Ontogeny of arterial macrophages defines their functions in homeostasis and inflammation

Arterial macrophages have different developmental origins, but the association of macrophage ontogeny with their phenotypes and functions in adulthood is still unclear. Here, we combine macrophage fate-mapping analysis with single-cell RNA sequencing to establish their cellular identity during homeostasis, and in response to angiotensin-II (AngII)-induced arterial inflammation. Yolk sac erythro-myeloid progenitors (EMP) contribute substantially to adventitial macrophages and give rise to a defined cluster of resident immune cells with homeostatic functions that is stable in adult mice, but declines in numbers during ageing and is not replenished by bone marrow (BM)-derived macrophages. In response to AngII inflammation, increase in adventitial macrophages is driven by recruitment of BM monocytes, while EMP-derived macrophages proliferate locally and provide a distinct transcriptional response that is linked to tissue regeneration. Our findings thus contribute to the understanding of macrophage heterogeneity, and associate macrophage ontogeny with distinct functions in health and disease. Arterial macrophages develop from either yolk sac or bone marrow progenitors. Here, the author show that ageing-induced reduction of arterial macrophages is not replenished by bone marrow-derived cells, but under inflammatory conditions circulating monocytes are recruited to maintain homeostasis, while arterial macrophages of yolk sac origin carry out tissue repair.