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. 2016 Mar 31;7(3):e2167.
doi: 10.1038/cddis.2016.54.

Local proliferation initiates macrophage accumulation in adipose tissue during obesity

C Zheng  1 , Q Yang  1 , J Cao  1 , N Xie  1   2 , K Liu  3 , P Shou  1 , F Qian  1 , Y Wang  1 , Y Shi  1   4   5
Affiliations

Local proliferation initiates macrophage accumulation in adipose tissue during obesity

C Zheng et al. Cell Death Dis. .

Abstract

Obesity-associated chronic inflammation is characterized by an accumulation of adipose tissue macrophages (ATMs). It is generally believed that those macrophages are derived from peripheral blood monocytes. However, recent studies suggest that local proliferation of macrophages is responsible for ATM accumulation. In the present study, we revealed that both migration and proliferation contribute to ATM accumulation during obesity development. We show that there is a significant increase in ATMs at the early stage of obesity, which is largely due to an enhanced in situ macrophage proliferation. This result was obtained by employing fat-shielded irradiation and bone marrow reconstitution. Additionally, the production of CCL2, a pivotal chemoattractant of monocytes, was not found to be increased at this stage, corroborating with a critical role of proliferation. Nonetheless, as obesity proceeds, the role of monocyte migration into adipose tissue becomes more significant and those new immigrants further proliferate locally. These proliferating ATMs mainly reside in crown-like structures formed by macrophages surrounding dead adipocytes. We further showed that IL-4/STAT6 is a driving force for ATM proliferation. Therefore, we demonstrated that local proliferation of resident macrophages contributes to ATM accumulation during obesity development and has a key role in obesity-associated inflammation.

