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Real-Time In Vivo Imaging of Mouse Left Ventricle Reveals Fluctuating Movements of the Intercalated Discs

Authors :
Fuyu Kobirumaki-Shimozawa
Tomohiro Nakanishi
Togo Shimozawa
Takako Terui
Kotaro Oyama
Jia Li
William E. Louch
Shin’ichi Ishiwata
Norio Fukuda
Source :
Nanomaterials, Vol 10, Iss 3, p 532 (2020)
Publication Year :
2020
Publisher :
MDPI AG, 2020.

Abstract

Myocardial contraction is initiated by action potential propagation through the conduction system of the heart. It has been thought that connexin 43 in the gap junctions (GJ) within the intercalated disc (ID) provides direct electric connectivity between cardiomyocytes (electronic conduction). However, recent studies challenge this view by providing evidence that the mechanosensitive cardiac sodium channels Nav1.5 localized in perinexii at the GJ edge play an important role in spreading action potentials between neighboring cells (ephaptic conduction). In the present study, we performed real-time confocal imaging of the CellMask-stained ID in the living mouse heart in vivo. We found that the ID structure was not rigid. Instead, we observed marked flexing of the ID during propagation of contraction from cell to cell. The variation in ID length was between ~30 and ~42 μm (i.e., magnitude of change, ~30%). In contrast, tracking of α-actinin-AcGFP revealed a comparatively small change in the lateral dimension of the transitional junction near the ID (i.e., magnitude of change, ~20%). The present findings suggest that, when the heart is at work, mechanostress across the perinexii may activate Nav1.5 by promoting ephaptic conduction in coordination with electronic conduction, and, thereby, efficiently transmitting excitation-contraction coupling between cardiomyocytes.

Details

Language :
English
ISSN :
20794991
Volume :
10
Issue :
3
Database :
Directory of Open Access Journals
Journal :
Nanomaterials
Publication Type :
Academic Journal
Accession number :
edsdoj.b9179033fbdc427d92c3caf549bc2808
Document Type :
article
Full Text :
https://doi.org/10.3390/nano10030532