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Frequency-dependent drug screening using optogenetic stimulation of human iPSC-derived cardiomyocytes.

ABSTRACT: Side effects on cardiac ion channels are one major reason for new drugs to fail during preclinical evaluation. Herein we propose a simple optogenetic screening tool measuring extracellular field potentials (FP) from paced cardiomyocytes to identify drug effects over the whole physiological heart range, which is essential given the rate-dependency of ion channel function and drug action. Human induced pluripotent stem cell-derived cardiomyocytes were transduced with an adeno-associated virus to express Channelrhodopsin2 and plated on micro-electrode arrays. Global pulsed illumination (470?nm, 1?ms, 0.9?mW/mm²) was applied at frequencies from 1 to 2.5?Hz, which evoked FP simultaneously in all cardiomyocytes. This synchronized activation allowed averaging of FP from all electrodes resulting in one robust FP signal for analysis. Field potential duration (FPD) was ~25% shorter at 2.5?Hz compared to 1?Hz. Inhibition of hERG channels prolonged FPD only at low heart rates whereas Ca²⁺ channel block shortened FPD at all heart rates. Optogenetic pacing also allowed analysis of the maximum downstroke velocity of the FP to detect drug effects on Na⁺ channel availability. In principle, the presented method is well scalable for high content cardiac toxicity screening or personalized medicine for inherited cardiac channelopathies.

SUBMITTER: Lapp H

PROVIDER: S-EPMC5575076 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature

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Frequency-dependent drug screening using optogenetic stimulation of human iPSC-derived cardiomyocytes.

Lapp Hendrik H Bruegmann Tobias T Malan Daniela D Friedrichs Stephanie S Kilgus Carsten C Heidsieck Alexandra A Sasse Philipp P

Scientific reports 20170829 1

Side effects on cardiac ion channels are one major reason for new drugs to fail during preclinical evaluation. Herein we propose a simple optogenetic screening tool measuring extracellular field potentials (FP) from paced cardiomyocytes to identify drug effects over the whole physiological heart range, which is essential given the rate-dependency of ion channel function and drug action. Human induced pluripotent stem cell-derived cardiomyocytes were transduced with an adeno-associated virus to e ...[more]

PMID: 28851973

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Project description:Optogenetics provides an alternative to electrical stimulation to manipulate membrane voltage, and trigger or modify action potentials (APs) in excitable cells. We compare biophysically and energetically the cellular responses to direct electrical current injection versus optical stimulation mediated by genetically expressed light-sensitive ion channels, e.g., Channelrhodopsin-2 (ChR2). Using a computational model of ChR2(H134R mutant), we show that both stimulation modalities produce similar-in-morphology APs in human cardiomyocytes, and that electrical and optical excitability vary with cell type in a similar fashion. However, whereas the strength-duration curves for electrical excitation in ventricular and atrial cardiomyocytes closely follow the theoretical exponential relationship for an equivalent RC circuit, the respective optical strength-duration curves significantly deviate, exhibiting higher nonlinearity. We trace the origin of this deviation to the waveform of the excitatory current-a nonrectangular self-terminating inward current produced in optical stimulation due to ChR2 kinetics and voltage-dependent rectification. Using a unifying charge measure to compare energy needed for electrical and optical stimulation, we reveal that direct electrical current injection (rectangular pulse) is more efficient at short pulses, whereas voltage-mediated negative feedback leads to self-termination of ChR2 current and renders optical stimulation more efficient for long low-intensity pulses. This applies to cardiomyocytes but not to neuronal cells (with much shorter APs). Furthermore, we demonstrate the cell-specific use of ChR2 current as a unique modulator of intrinsic activity, allowing for optical control of AP duration in atrial and, to a lesser degree, in ventricular myocytes. For self-oscillatory cells, such as Purkinje, constant light at extremely low irradiance can be used for fine control of oscillatory frequency, whereas constant electrical stimulation is not feasible due to electrochemical limitations. Our analysis offers insights for designing future new energy-efficient stimulation strategies in heart or brain.

Dataset Information

Frequency-dependent drug screening using optogenetic stimulation of human iPSC-derived cardiomyocytes.

Publications

Frequency-dependent drug screening using optogenetic stimulation of human iPSC-derived cardiomyocytes.

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