An unrestrained proinflammatory M1 macrophage population induced by iron impairs wound healing in humans and mice
Anca Sindrilaru, … , Cord Sunderkötter, Karin Scharffetter-Kochanek
Anca Sindrilaru, … , Cord Sunderkötter, Karin Scharffetter-Kochanek
Published February 7, 2011
Citation Information: J Clin Invest. 2011;121(3):985-997. https://doi.org/10.1172/JCI44490.
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An unrestrained proinflammatory M1 macrophage population induced by iron impairs wound healing in humans and mice

Abstract

Uncontrolled macrophage activation is now considered to be a critical event in the pathogenesis of chronic inflammatory diseases such as atherosclerosis, multiple sclerosis, and chronic venous leg ulcers. However, it is still unclear which environmental cues induce persistent activation of macrophages in vivo and how macrophage-derived effector molecules maintain chronic inflammation and affect resident fibroblasts essential for tissue homeostasis and repair. We used a complementary approach studying human subjects with chronic venous leg ulcers, a model disease for macrophage-driven chronic inflammation, while establishing a mouse model closely reflecting its pathogenesis. Here, we have shown that iron overloading of macrophages — as was found to occur in human chronic venous leg ulcers and the mouse model — induced a macrophage population in situ with an unrestrained proinflammatory M1 activation state. Via enhanced TNF-α and hydroxyl radical release, this macrophage population perpetuated inflammation and induced a p16INK4a-dependent senescence program in resident fibroblasts, eventually leading to impaired wound healing. This study provides insight into the role of what we believe to be a previously undescribed iron-induced macrophage population in vivo. Targeting this population may hold promise for the development of novel therapies for chronic inflammatory diseases such as chronic venous leg ulcers.

Authors

Anca Sindrilaru, Thorsten Peters, Stefan Wieschalka, Corina Baican, Adrian Baican, Henriette Peter, Adelheid Hainzl, Susanne Schatz, Yu Qi, Andrea Schlecht, Johannes M. Weiss, Meinhard Wlaschek, Cord Sunderkötter, Karin Scharffetter-Kochanek

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Figure 2

The identified macrophage population mounts an unrestrained proinflammatory M1 activation phenotype and accumulates iron in CVUs.

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The identified macrophage population mounts an unrestrained proinflammat...
(A) Representative photomicrographs with double immunostaining of skin cryosections from AWs and CVUs for M1 and M2 macrophage activation markers TNF-α and CD206 or IL-12 and arginase-1. Nuclei were stained with DAPI. Scale bars: 100 μm. Dashed lines indicate the junction between eschar and wound margin. (B) Flow cytometry analysis of wound macrophages purified from AW tissue 2 and 5 days after wounding and CVUs gated according to side scatter (SSC) and CD68 and regated for CD68 and M1 marker TNF-α, CD68 and M2 marker Dectin-1, or TNF-α and Dectin-1. (C) Expression levels for M1 and M2 activation markers of macrophages isolated from 5 AWs and 6 CVUs by flow cytometry. Results are given in RFU (see Methods). Resident skin macrophages were pooled from NS (n ≥ 5). *P < 0.05, **P < 0.01, Student’s t test. (D) Representative photomicrographs of cryosections from CVU patients and AWs from healthy volunteers stained for iron by Perl Prussian blue and immunostained with CD163 for macrophages. Nuclei were stained with PI. High amounts of iron were identified within the CD163+ macrophages (filled arrows) and extracellular space (open arrows) in CVUs, but not AWs. Scale bars: 150 μm.