[Heart rate: when macrophages hit the note]

Area of Science:

• Cardiovascular Biology
• Immunology
• Cardiac Electrophysiology

Background:

• Macrophages are crucial for maintaining heart function under various conditions.
• A specific subset of macrophages resides in the atrioventricular node in mice and humans.
• These macrophages form direct connections with cardiomyocytes.

Purpose of the Study:

• To investigate the role of atrioventricular node macrophages in cardiac conduction.
• To explore the therapeutic potential of modulating macrophage function in heart arrhythmias.

Main Methods:

• Investigated macrophage-cardiomyocyte coupling via connexin-43 gap junctions.
• Studied the effects of connexin-43 deletion or macrophage absence on atrioventricular conduction.
• Analyzed the impact on nodal conduction and atrioventricular block progression.

Main Results:

• Macrophages in the atrioventricular node enhance conduction by accelerating cardiomyocyte repolarization.
• Deletion of connexin-43 in macrophages or lack of macrophages impairs nodal conduction.
• These alterations lead to progressive atrioventricular block.

Conclusions:

• Tissue-resident macrophages play a vital role in normal and aberrant cardiac conduction.
• Targeting macrophage function offers a potential therapeutic strategy for heart arrhythmias.
• Understanding macrophage-cardiomyocyte interactions is key for developing new treatments.