Abstract 16773: Ablation of Cardiac Myosin Binding Protein-C in Human iPSC- Engineered Cardiac Tissue Model Causes Increased Calcium Sensitivity and Accelerated Contractile Kinetics

• Published in: Circulation (New York, N.Y.) Vol. 138; no. Suppl_1 Suppl 1; p. A16773
• Main Authors: Ralphe, John C, de Lange, Willem J, Hernandez, Jonathan J, Jacobs, Derek R, Kreitzer, Caroline R
• Format: Journal Article
• Language: English
• Published: by the American College of Cardiology Foundation and the American Heart Association, Inc 06.11.2018
• ISSN: 0009-7322; 1524-4539
• DOI: 10.1161/circ.138.suppl_1.16773

Hypertrophic cardiomyopathy (HCM) is an inherited cardiac disease that can cause sudden cardiac arrest, diastolic dysfunction and heart failure. Mutations in cardiac myosin binding protein-C (cMyBP-C), a regulator of contractility, are among the most prevalent causes of HCM. cMyBP-C truncation mutations may affect as many as 1 in 1,600 Americans. Though murine models of cMyBP-C ablation have aided in understanding the role of cMyBP-C in health and disease, they are limited by differences in cardiac physiology between mice and humans. iPSC technology now allows researchers to study the effect of HCM mutations in iPSC-derived cardiomyocytes from HCM patients and controls, however differences in genetic background between patients and controls and clonal variation remain confounders.We hypothesized that cMyBP-C ablation in human cardiomyocytes would primarily alter cardiac contractility.CRISPR/Cas9 was used to introduce frame shift mutations in cMyBP-C in the well characterized DF19-9-11T human iPSC line. Human iPSCs were differentiated into cardiomyocytes and then cast into an integrated 3D engineered cardiac tissue (ECT) model for functional testing against non-targeted isogenic controls.Homozygous cMyBP-C ablation significantly accelerated contraction (CT100 = 219±3 vs. 235±5ms; p = 0.02) and early relaxation (RT50 = 144±2 vs. 167±4ms; p <0.001), while late relaxation was slowed (RT50-90 = 127±2 vs. 112±2ms; p <0.001; n=6 for each group). These accelerated contractile kinetics were accompanied by a significantly blunted response to adrenergic stimulation and an increase in Ca sensitivity. Heterozygous cMyBP-C ablation resulted in acceleration in relaxation kinetics (RT50 = 148±7 vs. 167±4ms; p = 0.04 and RT50-90 = 96±4 vs. 112±2ms; p = 0.002), without significantly affecting the rate of contraction.The accelerated kinetics of contraction and early relaxation in cMyBP-C null ECT provides important human evidence that cMyBP-C acts as a brake on cardiac contractility. These data provide strong evidence that the human model system can be used to study the function of cMyBP-C and provide a platform to test therapies that may rectify the contractile defects caused by cMyBP-C haploinsufficiency.