2-h time point post UMT. Ultrasonic microbubble delivery with or without VEGF improved the angiogenic properties, including the proliferation and/or migration activities, of senescent EPCs. Supernatants from young and senescent EPCs subjected to UMT-mediated VEGF transfection enhanced the proliferation and migration of human aortic endothelial cells (HAECs), and the supernatant of senescent EPCs enhanced proliferation more strongly than the supernatant from young EPCs. In the UMT groups, the stronger enhancing effect of the supernatant from senescent cells on HAEC proliferation was consistent with the higher intracellular VEGF pDNA copy number and level of protein production per cell in the supernatant from senescent cells in comparison to the supernatant from young EPCs. Given that limitations for cell therapies are the inadequate number of transplanted cells and/or insufficient cell angiogenesis, these findings provide a foundation for enhancing the therapeutic angiogenic effect of cell therapy with senescent EPCs in ischaemic cardiovascular diseases.

Gene Therapy Approach for Intervertebral Disc Degeneration: An Update

Intervertebral disc degeneration is the primary cause of back pain and associated with neurological disorders including radiculopathy, myelopathy, and paralysis. The currently available surgical treatments predominantly include the excision of pathological discs, resulting in the function loss, immobilization, and potential additional complications due to the altered biomechanics. Gene therapy approach involves gene transfer into cells, affects RNA and protein synthesis of the encoded genes in the recipient cells, and facilitates biological treatment. Relatively long-exerting therapeutic effects by gene therapy are potentially advantageous to treat slow progressive degenerative disc disease. In gene therapy, the delivery method and selection of target gene(s) are essential. Although gene therapy was first mediated by viral vectors, technological progress has enabled to apply nonviral vectors and polyplex micelles for the disc. While RNA interference successfully provides specific downregulation of multiple genes in the disc, clustered regularly interspaced short palindromic repeats (CRISPR) system has increased attention to alter the process of intervertebral disc degeneration. Then, more recent findings of our studies have suggested autophagy, the intracellular self-digestion, and recycling system under the negative regulation by the mammalian target of rapamycin (mTOR), as a gene therapy target in the disc. Here we briefly review backgrounds and applications of gene therapy for the disc, introducing strategies of autophagy and mTOR signaling modulation through selective RNA interference.

Experimental study of TNF-α receptor gene transfection by ultrasound-targeted microbubble destruction to treat collagen-induced arthritis in rats in vivo

Ultrasound-targeted microbubble destruction (UTMD) is a novel method for gene transfection. The aim of the present study was to identify the most suitable method of tumor necrosis factor (TNF)-α receptor (TNFR) gene transfection using UTMD for systemically treating a rat model of collagen-induced arthritis (CIA). Plasmids encoding the TNFR and enhanced green fluorescent protein (EGFP) with or without microbubbles were locally injected into the skeletal muscle and synovial membrane of CIA rats. The rats were divided into the following 6 groups: i) Group 1, plasmid + microbubble + ultrasound (muscle group); ii) group 2, plasmid + microbubble + ultrasound (joint group); iii) group 3, plasmid + ultrasound; iv) group 4, plasmid + microbubble; v) group 5, plasmid only and; vi) group 6, untreated controls. Rats were sacrificed at 2, 4 and 8 weeks of treatment. The transfection efficiency of the plasmids in the muscle or synovium was observed by fluorescence microscopy. Arthritis scores were calculated and serum levels of TNF-α were measured prior to and following treatment. Bilateral ankle joints were obtained and stained to observe synovial inflammation and the expression of TNF-α. EGFP expression was detected in all treated groups at each time point, and the fluorescence intensity of groups 1 and 2 was significantly greater than that of the other groups (P<0.05). For groups 1 and 2, the reductions in joint scores and serum levels of TNF-α were significant compared with the other groups (P<0.05). The number of synovial inflammatory cells and the synovial expression of TNF-α presented similar results among all experimental groups and no significant difference was observed between groups 1 and 2. Therefore, the results of the present study suggest that UTMD significantly enhanced the efficiency of TNFR gene transfection in the muscle and inflamed synovium of rats with. Regardless of whether the transfected TNFR gene was injected into the muscle or joint, it was continuously expressed in the rats for at least 8 weeks, which may improve arthritic symptoms and reduce the levels of inflammatory factors in the synovial tissues and peripheral blood.

Magnetic and Acoustically Active Microbubbles Loaded with Nucleic Acids for Gene Delivery

Targeted gene or drug delivery aims to locally accumulate the active agent and achieve the maximum local therapeutic effect at the target site while reducing unwanted effects at nontarget sites. A further development of the magnetic drug-targeting concept is combining it with an ultrasound-triggered delivery using magnetic microbubbles as a carrier for gene or drug delivery. For this purpose, selected magnetic nanoparticles (MNPs), phospholipids, and nucleic acid are assembled in the presence of perfluorocarbon gas into flexible formulations of magnetic lipospheres or microbubbles. This chapter describes the protocols for preparation of magnetic lipospheres and microbubbles for nucleic acid delivery, and it also describes the procedures for labeling the components of the bubbles (lipids, MNPs, and nucleic acids) for the visualization of the vectors and their characterization, such as magnetic responsiveness and ultrasound contrast effects. Protocols are given for the transfection procedure in adherent cells, evaluation of the association of the magnetic vectors with the cells, reporter gene expression analysis, and cell viability assessment.

Gene-Therapeutic Strategies Targeting Angiogenesis in Peripheral Artery Disease

The World Health Organization announced that cardiovascular disease is the number one cause of death globally, representing 31% of all global deaths. Coronary artery disease (CAD) affects approximately 5% of the US population aged 40 years and older. With an age-adjusted prevalence of approximately 12%, peripheral artery disease (PAD) affects at least 8 to 12 million Americans. Both CAD and PAD are caused by mainly atherosclerosis, the hardening and narrowing of arteries over the years by lipid deposition in the vascular bed. Despite the significant advances in interventions for revascularization and intensive medical care, patients with CAD or PAD who undergo percutaneous transluminal angioplasty have a persistent high rate of myocardial infarction, amputation, and death. Therefore, new therapeutic strategies are urgently needed for these patients. To overcome this unmet need, therapeutic angiogenesis using angiogenic growth factors has evolved in an attempt to stimulate the growth of new vasculature to compensate for tissue ischemia. After nearly 20 years of investigation, there is growing evidence of successful or unsuccessful gene therapy for ischemic heart and limb disease. This review will discuss basic and clinical data of therapeutic angiogenesis studies employing angiogenic growth factors for PAD patients and will draw conclusions on the basis of our current understanding of the biological processes of new vascularization.

