ExperimentalOptical capture and defibrillation in rats with monocrotaline-induced myocardial fibrosis 1 year after a single intravenous injection of adeno-associated virus channelrhodopsin-2
Introduction
Optogenetics is a new biomedical technology that combines genetic and photocontrol technologies. The principle is use of virus vector or transgenic animal methods to transfer the photosensitive protein gene into excitable cells such as nerve cells, muscle cells, and glandular cells, and to express the photosensitive protein on the cell membrane.1,2 Because most photosensitive proteins are light-gated ion channels and ion pumps, activation of the protein using light in a specific wavelength range can induce ion flow both inside or outside the cell, which can cause target cells to depolarize or hyperpolarize.3, 4, 5, 6 Cardiovascular studies that have used optogenetic techniques for cardiac pacing, resynchronization, termination of arrhythmias,7, 8, 9 and electrophysiological function detection10, 11, 12 are emerging and have shown the prospects and potential for optogenetic applications in the clinic.
Arrhythmogenic right ventricular cardiomyopathy, pulmonary hypertension, chronic heart failure, and other cardiac diseases can cause myocardial collagen deposition and fibrosis. The viable cardiomyocytes and collagen interlace with each other, and interstitial fibrosis may disrupt the electrical coupling between cardiomyocytes to form discontinuous conduction or ventricular reentry, promoting the development and spread of ventricular arrhythmias.13 There are no specific antifibrosis drugs, and the effective termination of malignant ventricular arrhythmia (MVA) caused by myocardial fibrosis is a problem worth considering. Researchers have used optogenetics to terminate ventricular tachycardia (VT)/ventricular fibrillation (VF) in vitro or in vivo after acute myocardial infarction.14,15 Light defibrillation has the advantages of no contact, easy pacing site (lighting area is the pacing site), and real-time synchronous excitation (spot area is synchronous excitation area) due to the noncontact nature of light propagation, the flexibility of beam movement, the plasticity of spot size and shape, and the nonspreading of the light focus.16, 17, 18, 19 Termination of VT/VF by optogenetics may be another important option to restore the heart’s electrophysiological function in future cardiovascular treatment.
In this study, we clarified the long-term stability of channelrhodopsin-2 (ChR2) transfection and tested the effects of light defibrillation after increasing myocardial fibrosis. We selected and observed rats for 1 year after viral injection during infancy, and we injected monocrotaline (MCT) to increase the degree of myocardial fibrosis and change cardiac morphology at 11 months as subjects for an in vivo study of light pacing and defibrillation. In addition, we selected the most common photosensitive protein ChR2 mutant ChR2(H134R) as the actuator, which can be irradiated by a 473-nm blue laser to realize the ion transient of the photosensitive current and generate the corresponding electrophysiological effect.20,21 ChR2(H134R) was transferred into the intact heart using adeno-associated virus 2/9 (AAV2/9).22
Section snippets
Materials and methods
The expanded materials and methods section can be found in the Supplemental Material and Supplemental Figure 1.
Phase evaluation of light stimulation and histologic results
Eight weeks after virus injection, the results showed that all parts of the rat heart could be captured using 473-nm blue light. This result showed that AAV transfection with ChR2 was effective. We obtained the light intensity thresholds needed to achieve complete rhythm capture at different pulse widths (Figures 1A–D). Immunofluorescence results showed that red immunofluorescence-labeled ChR2 was evenly distributed in the ventricles (Figure 1E). This was consistent with the in vivo light
Discussion
Cardiac optogenetics is a technique that uses light to regulate photocurrent production in cardiomyocytes expressing either excitatory or inhibitory photosensitive proteins. This study observed the long-term efficacy of AAV transfection with ChR2 and the functional validity of ChR2. We showed that the heart can be captured using light to perform light defibrillation for a long time.
In contrast to electrical pacing that raises the membrane potential above a threshold potential by giving an
Conclusion
AAV carrying the ChR2 gene enabled rats to survive and respond to light after 1 year with changes in heart morphology. In addition, light can increase the termination rate of ventricular arrhythmia on the basis of myocardial fibrosis.
Acknowledgment
The authors are grateful for kind support from Hubei Key Laboratory of Cardiology, Wuhan, China.
References (33)
- et al.
Molecular tools and approaches for optogenetics
Biol Psychiatry
(2012) - et al.
Cardiac fibrosis as a determinant of ventricular tachyarrhythmias
J Arrhythm
(2014) - et al.
No light without the dark: perspectives and hindrances for translation of cardiac optogenetics
Prog Biophys Mol Biol
(2020) - et al.
“Beauty is a light in the heart”: the transformative potential of optogenetics for clinical applications in cardiovascular medicine
Trends Cardiovasc Med
(2015) - et al.
Cardiac applications of optogenetics
Prog Biophys Mol Biol
(2014) - et al.
Light activation of channelrhodopsin-2 in excitable cells of Caenorhabditis elegans triggers rapid behavioral responses
Curr Biol
(2005) - et al.
Intra-tracheal gene delivery of aerosolized SERCA2a to the lung suppresses ventricular arrhythmias in a model of pulmonary arterial hypertension
J Mol Cell Cardiol
(2019) - et al.
Exploring the monocrotaline animal model for the study of pulmonary arterial hypertension: a network approach
Pulm Pharmacol Ther
(2015) - et al.
Suppression of re-entrant and multifocal ventricular fibrillation by the late sodium current blocker ranolazine
J Am Coll Cardiol
(2011) - et al.
Cardiac optogenetics: A novel approach to cardiovascular disease therapy
Europace
(2018)
Optogenetics. Nat Methods
Channelrhodopsin-2, a directly light-gated cation-selective membrane channel
Proc Natl Acad Sci U S A
Illuminating odors: when optogenetics brings to light unexpected olfactory abilities
Learn Mem
Optogenetics: the new molecular approach to control functions of neural cells in epilepsy, depression and tumors of the central nervous system
Am J Cancer Res
Optogenetic termination of cardiac arrhythmia: Mechanistic enlightenment and therapeutic application?
Front Physiol
Optogenetic hyperpolarization of cardiomyocytes terminates ventricular arrhythmia
Front Physiol
Cited by (0)
Funding sources: This work was supported by the National Natural Science Foundation of China (No. 81772044), Hainan Provincial Innovative Research Team Project (No. 2016CXTD012), and Hainan Provincial Personnel Support Project (No. 2019RC368).
Disclosures: The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- 1
Drs Jianyi Li and Long Wang contributed equally to this study.