Abstract
Since current experimental models of Atrial Fibrillation (AF) have significant limitations, we used human embryonic stem cells (hESCs) to generate an atrial-specific tissue model of AF for pharmacologic testing. We generated atrial-like cardiomyocytes (CMs) from hESCs which preferentially expressed atrial-specific genes, and had shorter action potential (AP) durations compared to ventricular-like CMs. We then generated confluent atrial-like CM sheets and interrogated them using optical mapping techniques. Atrial-like CM sheets (~1 cm in diameter) showed uniform AP propagation, and rapid re-entrant rotor patterns, as seen in AF could be induced. Anti-arrhythmic drugs were tested on single atrial-like CMs and cell sheets. Flecainide profoundly slowed upstroke velocity without affecting AP duration, leading to reduced conduction velocities (CVs), curvatures and cycle lengths of rotors, consistent with increased rotor organization and expansion. By contrast, consistent with block of rapid delayed rectifier K+ currents (Ikr) and AP prolongation in isolated atrial-like CMs, dofetilide prolonged APs and reduced cycle lengths of rotors in cell sheets without affecting CV. In conclusion, using our hESC-derived atrial CM preparations, we demonstrate that flecainide and dofetilide modulate reentrant arrhythmogenic rotor activation patterns in a manner that helps explain their efficacy in treating and preventing AF.
Highlights
Human pluripotent stem cell derived cardiomyocytes (CM) represent a promising and powerful tool for anti-arrhythmic drug (AAD) screening, and have been exploited to model a growing number of arrhythmogenic cardiac electrical disorders at a single cell level[9]
Flow cytometric analyses were performed on human embryonic stem cells (hESCs) before cardiac differentiation in order to ensure a high frequency of pluripotency markers and low frequency of differentiation (Supplemental Fig. 2) prior to cardiomyocyte induction
Despite showing AP properties typical of adult atrial CMs, the CMs generated with our atrial differentiation protocol displayed electrophysiologic properties indicative of immaturity, including a relatively positive maximum diastolic potential, slow maximum upstroke velocities, and small action potential amplitudes (Table 1)[28, 29]
Summary
Human pluripotent stem cell (hPSC) derived cardiomyocytes (CM) represent a promising and powerful tool for anti-arrhythmic drug (AAD) screening, and have been exploited to model a growing number of arrhythmogenic cardiac electrical disorders at a single cell level[9]. A major step forward has been the refinement and validation of differentiation protocols that can enrich the atrial-like population to screen for the effects of drugs on human atrial electrophysiology[11]. Of our studies is to develop and validate a novel platform for AAD screening for the treatment of AF using hPSCs in multicellular constructs that can re-capitulate the macroscopic footprints of the human disease. Through directed differentiation of human embryonic stem cells (hESCs), we generated CMs with largely (>85%) atrial-like properties, indicated by mRNA expression patterns and single CM action potential (AP) profiles[12, 13]. We induced stable re-entrant spiral wave geometries (called rotors), which act as arrhythmogenic self-organized drivers in AF14–16, using rapid external pacing, and employed optical mapping techniques to study the electrical effects of two commonly used AADs (i.e. flecainide and dofetilide) for AF treatment. The significance and limitations of our findings are discussed in the context of AF and its treatment
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