Delayed Repolarization Caused by hERG Block With Different Drug Modalities Can Be Detected in Stem Cell-Derived...

Area of Science:

• Cardiovascular Pharmacology
• Stem Cell Biology
• Molecular Toxicology

Background:

• Conventional in vitro cardiac models struggle with oligonucleotide assessment due to limitations in transfection and extended culture.
• Human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CM) provide a suitable platform for prolonged agent evaluation and recording.
• Previous studies indicated a 48-hour chronic protocol is needed to observe siRNA effects on hERG in stable cell lines.

Purpose of the Study:

• To investigate delayed cardiac repolarization in hiPSC-CM induced by hERG-targeting siRNA.
• To compare the time course of drug-induced and siRNA-induced hERG channel dysfunction.
• To establish optimal assessment times for gene silencing effects on cardiac electrophysiology.

Main Methods:

• Field potentials (FPs) were recorded using a multielectrode array (MEA) in hiPSC-CM.
• Exposure to moxifloxacin and pentamidine assessed acute drug effects on FP duration (FPD).
• Transfection with hERG-targeting siRNA was performed, with mRNA expression and FPD monitored at various time points (6, 24, 48 hours).

Main Results:

• Moxifloxacin induced FPD prolongation within 10 minutes; pentamidine required 24 hours.
• hERG siRNA reduced mRNA expression by 6 hours post-transfection.
• Significant FPD prolongation was observed 24 hours post-transfection, with maximal effects at 48 hours, indicating protein turnover time.

Conclusions:

• MEA recordings in hiPSC-CM can detect disruptions in cardiac repolarization from diverse mechanisms affecting hERG.
• Mechanisms include direct channel blockade, protein trafficking inhibition, and gene silencing via siRNA.
• Indirect hERG knockdown via gene silencing necessitates at least 48 hours post-treatment assessment in hiPSC-CM to detect delayed repolarization.