Matsuyama Taka-Aki, Tanaka Hideo, Ishibashi-Ueda Hatsue, Takamatsu Tetsuro
Department of Pathology and Cell Regulation, Kyoto Prefectural University of Medicine Graduate School of Medical Science, Kyoto, Japan.
Department of Pathology, National Cerebral and Cardiovascular Center, Suita, Osaka, Japan.
J Histochem Cytochem. 2017 Nov;65(11):655-667. doi: 10.1369/0022155417730280. Epub 2017 Sep 13.
Surviving Purkinje fibers in myocardial infarct are regarded as an important substrate in arrhythmogenesis. However, poorly understood are functional properties of Purkinje fibers in the infarcted heart. We sought to visualize intracellular Ca ([Ca]) dynamics of Purkinje fiber networks in the mouse myocardial infarct. Using 3- to 4-day-old or 7- to 9-day-old infarcted hearts after the left coronary-artery ligation corresponding, respectively, to acute or healing phase, we conducted rapid fluo4-fluorescence imaging on the endocardial surface of the left ventricular septum by macro-zoom fluorescence microscopy and rapid-scanning confocal microscopy. In contrast with the intact heart, where uniform Ca transients propagated rapidly, the infarcted heart exhibited slow, non-uniform impulse propagations. On confocal microscopy, Purkinje fibers in the peri-infarct zone exhibited non-uniform [Ca] dynamics: beat-to-beat alternans of the Ca transient amplitude in and among the individual fibers, whereas the intact fibers exhibited uniform Ca transients. Such non-uniform [Ca] dynamics were more conspicuous in the acute infarcted hearts than in the healing ones. In accordance with [Ca] dynamics, fixed fluo4-loaded heart preparations exhibited definitive connexin-40 plaques in the peri-infarct Purkinje fibers, whereas the subjacent myocardium presented coagulative necrosis and granulation tissues, respectively. The surviving Purkinje fibers in the peri-infarct zone exhibited non-uniform [Ca] dynamics, which may lead to arrhythmogenesis.
心肌梗死中存活的浦肯野纤维被认为是心律失常发生的重要基质。然而，梗死心脏中浦肯野纤维的功能特性却鲜为人知。我们试图观察小鼠心肌梗死中浦肯野纤维网络的细胞内钙（[Ca]）动力学。使用左冠状动脉结扎后3至4天或7至9天的梗死心脏，分别对应急性或愈合期，我们通过宏观变焦荧光显微镜和快速扫描共聚焦显微镜对左心室间隔的心内膜表面进行了快速fluo4荧光成像。与完整心脏中均匀的钙瞬变快速传播不同，梗死心脏表现出缓慢、不均匀的冲动传播。在共聚焦显微镜下，梗死周边区的浦肯野纤维表现出不均匀的[Ca]动力学：单个纤维内和纤维间钙瞬变幅度的逐搏交替，而完整纤维表现出均匀的钙瞬变。这种不均匀的[Ca]动力学在急性梗死心脏中比在愈合心脏中更明显。根据[Ca]动力学，固定的fluo4负载心脏标本在梗死周边的浦肯野纤维中显示出明确的连接蛋白40斑块，而下方心肌分别呈现凝固性坏死和肉芽组织。梗死周边区存活的浦肯野纤维表现出不均匀的[Ca]动力学，这可能导致心律失常的发生。
