Efferocytosis induces macrophage proliferation to help resolve tissue injury

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Macrophage efferocytosis of apoptotic cells is crucial for tissue repair.
• Signaling molecules from degraded apoptotic cells can promote resolution.
• The specific mechanisms amplifying efferocytosis benefits require further elucidation.

Purpose of the Study:

• To investigate the role of apoptotic cell DNA hydrolysis products in macrophage proliferation and resolution signaling.
• To identify the molecular pathways involved in efferocytosis-induced macrophage expansion.
• To determine the in vivo relevance of this pathway in models of inflammation and disease regression.

Main Methods:

• Utilized in vitro and in vivo models including zymosan-induced peritonitis, dexamethasone-induced thymocyte apoptosis, and atherosclerosis regression.
• Employed genetic manipulation (hematopoietic Rictor deletion, macrophage Rictor/DNase2a silencing) to probe pathway function.
• Analyzed macrophage proliferation, apoptotic cell clearance, and tissue resolution markers.

Main Results:

• Nucleotides from apoptotic cell DNA hydrolysis by DNase2a activate DNA-PKcs-mTORC2/Rictor, increasing Myc and promoting non-inflammatory macrophage proliferation.
• Efferocytosis-induced macrophage proliferation was observed in vitro and in multiple mouse models.
• Hematopoietic Rictor deletion or DNase2a silencing impaired macrophage proliferation, efferocytosis, and tissue resolution in disease models.

Conclusions:

• Apoptotic cell-derived nucleotides act as signaling molecules that amplify the resolution process by increasing the number of resolving macrophages.
• The DNase2a-DNA-PKcs-mTORC2/Rictor-Myc pathway is a key mechanism linking efferocytosis to macrophage proliferation and tissue repair.
• Targeting this pathway could offer novel therapeutic strategies for inflammatory diseases and promoting tissue regeneration.