Optical capture and defibrillation in rats with monocrotaline-induced myocardial fibrosis 1 year after a single intravenous injection of adeno-associated virus channelrhodopsin-2.

BACKGROUND: Optogenetics uses light to regulate cardiac rhythms and terminate malignant arrhythmias. OBJECTIVE: The purpose of this study was to investigate the long-term validity of optical capture properties based on virus-transfected channelrhodopsin-2 (ChR2) and evaluate the effects of optogenetic-based defibrillation in an in vivo rat model of myocardial fibrosis enhanced by monocrotaline (MCT). METHODS: Fifteen infant rats received jugular vein injection of adeno-associated virus (AAV). After 8 weeks, 5 rats were randomly selected to verify the effectiveness ChR2 transfection. The remaining rats were administered MCT at 11 months. Four weeks after MCT, the availability of 473-nm blue light to capture heart rhythm in these rats was verified again. Ventricular tachycardia (VT) and ventricular fibrillation (VF) were induced by burst stimulation on the basis of enhanced myocardial fibrosis, and the termination effects of the optical manipulation were tested. RESULTS: Eight weeks after AAV injection, there was ChR2 expression throughout the ventricular myocardium as reflected by both fluorescence imaging and optical pacing. Four weeks after MCT, significant myocardial fibrosis was achieved. Light could still trigger the corresponding ectopic heart rhythm, and the pulse width and illumination area could affect the light capture rate. VT/VF was induced successfully in 1-year-observation rats, and the rate of termination of VT/VF under light was much higher than that of spontaneous termination. CONCLUSION: Viral ChR2 transfection can play a long-term role in the rat heart, and light can successfully regulate heart rhythm and defibrillate after cardiac fibrosis.

Near-infrared light driven tissue-penetrating cardiac optogenetics via upconversion nanoparticles in vivo.

This study determines whether near-infrared (NIR) light can drive tissue-penetrating cardiac optical control with upconversion luminescent materials. Adeno-associated virus (AAV) encoding channelrhodopsin-2 (ChR2) was injected intravenously to rats to achieve ChR2 expression in the heart. The upconversion nanoparticles (UCNP) NaYF4:Yb/Tm or upconversion microparticles (UCMP) NaYF4 to upconvert blue light were selected to fabricate freestanding polydimethylsiloxane films. These were attached on the ventricle and covered with muscle tissue. Additionally, a 980-nm NIR laser was programmed and illuminated on the film or the tissue. The NIR laser successfully captured ectopic paced rhythm in the heart, which displays similar manipulation characteristics to those triggered by blue light. Our results highlight the feasibility of tissue-penetration cardiac optogenetics by NIR and demonstrate the potential to use external optical manipulation for non-invasive or weakly invasive applications in cardiovascular diseases.

MicroRNA-155 inhibition attenuates endoplasmic reticulum stress-induced cardiomyocyte apoptosis following myocardial infarction via reducing macrophage inflammation.

Endoplasmic reticulum stress (ERS)-induced cardiomyocyte apoptosis plays an important role in the pathological process following myocardial infarction (MI). Macrophages that express microRNA-155 (miR-155) mediate cardiac inflammation, fibrosis, and hypertrophy. Therefore, we investigated if miR-155 regulates ERS-induced cardiomyocyte apoptosis after MI using a mouse model, lipopolysaccharide (LPS)-induced rat bone marrow derived macrophages (BMDMs)and hypoxia-induced neonatal rat cardiomyocytes (NRCMs). In vivo, miR-155 levelswere significantly higher in the MI group compared to the sham group. MI increasedmacrophage infiltration, nuclear factor-κB (NF-κB) activation, ERS induced-apoptosis, and SOCS1 expression, all of which were attenuated by the miR-155 antagomir, with the exception of SOCS1 expression. Additionally, post-MI cardiac dysfunction was significantly improved by miR-155 inhibition. In vitro, LPS upregulated miR-155 expression in BMDMs, and the miR-155 antagomir decreased LPS-induced macrophage inflammation and NF-κB pathway activation, but increased expression of SOCS1. Hypoxia increased NF-κB pathway activation, ERS marker expression, and apoptosis in NRCMs. Interestingly, conditioned medium from LPS-induced macrophages in combination with the miR-155 antagomir decreased, while the miR-155 agomir increased, the hypoxia-induced effects in NRCM's. The miR-155 agomir effects were reversed by inhibiting the NF-κB pathway in cardiomyocytes. Moreover, SOCS1 knockdown in LPS-induced macrophages promoted NF-κB pathway activation and ERS-induced cardiomyocyte apoptosis in the hypoxia-induced NRCMs, but the SOCS1-siRNA-induced effects were markedly decreased by miR-155 antagomir treatment. These data suggest that miR-155 inhibition attenuates ERS-induced cardiomyocyte apoptosis after MI via reducing macrophage inflammation through the SOCS1/NF-κB pathway.

