Objective Wound monocyte-derived macrophage plasticity controls the initiation and resolution of inflammation that are critical for proper healing, however, in diabetes, the resolution of inflammation fails to occur. In diabetic wounds, the kinetics of blood-monocyte recruitment and the mechanisms that control in vivo monocyte/macrophage differentiation remain unknown. Approach and Results Here, we characterized the kinetics and function of Ly6CHi[Lin− (CD3−CD19−NK1.1−Ter-119−)Ly6G−CD11b+] and Ly6CLo[Lin− (CD3−CD19−NK1.1−Ter-119−)Ly6G−CD11b+] monocyte/macrophage subsets in normal and diabetic wounds. Using flow-sorted tdTomato-labeled Ly6CHi monocyte/macrophages, we show Ly6CHi cells transition to a Ly6CLo- phenotype in normal wounds, whereas in diabetic wounds, there is a late, second influx of Ly6CHi cells that fail transition to Ly6CLo. The second wave of Ly6CHi cells in diabetic wounds corresponded to a spike in MCP-1 and selective administration of anti-MCP-1 reversed the second Ly6CHi influx and improved wound healing. To examine the in vivo phenotype of wound monocyte/macrophages, RNA-seq-based transcriptome profiling was performed on flow-sorted Ly6CHi[Lin−Ly6G−CD11b+] and Ly6CLo[Lin−Ly6G−CD11b+] cells from normal and diabetic wounds. Gene transcriptome profiling of diabetic wound Ly6CHi cells demonstrated differences in pro-inflammatory and pro-fibrotic genes compared to controls. Conclusions Collectively, these data identify kinetic and functional differences in diabetic wound monocyte/macrophages and demonstrate that selective targeting of CD11b+Ly6CHi monocyte/macrophages is a viable therapeutic strategy for inflammation in diabetic wounds.

Highlights d Setdb2 regulates macrophage plasticity during normal and pathologic wound repair d Setdb2 expression in wound macrophages depends on IFN-I/ JAK/STAT1 signaling d This pathway is altered in chronic diabetic wounds because of failed surge of IFN-I d Elevated uric acid in diabetic wounds is driven by Setdb2 regulation of Xdh

Abdominal aortic aneurysms (AAAs) are a life-threatening disease for which there is a lack of effective therapy preventing aortic rupture. During AAA formation, pathological vascular remodeling is driven by macrophage infiltration, and the mechanisms regulating macrophage-mediated inflammation remain undefined. Recent evidence suggests that an epigenetic enzyme, JMJD3, plays a critical role in establishing macrophage phenotype. Using single-cell RNA sequencing of human AAA tissues, we identified increased JMJD3 in aortic monocyte/macrophages resulting in up-regulation of an inflammatory immune response. Mechanistically, we report that interferon-β regulates Jmjd3 expression via JAK/STAT and that JMJD3 induces NF-κB–mediated inflammatory gene transcription in infiltrating aortic macrophages. In vivo targeted inhibition of JMJD3 with myeloid-specific genetic depletion (JMJD3f/fLyz2Cre+) or pharmacological inhibition in the elastase or angiotensin II–induced AAA model preserved the repressive H3K27me3 on inflammatory gene promoters and markedly reduced AAA expansion and attenuated macrophage-mediated inflammation. Together, our findings suggest that cell-specific pharmacologic therapy targeting JMJD3 may be an effective intervention for AAA expansion.

Macrophages play a critical role in the establishment of a regulated inflammatory response following tissue injury. Following injury, CCR2 monocytes are recruited from peripheral blood to wound tissue, and direct the initiation and resolution of inflammation that is essential for tissue repair. In pathologic states where chronic inflammation prevents healing, macrophages fail to transition to a reparative phenotype. Using a murine model of cutaneous wound healing, we found that CCR2-deficient mice (CCR2 ) demonstrate significantly impaired wound healing at all time points postinjury. Flow cytometry analysis of wounds from CCR2 and WT mice revealed a significant decrease in inflammatory, Ly6C recruited monocyte/macrophages in CCR2 wounds. We further show that wound macrophage inflammatory cytokine production is decreased in CCR2 wounds. Adoptive transfer of mT/mG monocyte/macrophages into CCR2 and CCR2 mice demonstrated that labeled cells on days 2 and 4 traveled to wounds in both CCR2 and CCR2 mice. Further, adoptive transfer of monocyte/macrophages from WT mice restored normal healing, likely through a restored inflammatory response in the CCR2-deficient mice. Taken together, these data suggest that CCR2 plays a critical role in the recruitment and inflammatory response following injury, and that wound repair may be therapeutically manipulated through modulation of CCR2.

Objective: Sepsis represents an acute life-threatening disorder resulting from a dysregulated host response. For patients who survive sepsis, there remains long-term consequences, including impaired inflammation, as a result of profound immunosuppression. The mechanisms involved in this long-lasting deficient immune response are poorly defined. Approach and Results: Sepsis was induced using the murine model of cecal ligation and puncture. Following a full recovery period from sepsis physiology, mice were subjected to our wound healing model and wound macrophages (CD11b+, CD3−, CD19−, Ly6G−) were sorted. Post-sepsis mice demonstrated impaired wound healing and decreased reepithelization in comparison to controls. Further, post-sepsis bone marrow–derived macrophages and wound macrophages exhibited decreased expression of inflammatory cytokines vital for wound repair (IL [interleukin]-1β, IL-12, and IL-23). To evaluate if decreased inflammatory gene expression was secondary to epigenetic modification, we conducted chromatin immunoprecipitation on post-sepsis bone marrow–derived macrophages and wound macrophages. This demonstrated decreased expression of Mll1 , an epigenetic enzyme, and impaired histone 3 lysine 4 trimethylation (activation mark) at NFκB (nuclear factor kappa-light-chain-enhancer of activated B cells)-binding sites on inflammatory gene promoters in bone marrow–derived macrophages and wound macrophages from postcecal ligation and puncture mice. Bone marrow transplantation studies demonstrated epigenetic modifications initiate in bone marrow progenitor/stem cells following sepsis resulting in lasting impairment in peripheral macrophage function. Importantly, human peripheral blood leukocytes from post-septic patients demonstrate a significant reduction in MLL1 compared with nonseptic controls. Conclusions: These data demonstrate that severe sepsis induces stable mixed-lineage leukemia 1–mediated epigenetic modifications in the bone marrow, which are passed to peripheral macrophages resulting in impaired macrophage function and deficient wound healing persisting long after sepsis recovery.