Mature cardiac tissues modeling Duchenne muscular dystrophy related cardiomyopathy

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Abstract Background The major cause of mortality in patients with Duchenne muscular dystrophy (DMD) is cardiomyopathy. This disease is caused by dystrophin gene mutations that result in the loss of dystrophin protein. Gene replacement therapies have been approved for skeletal muscle symptoms of DMD. However, these therapeutic modalities are not indicated for cardiomyopathy due to their low efficiency of delivery to the heart. Despite the significant unmet needs, a limitation in this area of research is the divergence of cardiomyopathy symptoms in model animals from those in patients. Alternatively, cardiomyocytes differentiated from patient-derived iPS cells have recently been analyzed. However, existing results are based on a single time point analysis and do not model disease progression or non-cardiomyocyte involvement. Purpose Our research aims to establish an in vitro model that can reproduce the pathological progression of DMD cardiomyopathy. Methods We have generated cardiac organoids and engineered heart tissues (EHTs) from patient-derived iPS cells, consisting of cardiomyocytes and epicardial-derived non-cardiomyocytes. An iPS cell line in which the dystrophin mutation was repaired by genome editing was used as a control. The cardiac organoids or EHTs were subjected to transient activation of fatty acid metabolism to promote the maturation of iPS-derived cardiomyocytes. Pathological conditions were then induced in these 3D-models by applying loads that mimicked the DMD-disease environment. Results The mature cardiac organoids displayed adult-like gene expression profiles in the components of dystrophin-associated-protein-complex and calcium handling. After continuous mechanical loading, cell death appeared in DMD-EHTs, although there was only a slight decrease in contractility and fibrosis. Elevated mitochondrial ROS production and DNA damage were observed as a part of the cell death mechanism. Furthermore, pathological stimuli in addition to mechanical loading reproduced progressive contractile dysfunction and further increase in fibrosis in DMD-EHTs. Conclusions From these observations, we concluded that our DMD-EHT model recapitulate the pathological development of DMD-cardiomyopathy. These results suggest that the key factors involved in the progression of DMD cardiomyopathy are (i) the fragility of cardiomyocytes to stress in early stages and (ii) the involvement of non-cardiomyocytes such as fibrosis. Our model provides insight into the molecular mechanisms underlying disease progression and novel therapeutic targets.

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