ABSTRACT
Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) have enormous potential for the study of human cardiac disorders. However, their physiological immaturity severely limits their utility as a model system and their adoption for drug discovery. Here, we describe maturation media designed to provide oxidative substrates adapted to the metabolic needs of human iPSC (hiPSC)-CMs. Compared with conventionally cultured hiPSC-CMs, metabolically matured hiPSC-CMs contract with greater force and show an increased reliance on cardiac sodium (Na+) channels and sarcoplasmic reticulum calcium (Ca2+) cycling. The media enhance the function, long-term survival, and sarcomere structures in engineered heart tissues. Use of the maturation media made it possible to reliably model two genetic cardiac diseases: long QT syndrome type 3 due to a mutation in the cardiac Na+ channel SCN5A and dilated cardiomyopathy due to a mutation in the RNA splicing factor RBM20. The maturation media should increase the fidelity of hiPSC-CMs as disease models.
Subject(s)
Culture Media/pharmacology , Induced Pluripotent Stem Cells/cytology , Induced Pluripotent Stem Cells/metabolism , Myocytes, Cardiac/cytology , Myocytes, Cardiac/metabolism , Calcium/metabolism , Cardiac Conduction System Disease/genetics , Cardiac Conduction System Disease/physiopathology , Cardiomyopathy, Dilated/pathology , Cardiomyopathy, Dilated/physiopathology , Gene Expression Regulation/drug effects , Heart/drug effects , Heart/physiopathology , Humans , Induced Pluripotent Stem Cells/drug effects , Long QT Syndrome/genetics , Long QT Syndrome/physiopathology , Membrane Potentials/drug effects , Models, Biological , Myocardial Contraction/drug effects , Myocytes, Cardiac/drug effects , Phenotype , Tissue EngineeringABSTRACT
Lamin A/C (LMNA) is one of the most frequently mutated genes associated with dilated cardiomyopathy (DCM). DCM related to mutations in LMNA is a common inherited cardiomyopathy that is associated with systolic dysfunction and cardiac arrhythmias. Here we modelled the LMNA-related DCM in vitro using patient-specific induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). Electrophysiological studies showed that the mutant iPSC-CMs displayed aberrant calcium homeostasis that led to arrhythmias at the single-cell level. Mechanistically, we show that the platelet-derived growth factor (PDGF) signalling pathway is activated in mutant iPSC-CMs compared to isogenic control iPSC-CMs. Conversely, pharmacological and molecular inhibition of the PDGF signalling pathway ameliorated the arrhythmic phenotypes of mutant iPSC-CMs in vitro. Taken together, our findings suggest that the activation of the PDGF pathway contributes to the pathogenesis of LMNA-related DCM and point to PDGF receptor-ß (PDGFRB) as a potential therapeutic target.
Subject(s)
Cardiomyopathy, Dilated/genetics , Lamin Type A/genetics , Mutation , Platelet-Derived Growth Factor/metabolism , Receptor, Platelet-Derived Growth Factor beta/metabolism , Signal Transduction , Arrhythmias, Cardiac/metabolism , Arrhythmias, Cardiac/pathology , Calcium/metabolism , Cells, Cultured , Chromatin/chemistry , Chromatin/genetics , Chromatin/metabolism , Chromatin Assembly and Disassembly/genetics , Haploinsufficiency/genetics , Homeostasis , Humans , In Vitro Techniques , Induced Pluripotent Stem Cells/pathology , Models, Biological , Myocytes, Cardiac/metabolism , Myocytes, Cardiac/pathology , Nonsense Mediated mRNA Decay , RNA, Messenger/analysis , RNA, Messenger/genetics , Single-Cell AnalysisABSTRACT
BACKGROUND: Hypertrophic cardiomyopathy (HCM) is frequently caused by mutations in myosin-binding protein C3 ( MYBPC3) resulting in a premature termination codon (PTC). The underlying mechanisms of how PTC mutations in MYBPC3 lead to the onset and progression of HCM are poorly understood. This study's aim was to investigate the molecular mechanisms underlying the pathogenesis of HCM associated with MYBPC3 PTC mutations by utilizing human isogenic induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). METHODS: Isogenic iPSC lines were generated from HCM patients harboring MYBPC3 PTC mutations (p.R943x; p.R1073P_Fsx4) using genome editing. Comprehensive phenotypic and transcriptome analyses were performed in the iPSC-CMs. RESULTS: We observed aberrant calcium handling properties with prolonged decay kinetics and elevated diastolic calcium levels in the absence of structural abnormalities or contracile dysfunction in HCM iPSC-CMs as compared to isogenic controls. The mRNA expression levels of MYBPC3 were significantly reduced in mutant iPSC-CMs, but the protein levels were comparable among isogenic iPSC-CMs, suggesting that haploinsufficiency of MYBPC3 does not contribute to the pathogenesis of HCM in vitro. Furthermore, truncated MYBPC3 peptides were not detected. At the molecular level, the nonsense-mediated decay pathway was activated, and a set of genes involved in major cardiac signaling pathways was dysregulated in HCM iPSC-CMs, indicating an HCM gene signature in vitro. Specific inhibition of the nonsense-mediated decay pathway in mutant iPSC-CMs resulted in reversal of the molecular phenotype and normalization of calcium-handling abnormalities. CONCLUSIONS: iPSC-CMs carrying MYBPC3 PTC mutations displayed aberrant calcium signaling and molecular dysregulations in the absence of significant haploinsufficiency of MYBPC3 protein. Here we provided the first evidence of the direct connection between the chronically activated nonsense-mediated decay pathway and HCM disease development.