Heart function is governed by three dynamic systems that control excitation-Ca2+ signaling-contraction in cardiac muscle cells. Dysregulation of these systems lead to cardiac arrhythmias, sudden death, and heart failure. We develop and use photonics technologies to shine light deep into the cellular and molecular details to investigate these dynamic systems. We use epi-fluorescence microscopy and voltage-sensitive indicator to study electrophysiology, confocal-fluorescence imaging and Ca2+ indicator to study Ca2+ signaling system, and second harmonic generation and 2-photon fluorescence microscopy to study the Ca2+ and contraction coupling in sub-cellular microdomains. I will present our research using photonics to decipher heart disease mechanisms.
KEYWORDS: Calcium, Harmonic generation, Luminescence, Heart, Two photon imaging, Second-harmonic generation, Microscopes, Control systems, Line scan image sensors, Signal detection
The objective of this study was to develop a method for simultaneously measuring the calcium and contraction dynamics of single, live cardiomyocytes at high spatial resolutions. Such measurements are important to investigate local calcium release and the mechanical response at the sarcomere level (i.e. the basic unit of contraction), which have important implications in cardiac dysfunction and arrhythmias in conditions such as hypertension, atrial fibrillation, and myocardial infarction. Here, we describe a multimodal second harmonic generation (SHG) and two photon fluorescence (2PF) microscopy technique that is used to simultaneously measure subsarcomere calcium and contraction events at high spatial and temporal resolutions. The method takes advantage of the label-free nature of SHG for imaging the sarcomeres and the high spatial colocalization of the SHG signal and the fluorescence signal excited from calcium indicators. This microscope was used to measure calcium sparks and waves and associated contractions in subcellular microdomains, leading to the generation of subcellular strain. We anticipate this new imaging tool will play an important role in studying mechanical stress-induced heart disease.
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