The synergistic bactericidal effect of vancomycin on UTMD treated biofilm involves damage to bacterial cells and enhancement of metabolic activities

In this study, the synergistic effect of vancomycin, a cell wall synthesis inhibitor, and ultrasound-targeted microbubble destruction (UTMD), on cell viability of Staphylococcus epidermidis, embedded in biofilm, was investigated. Biofilms are the leading causes of antibiotic-resistant bacterial infections of medical implants and prosthetics worldwide. The antibiotic-resistant nature of biofilm-embedded pathogens poses a critical challenge to the medical community. Previously, studies have demonstrated the efficacy of using ultrasound waves and UTMD in circumventing this problem. However, the mechanism(s) underlying this phenomenon was not clear. Here, the present study showed that both ultrasound and UTMD damaged the cell wall structure of S. epidermidis, and floccules and fragments from damaged cells were observed on transmission electron microscope micrograph. However, the cell membrane integrity was not seriously affected by treatments, and the treatment increased the metabolic activity levels of the dormant biofilm-embedded bacteria, detected by confocal laser scanning microscope and flow cytometry, which could make them susceptible to the effect of the antibiotic. Thus, the biological mechanism underlying the efficacy of the combined treatment involving UTMD and vancomycin in the case of S. epidermidis biofilm was dissected, which may be utilized for further investigations on other biofilm pathogens before clinical use.

Polymer-Based Materials in Cancer Treatment: From Therapeutic Carrier and Ultrasound Contrast Agent to Theranostic Applications

The emergence of theranostics with ultrasound technology is a promising development, as it opens pathways to providing more effective treatments for cancer. Advancements in ultrasound imaging would give a more detailed and accurate image for better diagnosis and treatment planning. Polymeric ultrasound contrast agents (UCAs) are appealing because they are stable and easily modified for active targeting. In addition, a better therapy could be achieved in conjunction with advancements in UCAs. The active targeting not only makes the precise imaging possible, but also leads to targeted delivery of active components to specific local treatment sites. A polymeric nanocarrier with surface bioconjugation is the key to prolonging the bioavailability of the encapsulated drugs or genes and the capacity to target the specific tumor site. Using ultrasound with other imaging modalities will open more precise and better ways for diagnosis and therapy and bring us a step closer to personalized medicine. This review focuses on polymer-based materials of UCAs, multimodal imaging agents and therapeutic carriers that have been currently explored for their theranostic applications involving ultrasound for cancer diagnosis and treatment.

Therapeutic Effects of Microbubbles Added to Combined High-Intensity Focused Ultrasound and Chemotherapy in a Pancreatic Cancer Xenograft Model

Objective

To investigate whether high-intensity focused ultrasound (HIFU) combined with microbubbles enhances the therapeutic effects of chemotherapy.

Materials and Methods

A pancreatic cancer xenograft model was established using BALB/c nude mice and luciferase-expressing human pancreatic cancer cells. Mice were randomly assigned to five groups according to treatment: control (n = 10), gemcitabine alone (GEM; n = 12), HIFU with microbubbles (HIFU + MB, n = 11), combined HIFU and gemcitabine (HIGEM; n = 12), and HIGEM + MB (n = 13). After three weekly treatments, apoptosis rates were evaluated using the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling assay in two mice per group. Tumor volume and bioluminescence were monitored using high-resolution 3D ultrasound imaging and in vivo bioluminescence imaging for eight weeks in the remaining mice.

Results

The HIGEM + MB group showed significantly higher apoptosis rates than the other groups (p < 0.05) and exhibited the slowest tumor growth. From week 5, the tumor-volume-ratio relative to the baseline tumor volume was significantly lower in the HIGEM + MB group than in the control, GEM, and HIFU + MB groups (p < 0.05). Despite visible distinction, the HIGEM and HIGEM + MB groups showed no significant differences.

Conclusion

High-intensity focused ultrasound combined with microbubbles enhances the therapeutic effects of gemcitabine chemotherapy in a pancreatic cancer xenograft model.

Smart micro/nanoparticles in stimulus-responsive drug/gene delivery systems

New achievements in the realm of nanoscience and innovative techniques of nanomedicine have moved micro/nanoparticles (MNPs) to the point of becoming actually useful for practical applications in the near future. Various differences between the extracellular and intracellular environments of cancerous and normal cells and the particular characteristics of tumors such as physicochemical properties, neovasculature, elasticity, surface electrical charge, and pH have motivated the design and fabrication of inventive "smart" MNPs for stimulus-responsive controlled drug release. These novel MNPs can be tailored to be responsive to pH variations, redox potential, enzymatic activation, thermal gradients, magnetic fields, light, and ultrasound (US), or can even be responsive to dual or multi-combinations of different stimuli. This unparalleled capability has increased their importance as site-specific controlled drug delivery systems (DDSs) and has encouraged their rapid development in recent years. An in-depth understanding of the underlying mechanisms of these DDS approaches is expected to further contribute to this groundbreaking field of nanomedicine. Smart nanocarriers in the form of MNPs that can be triggered by internal or external stimulus are summarized and discussed in the present review, including pH-sensitive peptides and polymers, redox-responsive micelles and nanogels, thermo- or magnetic-responsive nanoparticles (NPs), mechanical- or electrical-responsive MNPs, light or ultrasound-sensitive particles, and multi-responsive MNPs including dual stimuli-sensitive nanosheets of graphene. This review highlights the recent advances of smart MNPs categorized according to their activation stimulus (physical, chemical, or biological) and looks forward to future pharmaceutical applications.

Diagnostic imaging advances in murine models of colitis

Inflammatory bowel diseases (IBD) such as Crohn’s disease and ulcerative colitis are chronic-remittent inflammatory disorders of the gastrointestinal tract still evoking challenging clinical diagnostic and therapeutic situations. Murine models of experimental colitis are a vital component of research into human IBD concerning questions of its complex pathogenesis or the evaluation of potential new drugs. To monitor the course of colitis, to the present day, classical parameters like histological tissue alterations or analysis of mucosal cytokine/chemokine expression often require euthanasia of animals. Recent advances mean revolutionary non-invasive imaging techniques for in vivo murine colitis diagnostics are increasingly available. These novel and emerging imaging techniques not only allow direct visualization of intestinal inflammation, but also enable molecular imaging and targeting of specific alterations of the inflamed murine mucosa. For the first time, in vivo imaging techniques allow for longitudinal examinations and evaluation of intra-individual therapeutic response. This review discusses the latest developments in the different fields of ultrasound, molecularly targeted contrast agent ultrasound, fluorescence endoscopy, confocal laser endomicroscopy as well as tomographic imaging with magnetic resonance imaging, computed tomography and fluorescence-mediated tomography, discussing their individual limitations and potential future diagnostic applications in the management of human patients with IBD.

