Basic/Translational Science -> Whole Animal Electrophysiology and Pharmacology (includes Neurohumoral Modulation) D-PO06 - Poster Session VI (ID 26) Poster

D-PO06-012 - Istaroxime Treatment Ameliorates Calcium Dysregulation In A Zebrafish Model Reminiscent Of Phospholamban R14del Cardiomyopathy (ID 641)

Abstract

Background: The heterozygous phospholamban (PLN) p.Arg14del (R14del) mutation is found in patients with dilated (DCM) or arrhythmogenic cardiomyopathy (ACM). Heterozygous carriers of PLN-R14del suffer a high risk of developing malignant ventricular arrhythmias and end-stage heart failure, leading to high mortality and a poor prognosis. The PLN-R14del mutation triggers cardiac contractile dysfunction and arrhythmogenesis through dysregulation of intracellular Ca2+ dynamics. Little is known about the pathophysiological processes leading to PLN-R14del induced cardiomyopathy, which is characterized by sub-epicardial accumulation of fibrofatty tissue, and a specific drug treatment is currently lacking.
Objective: To investigate the cardiac pathology of PLN R14del in early and late disease stages.
Methods: We generated a patient-specific PLN-R14del zebrafish model via homologous recombination and CRISPR/Cas9. Echocardiography, patch clamp, In vivo high-speed fluorescent and brightfield imaging in PLN-R14del adult and embryonic zebrafish was used to study cellular electrophysiology, cardiac calcium dynamics and contractility.
Results: In 25% of adult PLN-R14del hearts, we observed a severe morphological change displayed by a thicker layer of cells expressing an epicardial progenitor marker. Hallmarks of ACM were detected by the accumulation of immune cells, fibroblasts and fat in the epicardial region of the PLN-R14del hearts. Echocardiography revealed contractile pulsus alternans before overt structural changes occurred, which correlated at the cellular level with action potential duration (APD) alternans upon high frequency pacing. We found in PLN-R14del-GCaMP6f fish that the functional alterations are preceded by diminished Ca2+ transient amplitudes in embryonic hearts. Istaroxime treatment ameliorates the in vivo Ca2+ dysregulation, rescues the cellular APD alternans, while it improves cardiac relaxation.
Conclusion: We present novel insight into the pathophysiology of PLN-R14del cardiomyopathy and identify istaroxime as a potential novel drug for its treatment. Further research into this model will allow us to understand how early changes in calcium dynamics can lead to the observed late-stage PLN-R14del cardiomyopathy.
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