Gene transfer of a phospholamban-targeted antibody improves calcium handling and cardiac function in heart failure

Background: Abnormalities of intracellular calcium handling are widely recognized as a common hallmark of heart failure in animal models and humans. Modifying the interaction of phospholamban (PLB) with the sarcoplasmic reticulum ATPase (SERCA) by PLB mutants improves cardiac function but may also lead to heart failure. In this study we describe the in vivo effects of a new approach to modify the PLB-SERCA interaction using a recombinant, intracellularly expressed chicken-antibody derived protein (PLADP) targeting the cytoplasmic domain of PLB in the cardiomyopathic BIO 14.6 hamster. Methods and results: In vivo gene transfer was performed in 12-14-week-old BIO 14.6 cardiomyopathic hamsters using intracoronary delivery of adenovirus containing the PLADP or the β-galactosidase (LacZ) gene (8 × 10⁹ PFU per animal). A third group was injected with saline (Sham). Echocardiography was performed before and, together with hemodynamic measurements, repeated 4-5 days after gene transfer. Indo-1 calcium transients and myocyte contractility were measured in isolated cardiomyocytes from the BIO 14.6 hamster transfected with the PLADP. Gene expression (LacZ) was found in 54 ± 15% of cells throughout the heart without any signs of myocardial inflammation. Echocardiographic and hemodynamic indices of left ventricular function were significantly increased after gene transfer with the PLADP, compared to controls. Measurements of myocyte contractility and calcium transients in isolated cardiac myocytes from BIO 14.6 hamsters revealed improved intracellular calcium handling and contractility. Conclusion: In vivo adenoviral gene transfer with the PLADP resulted in short-term intracellular expression of a PLADP, improving LV function and enhancing myocardial contractility in the failing cardiomyopathic hamster heart. The PLADP enhanced contractility and cardiac function by improving intracellular calcium handling. Expression of antibody-derived protein represents a new approach to modify protein-protein interactions at the cellular level.