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Review
. 2021 Nov 18:12:769586.
doi: 10.3389/fphys.2021.769586. eCollection 2021.

Novel Optics-Based Approaches for Cardiac Electrophysiology: A Review

M Caroline Müllenbroich  1 , Allen Kelly  2 , Corey Acker  3 , Gil Bub  4 , Tobias Bruegmann  5 , Anna Di Bona  6 , Emilia Entcheva  7 , Cecilia Ferrantini  8 , Peter Kohl  9 , Stephan E Lehnart  10   11   12 , Marco Mongillo  13   14 , Camilla Parmeggiani  8 , Claudia Richter  15 , Philipp Sasse  16 , Tania Zaglia  13   14 , Leonardo Sacconi  8   9   17 , Godfrey L Smith  2
Affiliations
Review

Novel Optics-Based Approaches for Cardiac Electrophysiology: A Review

M Caroline Müllenbroich et al. Front Physiol. .

Abstract

Optical techniques for recording and manipulating cellular electrophysiology have advanced rapidly in just a few decades. These developments allow for the analysis of cardiac cellular dynamics at multiple scales while largely overcoming the drawbacks associated with the use of electrodes. The recent advent of optogenetics opens up new possibilities for regional and tissue-level electrophysiological control and hold promise for future novel clinical applications. This article, which emerged from the international NOTICE workshop in 2018, reviews the state-of-the-art optical techniques used for cardiac electrophysiological research and the underlying biophysics. The design and performance of optical reporters and optogenetic actuators are reviewed along with limitations of current probes. The physics of light interaction with cardiac tissue is detailed and associated challenges with the use of optical sensors and actuators are presented. Case studies include the use of fluorescence recovery after photobleaching and super-resolution microscopy to explore the micro-structure of cardiac cells and a review of two photon and light sheet technologies applied to cardiac tissue. The emergence of cardiac optogenetics is reviewed and the current work exploring the potential clinical use of optogenetics is also described. Approaches which combine optogenetic manipulation and optical voltage measurement are discussed, in terms of platforms that allow real-time manipulation of whole heart electrophysiology in open and closed-loop systems to study optimal ways to terminate spiral arrhythmias. The design and operation of optics-based approaches that allow high-throughput cardiac electrophysiological assays is presented. Finally, emerging techniques of photo-acoustic imaging and stress sensors are described along with strategies for future development and establishment of these techniques in mainstream electrophysiological research.

Keywords: arrhythmia; electrophysiology; fluorescence; heart; optogenetics.

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Conflict of interest statement

