Macrophages Facilitate Electrical Conduction in the Heart

Area of Science:

• Cardiology
• Immunology
• Electrophysiology

Background:

• The role of tissue-resident macrophages in maintaining normal heart function is not fully understood.
• Cardiac macrophages' specific contributions to the heart's electrical system remain largely unknown.

Purpose of the Study:

• To investigate the function of cardiac macrophages in the steady-state heart.
• To determine the involvement of cardiac macrophages in cardiac electrical conduction, particularly at the atrioventricular node.

Main Methods:

• Utilized mouse models with genetic modifications to study cardiac macrophages.
• Employed techniques including electrophysiology, optogenetics (photostimulation of channelrhodopsin-2), and genetic manipulation (conditional deletion of connexin 43).
• Investigated macrophage-cardiomyocyte coupling via connexin-43 gap junctions and simulated effects using computational modeling.

Main Results:

• Cardiac macrophages, expressing connexin 43, are interspersed with conducting cells in the distal atrioventricular node.
• Macrophages coupled to cardiomyocytes via gap junctions influence cardiomyocyte membrane potential and repolarization.
• Macrophage ablation or connexin 43 deletion in macrophages impaired atrioventricular conduction, leading to atrioventricular block in some models.

Conclusions:

• Cardiac macrophages play a significant role in facilitating normal electrical conduction through the atrioventricular node.
• These findings highlight macrophages as key players in both normal and aberrant cardiac electrical activity.
• Targeting cardiac macrophages may offer new therapeutic strategies for heart conduction disorders.