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Figures

Figure 1
Figure 1
Macrophage accumulation in adipose tissue is associated with in situ proliferation at the early stage of obesity. (a) Body weight of mice fed with ND and HFD (n=10 mice in each group). Error bars represent means±S.E.M. ***P<0.001. (b) Hematoxylin and eosin staining showing leukocyte infiltration in eAT and iAT. Scale bars, 100 μM. (c) Flow cytometric analysis of ATM accumulation in eAT and iAT from ND- or HFD-treated mice. Representative dot plots are shown. Numbers on the graphs indicate the percentage of gated events in total events recorded. (d) Flow cytometric analysis of EdU incorporation in ATMs from eAT and iAT of mice on ND or HFD. Mice were pulsed with 10 μg EdU/g body weight for 3 h. (e) Summarizing of the data in panel (d) are shown as means±S.E.M. n=3–4 mice in each group, *P<0.05, **P<0.01. (f) Immunofluorescence staining for EdU-incorporated ATMs in eAT of mice on ND or HFD. Scale bars, 100 μm. (g) Flow cytometric analysis of Ki67 expression in ATMs from eAT and iAT of mice on ND or HFD. (h) Summarizing of the data in panel (g) are shown as means±S.E.M. n=3–4 mice in each group, *P<0.05, **P<0.01. (i) Immunofluorescence staining for Ki67+ ATMs in eAT of mice on ND or HFD. Scale bars, 100 μm
Figure 2
Figure 2
Proliferation of ATMs at the early stage of genetic obesity. (a) Flow cytometric analysis of ATM accumulation in eAT and iAT from 7-week-old leptin receptor-deficient mice (Leprdb/db) and their heterozygous littermates (Leprdb/+). Representative dot plots are shown. Numbers on the graphs indicate the percentage of gated events in total events recorded. (b) Flow cytometric analysis of Ki67 expression in ATMs from eAT and iAT of 7-week-old leptin receptor-deficient mice (Leprdb/db) and heterozygous littermates (Leprdb/+). (c) Flow cytometric analysis of EdU incorporation in ATMs from eAT and iAT of Leprdb/db mice and their heterozygous siblings. (d) Summarizing of the data in panel (c) are shown as means±S.E.M. n=3–4 mice in each group, *P<0.05, **P<0.01
Figure 3
Figure 3
In situ proliferation dominates the initiation of ATM accumulation during obesity. (a) Schematic representation of fat-shielded irradiation and bone marrow transplantation. CD45.2 mice were shielded with lead above the abdomen before lethal irradiation, transplanted with CD45.1 bone marrow, left for reconstitution for 7 weeks, and subjected to diet treatment for 8–12 weeks. Chimerism analysis was performed on leukocytes in blood and eAT. (b) Percentage of chimerism in blood monocytes (CD11b+CD115+) from chimeric mice subjected to ND or HFD for either 8 or 12 weeks. (c) Contribution of CD45.1 donor-derived macrophages to ATM accumulation was analyzed on chimeric mice fed with ND or HFD for 8 or 12 weeks. (d) Contribution of CD45.1 donor-derived eosinophils to adipose tissue eosinophils was analyzed on chimeric mice subjected to ND or HFD for 8 or 12 weeks. The representative results shown in panels (b, c, and d) were from the same group of chimeric mice. (e) Flow cytometric analysis of EdU incorporation in ATMs from chimeric mice on HFD for 12 weeks
Figure 4
Figure 4
The level of CCL2 in adipose tissue and serum. (a) Flow cytometric analysis of CCL2 expression in leukocytes, endothelial cells, and stromal cells in eAT and iAT from ND- or HFD-treated mice. Representative dot plots are shown. CD45+ cells (R1) represent leukocytes, CD31+ cells (R2) represent endothelial cells, and CD45− CD31− cells (R3) represent stromal cells. (b and c) CCL2 expression level in serum of mice at early-stage (treated with diet for 8 weeks) (b) or relatively late-stage (treated with diet for >12 weeks) of obesity (c). Means±S.E.M. are shown. n=5–8 mice in each group, *P<0.05
Figure 5
Figure 5
Proliferating ATMs preferentially reside in CLSs. (a) Immunofluorescence showing the localization of Ki67+ ATMs in HFD-induced obese mice. Arrowheads indicate the ATMs outside CLSs. Scale bars, 100 μm. (b) Percentage of Ki67+ ATMs in CLSs and outside CLSs, summarizing 225 ATMs from 7 immunofluorescence pictures. ***P<0.001, Fisher's exact test
Figure 6
Figure 6
IL-4/STAT6 drives the proliferation of ATMs. (a) Ki67 expression in ATMs from eAT of WT and STAT6−/− mice treated with a complex of IL-4 and IL-4 antibody (to prolong the bioavailability of IL-4 in vivo) or PBS for 48 h. (b) Ki67 expression in ATMs from eAT of WT and STAT6−/− mice on HFD (n=10 in each group). Means±S.E.M. are shown
Figure 7
Figure 7
Schematic depiction of contribution of macrophage proliferation and monocyte recruitment to ATM accumulation in obesity. In lean mice, resident macrophages in adipose tissue are in quiescent status, maintaining a basal level of cellularity by self-renewal. At the early stage of obesity, these resident macrophages proliferate and lead to ATM accumulation, which is driven by stimuli released from adipocytes or/and other immune cells. At the late stage of obesity, ATM accumulation is further augmented by monocyte-derived macrophages, which also exhibit the proliferative capability. These proliferating macrophages always localize in the CLSs and surround the apoptotic adipocyte. Red nuclei indicate that the macrophages are proliferating
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References

    1. Weisberg SP, McCann D, Desai M, Rosenbaum M, Leibel RL, Ferrante AW Jr. Obesity is associated with macrophage accumulation in adipose tissue. J Clin Invest 2003; 112: 1796–1808. - PMC - PubMed
    1. Xu H, Barnes GT, Yang Q, Tan G, Yang D, Chou CJ et al. Chronic inflammation in fat plays a crucial role in the development of obesity-related insulin resistance. J Clin Invest 2003; 112: 1821–1830. - PMC - PubMed
    1. Johnson AMF, Olefsky JM. The origins and drivers of insulin resistance. Cell 2013; 152: 673–684. - PubMed
    1. Hotamisligil GS, Shargill NS, Spiegelman BM. Adipose expression of tumor necrosis factor-alpha: direct role in obesity-linked insulin resistance. Science 1993; 259: 87–91. - PubMed
    1. Uysal KT, Wiesbrock SM, Marino MW, Hotamisligil GS. Protection from obesity-induced insulin resistance in mice lacking TNF-alpha function. Nature 1997; 389: 610–614. - PubMed

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