Gene therapy for ocular diseases meditated by ultrasound and microbubbles (Review)

The eye is an ideal target organ for gene therapy as it is easily accessible and immune‑privileged. With the increasing insight into the underlying molecular mechanisms of ocular diseases, gene therapy has been proposed as an effective approach. Successful gene therapy depends on efficient gene transfer to targeted cells to prove stable and prolonged gene expression with minimal toxicity. At present, the main hindrance regarding the clinical application of gene therapy is not the lack of an ideal gene, but rather the lack of a safe and efficient method to selectively deliver genes to target cells and tissues. Ultrasound‑targeted microbubble destruction (UTMD), with the advantages of high safety, repetitive applicability and tissue targeting, has become a potential strategy for gene‑ and drug delivery. When gene‑loaded microbubbles are injected, UTMD is able to enhance the transport of the gene to the targeted cells. High‑amplitude oscillations of microbubbles act as cavitation nuclei which can effectively focus ultrasound energy, produce oscillations and disruptions that increase the permeability of the cell membrane and create transient pores in the cell membrane. Thereby, the efficiency of gene therapy can be significantly improved. The UTMD‑mediated gene delivery system has been widely used in pre‑clinical studies to enhance gene expression in a site‑specific manner in a variety of organs. With reasonable application, the effects of sonoporation can be spatially and temporally controlled to improve localized tissue deposition of gene complexes for ocular gene therapy applications. In addition, appropriately powered, focused ultrasound combined with microbubbles can induce a reversible disruption of the blood‑retinal barrier with no significant side effects. The present review discusses the current status of gene therapy of ocular diseases as well as studies on gene therapy of ocular diseases meditated by UTMD.

Optimization of ultrasound parameters for microbubble-nanoliposome complex-mediated delivery

Purpose:

The aim of this study was to identify the optimal ultrasound (US) parameters for gene and drug delivery.

Methods:

In order to target SkBr3, which is a breast cancer cell overexpressing the Her2 receptor, trastuzumab (Herceptin) was used. Micobubble-nanoliposome complex (MLC) was mixed with trastuzumab and stored overnight. Finally, MLC was combined with Her2_Ab. A US device equipped with a 1-MHz probe was used for delivery to the cell. Several parameters, including intensity (w/cm²), time (minutes), and duty cycle (%), were varied within a range from 1 w/cm², 1 minute, and 20% to 2 w/cm², 2 minutes, and 60%, respectively. A confocal laser scanning microscope (CLSM) was used to confirm the delivery of MLC to the cells after US treatment.

Results:

MLC with fluorescent dyes and trastuzumab was synthesized successfully. By delivering MLC with Her2_Ab to cells, the targeting effect of trastuzumab with MLC was confirmed by CLSM. The cell membranes showed green (fluorescein isothiocyanate) and red (Texas red) fluorescence but treatments with MLC without Her2_Ab did not show any fluorescence. Optimal conditions for US-mediated delivery were 1 or 2 w/cm², 2 minutes, and 60% (uptake ratio, 95.9% for 1 w/cm² and 95.7% for 2 w/cm²) for hydrophobic materials and 2 w/cm², 2 minutes, and 60% (uptake ratio, 95.0%) for hydrophilic materials.

Conclusion:

The greater the strength, duty cycle, and period of US application within the tested range, the more efficiently the fluorescent contents were conveyed.

Magnetic nanoparticle and magnetic field assisted siRNA delivery in vitro

This chapter describes how to design and conduct experiments to deliver siRNA to adherent cell cultures in vitro by magnetic force-assisted transfection using self-assembled complexes of small interfering RNA (siRNA) and cationic lipids or polymers that are associated with magnetic nanoparticles (MNPs). These magnetic complexes are targeted to the cell surface by the application of a gradient magnetic field. A further development of the magnetic drug-targeting concept is combining it with an ultrasound-triggered delivery using magnetic microbubbles as a carrier for gene or drug delivery. For this purpose, selected MNPs, phospholipids, and siRNAs are assembled in the presence of perfluorocarbon gas into flexible formulations of magnetic lipospheres (microbubbles). Methods are described how to accomplish the synthesis of magnetic nanoparticles for magnetofection and how to test the association of siRNA with the magnetic components of the transfection vector. A simple method is described to evaluate magnetic responsiveness of the magnetic siRNA transfection complexes and estimate the complex loading with magnetic nanoparticles. Procedures are provided for the preparation of magnetic lipoplexes and polyplexes of siRNA as well as magnetic microbubbles for magnetofection and downregulation of the target gene expression analysis with account for the toxicity determined using an MTT-based respiration activity test. A modification of the magnetic transfection triplexes with INF-7, fusogenic peptide, is described resulting in reporter gene silencing improvement in HeLa, Caco-2, and ARPE-19 cells. The methods described can also be useful for screening vector compositions and novel magnetic nanoparticle preparations for optimized siRNA transfection by magnetofection in any cell type.

Effects of therapeutic ultrasound on the nucleus and genomic DNA

In recent years, data have been accumulating on the ability of ultrasound to affect at a distance inside the cell. Previous conceptions about therapeutic ultrasound were mainly based on compromising membrane permeability and triggering some biochemical reactions. However, it was shown that ultrasound can access deep to the nuclear territory resulting in enhanced macromolecular localization as well as alterations in gene and protein expression. Recently, we have reported on the occurrence of DNA double-strand breaks in different human cell lines exposed to ultrasound in vitro with some insight into the subsequent DNA damage response and repair pathways. The impact of these observed effects again sways between extremes. It could be advantageous if employed in gene therapy, wound and bone fracture-accelerated healing to promote cellular proliferation, or in cancer eradication if the DNA lesions would culminate in cell death. However, it could be a worrying sign if they were penultimate to further cellular adaptations to stresses and thus shaking the safety of ultrasound application in diagnosis and therapy. In this review, an overview of the rationale of therapeutic ultrasound and the salient knowledge on ultrasound-induced effects on the nucleus and genomic DNA will be presented. The implications of the findings will be discussed hopefully to provide guidance to future ultrasound research.

An introduction to molecular imaging in radiation oncology: a report by the AAPM Working Group on Molecular Imaging in Radiation Oncology (WGMIR)

Molecular imaging is the direct or indirect noninvasive monitoring and recording of the spatial and temporal distribution of in vivo molecular, genetic, and/or cellular processes for biochemical, biological, diagnostic, or therapeutic applications. Molecular images that indicate the presence of malignancy can be acquired using optical, ultrasonic, radiologic, radionuclide, and magnetic resonance techniques. For the radiation oncology physicist in particular, these methods and their roles in molecular imaging of oncologic processes are reviewed with respect to their physical bases and imaging characteristics, including signal intensity, spatial scale, and spatial resolution. Relevant molecular terminology is defined as an educational assist. Current and future clinical applications in oncologic diagnosis and treatment are discussed. National initiatives for the development of basic science and clinical molecular imaging techniques and expertise are reviewed, illustrating research opportunities in as well as the importance of this growing field.

