Anna E. Boniakowski

Macrophage-Mediated Inflammation in Normal and Diabetic Wound Healing

The healing of cutaneous wounds is dependent on the progression through distinct, yet overlapping phases of wound healing, including hemostasis, inflammation, proliferation, and resolution/remodeling. The failure of these phases to occur in a timely, progressive fashion promotes pathologic wound healing. The macrophage (MΦ) has been demonstrated to play a critical role in the inflammatory phase of tissue repair, where its dynamic plasticity allows this cell to mediate both tissue-destructive and -reparative functions. The ability to understand and control both the initiation and the resolution of inflammation is critical for treating pathologic wound healing. There are now a host of studies demonstrating that metabolic and epigenetic regulation of gene transcription can influence MΦ plasticity in wounds. In this review, we highlight the molecular and epigenetic factors that influence MΦ polarization in both physiologic and pathologic wound healing, with particular attention to diabetic wounds.

Notch regulates macrophage-mediated inflammation in diabetic wound healing

Macrophages are essential immune cells necessary for regulated inflammation during wound healing. Recent studies have identified that Notch plays a role in macrophage-mediated inflammation. Thus, we investigated the role of Notch signaling on wound macrophage phenotype and function during normal and diabetic wound healing. We found that Notch receptor and ligand expression are dynamic in wound macrophages during normal healing. Mice with a myeloid-specific Notch signaling defect (DNMAMLfloxedLyz2Cre+) demonstrated delayed early healing (days 1–3) and wound macrophages had decreased inflammatory gene expression. In our physiologic murine model of type 2 diabetes (T2D), Notch receptor expression was significantly increased in wound macrophages on day 6, following the initial inflammatory phase of wound healing, corresponding to increased inflammatory cytokine expression. This increase in Notch1 and Notch2 was also observed in human monocytes from patients with T2D. Further, in prediabetic mice with a genetic Notch signaling defect (DNMAMLfloxedLyz2Cre+ on a high-fat diet), improved wound healing was seen at late time points (days 6–7). These findings suggest that Notch is critical for the early inflammatory phase of wound healing and directs production of macrophage-dependent inflammatory mediators. These results identify that canonical Notch signaling is important in directing macrophage function in wound repair and define a translational target for the treatment of non-healing diabetic wounds.

The Histone Methyltransferase, MLL1, Directs Macrophage-Mediated Inflammation in Wound Healing and is Altered in a Murine Model of Obesity and Type 2 Diabetes

Macrophages are critical for the initiation and resolution of the inflammatory phase of wound repair. In diabetes, macrophages display a prolonged inflammatory phenotype in late wound healing. Mixed-lineage leukemia-1 (MLL1) has been shown to direct gene expression by regulating nuclear factor-κB (NF-κB)–mediated inflammatory gene transcription. Thus, we hypothesized that MLL1 influences macrophage-mediated inflammation in wound repair. We used a myeloid-specific Mll1 knockout (Mll1f/fLyz2Cre+) to determine the function of MLL1 in wound healing. Mll1f/fLyz2Cre+ mice display delayed wound healing and decreased wound macrophage inflammatory cytokine production compared with control animals. Furthermore, wound macrophages from Mll1f/fLyz2Cre+ mice demonstrated decreased histone H3 lysine 4 trimethylation (H3K4me3) (activation mark) at NF-κB binding sites on inflammatory gene promoters. Of note, early wound macrophages from prediabetic mice displayed similarly decreased MLL1, H3K4me3 at inflammatory gene promoters, and inflammatory cytokines compared with controls. Late wound macrophages from prediabetic mice demonstrated an increase in MLL1, H3K4me3 at inflammatory gene promoters, and inflammatory cytokines. Prediabetic macrophages treated with an MLL1 inhibitor demonstrated reduced inflammation. Finally, monocytes from patients with type 2 diabetes had increased Mll1 compared with control subjects without diabetes. These results define an important role for MLL1 in regulating macrophage-mediated inflammation in wound repair and identify a potential target for the treatment of chronic inflammation in diabetic wounds.

Dysfunctional Wound Healing in Diabetic Foot Ulcers: New Crossroads

Purpose of ReviewDiabetic foot ulcerations (DFU) affect 25% of patients with diabetes mellitus during their lifetime and constitute a major health problem as they are often recalcitrant to healing due to a constellation of both intrinsic and extrinsic factors. The purpose of this review is to (1) detail the current mechanistic understanding of DFU formation and (2) highlight future therapeutic targets.Recent FindingsFrom a molecular perspective, DFUs exhibit a chronic inflammatory predisposition. In addition, increased local hypoxic conditions and impaired cellular responses to hypoxia are pathogenic factors that contribute to delayed wound healing. Finally, recent evidence suggests a role for epigenetic alterations, including microRNAs, in delayed DFU healing due to the complex interplay between genes and the environment.SummaryIn this regard, notable progress has been made in the molecular and genetic understanding of DFU formation. However, further studies are needed to translate preclinical investigations into clinical therapies.

Ly6CHi Blood Monocyte/Macrophage Drive Chronic Inflammation and Impair Wound Healing in Diabetes Mellitus

Objective— Wound monocyte-derived macrophage plasticity controls the initiation and resolution of inflammation that is critical for proper healing, however, in diabetes mellitus, 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 (monocyte chemoattractant protein-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 proinflammatory and profibrotic genes compared with 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.

