XB-ART-53796J Leukoc Biol January 1, 2017; 102 (3): 845-855.
Adipose tissue macrophages develop from bone marrow-independent progenitors in Xenopus laevis and mouse.
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.
PubMed ID: 28642277
PMC ID: PMC5574031
Article link: J Leukoc Biol
Genes referenced: atm itgam npffr1.1 ptprc rnf128 tal1
Article Images: [+] show captions
|Figure 1. AT Mϕs in X. laevis.(A) Anatomy of the visceral fat depot. Scale bar, 1 cm. (B) Histologic assessment of the fat body by hematoxylin and eosin staining. Scale bar, 100 μm. (C) Enzyme histochemistry and ultrastructure of the fat body stroma, and quantification of ATMs. ACP- and peroxidase (POD)-positive cells in the fat body (top). Scale bar, 50 μm. TEM image of the fat body (bottom left). Arrowheads indicate ATMs (leukocytes with abundant endocytic vesicles). Scale bar, 1 μm. ATM content and percentage of phagocytosing (phag+) cells in the stroma (bottom right). The raw data set is available at the Flow Repository under accession number FR-FCM-ZYZF. (D) FACS analysis of SCs. For TEM images of the sorted RBCs, ATMs, and Lym, and for additional details of the FACS analysis, see Supplemental Fig. 1A–D. (E–G) Identification of phagocytosing cells in AT stroma. Isolated SCs were incubated in vitro with fluorescent latex beads for 4 h. (H) Time-lapse sequence of a phagocytosing ATM. The entire time lapse sequence is shown as Supplemental Video 1. Scale bar, 25 μm. (I) ATMs with ingested fluorescent latex beads (arrows). Scale bar, 15 μm. (J) TEM images of ATMs. Scale bar, 1 μm. Additional TEM images of ATMs are shown in Supplemental Fig. 1A. ac = adipocyte, fb = fat body; FSC = forward scatter, lp = lamellipodia, Lym = lymphocytes, nc = nucleus, ov, ovary; phag− = cells without phagocytosed beads, phag+ = cells with phagocytosed beads, SSC = side scatter, st = stroma, ves = blood vessel, vs = vesicles.|
|Figure 2. Self-renewal of ATMs in X. laevis.(A) Isolated SCs were cultured in vitro and labeled with BrdU (indicated in red; n = 6). In the control experiment, cells were incubated with vehicle only (indicated in gray). Presence of BrdU+ cells was detected by FACS. The raw data set is available in the Flow Repository under accession number FR-FCM-ZYZG. (B) Characterization of BrdU+ cells with FACS. (C) Amount of BrdU+ ATMs after 2–4 h of incubation with BrdU. Histogram shows BrdU labeling after 4 h (n = 3). (D) SCs were cultured in vitro in soft agar. Colonies formed by SCs were detected after 24, 48, and 72 h. Arrow denotes cell-cell attachment site. Scale bar, 50 μm. (E) TEM images of SC colonies formed in soft agar. Representative images (E1-E3). Scale bar, 0.5 μm. cp = cytoplasm, FSC = forward scatter, Lym = lymphocytes, mt = mitochondria, nc = nucleus, SSC = side scatter.|