Abstract 354: Combination of Triiodothyronine and Dexamethasone with Flexible Matrigel Substrate Improves Structural and Electrophysiological Maturation of Human iPSC-derived Cardiomyocytes

Abstract

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) have promise for disease modeling and cell therapy, but electrophysiological immaturity (ie. large pacemaker currents, small I K1 ) and structural immaturity (ie. lack of t-tubules) remain major limitations. Here, we test whether the combination of triiodothyronine (T 3 ) and dexamethasone (Dex) with a soft Matrigel substrate improves hiPSC-CMs maturity. T 3 & Dex or vehicle were added to cardiac induction media for 14 days. Day 30 hiPSC-CMs were plated either on hard or soft Matrigel-coated substrate for 5 days and studied using confocal imaging and voltage clamp. T 3 & Dex treatment significantly increased the width and volume of hiPSC-CMs cultured on soft but not on hard substrate ( Fig.1 ). T 3 & Dex treated hiPSC-CMs exhibited organized subcellular Ca release ( Fig.2 ) and evidence of t-tubule development, possibly as a result of increased Bin-1 and Caveolin-3 membrane trafficking. The combination of T 3 & Dex and soft substrate increased Ca spark frequency and the amount of Ca released per spark ( Fig.3 ). T 3 & Dex treatment significantly accelerated Ca transient decay under field stimulation and increased sarcoplasmic reticulum Ca-ATPase activity. Compared to vehicle, T 3 & Dex treatment significantly improved electrophysiological maturity: Pacemaker current (I f ) density was 3-fold reduced (-2.7±0.35 vs. -6.2±1.3 pA/pF) and inward rectifier current (I K1 ) density was 4-fold increased (-19.3±2.2 vs. -4.4±0.5 pA/pF). Combining T 3 & Dex and soft Matrigel substrate enhances structural and functional maturation of hiPSC-CMs, which will increase the utility of hiPSC-CM for disease modeling and cell therapy.