Enterococcus faecalis sustained infection induces macrophage pro-resolution polarization.

Area of Science:

• Oral microbiology
• Immunology
• Endodontics

Background:

• Enterococcus faecalis is a common bacterium in persistent root canal infections.
• Asymptomatic apical periodontitis often involves chronic inflammation and bacterial presence.

Purpose of the Study:

• To examine macrophage responses during sustained Enterococcus faecalis infection.
• To understand macrophage polarization and function in the context of apical periodontitis.

Main Methods:

• THP-1 macrophages were infected with E. faecalis.
• Assessed phagocytosis, bacterial survival, ROS production, mitochondrial activity, and M1/M2 marker expression.
• Analyzed periapical tissue samples from human biopsies.

Main Results:

• E. faecalis induced macrophage apoptosis and necrosis.
• Surviving macrophages harbored bacteria, maintained mitochondrial activity, and showed increased internal ROS.
• A polarization towards M2 macrophages occurred, mirroring findings in human periapical tissues.

Conclusions:

• Sustained E. faecalis infection leads to macrophage death and a shift to an M2 pro-resolution phenotype.
• This suggests a non-resolved infectious process in apical periodontitis.