The Immunoregulatory Role of Programmed Death-Ligand 1 in Wound Healing Dynamics.

The adverse impact of chronic wounds is felt worldwide. The concerns for advanced wound care product are progressively increasing due to factors such as value for money spent in wound care products. Acute and Chronic wounds are managed in most health facilities in Ghana with sodium chloride (0.9%) infusion solution and povidone iodine fortified with metronidazole solution. The procedure is usually done by the nurse cleaning the wound with the saline solution wet gauze or cotton and then covered with the povidone iodine wet gauze for acute and chronic wounds. For chronic infected wounds, the wound is usually cleaned with saline solution and covered with wet gauze saline or currently with neomycin wound care spray or powdered antibiotics applied on the wounds. But it is popular as many wounds are covered with povidone iodine after wound cleaning in wound care practices in Ghana. Despite all these efforts, many wounds, especially chronic type wounds take a very long time to heal or sometimes fails to heal which reduce the quality of life of the people suffering from the menace. When it happens in this way, many resort to the use of local remedies to cause the wounds to heal but no avail, especially in Ghana where advanced treatment is scare. It is against this background that focal research in wound care was done in Ghana to come out with an innovative pharmaceutical wound care product effective for chronic and acute wounds healing to improve the quality of life of people as global burden of wounds escalates. In a Blind Observational Study for a period of five years in Ghana to observe the wound care products efficacy to heal wounds especially chronic types, the objective of the study was to examine a new product efficacy in chronic wound healing in the targeted population of patients with wounds. A product that has dual purpose of wound care as a cleaning and application agent, also has unique product pharmaceutical characteristics. A scalable, easy- to- use, multi-purpose, multi-use and cost-effective product, able to address the barriers or problems of wounds healing. The areas of consideration as far as wound care are concerned included: The study also sought to observe the product ability to control wound pains, control wound bleeding, control and prevent wound infection, remove wound debris, remove wound exudates effecting wounds healing at reduced healing time and with minimal scar in varied targeted patients’ population. Again, to observe the product with outcome of which to mitigate the long-term effect of chronic wounds like recurrent hospitalizations, financial burden, amputations, deformity, and frequent visit to hospital for wound care. One product, 9G Wound Solution (a cleaning and application product) manufactured by Pat J Health Company Limited, Ghana, was effective in wounds healing, especially, effective chronic wounds healing. The product was used to subject varied patients’ population with wounds on randomized basis, for wound care, and through observation the direct short, intermedial and long-term outcomes recorded of product effectiveness recorded. The outcome reported included control of wound pains, control of wound odor, control of bleeding, control of wound infection, removal of wounds exudates, removal of wound debris and ultimately reduced wound healing time to prevent wounds complications like amputations. The study was progressively extended across 10 regions in Ghana to cover 500 patient population with varied wounds. Patients’ population included those with Diabetic ulcers, Burns, pressure ulcers, venous ulcers, herpes zoster skin ulcers, Perineum wounds, Surgical abdomen-pelvic wounds, Traumatic wounds, Buruli Ulcers, gas gangrene wounds, and Mouth ulcers. The outcome of using the new wound care product were directly observed for the study period. By this observational study, the new product was observed to be superior to the controls as this product was able to heal 99% patients who had wounds, especially chronic wounds for many years, including 20years-old wound at reduced healing rate with no reoccurrence within the study period. The product scientifically readily released to the wound environment modulators capable to address the problems or barriers of wounds and simultaneously promoting modulators effective for wound healing. The product was not only effective in chronic wound healing at reduced time but also controlled wound pains shortly, controlled wound odor shortly, stopped wound bleeding, fought and controlled wound infection. However, using the product needed change of wound dressing every two days. The long-term effect of the product on target population not conclusively observed within the period of the research. We need to continuously observe the reported long-term effect of the product efficacy.

Research progress of exosomes derived from platelet-rich plasma in angiogenesis of chronic diabetic wounds.

Chapter 11 - Role of cytokines and chemokines in wound healing

PD-L1 promotes myofibroblastic activation of hepatic stellate cells by distinct mechanisms selective for TGF-β receptor I versus II.

