Adipose tissue macrophages develop from bone marrow–independent progenitors in Xenopus laevis and mouse.

ATMs develop from early myeloid progenitors, allowing monocyte‐independent ATM replenishment. ATMs have a metabolic impact in mammals as they contribute to metabolically harmful AT inflammation. The control of the ATM number may have therapeutic potential; however, information on ATM ontogeny is scarce. Whereas it is thought that ATMs develop from circulating monocytes, various tissue‐resident Mϕs are capable of self‐renewal and develop from BM‐independent progenitors without a monocyte intermediate. Here, we show that amphibian AT contains self‐renewing ATMs that populate the AT before the establishment of BM hematopoiesis. Xenopus ATMs develop from progenitors of aVBI. In the mouse, a significant amount of ATM develops from the yolk sac, the mammalian equivalent of aVBI. In summary, this study provides evidence for a prenatal origin of ATMs and shows that the study of amphibian ATMs can enhance the understanding of the role of the prenatal environment in ATM development. [ABSTRACT FROM AUTHOR]