Cardiac pacing could be a powerful tool for investigating mammalian cardiac electrical conduction systems as well as for treatment of certain cardiac pathologies. However, traditional electrical pacing using pacemaker requires an invasive surgical procedure. Electrical currents from the implanted electrodes can also cause damage to heart tissue, further restricting its utility. Optogenetic pacing has been developed as a promising, non-invasive alternative to electrical stimulation for controlling animal heart rhythms. It induces heart contractions by shining pulsed light on transgene-generated microbial opsins, which in turn activate the light gated ion channels in animal hearts. However, commonly used opsins in optogenetic pacing, such as channelrhodopsin-2 (ChR2), require short light wavelength stimulation (475 nm), which is strongly absorbed and scattered by tissue. Here, we performed optogenetic pacing by expression of recently engineered red-shifted microbial opsins, ReaChR and CsChrimson, in a well-established animal model, Drosophila melanogaster, using the 617 nm stimulation light pulses. The OCM technique enables non-invasive optical imaging of animal hearts with high speed and ultrahigh axial and transverse resolutions. We integrated a customized OCM system with the optical stimulation system to monitor the optogenetic pacing noninvasively. The use of red-sifted opsins enabled deeper penetration of simulating light at lower power, which is promising for applications of optogenetic pacing in mammalian cardiac pathology studies or clinical treatments in the future.
Jing Men, Airong Li, Jason Jerwick, Rudolph E. Tanzi, and Chao Zhou, "Non-invasive red light optogenetic pacing and optical coherence microscopy (OCM) imaging for drosophila melanogaster (Conference Presentation)," Proc. SPIE 10053, Optical Coherence Tomography and Coherence Domain Optical Methods in Biomedicine XXI, 100530R (Presented at SPIE BiOS: January 31, 2017; Published: 19 April 2017); https://doi.org/10.1117/12.2254839.5371723141001.
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