Background. Chronic diabetic foot ulcers and wounds are significant complications associated with diabetes, comprising approximately 85% of purulent-necrotic lesions affecting the lower extremities. The development of these wounds is influenced by pathogenetic factors such as hyperglycemia, neuropathy, and existing infections, which contribute to metabolic disturbances, including tissue hypoxia and the activation of proteolytic enzymes known as matrix metalloproteinases (MMPs). Aim. To explore the therapeutic potential of autologous plasminogen in facilitating the healing process of diabetic wounds through the modulation of MMP activity. Materials and Methods. The study enrolled 45 patients diagnosed with chronic diabetic wounds, who were assigned to two distinct groups. The control group (n=25) received conventional treatment approaches, while the intervention group consisted of 20 patients treated with autologous plasminogen applications. Results. After 18 days of treatment, a substantial reduction of 3.5-fold in MMP-2 and MMP-9 activity was observed within the intervention group, accompanied by complete wound closure in 16 patients. Additionally, four patients underwent autodermoplasty, successfully achieving wound defect closure through effective graft integration. In contrast, the control group exhibited consistently elevated MMP activity levels throughout the entire observation period. Conclusions. The activity of matrix metalloproteinases (MMPs) in chronic diabetic wounds reaches dramatic levels, making spontaneous wound healing impossible. The application of autologous Pg allows modulation of this activity and creates favorable conditions for wound healing by reducing excessive MMP activity, improving blood supply, and resolving inflammatory processes. Keywords: chronic wounds, diabetes mellitus, matrix metalloproteinases, plasminogen, autodermoplasty.

Surgical infection is one of the most important and important problems of modern medicine. The lack of a universal remedy and method of wound treatment, the difficulty of choosing universal tactics of management of patients with chronic wounds determines the need for further search for new treatments that stimulate reparative processes in chronic wounds, including morphological research methods. The role of cellular regulation in the pathogenesis of the restoration of the morphofunctional state of a chronic wound in the conditions of its damage remains undisclosed. Therefore, the aim of our study was to evaluate the role of myofibroblasts in the healing of chronic purulent-necrotic wounds in the treatment of mesenchymal stem cells using immunohistochemistry. In the experiment we obtained a model of chronic purulent-necrotic wound, which meets all the requirements for quality indicators in the study of morphological changes in chronic wounds and can then be used as a basis for preclinical research. The condition of chronic purulent-necrotic wounds in 120 rats was studied by histological and immunohistochemical methods. Chronic wound was modeled according to the original method of the author: during the formation of a standard skin defect in the interscapular area of the rat with a diameter of 1 cm, the surrounding tissue was superimposed ischemic metal structure to reduce blood flow in the wound area, which significantly slowed the delay. Treatment was started from 28 days from the beginning of wounding, which clinically and histologically corresponded to the chronicity of the wound process. Statistical processing of morphometric parameters was performed using the standard software package “Statistica 6.1”. It was found that the positive dynamics of healing of chronic wounds, using 0.025 % decasan solution, was observed mainly in the early stages (3-7 days), while mesenchymal stem cells (MSC) and MSC cloned in inert gases (MSC-IG) were effective at all stages of the study. The use of MSC and MSC-IG creates favorable conditions for the normal course of regenerative processes and epithelialization of wounds, providing anti-edema and anti-inflammatory effects with activation of myofibroblasts, which increases the healing efficiency of chronic purulent-necrotic wounds. Prospects for the use of MSC in the treatment of chronic wounds are shown.

Stalled healing in chronic wounds is a challenging problem for providers and remains multifactorial in etiology. Older adults with insulin-dependent diabetes are at very high risk. In this case report, two patients with large nonhealing wounds were considered for treatment with daily jet lavage irrigation in an attempt to remove the inflammatory products of their respective chronic wounds and eliminate the persisting biofilm bacteria. Several attempts were made to reduce treatments to two to three times per week, and negative-pressure wound therapy was initiated in both cases only to see the return of inflammation and necrosis of the wound bed. In both cases, the daily jet lavage irrigation was successful in creating a granulating wound bed that slowly healed over many months. One patient died with an open sacral pressure injury, and the other patient died 4 months after complete healing of a large heel pressure injury. The interesting observation is the necessity of daily high-intensity wound irrigation to correct the chronic infectious process. Diabetic chronic wounds in high-risk older adults are recalcitrant to standard wound treatments, and providers should consider daily jet lavage wound irrigation to deal with this problem.

