(3) Our study provides a mechanism of how the loss of tissue-resident macrophages is sensed and establishes the new concept that metabolic cues from the tissue microenvironment instruct the differentiation of recruited monocytes into lung macrophages.
(2) We found that fibroblasts produce 7alpha,25-dihydroxycholesterol in response to resident macrophage depletion, which recruits monocytes via the oxysterol receptor GPR183 to replenish macrophage niches in the lung.
(1) We used single-cell RNA-sequencing and new macrophage depletion models to identify niche-derived signals that promote monocyte-derived macrophages.
We discovered that cholesterol metabolites (oxysterols) recognized by the receptor GPR183 attract monocytes to repopulate depleted lung macrophage niches.