Insight concerning the mechanism of therapeutic ultrasound facilitating gene delivery: increasing cell membrane permeability or interfering with intracellular pathways?

Nonviral gene delivery methods encounter major barriers in plasmid DNA (pDNA) trafficking toward the nucleus. The present study aims to understand the role and contribution of therapeutic ultrasound (TUS), if any, in pDNA trafficking in primary cells such as fibroblasts and cell lines (e.g., baby hamster kidney [BHK]) during the transfection process. Using compounds that alter the endocytic pathways and the cytoskeletal network, we show that after TUS application, pDNA trafficking in the cytoplasm is not mediated by endocytosis or by the cytoskeletal network. Transfection studies and confocal analyses showed that the actin fibers impeded TUS-mediated transfection in BHK cells, but not in fibroblasts. Flow cytometric analyses indicated that pDNA uptake by cells occurs primarily when the pDNA is added before and not after TUS application. Taken together, these results suggest that TUS by itself operates as a mechanical force driving the pDNA through the cell membrane, traversing the cytoplasmic network and into the nucleus.

Genetic maneuvers to ameliorate ventricular function in heart failure: therapeutic potential and future implications

Gene therapy to treat heart failure has evolved into a growing field of investigation yielding remarkable results in preclinical models. Whether these results will persist in clinical trials remains to be seen. However, researchers still face a number of obstacles that need to be overcome before this treatment can be employed effectively. Efforts are required to identify better vectors with minimal side effects and maximal efficiency and durability. There is also a need to develop less invasive and more effective techniques to deliver these vectors. This review will discuss different methods to achieve these goals, the various pathologic mechanisms that have been targeted so far and those with strong potential for use in the future.

Micro- and nanobubbles: a versatile non-viral platform for gene delivery

Micro- and nanobubbles provide a promising non-viral strategy for ultrasound mediated gene delivery. Microbubbles are spherical gas-filled structures with a mean diameter of 1-8 μm, characterised by their core-shell composition and their ability to circulate in the bloodstream following intravenous injection. They undergo volumetric oscillations or acoustic cavitation when insonified by ultrasound and, most importantly, they are able to resonate at diagnostic frequencies. It is due to this behaviour that microbubbles are currently being used as ultrasound contrast agents, but their use in therapeutics is still under investigation. For example, microbubbles could play a role in enhancing gene delivery to cells: when combined with clinical ultrasound exposure, microbubbles are able to favour gene entry into cells by cavitation. Two different delivery strategies have been used to date: DNA can be co-administered with the microbubbles (i.e. the contrast agent) or 'loaded' in purposed-built bubble systems - indeed a number of different technological approaches have been proposed to associate genes within microbubble structures. Nanobubbles, bubbles with sizes in the nanometre order of magnitude, have also been developed with the aim of obtaining more efficient gene delivery systems. Their small sizes allow the possibility of extravasation from blood vessels into the surrounding tissues and ultrasound-targeted site-specific release with minimal invasiveness. In contrast, microbubbles, due to their larger sizes, are unable to extravasate, thus and their targeting capacity is limited to specific antigens present within the vascular lumen. This review provides an overview of the use of microbubbles as gene delivery systems, with a specific focus on recent research into the development of nanosystems. In particular, ultrasound delivery mechanisms, formulation parameters, gene-loading approaches and the advantages of nanometric systems will be described.

The role of gene therapy in regenerative surgery: updated insights

BACKGROUND

In the past two decades, regenerative surgeons have focused increasing attention on the potential of gene therapy for treatment of local disorders and injuries. Gene transfer techniques may provide an effective local and short-term induction of growth factors without the limits of other topical therapies. In 2002, Tepper and Mehrara accurately reviewed the topic: given the substantial advancement of research on this issue, an updated review is provided.

METHODS

Literature indexed in the National Center for Biotechnology Information database (PubMed) has been reviewed using variable combinations of keywords ("gene therapy," "regenerative medicine," "tissue regeneration," and "gene medicine"). Articles investigating the association between gene therapies and local pathologic conditions have been considered. Attention has been focused on articles published after 2002. Further literature has been obtained by analysis of references listed in reviewed articles.

RESULTS

Gene therapy approaches have been successfully adopted in preclinical models for treatment of a large variety of local diseases affecting almost every type of tissue. Experiences in abnormalities involving skin (e.g., chronic wounds, burn injuries, pathologic scars), bone, cartilage, endothelia, and nerves have been reviewed. In addition, the supporting role of gene therapies to other tissue-engineering approaches has been discussed. Despite initial reports, clinical evidence has been provided only for treatment of diabetic ulcers, rheumatoid arthritis, and osteoarthritis.

CONCLUSIONS

Translation of gene therapy strategies into human clinical trials is still a lengthy, difficult, and expensive process. Even so, cutting-edge gene therapy-based strategies in reconstructive procedures could soon set valuable milestones for development of efficient treatments in a growing number of local diseases and injuries.

The changing face of vascular interventional radiology: the future role of pharmacotherapies and molecular imaging

Interventional radiology has had to evolve constantly because there is the ever-present competition and threat from other specialties within medicine, surgery, and research. The development of new technologies, techniques, and therapies is vital to broaden the horizon of interventional radiology and to ensure its continued success in the future. In part, this change will be due to improved chronic disease prevention altering what we treat and in whom. The most important of these strategies are the therapeutic use of statins, Beta-blockers, angiotensin-converting enzyme inhibitors, and substances that interfere with mast cell degeneration. Molecular imaging and therapeutic strategies will move away from conventional techniques and nano and microparticle molecular technology, tissue factor imaging, gene therapy, endothelial progenitor cells, and photodynamic therapy will become an important part of interventional radiology of the future. This review looks at these new and exciting technologies.

