Recovery of Altered Diabetic Myofibroblast Heterogeneity and Gene Expression Are Associated with CD301b+ Macrophages

Macrophage and Neutrophil Dysfunction in Diabetic Wounds

Significance: The incidence of diabetes continues to rise throughout the world in an alarming rate. Diabetic patients often develop diabetic foot ulcers (DFUs), many of which do not heal. Non-healing DFUs are a major cause of hospitalization, amputation, and increased morbidity. Understanding the underlying mechanisms of impaired healing in DFU is crucial for its management. Recent Advances: This review focuses on the recent advancements on macrophages and neutrophils in diabetic wounds and DFUs. In particular, we discuss diabetes-induced dysregulations and dysfunctions of macrophages and neutrophils. Critical Issues: It is well established that diabetic wounds are characterized by stalled inflammation that results in impaired healing. Recent findings in the field suggest that dysregulation of macrophages and neutrophils plays a critical role in impaired healing in DFUs. The delineation of mechanisms that restore macrophage and neutrophil function in diabetic wound healing is the focus of intense investigation. Future Directions: The breadth of recently generated knowledge on the activity of macrophages and neutrophils in diabetic wound healing is impressive. Experimental models have delineated pathways that hold promise for the treatment of diabetic wounds and DFUs. These pathways may be useful targets for further clinical investigation.

Deep skin fibroblast-mediated macrophage recruitment supports acute wound healing

Epithelial and immune cells have long been appreciated for their contribution to the early immune response after injury; however, much less is known about the role of mesenchymal cells. Using single nuclei RNA-sequencing, we defined changes in gene expression associated with inflammation at 1-day post-wounding (dpw) in mouse skin. Compared to keratinocytes and myeloid cells, we detected enriched expression of pro-inflammatory genes in fibroblasts associated with deeper layers of the skin. In particular, SCA1+ fibroblasts were enriched for numerous chemokines, including CCL2, CCL7, and IL33 compared to SCA1- fibroblasts. Genetic deletion of Ccl2 in fibroblasts resulted in fewer wound bed macrophages and monocytes during injury-induced inflammation with reduced revascularization and re-epithelialization during the proliferation phase of healing. These findings highlight the important contribution of deep skin fibroblast-derived factors to injury-induced inflammation and the impact of immune cell dysregulation on subsequent tissue repair.

Using adjusted local assortativity with Molecular Pixelation unveils colocalization of membrane proteins with immunological significance

Advances in spatial proteomics and protein colocalization are a driving force in the understanding of cellular mechanisms and their influence on biological processes. New methods in the field of spatial proteomics call for the development of algorithms and open up new avenues of research. The newly introduced Molecular Pixelation (MPX) provides spatial information on surface proteins and their relationship with each other in single cells. This allows for in silico representation of neighborhoods of membrane proteins as graphs. In order to analyze this new data modality, we adapted local assortativity in networks of MPX single-cell graphs and created a method that is able to capture detailed information on the spatial relationships of proteins. The introduced method can evaluate the pairwise colocalization of proteins and access higher-order similarity to investigate the colocalization of multiple proteins at the same time. We evaluated the method using publicly available MPX datasets where T cells were treated with a chemokine to study uropod formation. We demonstrate that adjusted local assortativity detects the effects of the stimuli at both single- and multiple-marker levels, which enhances our understanding of the uropod formation. We also applied our method to treating cancerous B-cell lines using a therapeutic antibody. With the adjusted local assortativity, we recapitulated the effect of rituximab on the polarity of CD20. Our computational method together with MPX improves our understanding of not only the formation of cell polarity and protein colocalization under stimuli but also advancing the overall insight into immune reaction and reorganization of cell surface proteins, which in turn allows the design of novel therapies. We foresee its applicability to other types of biological spatial data when represented as undirected graphs.

