Abstract 13939: Triiodothyronine and Dexamethasone Enhances Electrophysiological Maturation of Human-Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Abstract

Background: Human induced pluripotent stem cell-derived cardiomyocyte (hiPSC-CM) technology opens new avenues for disease modeling and drug development. However, hiPSC-CMs remain functionally immature, which hinders their utility as a model of human cardiomyocytes. Objective: To improve the electrophysiological maturation of hiPSC-CMs. Methods and Results: Day 16 th hiPSC-CMs were treated with vehicle or 100 nmol/L triiodothyronine (T3) and 1 μmol/L Dexamethasone (Dex) for 14 days. On day 30 th , hiPSC-CMs were dissociated and replated as cell sheets or single cells. Optical mapping and patch-clamp technique were used to examine the electrophysiological properties of vehicle- and T3+Dex-treated hiPSC-CMs. T3+Dex-treated hiPSC-CMs had a slower spontaneous beating rate (vehicle 17 ± 0.8 vs . T3+Dex 12 ± 0.8 beats/min, P < 0.01), more hyperpolarized resting membrane potential (vehicle -65.04 ± 1.20 vs. T3+Dex -72.00 ± 1.10 mV, P < 0.01), faster maximal upstroke velocity (vehicle 86.08 ± 8.12 vs. T3+Dex 131.78 ± 8.49 mV/ms, P < 0.01), and shorter action potential duration at 90% repolarization (APD 90 , vehicle 550.44 ± 39.54 vs. T3+Dex 418.59 ± 21.58 ms, P < 0.01) compared to the vehicle. Changes in spontaneous activity and AP were mediated by decreasing the funny current (I f , vehicle -12.20 ± 2.15 vs. T3+Dex -6.98 ± 0.89 pA/pF at -120 mV, P < 0.05) and increasing the inward rectifier potassium current (I K1 , vehicle -4.62 ± 0.59 pA/pF vs . T3+Dex -18.79 ± 1.98 pA/pF at -120 mV, P < 0.01), the sodium current (I Na , vehicle -9.8 ± 1.86 vs. T3+Dex -44.9 ± 7.10 pA/pF at -30 mV, P < 0.01), and the rapidly and slowly activating delayed rectifier potassium currents (I Kr , 0.81 ± 0.07 vs. T3+Dex: 1.35 ± 0.19 pA/pF at 20 mV, P < 0.01; I Ks , vehicle 0.38 ± 0.06 vs. T3+Dex 0.72 ± 0.17 pA/pF at 40 mV, P < 0.05). Furthermore, T3+Dex-treated hiPSC-CM cell sheets (hiPSC-CCSs) exhibited a faster conduction velocity and shorter APD than the vehicle. Inhibition of I K1 by 100 μM BaCl 2 significantly slowed conduction velocity and prolonged APD in T3+Dex-treated hiPSC-CCSs but had no effect in the vehicle group, demonstrating the important role of I K1 for conduction velocity and APD. Conclusion: T3+Dex treatment is an effective approach to rapidly enhance electrophysiological maturation of hiPSC-CMs.