Focused ultrasound-induced blood-brain barrier disruption enhances the delivery of cytarabine to the rat brain

To investigate the feasibility of using focused ultrasound (FUS) with microbubbles for targeted delivery of cytarabine to the brain. Sprague-Dawly rats (weighing 200-250 g) received focused ultrasound with intravenous injection microbubbles. At 0, 2, 4, 8, and 24 hours (n=5 for each time point) after sonication, animals received intravenous administration of cytarabine at a normal dose of 4 mg/kg body weight. Additional five rats were given with a high dose (50 mg/kg body weight) of cytarabine alone. Blood-brain barrier (BBB) permeability and cerebral cytarabine were determined. FUS in conjunction with microbubbles caused a transient BBB opening. Sonication exposure promoted cytarabine accumulation at the sonicated site. Animals injected with a normal dose of cytarabine 2 hours after sonication had similar concentrations of cerebral cytarabine compared to those with higher cytarabine without sonication. FUS can temporarily open the BBB and thus facilitate the penetration of systemic cytarabine into the brain.

Ultrasound-enhanced delivery of antibiotics and anti-inflammatory drugs into the eye

Delivery of sufficient amounts of therapeutic drugs into the eye is often a challenging task. In this study, ultrasound application (frequencies of 400 KHz to 1 MHz, intensities of 0.3-1.0 W/cm(2) and exposure duration of 5 min) was investigated to overcome the barrier properties of cornea, which is a typical route for topical administration of ophthalmic drugs. Permeability of ophthalmic drugs, tobramycin and dexamethasone and sodium fluorescein, a drug-mimicking compound, was studied in ultrasound- and sham-treated rabbit corneas in vitro using a standard diffusion cell setup. Light microscopy observations were used to determine ultrasound-induced structural changes in the cornea. For tobramycin, an increase in permeability for ultrasound- and sham-treated corneas was not statistically significant. Increase of 46%-126% and 32%-109% in corneal permeability was observed for sodium fluorescein and dexamethasone, respectively, with statistical significance (p < 0.05) achieved at all treatment parameter combinations (compared with sham treatments) except for 1-MHz ultrasound applications for dexamethasone experiments. This permeability increase was highest at 400 kHz and appeared to be higher at higher intensities applied. Histologic analysis showed structural changes that were limited to epithelial layers of cornea. In summary, ultrasound application provided enhancement of drug delivery, increasing the permeability of the cornea for the anti-inflammatory ocular drug dexamethasone. Future investigations are needed to determine the effectiveness and safety of this application in in vivo long-term survival studies.

Magnetic and acoustically active microbubbles loaded with nucleic acids for gene delivery

Targeted gene or drug delivery aims to locally accumulate the active agent and achieve the maximum local therapeutic effect at the target-site while reducing unwanted effects at nontarget sites. A further development of the magnetic drug-targeting concept is combining it with an ultrasound-triggered delivery using magnetic microbubbles as a carrier for gene or drug delivery. For this purpose, selected magnetic nanoparticles (MNPs), phospholipids, and nucleic acid are assembled in the presence of perfluorocarbon gas into flexible formulations of magnetic lipospheres or microbubbles. This manuscript describes the protocols for preparation of magnetic lipospheres and microbubbles for nucleic acid delivery, and it also describes the procedures for labeling the components of the bubbles (lipids, MNPs, and nucleic acids) for the visualization of the vectors and their characterization, such as magnetic responsiveness and ultrasound contrast effects. Protocols are given for the transfection procedure in adherent cells, evaluation of the association of the magnetic vectors with the cells, reporter gene expression analysis, and cell viability assessment.

Therapeutic ultrasound promotes plasmid DNA uptake by clathrin-mediated endocytosis

BACKGROUND

Ultrasound (US) has been widely used to improve the efficiency of nonviral vector transfection. The mechanism of plasmid uptake is usually attributed to sonoporation, although there is not clear evidence for this attribution. Based on our previous results, we hypothesized that other mechanisms, such as endocytosis, could be involved in this process.

METHODS

NIH3T3 cells were transfected with plasmid vector pEGFP-N3 (4.7 kb) using a therapeutic US without microbubbles. Bioeffects such as calcium influx, reactive oxygen species (ROS) generation and membrane potential alterations were accessed with fluorescent dyes in real-time by confocal microscopy after US insonation. Localization of labeled plasmid DNA in cells was also monitored with endocytosis markers using an immunofluorescence assay.

RESULTS

US at 2 W/cm(2) with a duty-cycle of 20% for 30 s resulted in approximately 40% transfection efficiency but, at 1 W/cm(2) , resulted in a very low level of transfection. Both the production of ROS and calcium influx were augmented during the insonation, although they were stopped soon after turning off US, with the exception of calcium influx with 1 W/cm(2) . US also changed the cell membrane potential to the hyperpolarization state, which returned to the normal state soon after insonation. Labeled plasmids DNA could be co-localized with clathrin-mediated endocytosis marker but not with caveolin-1.

CONCLUSIONS

The present data indicate that plasmid DNA uptake promoted by US should occur via clathrin-mediated endocytosis.

Modelling ultrasound-induced mild hyperthermia of hyperplasia in vascular grafts

BACKGROUND

Expanded polytetrafluoroethylene (ePTFE) vascular grafts frequently develop occlusive neointimal hyperplasia as a result of myofibroblast over-growth, leading to graft failure. ePTFE exhibits higher ultrasound attenuation than native soft tissues. We modelled the selective absorption of ultrasound by ePTFE, and explored the feasibility of preventing hyperplasia in ePTFE grafts by ultrasound heating. Specifically, we simulated the temperature profiles of implanted grafts and nearby soft tissues and blood under ultrasound exposure. The goal was to determine whether ultrasound exposure of an ePTFE graft can generate temperatures sufficient to prevent cell growth on the graft without damaging nearby soft tissues and blood.

METHODS

Ultrasound beams from two transducers (1.5 and 3.2 MHz) were simulated in two graft/tissue models, with and without an intra-graft cellular layer mimicking hyperplasia, using the finite-difference time-domain (FDTD) method. The resulting power deposition patterns were used as a heat source for the Pennes bioheat equation in a COMSOL(®) Multiphysics heat transfer model. 50°C is known to cause cell death and therefore the transducer powers were adjusted to produce a 13°C temperature rise from 37°C in the ePTFE.

RESULTS

Simulations showed that both the frequency of the transducers and the presence of hyperplasia significantly affect the power deposition patterns and subsequent temperature profiles on the grafts and nearby tissues. While neither transducer significantly raised the temperature of the blood, the 1.5-MHz transducer was less focused and heated larger volumes of the graft and nearby soft tissues than the 3.2-MHz transducer. The presence of hyperplasia had little effect on the blood's temperature, but further increased the temperature of the graft and nearby soft tissues in response to either transducer. Skin cooling and blood flow play a significant role in preventing overheating of the native tissues.

CONCLUSIONS

Modelling shows that ultrasound can selectively heat ePTFE grafts and produce temperatures that cause cell death on the graft. The temperature increase in blood is negligible and that in the adjacent soft tissues may be minimized by skin cooling and using appropriate transducers. Therefore, ultrasound heating may have the potential to reduce neointimal hyperplasia and failure of ePTFE vascular grafts.