G-protein-coupled receptor 84 regulates acute inflammation in normal and diabetic skin wounds

Lipids have emerged as potent regulators of immune cell function. In the skin, adipocyte lipolysis increases the local pool of free fatty acids and is essential for coordinating early macrophage inflammation following injury. Here, we investigate G-protein-coupled receptor 84 (GPR84), a medium-chain fatty acid (MCFA) receptor, for its potential to propagate pro-inflammatory signaling after skin injury. GPR84 signaling was identified as a key component of regulating myeloid cell numbers and subsequent tissue repair through in vivo administration of a pharmacological antagonist and the MCFA decanoic acid. We found that impaired injury-induced dermal adipocyte lipolysis is a hallmark of diabetes, and lipidomic analysis demonstrated that MCFAs are significantly reduced in diabetic murine wounds. Furthermore, local administration of decanoic acid rescued myeloid cell numbers and tissue repair during diabetic wound healing. Thus, GPR84 is a readily targetable lipid signaling pathway for manipulating injury-induced tissue inflammation with beneficial effects on acute diabetic healing.

Topical Application of Siberian Pine Essential Oil Formulations Enhance Diabetic Wound Healing

This study aimed to develop novel topical formulations based on a natural component (0.5% of Siberian pine essential oil) and to assess its wound-healing capacity through macroscopic, histopathological, and biochemical examination. The phytochemical profile of Pinus sibirica essential oil (PSEO) and rheological analysis and safety potential of formulations were determined. The wound-healing effect was evaluated on an excision wound model in diabetic Wistar albino rats randomly divided into the following groups topically treated with (1) untreated, (2) 1% silver sulfadiazine, (3) ointment base, (4) gel base, (5) PSEO ointment, and (6) PSEO gel. Formulations containing PSEO were stable and safe for skin application. Three weeks of treatment with both PSEO formulations (ointment and gel) led to a significant reduction in wound size (98.14% and 96.28%, respectively) and a remarkably higher level of total hydroxyproline content (9.69 µg/mg and 7.26 µg/mg dry tissue, respectively) relative to the control group (65.97%; 1.81 µg/mg dry tissue). These findings were in correlation with histopathological results. Topically applied PSEO formulations were associated with a significant reduction in most of the measured pro-oxidants and enhanced activity of the antioxidant defense system enzymes (p < 0.05). Our findings showed that gel and ointment with PSEO demonstrated significant wound-repairing capabilities in the excision wound model.

Fibroblasts: Immunomodulatory factors in refractory diabetic wound healing

Diabetes is a systemic disease in which patients with diabetes may develop peripheral neuropathy of the lower extremities and peripheral vascular disease due to long-term continuous exposure to high glucose. Delayed wound healing in diabetes is one of the major complications of diabetes. Slow wound healing in diabetic patients is associated with high glucose toxicity. When the condition deteriorates, the patient needs to be amputated, which seriously affects the quality of life and even endangers the life of the patient. In general, the delayed healing of diabetes wound is due to the lack of chemokines, abnormal inflammatory response, lack of angiogenesis and epithelial formation, and fibroblast dysfunction. The incidence of several chronic debilitating conditions is increasing in patients with diabetes, such as chronic renal insufficiency, heart failure, and hepatic insufficiency. Fibrosis is an inappropriate deposition of extracellular matrix (ECM) proteins. It is common in diabetic patients causing organ dysfunction. The fibrotic mechanism of diabetic fibroblasts may involve direct activation of permanent fibroblasts. It may also involve the degeneration of fibers after hyperglycemia stimulates immune cells, vascular cells, or organ-specific parenchymal cells. Numerous studies confirm that fibroblasts play an essential role in treating diabetes and its complications. The primary function of fibroblasts in wound healing is to construct and reshape the ECM. Nowadays, with the widespread use of single-cell RNA sequencing (scRNA-seq), an increasing number of studies have found that fibroblasts have become the critical immune sentinel cells, which can detect not only the activation and regulation of immune response but also the molecular pattern related to the injury. By exploring the heterogeneity and functional changes of fibroblasts in diabetes, the manuscript discusses that fibroblasts may be used as immunomodulatory factors in refractory diabetic wound healing, providing new ideas for the treatment of refractory diabetic wound healing.