Optical mapping of optogenetically shaped cardiac action potentials

Abstract

Light-mediated silencing and stimulation of cardiac excitability, an important complement to electrical stimulation, promises important discoveries and therapies. To date, cardiac optogenetics has been studied with patch-clamp, multielectrode arrays, video microscopy, and an all-optical system measuring calcium transients. The future lies in achieving simultaneous optical acquisition of excitability signals and optogenetic control, both with high spatio-temporal resolution. Here, we make progress by combining optical mapping of action potentials with concurrent activation of channelrhodopsin-2 (ChR2) or halorhodopsin (eNpHR3.0), via an all-optical system applied to monolayers of neonatal rat ventricular myocytes (NRVM). Additionally, we explore the capability of ChR2 and eNpHR3.0 to shape action-potential waveforms, potentially aiding the study of short/long QT syndromes that result from abnormal changes in action potential duration (APD). These results show the promise of an all-optical system to acquire action potentials with precise temporal optogenetics control, achieving a long-sought flexibility beyond the means of conventional electrical stimulation.

“Beauty is a light in the heart”: The transformative potential of optogenetics for clinical applications in cardiovascular medicine1

“…A potentially beneficial use of optogenetics is to apply long, low-amplitude light stimuli to dynamically modulate AP shape in opsin-expressing cells. Karathanos et al (44) recently used simulations to show that light-based therapy produced better results than drug treatment for restoring healthy AP duration in a model of atrial cells under the conditions of short QT syndrome; these findings are in agreement with recent in vitro findings that demonstrated the use of optogenetic tools to shape APs in light-sensitized NVRM monolayers (45). At the organ scale, however, simulations showed that the efficacy of this therapy was greatly hindered by light attenuation effects; of particular concern was the fact that energy loss due to attenuation and photon scattering in the atrial wall resulted in more prominent AP elongation near the illuminated surface (the endocardium) than in the tissue depth.…”

Integrating cardiomyocytes from human pluripotent stem cells in safety pharmacology: has the time come?

“…However, the success of these approaches will, nevertheless, be determined by progress in improving the maturation status of hPSC‐CMs, that is, the more hPSC‐CMs resemble adult CMs, the less they will tolerate invasive techniques. For this reason, less invasive alternatives are being already being developed in parallel, with the interest in voltage‐sensitive dyes (Burridge et al , 2011) and optogenetics (Park et al , 2014; Chang Liao et al , 2015; Song et al , 2015) significantly rising (Dempsey et al , 2016). At present, their widespread implementation in drug screening is limited by the slow kinetics and the relatively low signal/noise ratio of voltage sensors, with data still requiring proper validation by low‐throughput patch clamp analyses.…”

Cardiac neuroanatomy - Imaging nerves to define functional control

“…99–105 Wang et al have been able to demonstrate that optogenetic stimulation of noradrenergic neurons in the locus cereleus of the brain inhibits parasympathetic cardiac vagal neuron outflow that results in tachycardia. 35 Their group have further evaluated the neural axis in the murine heart by identifying and stimulating a subpopulation of cardiomyocytes that bear the phenylethanolamine n-methyltransferase gene, which encodes the enzyme that converts norepinephrine to epinephrine, to exert control on heart rhythm through the use of optogenetics.…”