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Metabolic Maturation Media Improves Physiological Function of Human iPSC-derived Cardiomyocytes

ABSTRACT: iPSC-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. In this study, we describe a maturation media (MM) designed to provide oxidative substrates adapted to the metabolic needs of hiPSC-CMs as compared to standard RPMI/B27 media. RNA sequencing was performed to gain insight into the underlying molecular basis for the changes. Compared to baseline (day 21) conditions, three weeks subsequent exposure to MM (day 41) caused a significant differential expression in genes. GO analysis of the MM-differentially upregulated genes were informative, mapping to mitochondrial metabolism. Additionally, multiple Ca2+ cycling/sarcoplasmic reticulum (SR), sarcomeric, and ion channel genes were differentially expressed. These gene expression changes indicated that supplementation with oxidative substrates and subsequent metabolic changes might affect cardiomyocyte electrophysiology, Ca2+ cycling and contractility.

ORGANISM(S): Homo sapiens

PROVIDER: GSE151279 | GEO | 2020/06/30

REPOSITORIES: GEO

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Project description:Background: The phospholamban (PLN) p.Arg14del mutation belongs to the established causes of dilated cardiomyopathy, with the molecular disease mechanisms incompletely understood. We used human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes, CRISPR/Cas9 gene editing and patient heart samples to investigate the molecular pathomechanisms of PLN p.Arg14del cardiomyopathy. Methods and results: Patient dermal fibroblasts carrying the PLN p.Arg14del mutation were reprogrammed into hiPSC, isogenic controls were established by CRISPR/Cas9. Cells were differentiated into cardiomyocytes and characterized in 2D and 3D-engineered heart tissue (EHT) format. Mutant cardiomyocytes revealed significantly prolonged Ca2+ transient decay time, Ca2+-load dependent irregular beating pattern and lower peak force compared to isogenic controls. While this data support the reported super-inhibitory effect of PLN p.Arg14del on the sarcoplasmic/endoplasmic reticulum Ca2+ ATPase, an unchanged SR Ca2+ content argued against disturbed SR Ca2+ cycling as the sole cause of contractile dysfunction. Label-free proteomic analysis of p.Arg14del EHTs revealed less endoplasmic reticulum (ER), ribosomal and mitochondrial proteins. Electron microscopy showed dilation of the rough ER, large lipid droplets in close association with mitochondria and reduced mitochondrial number. Follow-up experiments confirmed impairment of the rough ER/mitochondria compartment and enhanced oxidative stress in PLN p.Arg14del. Relevance for human disease was demonstrated by immunohistochemistry of human heart samples. PLN p.Arg14del end-stage heart failure samples revealed perinuclear aggregates positive for ER marker proteins and oxidative stress in comparison to ischemic heart failure - and non-failing donor heart samples. Surprisingly, transduction of PLN p.Arg14del EHTs with the Ca2+ binding protein GCaMP6f reversed the contractile, molecular and morphological disease phenotype. Conclusion: This study identified impairment of the rough ER/mitochondria compartment without SR dysfunction as a novel disease mechanism underlying PLN p.Arg14del cardiomyopathy. The pathology was improved by Ca2+-scavenging, suggesting impaired local Ca2+ cycling as an important disease culprit.

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Metabolic Maturation Media Improves Physiological Function of Human iPSC-derived Cardiomyocytes

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