Low Resting Membrane Potential and Low Inward Rectifier Potassium Currents Are Not Inherent Features of hiPSC-Derived...

Area of Science:

• Cardiology
• Stem Cell Biology
• Electrophysiology

Background:

• Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) often exhibit a less negative resting membrane potential (RMP).
• This RMP difference is frequently attributed to reduced inward rectifier potassium currents (I_K1).
• Understanding ion channel function in hiPSC-CMs is crucial for their application in disease modeling and drug screening.

Purpose of the Study:

• To investigate and compare I_K1 density and RMP in hiPSC-CMs cultured under different conditions.
• To directly compare hiPSC-CMs with human native atrial and ventricular cardiomyocytes.
• To identify factors contributing to observed RMP variations in hiPSC-CMs.

Main Methods:

• Measurement of I_K1 and RMP in hiPSC-CMs (proprietary and commercial lines) cultured as monolayer (ML) or 3D engineered heart tissue (EHT).
• Direct comparison with cardiomyocytes from human right atrium (RA) and left ventricle (LV).
• Assessment of repolarization fraction and I_K,ACh response to differentiate chamber phenotypes.

Main Results:

• I_K1 density in ML- and EHT-hiPSC-CMs (proprietary line) was comparable to LV and RA CMs, respectively.
• A 2-fold lower I_K1 density was observed in EHT-hiPSC-CMs from the commercial line compared to the proprietary line.
• RMP in EHT-hiPSC-CMs from both lines resembled native RA and LV CMs.
• Repolarization and I_K,ACh responses indicated a predominantly ventricular phenotype in hiPSC-CMs/EHT.
• I_K1 levels in hiPSC-CMs are not universally low, suggesting technical issues may influence RMP measurements.

Conclusions:

• The inherent I_K1 current in hiPSC-CMs may not be as low as previously assumed.
• Observed low RMP in hiPSC-CMs could be influenced by experimental or technical factors rather than intrinsic cellular properties.
• hiPSC-CMs, particularly in EHT formats, show promise for recapitulating native cardiac electrophysiology.
• Further investigation into culture conditions and measurement techniques is warranted to optimize hiPSC-CM models.