Correcting Cardiac Microdomains Reverses Non-Ischemic Cardiomyopathy

Summary Heart failure (HF) is a major cardiac syndrome with high mortality and morbidity. Yet therapeutic options that primarily target failing heart muscle are lacking. The typical pathophysiology of failing cardiomyocytes is weakened calcium transients due to abnormal systolic calcium release from calcium channel and ryanodine receptor dyads and impaired diastolic removal due to altered SERCA2a activity. Impaired activity of the calcium handling proteins is linked to pathologic remodeling of t-tubules (TT) during heart failure. Specifically, during HF, TT microdomains are lost, with consequent disruption of the calcium handling machinery. We recently identified that a therapeutic target may exist in the calcium regulating cardiac bridging inte- grator 1 (cBIN1) which organizes TT microdomains. Exogenous cBIN1 therapy rescues HF in rodents. The over- all objective in this proposal is to identify whether the cBIN1-microdomain targeting gene therapy can be trans- lated to a large animal model of non-ischemic cardiomyopathy. Our central hypothesis is that cBIN1-microdo- mains are disrupted in a minipig model of chronic ventricular pacing-induced HF, which can be recovered by cBIN1 gene therapy for rescue cardiomyocyte microanatomy as well as cardiac function. Two aims are proposed to first explore abnormal remodeling of subcellular organelle and microdomains in failing cardiomyocytes from minipig hearts failing from pacing-induced HF. Using biochemical and imaging tools, we will also determine the critical pathophysiological point of myocardial remodeling at which HF progres- sion is irreversible. The second aim is proposed to study the efficacy of adeno associated virus 9 (AAV9)- transduced exogenous cBIN1 in rescuing myocardial dysfunction and HF progression. The minipig model of non- ischemic cardiomyopathy will be used to evaluate the therapeutic benefit of AAV9-cBIN1 gene therapy. Our preliminary data are striking that a single low dose of intravenous injection of AAV9-cBIN1 can fully normalize ejection fraction and induce reverse remodelling of dilated ventricles in minipigs with heart failure. Building on these preliminary studies, we will evaluate cBIN1 gene therapy in rescuing HF by monitoring echocardiography recordings, hemodynamics, systemic symptoms, and blood available markers, as well as sub- cellular organization of the TT membrane and the calcium handling machinery. Our contribution here is expected to identify whether and how cBIN1-microdomains are critical for cardiac function in failing minipig hearts. This contribution is significant because it will introduce a new HF therapeutic, which corrects calcium signaling abnormalities through preservation of cBIN1-microdomains at TT membrane. The proposed research is innovative because it introduces a new class of cardiac muscle specific therapy that will improve cardiac inotropy, cardiac lusitropy, and patient mortality.