Modeling polymorphic ventricular tachycardia at rest using patient-specific induced pluripotent stem cell-derived...

Area of Science:

• Cardiology
• Genetics
• Stem Cell Biology

Background:

• Mutations in the cardiac ryanodine receptor (RyR2) are linked to exercise-induced arrhythmias.
• The role of RyR2 mutations in polymorphic ventricular tachycardia (PMVT) at rest remains unclear.
• This study investigates a patient-specific model of PMVT at rest caused by an RyR2 mutation.

Purpose of the Study:

• To create a human-induced pluripotent stem cell (hiPSC)-based model of PMVT at rest.
• To investigate the functional consequences of a specific RyR2 mutation (RyR2-H29D) in cardiomyocytes.
• To compare the properties of patient-derived hiPSC cardiomyocytes with isogenic controls.

Main Methods:

• Generated patient-specific hiPSCs from blood samples of a PMVT patient with a heterozygous RyR2-H29D mutation.
• Differentiated hiPSCs into cardiomyocytes (hiPSCCMs).
• Utilized CRISPR/Cas9 to create isogenic controls by correcting the RyR2 mutation.
• Assessed molecular and functional properties using patch-clamp, confocal microscopy, and video-image analysis.

Main Results:

• RyR2-H29D hiPSCCMs displayed increased intracellular sarcoplasmic reticulum (SR) Ca2+ leak.
• The mutation exacerbated abnormal Ca2+ release by enhancing inositol 1,4,5-trisphosphate receptor activity.
• RyR2-H29D hiPSCCMs showed shortened action potentials, delayed afterdepolarizations, arrhythmias, and abnormal contractility compared to controls.
• Post-translational modifications caused by the mutation were reversible in isogenic controls.

Conclusions:

• The RyR2-H29D mutation in hiPSCCMs recapitulates key features of short-coupled PMVT at rest.
• Aberrant intracellular Ca2+ homeostasis is a key mechanism underlying the observed arrhythmias.
• This patient-specific hiPSC model provides insights into the pathophysiology of RyR2-associated arrhythmias.