Flexible and precise control of cardiac rhythm with blue light.

Optogenetics is an innovative method for precise control of biological function, which makes light manipulation displays more advantages than electric energy because of contactless spatial flexibility and cell-to-cell synchronous communication. The aim of this study was to perform different illumination modes with blue laser to investigate optical control of the mice hearts. In this study, we transfected the light sensitive protein ChR2(H134R) into mouse hearts, which were illuminated with a 473 nm laser on the Langendorff apparatus. We recorded all the signals of electrograms (EGs), epicardium monophasic action potential (MAPs) and light output signals to analyze myocardial electrical activity. EGs and MAP showed that ChR2 expression in the heart can be flexibly controlled by blue light across different illumination sites with corresponding triggered ectopic rhythm. Illumination intensity, pulse duration, and impulse frequency were associated with the light capture rate. Continuous illumination with the threshold intensity on the left ventricle had little influence on sinus rhythm and ventricular electrophysiology. Our results support that flexible control of the cardiac rhythm with optogenetics provides an innovative approach to cardiac research and therapy.

Inhibition of microRNA-155 attenuates sympathetic neural remodeling following myocardial infarction via reducing M1 macrophage polarization and inflammatory responses in mice.

Inflammation plays an important role in sympathetic neural remodeling induced by myocardial infarction (MI). MiR-155 is a vital regulator of inflammatory responses, and macrophage-secreted miR-155 promotes cardiac fibrosis and hypertrophy. However, whether miR-155 influences MI-induced sympathetic neural remodeling is not clear. Therefore, we examined the role of miR-155 in MI-induced sympathetic neural remodeling and the related mechanisms in both an mouse model and in lipopolysaccharide (LPS)-stimulated bone marrow-derived macrophages (BMDMs). Our data showed that miR-155 expression was significantly enhanced in the myocardial tissues of MI mice compared to sham mice. Also, MI up-regulated the electrophysiological parameters, M1 macrophage polarization, inflammatory responses, and suppressor of cytokine signaling 1 (SOCS1) expression, which coincided with the increased expression of sympathetic nerve remodeling markers(nerve growth factor, tyrosine hydroxylase and growth-associated protein 43). Except for SOCS1, these proteins were attenuated by miR-155 antagomir. In vitro, LPS-stimulation promoted miR-155 expression in BMDMs. Consistent with the in vivo findings, miR-155 antagomir diminished the LPS-induced M1 macrophage polarization, nuclear factor (NF)-κB activation, and the expression of pro-inflammatory factors and nerve growth factor; but it increased the expression of SOCS1. Inversely, miR-155 agomir significantly potentiated LPS-induced pathophysiological effects in BMDMs. MiR-155 agomir-induced effects were reversed by the NF-κB inhibitor. Mechanistically, treatment with siRNA against SOCS1 augmented the aforementioned LPS-mediated activities, which were antagonized by the addition of miR-155 antagomir. In conclusion, miR-155 inhibition downregulated NGF expression via decreasing M1 macrophage polarization and inflammatory responses dependent on the SOCS1/NF-κB pathway, subsequently diminishing MI-induced sympathetic neural remodeling and ventricular arrhythmias (VAs).