Enhancement of vancomycin activity against biofilms by using ultrasound-targeted microbubble destruction

Treating biofilm infections on implanted medical devices is formidable, even with extensive antibiotic therapy. The aim of this study was to investigate whether ultrasound (US)-targeted microbubble (MB) destruction (UTMD) could enhance vancomycin activity against Staphylococcus epidermidis RP62A biofilms. Twelve-hour biofilms were treated with vancomycin combined with UTMD. The vancomycin and MB (SonoVue) were used at concentrations of 100 μg/ml and 30% (vol/vol), respectively, in studies in vitro. After US exposure (0.08 MHz, 1.0 W/cm(2), 50% duty cycle, and 10-min duration), the biofilms were cultured at 37 °C for another 12 h. The results showed that many micropores were found in biofilms treated with vancomycin combined with UTMD. Biofilm densities (A(570) values) and the viable counts of S. epidermidis recovered from the biofilm were significantly decreased compared with those of any other groups. Furthermore, the highest percentage of dead cells was found, using confocal laser scanning microscopy, in the biofilm treated with vancomycin combined with UTMD. The viable counts of bacteria in biofilms in an in vivo rabbit model also confirmed the enhanced effect of vancomycin combined with UTMD. UTMD may have great potential for improving antibiotic activity against biofilm infections.

Intramembrane cavitation as a unifying mechanism for ultrasound-induced bioeffects

The purpose of this study was to develop a unified model capable of explaining the mechanisms of interaction of ultrasound and biological tissue at both the diagnostic nonthermal, noncavitational (<100 mW · cm(-2)) and therapeutic, potentially cavitational (>100 mW · cm(-2)) spatial peak temporal average intensity levels. The cellular-level model (termed "bilayer sonophore") combines the physics of bubble dynamics with cell biomechanics to determine the dynamic behavior of the two lipid bilayer membrane leaflets. The existence of such a unified model could potentially pave the way to a number of controlled ultrasound-assisted applications, including CNS modulation and blood-brain barrier permeabilization. The model predicts that the cellular membrane is intrinsically capable of absorbing mechanical energy from the ultrasound field and transforming it into expansions and contractions of the intramembrane space. It further predicts that the maximum area strain is proportional to the acoustic pressure amplitude and inversely proportional to the square root of the frequency (ε A,max ∝ P(A)(0.8f - 0.5) and is intensified by proximity to free surfaces, the presence of nearby microbubbles in free medium, and the flexibility of the surrounding tissue. Model predictions were experimentally supported using transmission electron microscopy (TEM) of multilayered live-cell goldfish epidermis exposed in vivo to continuous wave (CW) ultrasound at cavitational (1 MHz) and noncavitational (3 MHz) conditions. Our results support the hypothesis that ultrasonically induced bilayer membrane motion, which does not require preexistence of air voids in the tissue, may account for a variety of bioeffects and could elucidate mechanisms of ultrasound interaction with biological tissue that are currently not fully understood.

Influence of ultrasound induced cavitation on magnetic resonance imaging contrast in the rat liver in the presence of macromolecular contrast agent

OBJECTIVES

Local drug delivery by ultrasound (US)-induced cavitation is a promising strategy for increasing the drug concentration at the target location and for decreasing the systemic toxicity effects. The presence of microbubbles during sonication at the targeted location improves the likelihood for cavitation that can be exploited to increase the capillary permeability. The objective of this work was to evaluate the magnetic resonance imaging (MRI) contrast changes in hepatic tissue in vivo, induced by US-triggered cavitation and destruction of microbubbles (Sonovue), in the presence of a coinjected blood pool MRI contrast agent (Vistarem) used as a reporter macromolecule. The potential tissue damage induced by microbubbles destruction was also evaluated by histology.

METHOD

The change in the hepatic distribution of the macromolecular MRI contrast agent associated with cavitation was monitored at 1.5 T with a look-locker fast inversion recovery sequence to map the longitudinal relaxation rates, before and during 1 hour after intravenous administration of Vistarem and Sonovue. In 1 group of rats (n = 5), these microbubbles were immediately destroyed with a clinical echograph, using a high mechanical index (MI = 1.5) at low frequency (2 MHz). The control group (n = 7) received identical injections without application of US. The parametric relaxation rate images were computed, and the changes in time were analyzed to account for the potential effect of microbubble destruction by US on the permeability of the hepatic vessels. The animals were killed 1 day after the experiment for routine histology of the liver.

RESULTS

For both groups of animals, after an initial increase, a transient decay of the longitudinal relaxation rate was observed, followed by a constant plateau after 20 minutes. The analysis of the mean relaxation rates in the liver showed significant (P < 0.01) higher values for the group with destruction of microbubbles as compared with the control group. The US-triggered cavitation and destruction of microbubble with the proposed protocol suggests an increased concentration of Vistarem of a factor 2 in the hepatic tissue. No tissue damage was observed at the microscopic analysis.

CONCLUSION

The absence of tissue alterations indicates that the destruction of this US contrast agent could be safe in vivo under an appropriate choice of the sonication parameters. This approach opens new perspectives for translation toward clinical applications of local drug delivery. Ultrasound-mediated microbubble destruction may help in increasing the local concentration of a drug currently limited by the endothelial barrier. In addition, it may help in reducing the systemic toxicity to normal cells in standard chemotherapies, because the enhanced capillary permeability effect can be spatially adjusted by selecting the sonicated region.

Additive effect of low-frequency ultrasound and endothelial monocyte-activating polypeptide II on blood-tumor barrier in rats with brain glioma

Brain glioma is a malignant tumor which needs surgery followed by chemotherapy. Low-frequency ultrasound (LFU) and Optison could open blood-tumor barrier (BTB) selectively and noninvasively and thus increase the permeability of BTB. Endothelial monocyte-activating polypeptide II (EMAP-II) induces cytoskeletal remodeling in endothelial cells. In this study, we asked whether LFU, Optison, and/or EMAP-II used in combination have additive effects on increasing the permeability of BTB by tight junction (TJ)-associated protein-dependent manner and thus help understand the possible mechanisms for TJ-based drug delivery to the central nervous system through BTB. Evans Blue assay was used to measure the permeability of BTB in rat model of C6 glioma. The mRNA and protein levels of TJ-associated proteins, claudin-5, occludin, and ZO-1, were determined. Results showed that Evans blue content significantly increased and the mRNA and protein levels of claudin-5, occludin, and ZO-1 significantly reduced after the treatment in groups treated with EMAP-II and LFU combined with or without Optison (LFU+EMAP-II and LFU+Optison+EMAP-II groups) and in the group treated with LFU and Optison (LFU+Optison group). In conclusion, LFU and EMAP-II used in combination have additive effects on increasing the permeability of BTB and remodeling of TJ-associated proteins.

