Nerve-associated macrophages control adipose homeostasis across lifespan and restrain age-related inflammation

Age-related inflammation or 'inflammaging' is a key mechanism that increases disease burden and may control lifespan. How adipose tissue macrophages (ATMs) control inflammaging is not well understood in part because the molecular identities of niche-specific ATMs are incompletely known. Using intravascular labeling to exclude circulating myeloid cells and subsequent single-cell sequencing with orthogonal validation, we define the diversity and alterations in niche resident ATMs through lifespan. Aging led to depletion of vessel-associated macrophages (VAMs), expansion of lipid-associated macrophages (LAMs), and emergence of a unique subset of CD38+ age-associated macrophages (AAMs) in visceral white adipose tissue (VAT). Interestingly, CD169+CD11c- ATMs are enriched in a subpopulation of nerve-associated macrophages (NAMs) that declines with age. Depletion of CD169+ NAMs in aged mice increases inflammaging and impairs lipolysis suggesting that they are necessary for preventing catecholamine resistance in VAT. These findings reveal specialized ATMs control adipose homeostasis and link inflammation to tissue dysfunction during aging. Overall design: Stromal vascular fraction (SVF) cells were isolated via enzymatic digestion of visceral white adipose tissue (VAT) from young (2-month) and aged (21-month) WT C57B/6J male and female mice. Adipose tissue macrophages (ATMs) residing in the tissue parenchyma (CD45+CD45.2iv-CD3-CD19-SiglecF-F4/80+CD11b+) were isolated by fluorescence-activated cell sorting (FACS) and analyzed using scRNA-seq.