Institute for Experimental Cardiovascular Medicine, University Heart Center Freiburg - Bad Krozingen, Faculty of Medicine, University of Freiburg, Elsaesser Str. 2Q, 79110 Freiburg, Germany.
Centro Nacional de Investigaciones Cardiovasculares, Carlos III (CNIC), Myocardial Pathophysiology Area, Melchor Fernández Almagro 3, 28029 Madrid, Spain.
Cardiovasc Res. 2022 Feb 21;118(3):798-813. doi: 10.1093/cvr/cvab126.
Macrophages (MΦ), known for immunological roles, such as phagocytosis and antigen presentation, have been found to electrotonically couple to cardiomyocytes (CM) of the atrioventricular node via Cx43, affecting cardiac conduction in isolated mouse hearts. Here, we characterize passive and active electrophysiological properties of murine cardiac resident MΦ, and model their potential electrophysiological relevance for CM.
We combined classic electrophysiological approaches with 3D florescence imaging, RNA-sequencing, pharmacological interventions, and computer simulations. We used Cx3cr1eYFP/+ mice wherein cardiac MΦ are fluorescently labelled. FACS-purified fluorescent MΦ from mouse hearts were studied by whole-cell patch-clamp. MΦ electrophysiological properties include: membrane resistance 2.2±0.1 GΩ (all data mean±SEM), capacitance 18.3±0.1 pF, resting membrane potential -39.6±0.3 mV, and several voltage-activated, outward or inwardly rectifying potassium currents. Using ion channel blockers (barium, TEA, 4-AP, margatoxin, XEN-D0103, and DIDS), flow cytometry, immuno-staining, and RNA-sequencing, we identified Kv1.3, Kv1.5, and Kir2.1 as channels contributing to observed ion currents. MΦ displayed four patterns for outward and two for inward-rectifier potassium currents. Additionally, MΦ showed surface expression of Cx43, a prerequisite for homo- and/or heterotypic electrotonic coupling. Experimental results fed into development of an original computational model to describe cardiac MΦ electrophysiology. Computer simulations to quantitatively assess plausible effects of MΦ on electrotonically coupled CM showed that MΦ can depolarize resting CM, shorten early and prolong late action potential duration, with effects depending on coupling strength and individual MΦ electrophysiological properties, in particular resting membrane potential and presence/absence of Kir2.1.
Our results provide a first electrophysiological characterization of cardiac resident MΦ, and a computational model to quantitatively explore their relevance in the heterocellular heart. Future work will be focussed at distinguishing electrophysiological effects of MΦ-CM coupling on both cell types during steady-state and in patho-physiological remodelling, when immune cells change their phenotype, proliferate, and/or invade from external sources.
已知巨噬细胞（MΦ）具有免疫作用，例如吞噬作用和抗原呈递，现已发现其通过间隙连接蛋白 43（Cx43）与房室结的心肌细胞（CM）电偶联，从而影响分离的小鼠心脏中的心脏传导。在这里，我们描述了鼠心脏驻留巨噬细胞的被动和主动电生理特性，并建立了它们对 CM 潜在电生理相关性的模型。
我们结合了经典的电生理方法和 3D 荧光成像、RNA 测序、药理学干预和计算机模拟。我们使用 Cx3cr1eYFP/+ 小鼠，其中心脏 MΦ 被荧光标记。使用全细胞膜片钳技术研究从鼠心脏 FACS 纯化的荧光 MΦ。MΦ 的电生理特性包括：膜电阻 2.2±0.1 GΩ（所有数据均为平均值±SEM），电容 18.3±0.1 pF，静息膜电位-39.6±0.3 mV，以及几种电压激活的外向或内向整流钾电流。使用离子通道阻断剂（钡、TEA、4-AP、玛格毒素、XEN-D0103 和 DIDS）、流式细胞术、免疫染色和 RNA 测序，我们鉴定出 Kv1.3、Kv1.5 和 Kir2.1 为参与观察到的离子电流的通道。MΦ 显示出四种外向电流模式和两种内向整流钾电流模式。此外，MΦ 表面表达 Cx43，这是同型和/或异型电偶联的先决条件。实验结果被输入到一个原始的计算模型中，以描述心脏 MΦ 的电生理学。为了定量评估 MΦ 对电偶联 CM 的可能影响，进行了计算机模拟，结果表明 MΦ 可以使静息 CM 去极化，缩短早期和延长晚期动作电位持续时间，其影响取决于偶联强度和单个 MΦ 的电生理特性，特别是静息膜电位和 Kir2.1 的存在/缺失。
我们的研究结果提供了心脏驻留巨噬细胞的第一个电生理特征描述，并建立了一个计算模型来定量研究它们在异细胞心脏中的相关性。未来的工作将集中于区分 MΦ-CM 偶联在稳态和病理生理重塑期间对两种细胞类型的电生理影响，此时免疫细胞改变其表型、增殖和/或从外部来源入侵。
