Michael Rubart1, Wen Tao1, Xiao-Long Lu1, Simon J Conway1, Sean P Reuter1, Shien-Fong Lin2, Mark H Soonpaa1,3. 1. Wells Centre for Pediatric Research, Indiana University School of Medicine, 1044 West Walnut Street, Indianapolis, IN 46202, USA. 2. Institute of Biomedical Engineering, National Chiao Tung University, Hsinchu, Taiwan. 3. Krannert Institute of Cardiology, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
Abstract
AIMS: Recent studies have demonstrated electrotonic coupling between scar tissue and the surrounding myocardium in cryoinjured hearts. However, the electrical dynamics occurring at the myocyte-nonmyocyte interface in the fibrotic heart remain undefined. Here, we sought to develop an assay to interrogate the nonmyocyte cell type contributing to heterocellular coupling and to characterize, on a cellular scale, its voltage response in the infarct border zone of living hearts. METHODS AND RESULTS: We used two-photon laser scanning microscopy in conjunction with a voltage-sensitive dye to record transmembrane voltage changes simultaneously from cardiomyocytes and adjoined nonmyocytes in Langendorff-perfused mouse hearts with healing myocardial infarction. Transgenic mice with cardiomyocyte-restricted expression of a green fluorescent reporter protein underwent permanent coronary artery ligation and their hearts were subjected to voltage imaging 7-10 days later. Reporter-negative cells, i.e. nonmyocytes, in the infarct border zone exhibited depolarizing transients at a 1:1 coupling ratio with action potentials recorded simultaneously from adjacent, reporter-positive ventricular myocytes. The electrotonic responses in the nonmyocytes exhibited slower rates of de- and repolarization compared to the action potential waveform of juxtaposed myocytes. Voltage imaging in infarcted hearts expressing a fluorescent reporter specifically in myofibroblasts revealed that the latter were electrically coupled to border zone myocytes. Their voltage transient properties were indistinguishable from those of nonmyocytes in hearts with cardiomyocyte-restricted reporter expression. The density of connexin43 expression at myofibroblast-cardiomyocyte junctions was ∼5% of that in the intercalated disc regions of paired ventricular myocytes in the remote, uninjured myocardium, whereas the ratio of connexin45 to connexin43 expression levels at heterocellular contacts was ∼1%. CONCLUSION: Myofibroblasts contribute to the population of electrically coupled nonmyocytes in the infarct border zone. The slower kinetics of myofibroblast voltage responses may reflect low electrical conductivity across heterocellular junctions, in accordance with the paucity of connexin expression at myofibroblast-cardiomyocyte contacts. Published on behalf of the European Society of Cardiology. All rights reserved.
AIMS: Recent studies have demonstrated electrotonic coupling between scar tissue and the surrounding myocardium in cryoinjured hearts. However, the electrical dynamics occurring at the myocyte-nonmyocyte interface in the fibrotic heart remain undefined. Here, we sought to develop an assay to interrogate the nonmyocyte cell type contributing to heterocellular coupling and to characterize, on a cellular scale, its voltage response in the infarct border zone of living hearts. METHODS AND RESULTS: We used two-photon laser scanning microscopy in conjunction with a voltage-sensitive dye to record transmembrane voltage changes simultaneously from cardiomyocytes and adjoined nonmyocytes in Langendorff-perfused mouse hearts with healing myocardial infarction. Transgenic mice with cardiomyocyte-restricted expression of a green fluorescent reporter protein underwent permanent coronary artery ligation and their hearts were subjected to voltage imaging 7-10 days later. Reporter-negative cells, i.e. nonmyocytes, in the infarct border zone exhibited depolarizing transients at a 1:1 coupling ratio with action potentials recorded simultaneously from adjacent, reporter-positive ventricular myocytes. The electrotonic responses in the nonmyocytes exhibited slower rates of de- and repolarization compared to the action potential waveform of juxtaposed myocytes. Voltage imaging in infarcted hearts expressing a fluorescent reporter specifically in myofibroblasts revealed that the latter were electrically coupled to border zone myocytes. Their voltage transient properties were indistinguishable from those of nonmyocytes in hearts with cardiomyocyte-restricted reporter expression. The density of connexin43 expression at myofibroblast-cardiomyocyte junctions was ∼5% of that in the intercalated disc regions of paired ventricular myocytes in the remote, uninjured myocardium, whereas the ratio of connexin45 to connexin43 expression levels at heterocellular contacts was ∼1%. CONCLUSION: Myofibroblasts contribute to the population of electrically coupled nonmyocytes in the infarct border zone. The slower kinetics of myofibroblast voltage responses may reflect low electrical conductivity across heterocellular junctions, in accordance with the paucity of connexin expression at myofibroblast-cardiomyocyte contacts. Published on behalf of the European Society of Cardiology. All rights reserved.
Authors: Sanne de Jong; Toon A B van Veen; Harold V M van Rijen; Jacques M T de Bakker Journal: J Cardiovasc Pharmacol Date: 2011-06 Impact factor: 3.105
Authors: Charles E Murry; Mark H Soonpaa; Hans Reinecke; Hidehiro Nakajima; Hisako O Nakajima; Michael Rubart; Kishore B S Pasumarthi; Jitka Ismail Virag; Stephen H Bartelmez; Veronica Poppa; Gillian Bradford; Joshua D Dowell; David A Williams; Loren J Field Journal: Nature Date: 2004-03-21 Impact factor: 49.962
Authors: T Alexander Quinn; Patrizia Camelliti; Eva A Rog-Zielinska; Urszula Siedlecka; Tommaso Poggioli; Eileen T O'Toole; Thomas Knöpfel; Peter Kohl Journal: Proc Natl Acad Sci U S A Date: 2016-12-07 Impact factor: 11.205
Authors: Menahem Y Rotenberg; Naomi Yamamoto; Erik N Schaumann; Laura Matino; Francesca Santoro; Bozhi Tian Journal: Proc Natl Acad Sci U S A Date: 2019-10-17 Impact factor: 11.205
Authors: Francisca Schultz; Pamela Swiatlowska; Anita Alvarez-Laviada; Jose L Sanchez-Alonso; Qianqian Song; Antoine A F de Vries; Daniël A Pijnappels; Emily Ongstad; Vania M M Braga; Emilia Entcheva; Robert G Gourdie; Michele Miragoli; Julia Gorelik Journal: FASEB J Date: 2019-07-05 Impact factor: 5.191