| Abstrakt: |
Human-induced pluripotent stem cells derived cardiomyocytes (hiPSC-CMs) are a virtually endless source of human cardiomyocytes that may become a great tool for safety pharmacology; however, their electrical phenotype is immature: they show spontaneous action potentials (APs) and an unstable and depolarized resting membrane potential (RMP) because of lack of IK1. Such immaturity hampers their application in assessing drug safety. The electronic overexpression of IK1(e.g., through the dynamic clamp (DC) technique) is an option to overcome this deficit. In this computational study, we aim to estimate how much IK1is needed to bring hiPSC-CMs to a stable and hyperpolarized RMP and which mathematical description of IK1is most suitable for DC experiments. We compared five mature IK1formulations (Bett, Dhamoon, Ishihara, O’Hara-Rudy, and ten Tusscher) with the native one (Paci), evaluating the main properties (outward peak, degree of rectification), and we quantified their effects on AP features (RMP, V˙max, APD50, APD90(AP duration at 50 and 90% of repolarization), and APD50/APD90) after including them in the hiPSC-CM mathematical model by Paci. Then, we automatically identified the critical conductance for IK1( GK1, critical), the minimally required amount of IK1suppressing spontaneous activity. Preconditioning the cell model with depolarizing/hyperpolarizing prepulses allowed us to highlight time dependency of the IK1formulations. Simulations showed that inclusion of mature IK1formulations resulted in hyperpolarized RMP and higher V˙max, and observed GK1, criticaland the effect on AP duration strongly depended on IK1formulation. Finally, the Ishihara IK1led to shorter (−16.3%) and prolonged (+6.5%) APD90in response to hyperpolarizing and depolarizing prepulses, respectively, whereas other models showed negligible effects. Fine-tuning of GK1is an important step in DC experiments. Our computational work proposes a procedure to automatically identify how much IK1current is required to inject to stop the spontaneous activity and suggests the use of the Ishihara IK1model to perform DC experiments in hiPSC-CMs. |
