Tsuji Yumika, Ogata Takehiro, Mochizuki Kentaro, Tamura Shoko, Morishita Yuma, Takamatsu Tetsuro, Matoba Satoaki, Tanaka Hideo
Department of Pathology and Cell Regulation and, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Department of Cardiovascular Medicine, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kyoto, Japan.
Front Physiol. 2024 Feb 23;15:1352911. doi: 10.3389/fphys.2024.1352911. eCollection 2024.
Composite population of myofibroblasts (MFs) within myocardial tissue is known to alter impulse propagation, leading to arrhythmias. However, it remains unclear whether and how MFs alter their propagation patterns when contacting cardiomyocytes (CMs) without complex structural insertions in the myocardium. We attempted to unveil the effects of the one-sided, heterocellular CM-MF connection on the impulse propagation of CM monolayers without the spatial insertion of MFs as an electrical or mechanical obstacle. We evaluated fluo8-based spatiotemporal patterns in impulse propagation of neonatal rat CM monolayers cultured on the microporous membrane having 8-μm diameter pores with co-culture of MFs or CMs on the reverse membrane side (CM-MF model or CM-CM model, respectively). During consecutive pacing at 1 or 2 Hz, the CM monolayers exhibited forward impulse propagation from the pacing site with a slower conduction velocity () and a larger coefficient of directional variation in the CM-MF model than that in the CM-CM model in a frequency-dependent manner (2 Hz >1 Hz). The localized placement of an MF cluster on the reverse side resulted in an abrupt segmental depression of the impulse propagation of the upper CM layer, causing a spatiotemporally non-uniform pattern. Dye transfer of the calcein loaded in the upper CM layer to the lower MF layer was attenuated by the gap-junction inhibitor heptanol. Immunocytochemistry identified definitive connexin 43 (Cx43) between the CMs and MFs in the membrane pores. MF-selective Cx43 knockdown in the MF layer improved both the velocity and uniformity of propagation in the CM monolayer. Heterocellular Cx43 gap junction coupling of CMs with MFs alters the spatiotemporal patterns of myocardial impulse propagation, even in the absence of spatially interjacent and mechanosensitive modulations by MFs. Moreover, MFs can promote pro-arrhythmogenic impulse propagation when in face-to-face contact with the myocardium that arises in the healing infarct border zone.
已知心肌组织中的成肌纤维细胞（MFs）复合群体可改变冲动传导，导致心律失常。然而，当MFs在心肌中不进行复杂结构插入而与心肌细胞（CMs）接触时，它们是否以及如何改变其传导模式仍不清楚。我们试图揭示单侧异细胞CM-MF连接对CM单层冲动传导的影响，而MFs不进行空间插入作为电或机械障碍。我们评估了在直径为8μm的微孔膜上培养的新生大鼠CM单层冲动传导中基于fluo8的时空模式，MFs或CMs分别在反向膜侧共培养（分别为CM-MF模型或CM-CM模型）。在1或2Hz的连续起搏期间，CM单层在CM-MF模型中表现出从起搏部位向前的冲动传导，其传导速度较慢，且方向变化系数比CM-CM模型中更大，呈频率依赖性（2Hz>1Hz）。MF簇在反面的局部放置导致上层CM层的冲动传导突然节段性抑制，从而产生时空不均匀模式。加载在上层CM层中的钙黄绿素向下层MF层的染料转移被缝隙连接抑制剂庚醇减弱。免疫细胞化学鉴定了膜孔中CMs和MFs之间明确的连接蛋白43（Cx43）。MF层中MF选择性Cx43敲低改善了CM单层中传导的速度和均匀性。即使在没有MFs的空间相邻和机械敏感调节的情况下，CMs与MFs的异细胞Cx43缝隙连接耦合也会改变心肌冲动传导的时空模式。此外，当MFs与愈合梗死边缘区出现的心肌面对面接触时，它们可促进致心律失常的冲动传导。