The Clinical Impact of Cardiology Consultation Prior to Major Vascular Surgery

Objective: To understand statewide variation in preoperative cardiology consultation prior to major vascular surgery and to determine whether consultation was associated with differences in perioperative myocardial infarction (poMI). Summary Background Data: Medical consultation prior to major vascular surgery is obtained to reduce perioperative risk. Despite perceived benefit of preoperative consultation, evidence is lacking specifically for major vascular surgery on the effect of preoperative cardiac consultation. Methods: Patient and clinical data were obtained from a statewide vascular surgery registry between January 2012 and December 2014. Patients were risk stratified by revised cardiac risk index category and compared poMI between patients who did or did not receive a preoperative cardiology consultation. We then used logistic regression analysis to compare the rate of poMI across hospitals grouped into quartiles by rate of preoperative cardiology consultation. Results: Our study population comprised 5191 patients undergoing open peripheral arterial bypass (n = 3037), open abdominal aortic aneurysm repair (n = 332), or endovascular aneurysm repair (n = 1822) at 29 hospitals. At the patient level, after risk-stratification by revised cardiac risk index category, there was no association between cardiac consultation and poMI. At the hospital level, preoperative cardiac consultation varied substantially between hospitals (6.9%–87.5%, P <0.001). High preoperative consulting hospitals (rate >66%) had a reduction in poMI (OR, 0.52; confidence interval: 0.28–0.98; P <0.05) compared with all other hospitals. These hospitals also had a statistically greater consultation rate with a variety of medical specialties. Conclusions: Preoperative cardiology consultation for vascular surgery varies greatly between institutions, and does not appear to impact poMI at the patient level. However, reduction of poMI was noted at the hospitals with the highest rate of preoperative cardiology consultation as well as a variety of medical services, suggesting that other hospital culture effects play a role.

Impact of a resident's sex on intraoperative entrustment of surgery trainees

Background: Optimizing intraoperative education is critical for development of autonomous residents. Faculty decisions concerning intraoperative entrustment determine the degree to which a resident gains intraoperative responsibility. Accordingly, residents exhibit entrustable behaviors that further faculty entrustment in the operating room. Little empiric evidence exists evaluating how the sex of a resident influences faculty‐resident decisions of entrustment. Studies involving perception‐based measurements of autonomy report inequities for women residents. We sought to assess faculty behaviors in entrustment in relation to resident sex using OpTrust, a third‐party objective measurement tool. Methods: From September 2015 to June 2017 at the University of Michigan, surgical cases were observed and entrustment behaviors were rated using OpTrust. Critical case sampling was used to generate variation in operation type, case difficulty, faculty‐resident pairings, faculty experience, and the level of the residents training. Independent sample t‐tests were conducted to compare faculty entrustment scores, as well as resident entrustability scores. Results: A total of 56 faculty and 73 residents were observed across 223 surgical cases from 4 surgical specialties: general, plastic, thoracic, and vascular. There was no difference in faculty entrustment or entrustability scores between women and men (2.54 vs 2.35, P = .117 and 2.32 vs 2.22, P = .393, respectively). Conclusion: Using OpTrust scores, we found that a residents sex does not appear to influence faculty entrustment in the OR. Faculty entrustment scores for women and men residents are similar across cases. This observation suggests that during the intraoperative interaction, faculty are not extending entrustment or opportunities for autonomy differently to women or men. Future research is needed to identify and measure perioperative elements that inform resident autonomy, which may contribute to inequities for women residents.

Murine macrophage chemokine receptor CCR2 plays a crucial role in macrophage recruitment and regulated inflammation in wound healing

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, Ly6CHi 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.

Bridging the gap: The intersection of entrustability and perceived autonomy for surgical residents in the OR

BACKGROUND Faculty entrustment decisions affect resident entrustability behaviors and surgical autonomy. The relationship between entrustability and autonomy is not well understood. This pilot study explores that relationship. METHODS 108 case observations were completed. Entrustment behaviors were rated using OpTrust. Residents completed a Zwisch self-assessment to measure surgical autonomy. Resident perceived autonomy was collected for 67 cases used for this pilot study. RESULTS Full entrustability was observed in 5 of the 108 observed cases. Residents in our study did not report full autonomy. Spearmans rank correlation coefficient identified that resident entrustability was positively correlated with perceived resident autonomy (ρ = 0.66, p < 0.05). Ordinal logistic regression assessed the relationship between resident entrustability and autonomy. The relationship persisted while controlling for PGY level, gender, and case complexity (OR = 8.42, SEM = 4.54, p < 0.000). CONCLUSIONS Resident entrustability is positively associated with perceived autonomy, yet full entrustability is not translating to the perception of full autonomy for residents.

The effects of preoperative cardiology consultation prior to elective abdominal aortic aneurysm repair on patient morbidity

Objectives The relationship between preoperative medical consultations and postoperative complications has not been extensively studied. Thus, we investigated the impact of preoperative consultation on postoperative morbidity following elective abdominal aortic aneurysm repair. Methods A retrospective review was conducted on 469 patients (mean age 72 years, 20% female) who underwent elective abdominal aortic aneurysm repair from June 2007 to July 2014. Data elements included detailed medical history, preoperative cardiology consultation, and postoperative complications. Primary outcomes included 30-day morbidity, consult-specific morbidity, and mortality. A bivariate probit regression model accounting for the endogeneity of binary preoperative medical consult and patient variability was estimated with a maximum likelihood function. Results Eighty patients had preoperative medical consults (85% cardiology); thus, our analysis focuses on the effect of cardiac-related preoperative consults. Hyperlipidemia, increased aneurysm size, and increased revised cardiac risk index increased likelihood of referral to cardiology preoperatively. Surgery type (endovascular versus open repair) was not significant in development of postoperative complications when controlling for revised cardiac risk index (p = 0.295). After controlling for patient comorbidities, there was no difference in postoperative cardiac-related complications between patients who did and did not undergo cardiology consultation preoperatively (p = 0.386). Conclusions When controlling for patient disease severity using revised cardiac risk index risk stratification, preoperative cardiology consultation is not associated with postoperative cardiac morbidity.