Optocardiography and Electrophysiology Studies of Ex Vivo Langendorff-perfused Hearts

Abstract

Small animal models are most commonly used in cardiovascular research due to the availability of genetically modified species and lower cost compared to larger animals. Yet, larger mammals are better suited for translational research questions related to normal cardiac physiology, pathophysiology, and preclinical testing of therapeutic agents. To overcome the technical barriers associated with employing a larger animal model in cardiac research, we describe an approach to measure physiological parameters in an isolated, Langendorff-perfused piglet heart. This approach combines two powerful experimental tools to evaluate the state of the heart: electrophysiology (EP) study and simultaneous optical mapping of transmembrane voltage and intracellular calcium using parameter sensitive dyes (RH237, Rhod2-AM). The described methodologies are well suited for translational studies investigating the cardiac conduction system, alterations in action potential morphology, calcium handling, excitation-contraction coupling and the incidence of cardiac alternans or arrhythmias. Video Link The video component of this article can be found at https://www.jove.com/video/60472/ 18,19. Indeed, simultaneous dual imaging of voltage and calcium-sensitive fluorescent probes allows for the assessment of electrical activity, calcium handling and excitation-contraction coupling at the tissue level

Minimally invasive system to reliably characterize ventricular electrophysiology from living donors

“…Here we show that AP duration and morphology are comparable in slices from transmural core biopsies and tissue blocks from the same pig ventricular regions. Median APD values (117 ms and 111 ms in the biopsy and block slices, respectively) are slightly lower than previously published values in experimental works on multicellular preparations 40 – 44 , which could be explained by the fact that our pig samples come from piglets and young pigs. Indeed, in our APD measures we could observe a trend to shorter APD in those from piglets as compared to those from adult pigs.…”

Stop the beat to see the rhythm: excitation-contraction uncoupling in cardiac research

“…In fact, in the last three years alone, blebbistatin was used twice as often (1,29,36,41,51,56,59,69,74,76,78,83,85,87) as any other uncoupler for imaging applications (25,27,33,46,54,55,80). The use of BDM/DAM and CytoD for optical mapping has essentially ceased, yet due to its lower cost, BDM/DAM may still be a reasonable choice for larger animal (i.e., non-rodent) studies (10,23,25,35,52,70,77), which require larger amounts of an EC uncoupler (72). Clearly, blebbistatin is currently the most popular choice in cardiac optical mapping (Figure 1), as it can be used at much lower concentrations and is less toxic compared to the other EC uncouplers (5,20,48,67).…”

KairoSight: Open-Source Software for the Analysis of Cardiac Optical Data Collected From Multiple Species

“…Animal procedures were approved by the Institutional Animal Care and Use Committee of the Children's Research Institute and followed the National Institutes of Health's Guide for the Care and Use of Laboratory Animals. All animals were euthanized by exsanguination under anesthesia following heart excision, as previously described in detail (Jaimes et al, 2019a;Swift et al, 2019). Experimental data were acquired from isolated, intact hearts that were maintained on a temperature-controlled (37 • C), constant-pressure (70 mmHg) Langendorff-perfusion system.…”

“…To date, cardiac optical mapping, also known as optocardiography (Boukens and Efimov, 2014;George and Efimov, 2019;Swift et al, 2019), has been used to investigate changes in electrical activity, spiral wave formation (Jalife, 2003), excitation-contraction coupling (Christoph et al, 2017), sarcoplasmic reticulum-specific calcium cycling (Wang et al, 2014), metabolic status (Mercader et al, 2012;Wengrowski et al, 2014;Kuzmiak-Glancy et al, 2015;Jaimes et al, 2016a;Garrott et al, 2017), the efficacy of ablation therapies (Swift et al, 2014), stem-cell engraftment (Costa et al, 2012;Shiba et al, 2012;Filice et al, 2020), cardiotoxicity (Jaimes et al, 2019b), and the pathobiology of heart failure (Spragg and Kass, 2006; Abbreviations: APD 80 , action potential duration at 80% repolarization; AUF, arbitrary units of fluorescence; Ca 2+ , intracellular calcium; CaD 80 , calcium transient duration at 80% reuptake; dF/F0, change in fluorescence over baseline; hiPSC-CM, human induced pluripotent stem cell-derived cardiomyocytes; PCL, pacing cycle length; SNR, signal-to-noise ratio; V m , transmembrane voltage. Ng et al, 2014;Zasadny et al, 2020).…”