Introduction: Cardiac-related drug discovery and toxicity screening and inherited cardiac disorder study are hampered by the lack of suitable in-vitro human models and relevant functional assays. A potential solution to this cell-sourcing challenge may be the recently-described human induced pluripotent stem cells (hiPSCs) technology. The congenital long QT syndrome (LQTS) is a familial arrhythmogenic syndrome caused by abnormal ion channel function leading to action-potential prolongation and life-threatening arrhythmias and sudden cardiac death.
Aims:(1)To develop patient-specific hiPSCs disease models of the most common congenital LQTS subtypes.(2)To develop novel functional assays using transgenic fluorescent reporters to characterize the hiPSCs-derived cardiomyocytes (hiPSCs-CMs) in a high-throughput manner.(3)To evaluate the assays ability to study the congenital and drug-induced LQTS.
Results: Patient-specific hiPSCs lines were established from a healthy individual and three LQTS patients carrying different mutation-subtypes: LQTS1, LQTS2 and LQTS3. The hiPSCs were coaxed to differentiate into cardiomyocytes. Extracellular electrograms recordings revealed that LQTS-hiPSC-CMs recapitulated the disease phenotype showing prolonged field potential duration. Interestingly, these recordings also revealed subtype-specific patterns similar to subtype-specific T-wave patterns in the patients’ ECGs. We next established high-throughput novel transgenic functional assays to characterize the functional properties of hiPSCs-CMs: a novel protein-based genetically-encoded fluorescent voltage indicator (ArcLight) and calcium indicator (GCaMP). LQTS-hiPSC-CMs, lentivirally transfected with ArcLight, displayed action-potential-like fluorescence transients, positive chronotropic response to beta-adrenergic stimuli (isoproterenol-1µM) and transient prolongation by potassium channel blocker (E4031-500nM). LQTS-hiPSC-CMs transfected with GCaMP presented typical calcium transients in addition to arrhythmogenic double-humped transients.
Conclusions: The combined use of patient-specific hiPSCs model and novel transgenic fluorescent-based functional assays provide a unique tool for disease modeling, functional drug screening, and drug discovery.
