Triiodothyronine and dexamethasone alter potassium channel expression and promote electrophysiological maturation of human-induced pluripotent stem cell-derived cardiomyocytes

Background: Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have emerged as a promising tool 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: On day 16 of cardiac differentiation, hiPSC-CMs were treated with 100 nmol/L triiodothyronine (T3) and 1 mu mol/L Dexamethasone (Dex) or vehicle for 14 days. On day 30, vehicle- and T3 + Dex-treated hiPSC-CMs were dissociated and replated either 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. Compared to vehicle, T3 + Dex-treated hiPSC-CMs had a slower spontaneous beating rate, more hyperpolarized resting membrane potential, faster maximal upstroke velocity, and shorter action potential duration. Changes in spontaneous activity and action potential were mediated by decreased hyperpolarization-activated current (I-f) and increased inward rectifier potassium currents (I-K1), sodium currents (I-Na), and the rapidly and slowly activating delayed rectifier potassium currents (I-Kr and I-Ks, respectively). Furthermore, T3 + Dex-treated hiPSC-CM cell sheets (hiPSC-CCSs) exhibited a faster conduction velocity and shorter action potential duration than the vehicle. Inhibition of I-K1 by 100 mu M BaCl2 significantly slowed conduction velocity and prolonged action potential duration in T3 + Dex-treated hiPSC-CCSs but had no effect in the vehicle group, demonstrating the importance of I-K1 for conduction velocity and action potential duration. Conclusion: T3 + Dex treatment is an effective approach to rapidly enhance electrophysiological maturation of hiPSC-CMs.

Automated summary

The study aimed to enhance the electrophysiological maturation of hiPSC-CMs using T3 and Dex treatment, resulting in improvements in spontaneous beating rate and action potential duration. The changes were attributed to alterations in ion channels, highlighting the significance of I-f, I-K1, I-Na, and I-Kr/Ks in modulating cellular electrophysiology. The findings suggest that T3 + Dex treatment is an effective strategy for promoting the maturation of hiPSC-CMs.