Acute and Long-Term Optical Mapping of hiPSC-Derived Cardiac Sheets Expressing Genetically-Encoded Voltage Indicator for Drug Testing and Arrhythmia Monitoring

Recently, there is an increased interest in using human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) for purposes of cardiac disease modeling, drug testing and screening. Few of them, however, have utilized hiPSC-CMs multicellular models for understanding of complex cardiac electrophysiological phenomena (i.e. conduction and reentry), and none have addressed long-term and repeated phenotyping strategies.

Objective:
To combine hiPSC-CMs with a genetically-encoded voltage indicator (ArcLight) in two-dimensional multicellular cardiac-sheets (hiPSC-CSs); to derive a unique model that enables long-term and repeated experimentation, and to explore drug-induced effects on normal conduction and arrhythmogenesis.

Methods and Results:
hiPSC-CSs (0.5cm diameter) were generated from transgenic hiPSC-CMs expressing ArcLight (ArcLight-hiPSC-CSs) and inspected under a customized optical mapping setup. Loading of ArcLight-hiPSC-CSs with the voltage sensitive dye (VSD) Di-4-ANBDQBS enabled sequential monitoring of action-potential wave propagation and construction of activation and action potential duration (APD) maps from both indicators’ signals. ArcLight-based mapping displayed equivalent conduction velocities (CVs) to VSD-based mapping, and importantly, was superior in terms of signal-to-noise ratio (SNR) and photoviability. Moreover, it allowed repeated phenotyping over weeks. Administration of Carbenoxolone, Lidocaine and Quidnidine resulted in CV slowing in the tested ArcLight-hiPSC-CSs. Quinidine and Dofetilide, on the other hand, have prolonged APD, and the latter induced arrhythmia in a dose-response manner, which could be mapped in detail. Finally, we induced stable spiral-waves in ArcLight-hiPSC-CSs by systematic programmed electrical stimulation. Further phase-mapping analysis enabled quantitative assessment of rotor biophysical parameters (curvature and frequency).

Conclusions:
(1) A large-scale ArcLight-hiPSC-CS model and an optical-mapping system were established in order to study conduction and arrhythmogenesis. (2) In comparison to VSD-based mapping, ArcLight-based mapping offers valid CV assessment, superior SNR and minimal cellular-toxicity. (3) It also provides a reliable and a robust solution for long-term and repeated phenotyping, as well as (4) a powerful tool for drug-testing and arrhythmia investigation.