CA is an owner and employee of Potentiometric Probes, which develops and sells voltage-sensitive dyes. GS is a non-salaried, founder, executive and Chief Scientific Offer of Clyde Biosciences Ltd (UK). The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Multi-site voltage and Ca2+ recording. (A) Scheme of the Random Access Multi-Photon (RAMP) microscope based on two orthogonally-mounted acousto-optical deflectors (AODs -x and -y) for laser scanning. Inset shows the emission spectra of the Ca2+ indicator (in dark gray) and voltage sensitive dye (in light gray) together with their fluorescence filter acquisition band. (B) Image of a stained rat ventricular cardiac cell: di-4-ANE(F)PPTEA in red and GFP-certified Fluoforte in green. Scale bar: 5 μm (C) Real time fluorescence traces collected from the scanned sites indicated in white in (B): surface sarcolemma (SS) and five T-tubules (TTi). Membrane voltage is shown in red and Ca2+ in green. Reproduced and modified from Crocini et al. (2014).
Figure 2
Figure 2
A-tubules provide Ca2+ signaling super-hubs for atrial excitation-contraction coupling. (A) Confocal live imaging of di-8-ANEPPS stained (di8) TAT structures visualized as skeleton (pink). N, nucleus. Scale bar 10 μm. Histogram showing the TAT component orientations and Gaussian fit. Abundant AT (0°) vs. sparse TT (90°) components. (B) Cartoon of a cylindrical AT model. AT width (δ) measurements were used to estimate the surface area (AAT); LAT, AT component length. AT width was determined from optical cross sections (brackets) using the local STED signal distribution and compared between VCM vs. ACM as bar graph. Scales 200 nm. (C) Electron tomography images and segmentation of a longitudinally sectioned and a cross-sectioned AT structure. Scales 200 nm. Red color indicating AT-SR junctions ≤ 15 nm in gap width containing RyR2 densities. Red triangles mark two exemplary electron densities compatible with RyR2 channels. (D) Confocal negative contrast visualization of intracellular AT structures and transversal line scanning (yellow triangles) of intracellular Ca2+ imaging (fluo-4). A field potential-evoked Ca2+ transient is activated at AT and subsurface (S) structures; black diamonds, off-membrane cytosolic sites; F25, Ca2+ signal onset at 25 % signal amplitude; ΔF/F0, normalized fluorescence intensity ratio as indicated by look-up-table; N, nucleus. (E) Two-photon action potential recordings from specific TAT components labeled with the voltage-sensitive dye di-4-ANE(F)PTEA (2 μM). Normalized fluorescence traces (ΔF/F0) were recorded from the scan regions indicated by color. At AT, TT, and SS membranes structures the simultaneous action potential activation upon pacing (black arrowheads) is apparent. Grouped bar graph showing no significant difference for action potential onset (the time interval between the end of the stimulus and the rise of the fluorescence signal above a threshold of 4 % ΔF/F0. AT, A-tubule; TT, T-tubule; SS, subsurface membrane site. NS, not significant. Adapted from Brandenburg et al. (2016b).
Figure 3
Figure 3
(A) Optical setup for real-time closed-loop optogenetic stimulation with a digital micromirror device (DMD) in response to ongoing cardiac activity, simultaneously optically mapped with a sCMOS camera. (B) Exemplary customizable stimulation pattern and cardiac excitation wavefronts. Modified from Scardigli et al. (2018b).
Figure 4
Figure 4
The heart is a multicellular network of excitable and non-excitable cells, which have been targeted with various opsins for optogenetic investigation. Modified from Zaglia et al. (2019).
Figure 5
Figure 5
All-optical cardiac electrophysiology and the toolkit of optogenetic actuators and reporters. (A) Advantages of all-optical cardiac electrophysiology using optogenetic tools. (B) Spectral compatibility of optogenetic actuators and reporters for voltage (GEVI) and calcium (GECI) with the possibility for bi-directional control (depolarization and hyperpolarization) of cardiac excitation. Reproduced with permission from Entcheva and Kay (2021).
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References

    1. Optogenetics at Stanford. Available online at: https://web.stanford.edu/group/dlab/optogenetics (accessed March 11, 2020).
    1. Abdelfattah A. S., Kawashima T., Singh A., Novak O., Liu H., Shuai Y., et al. . (2019). Bright and photostable chemigenetic indicators for extended in vivo voltage imaging. Science 365, 699–704. 10.1126/science.aav6416 - DOI - PubMed
    1. Acker C. D., Yan P., Loew L. M. (2011). Single-voxel recording of voltage transients in dendritic spines. Biophys. J. 101, L11–L13. 10.1016/j.bpj.2011.06.021 - DOI - PMC - PubMed
    1. Acker C. D., Yan P., Loew L. M. (2020). Recent progress in optical voltage-sensor technology and applications to cardiac research: from single cells to whole hearts. Prog. Biophys. Mol. Biol. 154, 3–10. 10.1016/j.pbiomolbio.2019.07.004 - DOI - PMC - PubMed
    1. Akturk S., Gu X., Kimmel M., Trebino R. (2006). Extremely simple single-prism ultrashort-pulse compressor. Optics Express 14, 10101–10108. 10.1364/OE.14.010101 - DOI - PubMed

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