Chronic intermittent tachypacing by an optogenetic approach induces arrhythmia vulnerability in human engineered heart tissue

Abstract

Aims Chronic tachypacing is commonly used in animals to induce cardiac dysfunction and to study mechanisms of heart failure and arrhythmogenesis. Human induced pluripotent stem cells (hiPSC) may replace animal models to overcome species differences and ethical problems. Here, 3D engineered heart tissue (EHT) was used to investigate the effect of chronic tachypacing on hiPSC-cardiomyocytes (hiPSC-CMs). Methods and results To avoid cell toxicity by electrical pacing, we developed an optogenetic approach. EHTs were transduced with lentivirus expressing channelrhodopsin-2 (H134R) and stimulated by 15 s bursts of blue light pulses (0.3 mW/mm2, 30 ms, 3 Hz) separated by 15 s without pacing for 3 weeks. Chronic optical tachypacing did not affect contractile peak force, but induced faster contraction kinetics, shorter action potentials, and shorter effective refractory periods. This electrical remodelling increased vulnerability to tachycardia episodes upon electrical burst pacing. Lower calsequestrin 2 protein levels, faster diastolic depolarization (DD) and efficacy of JTV-519 (46% at 1 µmol/L) to terminate tachycardia indicate alterations of Ca2+ handling being part of the underlying mechanism. However, other antiarrhythmic compounds like flecainide (69% at 1 µmol/L) and E-4031 (100% at 1 µmol/L) were also effective, but not ivabradine (1 µmol/L) or SEA0400 (10 µmol/L). Conclusion We demonstrated a high vulnerability to tachycardia of optically tachypaced hiPSC-CMs in EHT and the effective termination by ryanodine receptor stabilization, sodium or hERG potassium channel inhibition. This new model might serve as a preclinical tool to test antiarrhythmic drugs increasing the insight in treating ventricular tachycardia.

Case Report on: Very Early Afterdepolarizations in HiPSC-Cardiomyocytes—An Artifact by Big Conductance Calcium Activated Potassium Current (Ibk,Ca)

“…In some APs the notch was followed by a peculiar oscillation during plateau phase of the AP. This peculiarity of notch/oscillation was only observed in some of independent differentiation batches of the C25 cell line, but never in any other of three in-house cell lines or five commercial cell lines investigated with sharp microelectrodes as previously described [5,9,[27][28][29][30]. When the notch/oscillation was detected in one EHT, all impalements showed this peculiarity including all EHTs from this differentiation batch.…”

Comparison of 10 Control hPSC Lines for Drug Screening in an Engineered Heart Tissue Format

“…We circumvented this obstacle with electrical pacing of the tissues during the experiment and highly recommend analysis under frequency-controlled conditions for drug screening. As incorporation of an electrical pacing system is technically not always feasible, emerging technologies for optical stimulation could be of value ( Lemme et al., 2020 ; Molokanova et al., 2017 ). Of note, pacing frequency might interfere with the results as prolongation in FPD was only visible at certain pacing frequencies ( Lapp et al., 2017 ) and many positive inotropic effects are only observed at low pacing rate ( Saleem et al., 2020 ).…”

Mitochondrial and Sarcoplasmic Reticulum Interconnection in Cardiac Arrhythmia

“…Under a chronic optical tachypacing protocol, the tissue remodeling showed a propensity for tachycardic episodes when submitted to a burst pacing protocol. This propensity was abolished when JTV519 was administered ( Lemme et al, 2019 ). In addition, in guinea-pig ventricular muscles subjected to no-flow ischemia followed by reperfusion, JTV519 administration significantly improved post-ischemic contractile recovery.…”