Cardiotoxicity screening with simultaneous optogenetic pacing, voltage imaging and calcium imaging

Area of Science:

• Cardiovascular Pharmacology
• Stem Cell Biology
• Electrophysiology

Background:

• The Comprehensive in vitro Proarrhythmia Assay (CiPA) initiative aims to develop reliable in vitro tests for predicting clinical Torsades de Pointes (TdP).
• Existing assays often lack the ability to simultaneously assess multiple electrophysiological parameters crucial for predicting cardiotoxicity.

Purpose of the Study:

• To develop and validate a novel cardiotoxicity assay using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs).
• To simultaneously measure action potential (AP) waveforms and Ca(2+) transients (CT) for comprehensive electrophysiological assessment.
• To utilize optogenetic pacing for controlled electrophysiological stimulation.

Main Methods:

• Employed the Optopatch platform for all-optical electrophysiology.
• Co-cultured hiPSC-CMs expressing the CaViar voltage/calcium reporter and CheRiff channelrhodopsin for optical pacing.
• Screened 12 compounds for effects on AP and CT parameters under spontaneous and paced conditions (1Hz, 2Hz).

Main Results:

• The CaViar reporter provided high signal-to-noise ratio AP and CT measurements with minimal phototoxicity.
• Several compounds demonstrated significant effects: quinidine, flecainide, E-4031, digoxin, and cisapride prolonged APs, while verapamil and nifedipine shortened them.
• Early afterdepolarizations (EADs) were induced by quinidine, flecainide, and cisapride. Compound effects on AP rise time and CT amplitude were also observed.

Conclusions:

• The Optopatch platform offers a robust method for simultaneous AP and CT measurements in hiPSC-CMs.
• This assay addresses the CiPA initiative's goals by providing a comprehensive tool for cardiotoxicity assessment.
• The developed assay facilitates direct comparison of in vitro findings with human clinical data for improved drug safety evaluation.