Convergence between Microglia and Peripheral Macrophages Phenotype during Development and Neuroinflammation

Area of Science:

• Neuroscience
• Immunology
• Cell Biology

Background:

• Microglia, the brain's resident immune cells, originate from yolk sac precursors.
• Distinct markers are believed to differentiate microglia from peripheral macrophages.
• Understanding these differences is crucial for neuroinflammatory research.

Purpose of the Study:

• To investigate age-dependent variations in microglia and peripheral macrophage phenotypes.
• To determine if peripheral macrophages express known microglia-specific markers.
• To examine marker expression under physiological and neuroinflammatory conditions.

Main Methods:

• Transcriptome profiling of microglia across the lifespan.
• Comparison with peripheral macrophages in wild-type and bone marrow chimera mouse models.
• Analysis under physiological and chronic neuroinflammatory settings.

Main Results:

• Phenotypic differences between microglia and peripheral macrophages are age-dependent.
• Peripheral macrophages express common microglia markers (e.g., Fcrls, P2ry12, Tmem119, Trem2) during development.
• CNS-infiltrating macrophages acquire microglial markers during chronic neuroinflammation.

Conclusions:

• Microglia-specific markers are not exclusive and vary with age and pathology.
• The central nervous system niche can induce microglial phenotypes in peripheral myeloid cells.
• Myeloid cell plasticity suggests a functional convergence, impacting neuroinflammatory and cell therapy strategies.