Abstract 20662: Variations in Local Calcium Signaling in Adjacent Cardiomyocytes of the Intact Mouse Heart Detected With Two-Dimensional Confocal Microscopy
Coordinated Ca release in the heart ensures efficient myocardial contraction and electrical stability. Dyssynchronous Ca release within individual cardiomyocytes has been linked to cellular contractile dysfunction. Differences in Ca kinetics in adjacent cells may also provide a substrate for inefficient contraction and arrhythmias. We present an approach to quantify local Ca signals related to the geometry of adjacent cardiomyocytes within the intact heart using 2D confocal microscopy. We observe significant differences in Ca kinetics between adjacent cardiomyocytes.
Methods: Ca transients (CaT, Fluo-8 AM) and cell membranes (Di-4 ANEPPS) were visualized in an epicardial area of 465 μm by 315 μm (12 to 20 cells) in Langendorff-perfused mouse hearts. Images (55/second) from a series of CaT at steady state stimulation (250 ms cycle length) were registered to their relative timepoint in the cardiac cycle to restore local CaT with a temporal resolution of 2 ms. Variation of local CaT within a cardiomyocyte (INTRA) and between adjacent cardiomyocytes (INTER) were compared with regard to amplitude, time to peak (TTP) and time constant of decay (TAU).
Results: Temporal registration of images from successive CaT yielded local signals with good signal/noise ratio (N= 4 hearts, n= 8 regions). Along the long axis but not along the short axis of cardiomyocyte orientation the variation of CaT amplitude was significantly larger between that within cells (INTER 51.49 ±23.57% vs. INTRA <0.01 ±0.001% of global Ca amplitude). Variation in TTP Ca was comparable in all directions, but TAU also tended to vary more along the long axis (INTER 68.50 ±27.03% vs. INTRA 37.74 ±13.17%). Isoproterenol (10 μM) significantly increased the differences in TAU between adjacent cardiomyocytes along the short axis but not along the long axis.
Summary: We present an approach to detect and analyze local Ca signals in Langendorff-perfused intact mouse hearts with high temporal and spatial resolution, taking into account 2D orientation of the cells. We observed significant differences in the synchrony of Ca signals along the long and short axis of adjacent cardioymyocytes. Alterations in synchrony of Ca signals in neighboring cells may contribute to the substrate in cardiac remodeling.
Author Disclosures: K.P. Hammer: None. B.M. Pieske: None. F.R. Heinzel: None.
- © 2014 by American Heart Association, Inc.