A visible, targeted high-efficiency gene delivery and transfection strategy

Repairing the heart: State-of the art delivery strategies for biological therapeutics

Myocardial infarction (MI) is one of the leading causes of mortality worldwide. It is caused by an acute imbalance between oxygen supply and demand in the myocardium, usually caused by an obstruction in the coronary arteries. The conventional therapy is based on the application of (a combination of) anti-thrombotics, reperfusion strategies to open the occluded artery, stents and bypass surgery. However, numerous patients cannot fully recover after these interventions. In this context, new therapeutic methods are explored. Three decades ago, the first biologicals were tested to improve cardiac regeneration. Angiogenic proteins gained popularity as potential therapeutics. This is not straightforward as proteins are delicate molecules that in order to have a reasonably long time of activity need to be stabilized and released in a controlled fashion requiring advanced delivery systems. To ensure long-term expression, DNA vectors-encoding for therapeutic proteins have been developed. Here, the nuclear membrane proved to be a formidable barrier for efficient expression. Moreover, the development of delivery systems that can ensure entry in the target cell, and also correct intracellular trafficking towards the nucleus are essential. The recent introduction of mRNA as a therapeutic entity has provided an attractive intermediate: prolonged but transient expression from a cytoplasmic site of action. However, protection of the sensitive mRNA and correct delivery within the cell remains a challenge. This review focuses on the application of synthetic delivery systems that target the myocardium to stimulate cardiac repair using proteins, DNA or RNA.

Ultrasound-targeted microbubble destruction in gene therapy: A new tool to cure human diseases

Human gene therapy has made significant advances in less than two decades. Within this short period of time, gene therapy has proceeded from the conceptual stage to technology development and laboratory research, and finally to clinical trials for the treatment of a variety of deadly diseases. Cardiovascular disease, cancer, and stroke are leading causes of death worldwide. Despite advances in medical, interventional, radiation and surgical treatments, the mortality rate remains high, and the need for novel therapies is great. Gene therapy provides an efficient approach to disease treatment. Notable advances in gene therapy have been made for genetic disorders, including severe combined immune deficiency, chronic granulomatus disorder, hemophilia and blindness, as well as for acquired diseases, including cancer and neurodegenerative and cardiovascular diseases. However, lack of an efficient delivery system to target cells as well as the difficulty of sustained expression of transgenes has hindered advancements in gene therapy. Ultrasound targeted microbubble destruction (UTMD) is a promising approach for target-specific gene delivery, and it has been successfully investigated for the treatment of many diseases in the past decade. In this paper, we review UTMD-mediated gene delivery for the treatment of cardiovascular diseases, cancer and stroke.

Improving the efficacy of therapeutic angiogenesis by UTMD-mediated Ang-1 gene delivery to the infarcted myocardium

This study aimed to verify the feasibility and efficacy of ultrasound-targeted microbubble destruction (UTMD)-mediated angiopoietin-1 (Ang-1) gene delivery into the infarcted myocardium. Microbubbles carrying anti-intercellular adhesion molecule-1 (ICAM-1) antibody were prepared and identified. The microbubbles carrying anti-ICAM-1 antibody selectively adhered to the interleukin (IL)-1β-stimulated ECV304 cells and to the ischemic vascular endothelium, and the infarct area was examined to evaluate the targeting ability of ICAM-1 microbubbles in vitro and in vivo. The intravenous administration of the Ang-1 gene was carried out by UTMD in rabbits with acute myocardial infarction (AMI). The rabbits were divided into the control (no treatment), non-targeted microbubble destruction (non-TMB) and the ICAM-1 TMB (TMB) group. Gene delivery by direct intramyocardial injection (IMI) served as a reference. Two weeks later, regional myocardial perfusion and cardiac function were evaluated by echocardiography, and Ang-1 gene-mediated angiogenesis was assessed histologically and biochemically. The results revealed that the ICAM-1-targeted microbubbles selectively adhered to the IL-1β-stimulated ECV304 cells in vitro and to the ischemic vascular endothelium in the infarct area of the rabbits with AMI. Two weeks after the delivery of the Ang-1 gene, compared with the non-TMB group, left ventricular function and myocardial perfusion at the infarct area had improved in the TMB and IMI group (p<0.01). Ang-1 gene expression was detectable in the non-TMB, TMB and IMI group, while its expression was higher in the latter 2 groups (all p<0.01). The microvascular density (MVD) of the infarct area in the non-TMB, TMB and IMI group was 65.6±4.4, 96.7±2.1 and 100.7±3.6, respectively (p<0.01). The findings of our study indicate that UTMD-mediated gene delivery may be used to successfully deliver the Ang-1 gene to the infarcted myocardium, thus improving the efficacy of therapeutic angiogenesis. This may provide a novel strategy for future gene therapy.