Ultrasonic microbubble-mediated gene delivery causes phenotypic changes of human aortic endothelial cells

Ultrasound, in combination with microbubbles, serves as a feasible nonviral method in vascular gene delivery. However, the effects of ultrasonic microbubble transfection (UMT) on vascular endothelial cells remained unclear. We therefore investigated whether UMT itself causes phenotypic changes of the human aortic endothelial cells (HAEC) in vitro. HAEC were cultured with solution containing luciferase reporter gene and microbubbles followed by exposure to ultrasound of selected parameters. Thereafter, the proliferation and migration activities of HAEC were investigated. Real-time RT-PCR and/or western blotting were performed to assess expression profile of HAEC, including growth-related factors (vascular endothelial growth factor, fins-like tyrosine kinase-1 [Flt-1] and kinase insert domain-containing receptor [KDR]), coagulatory factor (von Willebrand factor), vasodilatory enzyme (endothelial nitric oxide synthase), gap junctional protein connexin43 and adhesion molecules (P-selectin, intercellular adhesion molecule 1 and vascular cell adhesion molecule 1). The results showed that in conditions where UMT lead to expression of luciferase, proliferation capacity is enhanced (p<0.001), partly attributable to the effect of ultrasound (p<0.05), after excluding the effect of contact inhibition. In addition, the expression of KDR and Flt-1 were found increased at either the mRNA level, protein level, or both (p<0.05). Other markers did not have significant changes (all p>0.2). Similarly, the migration capacity was minimally changed (p>0.3). In conclusion, UMT causes phenotypic changes of HAEC by enhancing proliferation and upregulating KDR and Flt-1, while possesses no obvious adverse effect on viable transfected cells. Further investigation is required to clarify the impact of these changes by UMT in vivo.

Partial restoration of left ventricular systolic function by asPLB gene transfer using ultrasound-mediated microbubble destruction

In vitro and in vivo studies have demonstrated that inhibition of phospholamban (PLB) expression in myocardium can restore left ventricular systolic function in failing heart. Ultrasound mediated microbubble destruction provides a new option for noninvasive gene transfer in heart. In this study, we transferred pAAV-antisense phospholamban (pAAV-asPLB) to the hearts of myocardial infarction (MI) mice, using ultrasound mediated microbubble destruction. Then we estimated the protein levels of PLB, Ser16-PLB and cardiac sarcoplasmic reticulum Ca(2+) ATPase (SERCA). The left ventricular ejection fraction (LVEF), fraction shortening (FS) and SERCA activity were measured as well. MI mice were generated by ligating the left anterior descending coronary artery. Microbubbles were prepared by sonicated perfluorocarbon gas with dextrose and albumin. A mixture of pAAV-asPLB plasmid and microbubble was injected via tail vein while the heart was simultaneously exposed to ultrasound via transthoracic insonation. Three weeks later, LVEF (48.2+/-5.18% vs 39.1+/-5.38%, p<0.05), FS (19.6+/-2.59% vs 16.0+/-2.29%, p<0.05), SERCA activity (3.00+/-0.29 vs 2.12+/-0.30, p<0.05) and Ser16-PLB protein level (0.8+/-0.25 vs 0.46+/-0.18, p<0.05) were increased while PLB protein level (1.45+/-0.38 vs 2.05+/-0.31, p<0.05) was decreased compared with the MI mice with saline injection. The above parameters in MI mice with only pAAV-asPLB plasmid injection or pAAV-asPLB plasmid combined with ultrasound alone were not significantly improved. pAAV-LacZ was used as a reporter gene to determine the efficiency and localization of transfection. The expression of beta-galactosidase was not found in liver, lung and brain, but found only in tubular epithelial cells of kidney and found in heart. These results confirm that asPLB gene transfection can be achieved by ultrasound mediated microbubble destruction with organ specificity. The effective transfection can partly restore heart function in MI mice.

A novel magnetic crystal-lipid nanostructure for magnetically guided in vivo gene delivery

Cancer gene therapy requires a safe and effective gene delivery system. Polymer- and lipid-coated magnetic nanocrystals have been used to deliver silencing RNA, but synthesizing these magnetic vectors is difficult. Here, we show that a new nanoparticle formulation can be magnetically guided to deliver and silence genes in cells and tumours in mice. This formulation, termed LipoMag, consists of an oleic acid-coated magnetic nanocrystal core and a cationic lipid shell. When compared with the commercially available PolyMag formulation, LipoMag displayed more efficient gene silencing in 9 of 13 cell lines, and better anti-tumour effects when systemically administered to mice bearing gastric tumours. By delivering an optimized sequence of a silencing RNA that targets the epidermal growth factor receptor of tumour vessels, the intended therapeutic benefit was achieved with no evident adverse immune reaction or untoward side effects.

Gene transfection to retinal ganglion cells mediated by ultrasound microbubbles in vitro

RATIONALE AND OBJECTIVES

To investigate the expression levels of green fluorescence protein (GFP) into retinal ganglion cells (RGCs) in vitro by ultrasound-mediated microbubble destruction (UMMD) and assess the effect of bcl-xl gene on N-methyl-D-aspartate (NMDA)-induced apoptosis in the cultured RGCs by UMMD.

MATERIALS AND METHODS

pEGFP-N1 was transfected to RGCs in vitro by UMMD and liposome was used as the control. The transfection effect was detected using microscope and flow cytometry qualitatively and quantitatively. Monotetrazolium was adopted to measure the cell vitality. NMDA was used to induce apoptosis in the cultured RGCs, and the bcl-xl gene was transfected into RGCs by UMMD before NMDA-induced apoptosis. The expression of bcl-xl protein in RGCs was assessed by immunohistochemistry assay. The amorphous character of RGCs was revealed by acridine orange and ethidium bromide staining. DNA fragment was detected by agarose gel electrophoresis.

RESULTS

Ultrasound combined with microbubbles enhanced gene transfection to the cultured cells in some condition. The average transfection rate of pEGFP-N1 with UMMD was 25%. Both ultrasound and microbubble had no effect on cell viability. The expression of bcl-xl protein in transfected and non-transfected RGCs was significantly different. Less apoptotic bodies and no representative DNA fragment were detected in the treatment group.

CONCLUSIONS

Microbubble destruction can enhance the reporter gene transfection and expression and have a good target. Transfection of bcl-xl gene has an anti-apoptosis effect on the cultured RGCs induced by NMDA with UMMD.

