Abstract
The cardiac action potential (AP) is vital for understanding healthy and diseased cardiac biology and drug safety testing. However, techniques for high throughput cardiac AP measurements have been limited. Here, we introduce a novel technique for reliably increasing the coupling of cardiomyocyte syncytium to planar multiwell microelectrode arrays, resulting in a stable, label-free local extracellular action potential (LEAP). We characterized the reliability and stability of LEAP, its relationship to the field potential, and its efficacy for quantifying AP morphology of human induced pluripotent stem cell derived and primary rodent cardiomyocytes. Rise time, action potential duration, beat period, and triangulation were used to quantify compound responses and AP morphology changes induced by genetic modification. LEAP is the first high throughput, non-invasive, label-free, stable method to capture AP morphology from an intact cardiomyocyte syncytium. LEAP can accelerate our understanding of stem cell models, while improving the automation and accuracy of drug testing.
Highlights
Electrical activation of cardiomyocytes initiates and controls downstream contraction of the human heart
We demonstrate that local extracellular action potential (LEAP) is distinct from traditional electroporation techniques, does not affect the underlying electrophysiology, and agrees with simultaneous measurements of the cardiac field potential (FP) in the absence and presence of drugs known to affect cardiac electrophysiology
Cardiomyocytes form a spontaneously beating syncytium and produce a cardiac FP signal that may be detected by microelectrodes embedded in the culture plate substrate
Summary
Electrical activation of cardiomyocytes initiates and controls downstream contraction of the human heart. The standard for high throughput in vitro multiwell measurements of cardiac electrophysiology has been multiwell microelectrode array (MEA) technology[4,16,17,18,19] Such devices measure the extracellular field potential (FP) from cardiomyocytes adhered to the MEA substrate[20]. A number of recent devices have utilized 3-D electrodes to acquire AP signals over longer timescales[28,29], but no commercial implementations exist on a multiwell scale Outside of these approaches, published observations indicate that AP measurements may be made from cardiomyocytes attached to planar MEAs that spontaneously and sporadically exhibit high coupling coefficients[22], presumably due to strong attachment of the cell monolayer to the electrode producing a high sealing resistance. These observations are infrequent, though, preventing the development of a practical and reliable AP assay
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