Abstract
To overcome the limitations and misjudgments of conventional prediction of arrhythmic cardiotoxicity, we have developed an on-chip in vitro predictive cardiotoxicity assay using cardiomyocytes derived from human stem cells employing a constructive spatiotemporal two step measurement of fluctuation (short-term variability; STV) of cell's repolarization and cell-to-cell conduction time, representing two origins of lethal arrhythmia. Temporal STV of field potential duration (FPD) showed a potential to predict the risks of lethal arrhythmia originated from repolarization dispersion for false negative compounds, which was not correctly predicted by conventional measurements using animal cells, even for non-QT prolonging clinical positive compounds. Spatial STV of conduction time delay also unveiled the proarrhythmic risk of asynchronous propagation in cell networks, whose risk cannot be correctly predicted by single-cell-based measurements, indicating the importance of the spatiotemporal fluctuation viewpoint of in vitro cell networks for precise prediction of lethal arrhythmia reaching clinical assessment such as thorough QT assay.
Highlights
To overcome the limitations and misjudgments of conventional prediction of arrhythmic cardiotoxicity, we have developed an on-chip in vitro predictive cardiotoxicity assay using cardiomyocytes derived from human stem cells employing a constructive spatiotemporal two step measurement of fluctuation of cell’s repolarization and cell-to-cell conduction time, representing two origins of lethal arrhythmia
To study the spatiotemporal increase of uncertainty of human cardiomyocytes (hCMs) response, we have developed the on-chip cell network cultivation system, in which extra-cellular signals of hCMs can be measured using a multi electrode array (MEA), and spatial arrangement control of cells can be performed using agarose microstructures designed on MEA chip
As one of the potential candidates of a higher throughput approach that goes beyond hERG-mediated QT prolongation measurement, changes in field potential (FP) waveforms in MEA measurements have been examined as a surrogate means to measure arrhythmias equal to the existing ex vivo measurements[11,12,28,29]
Summary
To overcome the limitations and misjudgments of conventional prediction of arrhythmic cardiotoxicity, we have developed an on-chip in vitro predictive cardiotoxicity assay using cardiomyocytes derived from human stem cells employing a constructive spatiotemporal two step measurement of fluctuation (short-term variability; STV) of cell’s repolarization and cell-to-cell conduction time, representing two origins of lethal arrhythmia. The implementation of hCMs raises, the following two questions for global cardiac safety; whether replacement of animal cells with hCMs in the conventional in vitro screenings can give us more precise and accurate prediction of lethal arrhythmia in human; and, secondly, whether more precise complicated ventricular responses, such as TdP and/or VT/Vf can be evaluated using hCMs with newly developed in vitro assays, e.g., a new approaches of spatiotemporal measurement using an artificially constructed tissue-like hCM network model As these two questions are fundamental and deeply related to the origin of the mechanism of cardiovascular arrhythmia, the answers will lead us to the establishment of more precise in vitro assay, including spatiotemporal aspects, so called ‘quasi-in vivo assay’ using hCMs. Lethal arrhythmia is caused by the increase of response uncertainty of single cardiomyocytes (temporal aspect)[12] as a triggering factor and of cell-to-cell conductivity (spatial aspect) as an enhancement/suppression factor As isolated single cells are not desirable for stable screening, we adopted hCM clusters as a model for temporal fluctuation measurement, and the following lined-up cell network assay as a model for spatial fluctuation measurement
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