As a prerequisite to clinical application, we determined the long-term therapeutic effectiveness and safety of adeno-associated viral (AAV) S100A1 gene therapy in a preclinical, large animal model of heart failure. S100A1, a positive inotropic regulator of myocardial contractility, becomes depleted in failing cardiomyocytes in humans and various animal models, and myocardial-targeted S100A1 gene transfer rescues cardiac contractile function by restoring sarcoplasmic reticulum calcium Ca2+ handling in acutely and chronically failing hearts in small animal models. We induced heart failure in domestic pigs by balloon-occlusion of the left circumflex coronary artery, resulting in myocardial infarction. After 2 weeks, when the pigs displayed significant left ventricular contractile dysfunction, we administered through retrograde coronary venous delivery, AAV9-S100A1 to the left ventricular non-infarcted myocardium. AAV9-luciferase and saline treatment served as control. At 14 weeks, both control groups showed significantly decreased myocardial S100A1 protein expression along with progressive deterioration of cardiac performance and left ventricular remodeling. AAV9-S100A1 treatment prevented and reversed this phenotype by restoring cardiac S100A1 protein levels. S100A1 treatment normalized cardiomyocyte Ca2+ cycling, sarcoplasmic reticulum calcium handling and energy homeostasis. Transgene expression was restricted to cardiac tissue and extra-cardiac organ function was uncompromised indicating a favorable safety profile. This translational study shows the pre-clinical feasibility, long-term therapeutic effectiveness and a favorable safety profile of cardiac AAV9-S100A1 gene therapy in a preclinical model of heart failure. Our study presents a strong rational for a clinical trial of S100A1 gene therapy for human heart failure that could potentially complement current strategies to treat end-stage heart failure.

Low levels of the molecular inotrope S100A1 are sufficient to rescue post-ischemic heart failure (HF). As a prerequisite to clinical application and to determine the safety of myocardial S100A1 DNA-based therapy, we investigated the effects of high myocardial S100A1 expression levels on the cardiac contractile function and occurrence of arrhythmia in a preclinical large animal HF model. At 2 weeks after myocardial infarction domestic pigs presented significant left ventricular (LV) contractile dysfunction. Retrograde application of AAV6-S100A1 (1.5 × 1013 tvp) via the anterior cardiac vein (ACV) resulted in high-level myocardial S100A1 protein peak expression of up to 95-fold above control. At 14 weeks, pigs with high-level myocardial S100A1 protein overexpression did not show abnormalities in the electrocardiogram. Electrophysiological right ventricular stimulation ruled out an increased susceptibility to monomorphic ventricular arrhythmia. High-level S100A1 protein overexpression in the LV myocardium resulted in a significant increase in LV ejection fraction (LVEF), albeit to a lesser extent than previously reported with low S100A1 protein overexpression. Cardiac remodeling was, however, equally reversed. High myocardial S100A1 protein overexpression neither increases the occurrence of cardiac arrhythmia nor causes detrimental effects on myocardial contractile function in vivo. In contrast, this study demonstrates a broad therapeutic range of S100A1 gene therapy in post-ischemic HF using a preclinical large animal model.

Purpose: Low plasma concentrations of the amino acid homoarginine (HA) have been shown to correlate with adverse cardiovascular outcome, particularly in patients with chronic kidney disease. The present study sought to investigate the effect of HA treatment on cardiac remodeling in rats undergoing artificially induced renal insufficiency by 5/6 nephrectomy (5/6 Nx). Methods: A total of 33 male Wistar rats were randomly divided into sham and 5/6 Nx groups, receiving either placebo treatment or 400 mg·kg−1·day−1 HA over a 4-week period. Results: 5/6 Nx per se resulted in adverse myocardial remodeling with aggravated cardiac function and associated cardiac overload as the most obvious alteration (−23% ejection fraction, P < 0.0001), as well as increased myocardial fibrosis (+80%, P = 0.0005) compared to placebo treated sham animals. HA treatment of 5/6 Nx rats has led to an improvement of ejection fraction (+24%, P = 0.0003) and fractional shortening (+21%, P = 0.0126), as well as a decrease of collagen deposition (−32%, P = 0.0041), left ventricular weight (−14%, P = 0.0468), and myocyte cross-sectional area (−12%, P < 0.0001). These changes were accompanied by a downregulation of atrial natriuretic factor (−65% P < 0.0001) and collagen type V alpha 1 chain (−44%, P = 0.0006). Sham animals revealed no significant changes in cardiac function, myocardial fibrosis, or any of the aforementioned molecular changes after drug treatment. Conclusion: Dietary HA supplementation appears to have the potential of preventing cardiac remodeling and improving heart function in the setting of chronic kidney disease. Our findings shed new light on HA as a possible new therapeutic agent for patients at high cardiovascular risk.

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Myocardial in vivo gene delivery is a valuable technique to investigate the relevance of a protein of interest on cardiac contractile function, hypertrophy, and energy state in healthy animals as well as in a variety of models of cardiovascular disease. Rodent models are used to screen effects and to investigate molecular mechanisms, while large animal models, more closely reflecting human anatomy, physiology, and function, are inevitable for translational therapeutic approaches. The gene of interest, whose expression is driven by a non-cardioselective or cardioselective promotor is cloned into a viral vector. This vehicle is then delivered using an appropriate administration route to target the heart and to achieve efficient protein expression in myocardium. Here we describe myocardial gene therapy in small and large animal models of postischemic heart failure used to reveal the positive inotrope, antihypertrophic, and pro-energetic action of the small calcium sensor protein S100A1.

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