A European multi‐center trial investigating the anti‐restenotic effect of intravascular sonotherapy after stenting of de novo lesions (EUROSPAH: EUROpean Sonotherapy Prevention of Arterial Hyperplasia)

BACKGROUND

Intravascular sonotherapy (IST) reduces neointimal hyperplasia post-stenting in animal studies. Euro-SPAH is a multi-center, double blind, randomized trial investigating the efficacy of IST to reduce in-stent late loss.

METHODS

Patients with angina or silent ischaemia with stented de novo lesions were randomised to sham or IST. The sample size had a 90% power to detect a late loss difference of 0.21 mm at 6 months. The secondary endpoints were MACE at 1, 6, 12 months and neo-intimal hyperplasia on IVUS at 6 months.

RESULTS

At 23 sites in Europe, 403 patients were randomized, with successful treatment with sham or IST in 95.6%. There were no significant differences between the groups in terms of baseline demographics or lesion characteristics. Angiographic follow-up was obtained in 89%. In-stent late loss was not significantly different. The restenosis rate at 6 months was 23% in the IST group versus 25% in the sham group. The IVUS measurements confirm the absence of effect of IST on neointimal hyperplasia. At one year, the event-free survival did not significantly differ between the two groups.

CONCLUSION

The use of sonotherapy following stent implantation in de novo lesions does not reduce intra-stent neointimal hyperplasia, or effect the angiographic restenosis rate compared to sham treatment.

Gene therapy and intracytoplasmatic sperm injection (ICSI) - a review

Human gene therapy (HGT), the treatment or prevention of disease by gene transfer is, regarded by many, as a potential revolution in medicine, because gene therapies target the causes of disease, whereas most current drugs treat the symptoms. Micro-assisted fertilization in the form of intracytoplasmatic sperm injection (ICSI) has truly revolutionized the treatment options for couples with impaired semen quality, and those with both obstructive and non-obstructive azoospermia. ICSI involves the injection of a single sperm directly into the cytoplasm of a mature egg (oocyte) using a glass needle (pipette). Fertilization with this technique occurs in 50%-80% of injected oocytes, but may damage a small percentage of them. With gene therapy, there are new and varied strategies for gene transfer and genome sequence manipulation with improved methodologies that use the technique of microinjection such as the intracytoplasmatic sperm injection-mediated transgenesis (ICSI-Tr), active transgenesis or the pronuclear microinjection technique. This review will look at these methods as well as their potential applications and limitations.

Therapeutic potential of low-intensity ultrasound (part 2): biomolecular effects, sonotransfection, and sonopermeabilization

Part one of this review focused on the thermal and mechanical effects of low-intensity ultrasound (US). In this second and final part of the review, we will focus on and discuss various aspects of low-intensity US, with emphasis on the biomolecular effects, US-mediated gene transfection (sonotransfection), and US-mediated permeabilization (sonopermeabilization). Sonotransfection of different cell lines in vitro and target tissues in vivo have been reported. Optimization experiments have been done and different mechanisms investigated. It has also been found that several genes can be up-regulated or down-regulated by sonication. As to the potential therapeutic applications, systemic or local sonotransfection might also be a safe and effective gene therapy method in effecting the cure of local and systemic disorders. Gene regulation of target cells may be utilized in modifying cellular response to a treatment, such as increasing the sensitivity of diseased cells while making normal cells resistant to the side effects of a treatment. Advances in sonodynamic therapy and drug sonopermeabilization also offer an ever-increasing array of therapeutic options for low-intensity US.

Gene therapy approach for disc degeneration and associated spinal disorders

Disc degeneration is deeply associated with many spinal disorders and thus has a significant clinical impact on society. The currently available surgical treatment often necessitates removing a pathological disc and spinal fusion. However, it is also well known that these surgical treatments have many potential problems including invasion and cost. Therefore, biological approaches for regenerating these pathological discs have received much attention. Gene therapy is one of these biological approaches. Gene therapy involves the transfer of genes to cells so the recipient cells express these genes and thereby synthesize the RNA and protein they encode in a continuous fashion. One of the significant advantages of gene therapy is that we can expect a lasting duration of biological effect which is potentially beneficial for most disc degeneration associated disorders, as they are, by nature, chronic conditions. Originally, gene therapy was mediated by viral vectors, but recent technological progress has enabled us to opt for non-virus-mediated gene therapy for the disc. Furthermore, the development of the RNA interference technique has enabled us to down-regulate a specific gene expression in the disc opening the door for a new generation of intradiscal gene therapy.

Effective gene delivery with liposomal bubbles and ultrasound as novel non-viral system

We developed the novel liposomal bubbles (Bubble liposomes) containing ultrasound imaging gas, perfluoropropane. Bubble liposomes were made of pegylated liposomes and were smaller than conventional microbubbles. Bubble liposomes also had a function as imaging agents in cardiosonography. In addition, Bubble liposomes could deliver plasmid DNA into various types of cells in vitro without cytotoxicity by the combination of ultrasound. In vivo gene delivery, Bubble liposomes could deliver plasmid DNA into mouse femoral artery by the transdermally exposure of ultrasound. This transfection efficiency was more effectively than lipofection method. Interestingly, the gene expression was only observed at the site of ultrasound exposure. Therefore, we concluded that Bubble liposomes could be good tools to establish tissue-specific gene delivery system as well as ultrasound imaging agents.

Micelles and nanoparticles for ultrasonic drug and gene delivery

Drug delivery research employing micelles and nanoparticles has expanded in recent years. Of particular interest is the use of these nanovehicles that deliver high concentrations of cytotoxic drugs to diseased tissues selectively, thus reducing the agent's side effects on the rest of the body. Ultrasound, traditionally used in diagnostic medicine, is finding a place in drug delivery in connection with these nanoparticles. In addition to their non-invasive nature and the fact that they can be focused on targeted tissues, acoustic waves have been credited with releasing pharmacological agents from nanocarriers, as well as rendering cell membranes more permeable. In this article, we summarize new technologies that combine the use of nanoparticles with acoustic power both in drug and gene delivery. Ultrasonic drug delivery from micelles usually employs polyether block copolymers and has been found effective in vivo for treating tumors. Ultrasound releases drug from micelles, most probably via shear stress and shock waves from the collapse of cavitation bubbles. Liquid emulsions and solid nanoparticles are used with ultrasound to deliver genes in vitro and in vivo. The small packaging allows nanoparticles to extravasate into tumor tissues. Ultrasonic drug and gene delivery from nanocarriers has tremendous potential because of the wide variety of drugs and genes that could be delivered to targeted tissues by fairly non-invasive means.