New progress in angiogenesis therapy of cardiovascular disease by ultrasound targeted microbubble destruction

Angiogenesis plays a vital part in the pathogenesis and treatment of cardiovascular disease and has become one of the hotspots that are being discussed in the past decades. At present, the promising angiogenesis therapies are gene therapy and stem cell therapy. Besides, a series of studies have shown that the ultrasound targeted microbubble destruction (UTMD) was a novel gene delivery system, due to its advantages of noninvasiveness, low immunogenicity and toxicity, repeatability and temporal and spatial target specificity; UTMD has also been used for angiogenesis therapy of cardiovascular disease. In this review, we mainly discuss the combination of UTMD and gene therapy or stem cell therapy which is applied in angiogenesis therapy in recent researches, and outline the future challenges and good prospects of these approaches.

Ultrasound treatment increases transfection efficiency of low molecular weight chitosan in fibroblasts but not in KB cells

The aim of this study was to optimize transfection efficiency (TE) of the depolymerized low molecular weight (LW) chitosan with molecular weight (Mw) at 16 kDa and 54% degree of deacetylation (DDA) on three primary cells of fibroblast (F), dental pulp (P), and periodontal ligament (PDL). The effect of low frequency ultrasound treatment on the chitosan-DNA complexes prior transfection on TE was also evaluated. This LW chitosan required high N/P ratio (>34) to bind DNA completely. An N/P ratio above 56 tended to improve TE in most primary cells nearly at the level of Lipofectamine. Ultrasonication can reduce the aggregation and sizes of the chitosan-DNA microparticles. It increased TE of F cells at an N/P ratio above 34, which was higher than Lipofectamine. However, this ultrasound treatment caused loss of TE in KB cells. MTT assay of these chitosan-DNA complexes revealed no significant cytotoxicity to both KB and F cells. This LW chitosan has potential for further development into a safer alternative to gene delivery systems in various cells of interest; however the optimal conditions have to be adjusted, depending on each cell source.

Molecular properties of lysozyme-microbubbles: towards the protein and nucleic acid delivery

Microbubbles (MBs) have specific acoustic properties that make them useful as contrast agents in ultrasound imaging. The use of the MBs in clinical practice led to the development of more sensitive imaging techniques both in cardiology and radiology. Protein-MBs are typically obtained by dispersing a gas phase in the protein solution and the protein deposited/cross-linked on the gas-liquid interface stabilizes the gas core. Innovative applications of protein-MBs prompt the investigation on the properties of MBs obtained using different proteins that are able to confer them specific properties and functionality. Recently, we have synthesized stable air-filled lysozyme-MBs (LysMBs) using high-intensity ultrasound-induced emulsification of a partly reduced lysozyme in aqueous solutions. The stability of LysMBs suspension allows for post-synthetic modification of MBs surface. In the present work, the protein folded state and the biodegradability property of LysMBs were investigated by limited proteolysis. Moreover, LysMBs were coated and functionalized with a number of biomacromolecules (proteins, polysaccharides, nucleic acids). Remarkably, LysMBs show a high DNA-binding ability and protective effects of the nucleic acids from nucleases and, further, the ability to transform the bacteria cells. These results highlight on the possibility of using LysMBs for delivery of proteins and nucleic acids in prophylactic and therapeutic applications.