Subtype-specific promoter-driven action potential imaging for precise disease modelling and drug testing in hiPSC-derived cardiomyocytes

Translational perspective

Cardiomyocytes (CMs) generated from human induced pluripotent stem cells are an evolving platform to understand molecular disease mechanism and evaluate cardiovascular drugs. A major limitation of this system is that they represent a heterogeneous mix of ventricular-, atrial-, and nodal-like CMs. By expressing a voltage-sensitive fluorescent protein under the control of lineage-specific promoters, we developed a convenient system allowing high-throughput subtype-specific optical action potential (AP) imaging in these cells. This enables not only quantification of electrical phenotypes in patient-specific CMs but also subtype-specific investigation of drug effects, which may aid both drug development and safety pharmacology in the cardiovascular field.

Abstract

Aims

Cardiomyocytes (CMs) generated from human induced pluripotent stem cells (hiPSCs) are increasingly used in disease modelling and drug evaluation. However, they are typically a heterogeneous mix of ventricular-, atrial-, and nodal-like cells based on action potentials (APs) and gene expression. This heterogeneity and the paucity of methods for high-throughput functional phenotyping hinder the full exploitation of their potential. We aimed at developing a method for rapid, sequential, and subtype-specific phenotyping of hiPSC-CMs with respect to AP morphology and single-cell arrhythmias.

Methods and results

We used cardiac lineage-specific promoters to drive the expression of a voltage-sensitive fluorescent protein (VSFP-CR) in hiPSC-CMs, enabling subtype-specific optical AP recordings. In a patient-specific hiPSC model of long-QT syndrome type 1, AP prolongation and frequent early afterdepolarizations were evident in mutant ventricular- and atrial like, but not in nodal-like hiPSC-CMs compared with their isogenic controls, consistent with the selective expression of the disease-causing gene. Furthermore, we demonstrate the feasibility of sequentially probing a cell over several days to investigate genetic rescue of the disease phenotype and to discern CM subtype-specific drug effects.

Conclusion

By combining a genetically encoded membrane voltage sensor with promoters that drive its expression in the major subtypes of hiPSC-CMs, we developed a convenient system for disease modelling and drug evaluation in the relevant cell type, which has the potential to advance the emerging utility of hiPSCs in cardiovascular medicine.