Inflammatory Ly6Chi monocytes and their conversion to M2 macrophages drive atherosclerosis regression
Karishma Rahman, … , P’ng Loke, Edward A. Fisher
Karishma Rahman, … , P’ng Loke, Edward A. Fisher
Published June 26, 2017
Citation Information: J Clin Invest. 2017;127(8):2904-2915. https://doi.org/10.1172/JCI75005.
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Research Article Cardiology Vascular biology

Inflammatory Ly6Chi monocytes and their conversion to M2 macrophages drive atherosclerosis regression

Abstract

Atherosclerosis is a chronic inflammatory disease, and developing therapies to promote its regression is an important clinical goal. We previously established that atherosclerosis regression is characterized by an overall decrease in plaque macrophages and enrichment in markers of alternatively activated M2 macrophages. We have now investigated the origin and functional requirement for M2 macrophages in regression in normolipidemic mice that received transplants of atherosclerotic aortic segments. We compared plaque regression in WT normolipidemic recipients and those deficient in chemokine receptors necessary to recruit inflammatory Ly6Chi (Ccr2–/– or Cx3cr1–/–) or patrolling Ly6Clo (Ccr5–/–) monocytes. Atherosclerotic plaques transplanted into WT or Ccr5–/– recipients showed reduced macrophage content and increased M2 markers consistent with plaque regression, whereas plaques transplanted into Ccr2–/– or Cx3cr1–/– recipients lacked this regression signature. The requirement of recipient Ly6Chi monocyte recruitment was confirmed in cell trafficking studies. Fate-mapping and single-cell RNA sequencing studies also showed that M2-like macrophages were derived from newly recruited monocytes. Furthermore, we used recipient mice deficient in STAT6 to demonstrate a requirement for this critical component of M2 polarization in atherosclerosis regression. Collectively, these results suggest that continued recruitment of Ly6Chi inflammatory monocytes and their STAT6-dependent polarization to the M2 state are required for resolution of atherosclerotic inflammation and plaque regression.

Authors

Karishma Rahman, Yuliya Vengrenyuk, Stephen A. Ramsey, Noemi Rotllan Vila, Natasha M. Girgis, Jianhua Liu, Viktoria Gusarova, Jesper Gromada, Ada Weinstock, Kathryn J. Moore, P’ng Loke, Edward A. Fisher

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Figure 6

Lack of STAT6 in recipient mice prevents M2 macrophage enrichment of plaques and impairs atherosclerosis regression.

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Lack of STAT6 in recipient mice prevents M2 macrophage enrichment of pla...
Analysis of aortic arch plaques from mice 3 days after transplantation into Apoe–/– (Progr; n = 6), WT (Regr; n = 6), or Stat6–/– (n = 6) mice for (A) lesion area, (B) immunohistochemical staining for the macrophage marker CD68, (C) Oil red O staining for neutral lipid, and (D) immunohistochemical staining for the M1 macrophage marker MCP-1 and the M2 macrophage marker MR (CD206); **P < 0.001 compared with Apoe–/– progression group using 1-way ANOVA with Dunnett’s multiple comparisons testing. (E) Representative images of aortic plaques stained for CD68, Oil red O (ORO), MCP-1, and CD206, imaged at ×40 magnification. (F) qRT-PCR analysis of mRNA expression of newly recruited monocyte-derived macrophage marker (Apoe), CD206 (M2) (Arg1 and Cd206), and M1 (Ccl2) macrophage markers in CD68+ cells laser captured from the aortic arch plaques 3 days after transplant into WT and Stat6–/– recipient mice (n = 4–7 per group). *P < 0.05 using unpaired t testing.