Long-term continuous monitoring of arrhythmias in pigs with insertable cardiac monitors.

Arrhythmia detection is essential when assessing the safety of novel drugs and therapies in preclinical studies. Many short-term arrhythmia monitoring methods exist, including non-invasive ECG and Holter. However, there are no reliable, long-term, non-invasive, or minimally invasive methods for cardiac arrhythmia follow-up in large animals that allows free movement with littermates. A long follow-up time is needed when estimating the impact of long-lasting drugs or therapies, such as gene therapy. We evaluated the feasibility and performance of insertable cardiac monitors (ICMs) in pigs for minimally invasive, long-term monitoring of cardiac arrhythmias that allows free movement and species-specific behavior. Multiple implantation sites were tested to assess signal quality. ICMs recognized reliably many different arrhythmias but failed to detect single extrasystoles. They also over-diagnosed T-waves, resulting in oversensing. Muscle activity and natural startles of the animals caused noise, leading to a heterogeneous signal requiring post-recording evaluation. In spite of these shortcomings, the ICMs showed to be very useful for minimally invasive long-term monitoring of cardiac rhythm in pigs.

Caridac vein retroinjections provide an efficient approach for global left ventricular gene transfer with adenovirus and adeno-associated virus.

Heart failure (HF) is a major burden worldwide, and new therapies are urgently needed. Gene therapy is a promising new approach to treat myocardial diseases. However, current cardiac gene delivery methods for producing global myocardial effects have been inefficient. The aim of this study was to develop an endovascular, reproducible, and clinically applicable gene transfer method for global left ventricular (LV) transduction. Domestic pigs (n = 52) were used for the experiments. Global LV myocardium coverage was achieved by three retrograde injections into the three main LV vein branches. The distribution outcome was significantly improved by simultaneous transient occlusions of the corresponding coronary arteries and the main anastomotic veins of the retroinjected veins. The achieved cardiac distribution was visualized first by administering Indian Ink solution. Secondly, AdLacZ (2 × 1012vp) and AAV2-GFP (2 × 1013vg) gene transfers were performed to study gene transduction efficacy of the method. By retrograde injections with simultaneous coronary arterial occlusions, both adenovirus (Ad) and adeno-associated virus (AAV) vectors were shown to deliver an efficient transduction of the LV. We conclude that retrograde injections into the three main LV veins is a potential new approach for a global LV gene transfer.

Endocardial Gene Delivery Using NOGA Catheter System.

NOGA/MyoStar system uses low magnetic fields and endomyocardial electrical parameters, allowing precise endomyocardial injections of therapeutic agents to ischemic yet viable myocardium which is most likely to respond to the treatment. Preclinical and clinical studies have shown that NOGA/MyoStar guided intramyocardial injections are safe, feasible and a minimally invasive way to deliver gene therapy to the heart. Here we describe how to perform electroanatomical mapping and injections to hibernating myocardium in the preclinical studies.

AAV2-VEGF-B gene therapy failed to induce angiogenesis in ischemic porcine myocardium due to inflammatory responses.

Therapeutic angiogenesis induced by gene therapy is a promising approach to treat patients suffering from severe coronary artery disease. In small experimental animals, adeno-associated viruses (AAVs) have shown good transduction efficacy and long-term transgene expression in heart muscle and other tissues. However, it has been difficult to achieve cardiac-specific angiogenic effects with AAV vectors. We tested the hypothesis whether AAV2 gene transfer (1 × 1013 vg) of vascular endothelial growth factor B (VEGF-B186) together with immunosuppressive corticosteroid treatment can induce long-term cardiac-specific therapeutic effects in the porcine ischemic heart. Gene transfers were delivered percutaneously using direct intramyocardial injections, improving targeting and avoiding direct contact with blood, thus reducing the likelihood of immediate immune reactions. After 1- and 6-month time points, the capillary area was analyzed, myocardial perfusion reserve (MPR) was measured with radiowater positron emission tomography ([15O]H2O-PET), and fluorodeoxyglucose ([18F]FDG) uptake was used to evaluate myocardial viability. Clinical chemistry and immune responses were analyzed using standard methods. After 1- and 6-month follow-up, AAV2-VEGF-B186 gene transfer failed to induce angiogenesis and improve myocardial perfusion and viability. Here, we show that inflammatory responses attenuated the therapeutic effect of AAV2 gene transfer by significantly reducing successful transduction and long-term gene expression despite the efforts to reduce the likelihood of immune reactions and the use of targeted local gene transfer methods.

Large Animal Model for Evaluating the Efficacy of the Gene Therapy in Ischemic Heart.

Coronary artery disease is one of the significant causes of mortality and morbidity worldwide. Despite the progression of current therapeutics, a considerable proportion of coronary artery disease patients remain symptomatic. Gene therapy-mediated therapeutic angiogenesis offers a novel therapeutic method for improving myocardial perfusion and relieving symptoms. Gene therapy with different angiogenic factors has been studied in few clinical trials. Due to the novelty of the method, the progress of myocardial gene therapy is a continuous path from bench to bedside. Therefore, large animal models are needed for evaluating the safety and efficacy. The more the large animal model identifies the original disease and the endpoints used in clinics, the more predictable outcomes are from clinical trials. Here, we introduce a large animal model for evaluating the efficacy of the gene therapy in the ischemic porcine heart. We use clinically relevant imaging methods such as ultrasound imaging and 15H2O-PET. For targeting the gene transfers into the desired area, electroanatomical mapping is used. The aim of this method is: (1) to mimic chronic coronary artery disease, (2) to induce therapeutic angiogenesis at hypoxic areas of the heart, and (3) to evaluate the safety and efficacy of the gene therapy by using relevant endpoints.