Zebrafish: a novel research tool for cardiac (patho)electrophysiology and ion channel disorders

Abstract

The zebrafish is a cold-blooded tropical freshwater teleost with two-chamber heart morphology. A major advantage of the zebrafish for heart studies is that the embryo is transparent, allowing for easy assessment of heart development, heart rate analysis and phenotypic characterization. Moreover, rapid and effective gene-specific knockdown can be achieved using morpholino oligonucleotides. Lastly, zebrafish are small in size, are easy to maintain and house, grow fast, and have large offspring size, making them a cost-efficient research model. Zebrafish embryonic and adult heart rates as well as action potential (AP) shape and duration and electrocardiogram morphology closely resemble those of humans. However, whether the zebrafish is truly an attractive alternative model for human cardiac electrophysiology depends on the presence and gating properties of the various ion channels in the zebrafish heart, but studies into the latter are as yet limited. The rapid component of the delayed rectifier K+ current (IKr) remains the best characterized and validated ion current in zebrafish myocytes, and zebrafish may represent a valuable model to investigate human IKr channel-related disease, including long QT syndrome. Arguments against the use of zebrafish as model for human cardiac (patho)electrophysiology include its cold-bloodedness and two-chamber heart morphology, absence of t-tubuli, sarcoplamatic reticulum function, and a different profile of various depolarizing and repolarizing ion channels, including a limited Na+ current density. Based on the currently available literature, we propose that zebrafish may constitute a relevant research model for investigating ion channel disorders associated with abnormal repolarization, but may be less suitable for studying depolarization disorders or Ca2+-modulated arrhythmias.

Genetics and Disease of Ventricular Muscle

“…Murine models have several limitations, however, including the time and expense of generating, breeding, and aging adequate numbers of experimental mice. Zebrafish are rapidly gaining popularity as a model organism because they are easy to breed, have rapid development and numerous progeny, and genetic manipulation can be readily achieved (Lieschke and Currie 2007;Dahme et al 2009;Santoriello and Zon 2012;Verkerk and Remme 2012). Two distinctive properties of zebrafish during the first weeks of life are their transparency, which enables heart development and function to be directly observed in real time, and their independence from a functioning circulatory system for oxygen supply to the tissues.…”

Generating an In Vitro 3D Cell Culture Model from Zebrafish Larvae for Heart Research

“…The intrinsic contraction frequency of the ZFHAs is also akin to that of the adult human heart rate (60-90 beats min −1 at rest). The similarity in heart rate between ZF (at 20°C) and humans (at 37°C) is driven by an action potential with a very similar waveform; both have a prominent plateau phase, which reflects similarities in their underlying ion channel profiles (Brette et al, 2008;Nemtsas et al, 2010;Verkerk and Remme, 2012). Rodents, in contrast, have ∼10 times faster heart rates, and their action potential lacks a significant plateau phase, which is reflected in their ion channel expression (Li et al, 1999;Nerbonne et al, 2001).…”

“…Furthermore, this method does not require the use of protected animals, thus supporting the tenets of the 3Rs of animal research (replacement, reduction and refinement). The similarity between ZF and human cardiac action potentials and the underlying ion channels have already been investigated in detail (Brette et al, 2008;Nemtsas et al, 2010;Verkerk and Remme, 2012;Bovo et al, 2013), as have the regenerative capabilities of the ventricle (Major and Poss, 2007;Kikuchi et al, 2010 knock-downs could be used to target aspects of cardiac maturation including myocyte proliferation, regeneration, conductivity and ion channel function. Thus, we see ZFHAs complementing current in vitro investigative strategies (i.e.…”

“…This method builds on previous work by Grunow et al (2011) and Mehnert et al (2013) for salmonids but also offers new investigative potential by virtue of the role of ZF as a model organism for cardiac research. Work by us (Brette et al, 2008) and others (Nemtsas et al, 2010;Verkerk and Remme, 2012;Bovo et al, 2013) clearly shows that the ZF heart is a relevant model for human cardiac ion channel disorders, particularly those associated with cardiac repolarisation. ZF are also an established model species for environmental and (eco) toxicology testing (Strähle et al, 2011;Busch et al, 2011), with recent work focusing on the effect of pollutants on the ZF cardiovascular system (Parker et al, 2014).…”

Functional characterization of developing heart in embryos using Electric Potential Sensors

“…This is mainly because zebrafish electrocardiogram (ECG) waveform possesses a remarkable resemblance to those of humans [2]. Although its heart morphology has only a two-chambered heart (compared with the four-chambered human heart) and a simple fully functioning circulatory system, the zebrafish has been suggested as a useful model organism for studies of human heart development and cardiac patho-electrophysiology.…”