Cardiac resident macrophages in AV node conduction

房室（AV）传导异常是常见的，如果不进行治疗， 起搏器我们最近发现巨噬细胞栖息在小鼠和人类的房室结中， Cd 11 bDTR小鼠中巨噬细胞的消耗导致完全AV阻滞。在正常的鼠房室结中， 巨噬细胞通过连接蛋白43与传导细胞电偶联。这种电紧张耦合产生了一种 巨噬细胞和传导性心肌细胞之间的源库关系。遗传干扰 巨噬细胞-肌细胞偶联减弱房室传导，而光遗传学增强通讯 改善房室结功能。这些数据，我们最近发表在细胞，建立居民， 巨噬细胞增加房室结传导的保真度。我们继续这项工作， 在巨噬细胞耗竭后的研究中，发现所有患有AV阻滞的小鼠都死亡。在为此做的前期工作中， 应用中，我们采用了一种小鼠植入式起搏器系统，并能够为小鼠起搏数周。 周我们建议在Cd 11bDTR小鼠中使用这种技术。我们会进行研究， AV结巨噬细胞的功能，以推进我们的长期翻译目标， 巨噬细胞靶向疗法作为传导障碍的新选择。我们会在心脏植入起搏器 Cd 11bDTR小鼠，并在巨噬细胞耗竭后将其起搏长达三个月。我们将检验这个假设 如果用起搏器支持小鼠，AV结传导将自发恢复， 组织巨噬细胞的恢复。我们将通过心电图遥测结合 体内电生理和离体光学标测研究，以提供AV的全面评估 节点功能恢复后，我们将分离房室结，以研究细胞和结构景观， 特别关注巨噬细胞数量、亚群异质性和FACS空间分布，单细胞 RNA测序和成像。利用联体共生，我们将确定心脏巨噬细胞是否重新繁殖 来自循环单核细胞或来自组织祖细胞。我们将进一步测试增强组织 巨噬细胞数量将影响房室结恢复。由于小鼠房室结巨噬细胞减少， 缺乏巨噬细胞集落刺激因子（M-CSF），我们将用M-CSF治疗巨噬细胞耗尽的小鼠， 检验这样的治疗将增加剩余AV结巨噬细胞的局部增殖的假设，和 从而引导房室结传导的恢复。我们还将探讨其他生长激素的影响， 骨髓细胞补充在一个翻译的目标，我们将研究巨噬细胞，其他非心肌细胞和 从房室传导阻滞患者获得的人类房室结的结构重塑过程。我们的协作 应用程序联合了一个跨学科的团队，在电生理学，免疫学和 生物工程虽然这项新的研究计划雄心勃勃，但我们相信我们的初步数据表明， 可行性，并为我们提供了一个独特的机会，研究具有高度临床相关性的问题。

Atrioventricular (AV) conduction abnormalities are common and potentially lethal if not treated with a pacemaker. We recently discovered that macrophages inhabit the mouse and human AV node, and that depletion of macrophages in the Cd11bDTR mouse leads to complete AV block. In the normal murine AV node, macrophages electrically couple to conducting cells via connexin 43. This electrotonic coupling creates a source-sink relationship between macrophages and conducting cardiomyocytes. Genetic interference with macrophage-myocyte coupling weakened AV conduction while optogenetically enhanced communication improved AV node function. These data, which we recently published in Cell, establish that resident macrophages augment the fidelity of AV node conduction. We have continued this work by performing survival studies after macrophage depletion, finding that all mice with AV block die. In preliminary work for this application, we adopted an implantable pacemaker system for mice, and were able to pace mice for several weeks. We here propose to use this technique in Cd11bDTR mice. We will conduct studies to better understand the function of AV node macrophages in order to advance our long-term translational goal to one day develop macrophage-targeted therapeutics as a new option for conduction disorders. We will implant pacemakers into Cd11bDTR mice and pace them for up to three months after macrophage depletion. We will test the hypothesis that, if the mice are supported with a pacemaker, spontaneous recovery of AV node conduction will occur due to recovery of tissue macrophages. We will test for AV node recovery by ECG telemetry in conjunction with in vivo electrophysiological and ex vivo optical mapping studies to provide a comprehensive assessment of AV node function. After recovery, we will isolate AV nodes to investigate the cellular and structural landscape with special focus on macrophage numbers, subset heterogeneity and spatial distribution by FACS, single-cell RNA-sequencing and imaging. Using parabiosis, we will determine whether cardiac macrophages repopulate from circulating monocytes or from tissue progenitors. We will further test whether enhancing tissue macrophage numbers will influence AV node recovery. Since AV node macrophages are reduced in mice lacking macrophage colony stimulating factor (M-CSF), we will treat macrophage-depleted mice with M-CSF to test the hypothesis that such treatment will increase local proliferation of remaining AV node macrophages, and thus ushers in recovery of AV node conduction. We will also explore other growth hormones with influence on myeloid cell replenishment. In a translational aim, we will study macrophages, other non-cardiomyocytes and structural remodeling processes in human AV nodes obtained from patients with AV block. Our collaborative application unites an interdisciplinary team with expertise in electrophysiology, immunology and bioengineering. While the novel research plan is ambitious, we believe that our preliminary data demonstrate feasibility and provide us with a unique opportunity to study a question with high clinical relevance.