Arterial Resident But Not Monocyte-Derived Macrophages Require Endothelial CSF1.

Arterial endothelial cell–derived CSF1 is essential for maintaining intimal tissue-resident macrophages in healthy aortas and in 4-week foam cell lesions of Ldlr-/- mice.

• Why it matters: Tissue-resident macrophages persist in atherosclerosis-prone intima, but the specific local CSF1 sources that sustain their niche—and whether monocyte-derived macrophages depend on the same signals—were unclear.
• What they did: Using conditional Csf1 gene deletion (including endothelial-specific and mesenchymal-specific) and systemic CSF1 antibody blockade in normal or hypercholesterolemic Ldlr-/- mice, the study combined Cx3cr1 lineage tracing, Ccr2 tracing, bone marrow transplantation, and en face immunoconfocal macrophage counting.
• The result: Endothelial CSF1 supported T-RMø proliferation and retention, while mesenchymal CSF1 supported adventitial macrophages; endothelial CSF1 was required for optimal macrophage accumulation in 4-week foam cell lesions and for T-RMø maintenance but not monocyte-derived macrophages in atherosclerotic lesions.

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