Abstract 13976: Optogenetic Monitoring of Endocardial Calcium Transients in vivo Using a Minimally Invasive Fiber Optic Approach

Rationale: In vivo electrophysiology and contraction can be studied very well using minimally invasive methods. Contrarily, myocardial calcium signaling cannot be studied in vivo, although it is a crucial aspect of cardiac remodeling. Objective: We aimed to establish a method that can be used to study myocardial calcium signaling in vivo. Methods and Results: We employed the optogenetic fluorescent calcium sensor GCaMP3 to record calcium transients from the left ventricular endocardium of closed chest mice (n=8, inducible, cardiomyocyte[[Unsupported Character - Codename ­]]specific GCaMP3 transgenic overexpression). Excitation of the sensor and detection of fluorescence emission was done using a thin plastic optical fiber (250 μm) that was introduced via the carotid artery into the left ventricular cavity. Combining optogenetics with fiber optics, we were able to record endocardial calcium transients with good signal to noise ratio (6.9 ± 0.2) for up to 30 minutes at physiological heart rates, without...