Modeling and rescue of Duchenne muscular dystrophy cardiomyopathy using human induced pluripotent-derived cardiomyocytes

Abstract

Duchenne muscular dystrophy (DMD) is the most common muscular dystrophy and affects 1:5000 boys born in the United States. DMD is a result of mutations in the dystrophin (DMD) gene that leads to the absence of the full length cytoskeletal protein dystrophin, which is expressed in skeletal muscle, brain, and heart. The absence of dystrophin leads to weakness of not only the skeletal muscle but also the heart. With advances in treatment for DMD, patients are living longer but a cardiomyopathic phenotype has been uncovered. DMD associated cardiomyopathy is nearly ubiquitous and is the leading cause of death with adults with DMD. There have been limited studies and therapies for dystrophic heart failure thus far, and there is a critical need to identify the pathophysiology and develop effective therapeutic regimens. In this thesis, I hypothesized that DMD cardiomyopathy could be modeled using DMD patient-specific human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-derived CMs) to identify physiological changes and future drug therapies. To explore and define therapies for DMD cardiomyopathy, we used DMD patient-specific and dystrophin null isogenic hiPSC-derived CMs to examine the physiological response to adrenergic agonists and -blocker treatment. We further examined these agents in vivo using wildtype and the mdx mouse model. At baseline and following adrenergic stimulation, DMD hiPSC-derived CMs had a significant increase in arrhythmic calcium traces compared to isogenic controls. Further, these arrhythmias were significantly decreased with propranolol treatment. Using telemetric monitoring, we observed that mdx mice, which lack dystrophin, and were stimulated with isoproterenol had an arrhythmic death and the lethal arrhythmias were rescued, in part, by propranolol pretreatment. Using single cell and bulk RNA-seq, we compared DMD and control hiPSC-derived CMs, mdx mice and control mice (in the presence or absence of propranolol and isoproterenol) and defined pathways that were perturbed under baseline conditions and pathways that were normalized following propranolol treatment in the mdx model. We also undertook transcriptome analysis of human DMD left ventricle samples and found that DMD hiPSC-derived CMs have similar dysregulated pathways as the human DMD heart. We further determined that relatively few DMD patients see a cardiovascular specialist or receive β-blocker therapy. The results of these experiments highlight important mechanisms and therapeutic interventions from human to animal and back to human in the dystrophic heart. Importantly, these results may serve as a platform to elucidate further mechanisms of DMD cardiomyopathy and serve as a platform for testing novel therapies. Our results also provide a rationale for an adequately powered clinical study that examines the impact of β-blocker therapy in patients with dystrophinopathies.