348 Chapter 13 Cardiomyopathies are disorders of the myocardium caused by a wide variety of factors, leading to cardiac dysfunction, aggravated by arrhythmias, heart failure, and sudden cardiac death. The prevalence is estimated based on genetic screenings, as high as 1:500 for hypertrophic cardiomyopathy (HCM), 1:250 for dilated cardiomyopathy (DCM), and 1:1000 for arrhythmogenic cardiomyopathy (ACM).1,2 These numbers, however, are probably underestimated as the majority of individuals have incomplete and/or late-onset disease expression. Numerous mutations in various pathways crucial for cardiac function have been linked to these cardiomyopathies. However, the underlying genetic mutation has only been identified in approximately 35% of DCM, and 50% of the HCM and ACM cases.1 Genetic mutations unfortunately have low predictability when it comes to the onset of disease and progression. Therefore, cell models used in the early phases of drug discovery and the significant difference in treatment responses among patients hold promise as predictors for the phenotype onset in the patients. Moreover, the understanding of the pathophysiological and molecular mechanisms that underlie the onset of pathological features of genetic cardiomyopathies is crucial to developing novel targets for therapeutics. In vitro disease modeling can help to model the onset of the first variable phenotypic presentations and, therefore, forms a scalable platform for human disease modeling, drug discovery, and the clinical validation of novel therapeutic developments. In this thesis, we used the crucial pathways in cardiogenesis for a recent discovery in the massive expansion and biobanking of hiPSC-CMs. Next, we used this technology and combined metabolically matured hiPSC-CMs to produce both 2D and 3D in vitro models. Importantly, in vitro models are suitable for modeling healthy and pathological cardiac tissues, and we provide several lines of evidence to confirm this hypothesis. Finally, we combine findings from the previous chapters with insights from other studies and discuss the current developments in cardiac in vitro models, pathophysiology, and the underlying pathways of PLN-R14del cardiomyopathy. In addition, new tools are being developed to facilitate our progress. We finally suggest a roadmap for employing these non-animal platforms in assessing early-onset disease phenotyping and novel therapeutic screening. PART ONE: CLUES FROM HEART DEVELOPMENT TOWARDS OPTIMIZED HIPSC-CMS MODELS From cardiogenesis to in vitro proliferation of human cardiomyocytes Cell cycle activity in human adult CMs decreases within the first months after birth and is very sparse in the human adult myocardium. As described in Chapter 2, many pathways have been investigated over the past decades for their capacity to regulate heart growth versus the molecular targets that promote in vitro cardiomyocyte proliferation. Pushing the level of understanding of the mechanisms controlling human cardiomyocyte proliferation
RkJQdWJsaXNoZXIy MTk4NDMw