While qualitative aspects of dermal repair differ in wounds of different types, duration, and depths, all wounds must be resurfaced by epidermal keratinocytes before they can be deemed “healed.” Epidermal keratinocytes undergo a series of activation steps in acute wound healing, which are likely to be regulated by autocrine growth control mechanims. The state of epidermal keratinocyte activation in chronic venous wounds is examined in this study in relationship to the correct expression of these changes in acute wound healing. The expression of endogenous growth factor pathways in chronic wounds is presented and changes in the growth activation associated with healing of chronic wounds are studied. The results of this study establish that growth activation of the epidermis is not defective in chronic wounds. The activation of epidermis is likely to be regulated by endogenous keratinocyte cytokine and receptor pathways, suggesting that addition of exogenous epidermal mitogens to chronic wounds is unlikely to further alter epidermal healing. In contrast, some of the therapeutic benefits of hydrocolloid dressings in promoting healing of chronic wounds may be related to their ability to suppress excessive keratinocyte proliferation and activation in chronic wounds.

Macrophages are immune cells known to have a diverse array of functions dependant on the local tissue environment. This thesis aimed to investigate the role of macrophages in the skin. The first aim was to study if targeting inflammatory cytokines and cellular pathways was able to improve the rate of wound closure in acute and/or chronic wounds. These inflammatorypathways included the IL-17/IL-23 axis, the IL-33/ST2 pathway and the NLRP3 inflammasome. The next aim was to identify the role of macrophages in UV irradiation, specifically neonatal UV and the long-term effects in the skin and on local immune suppression. Finally, we aimed to identify the long-term effects of inflammation in the skin on the resident macrophage populations, studying the kinetics of their self-renewal.Macrophages play a vital role in wound healing, with either excessive or insufficient infiltration both causing to impaired healing responses. Current therapies for chronic wounds have poor prognosis and outcomes, and as such the development of alternative treatments are required. We found IL-17 and IL-23 inhibition improved wound closure in obese, diabetic mice by switching the macrophage phenotype from pro-inflammatory to pro-healing. IL-17 secreted from gamma delta T-cells significantly impaired wound closure, and the inhibition of IL-17 and its upstream regulator IL-23 by blocking antibodies was able to significantly improve chronic wound healing by increasing the percentage of alternatively activated, pro-healing macrophages.IL-33 is a molecule that can function as an alarmin through its receptor, ST2. We used ST2-/- mice to assess the action of IL-33 during wound healing. We found ST2-/- mice had impaired wound closure, reduced angiogenesis and altered collagen deposition/remodelling compared to BALB/C controls. There was increased neutrophilic infiltrate and altered macrophage polarisation in ST2-/- mice wounds. These results indicate that ST2 signalling is important for macrophage differentiation, which may improve wound closure, increase angiogenesis and delay or prevent scarring.The NLRP3 inflammasome has been implicated in a variety of inflammatory diseases. We used MCC950, a water-soluble small molecule inhibitor of NLRP3 in a chronic wound healing mouse model in an attempt to improve wound healing. We failed to identify any significant differences in the rate of wound healing, or angiogenesis in MCC950-treated mice compared to controls. Our results indicated that the NLRP3 inflammasome is not significantly involved in chronic wound healing.UVR has been repeatedly reported to induce immune suppression, one of the driving factors for tumour formation. Delayed-type contact hypersensitivity (CHS) is the leading mechanism for testing UVR-mediated immune suppression. We found the depletion of macrophages in neonates using clodronate liposomes before, during and after insult of a single burning dose of UVR was able to prevent a long-term local immune suppression, mediated by CD4+ regulatory T-cells. We also defined the changing resident myeloid cells in the skin as a response to UV exposure, and opened up new avenues of research to follow on from this work.Langerhans cells are a well-studied resident immune cell in the epidermis, with hundreds of publications identifying their origin, from the yolk-sac/foetal liver and their method of self-renewal under homeostatic conditions, and their ability to be renewed bymonocytes with the presence of chronic inflammation. A lesser studied resident macrophage population in the skin involves the resident dermal macrophages, which have been implicated in conditions such as wound healing and hair follicle cycling. We aimed to use a multicolour, fluorescent lineage-tracing model to investigate the mechanism of renewal of dermal macrophages in homeostasis, and inflammation. Unfortunately, the model chosen for this project was insufficient for this particular study and we were unable to gather any useful information from this project. This thesis has identified a list of molecules and cytokines that are either important or not for macrophage polarisation and the effects on wound healing in both chronic and acute wound healing scenarios. I have also identified a link between phagocytic myeloid cells and UV-induced immunosuppression and subsequent hapten-controlled inflammation in contact-hypersensitivity. Finally, a shift in long-term resident macrophages has also been identified following UV-irradiation, which may play a role in immune suppression and contact hypersensitivity.

Currently, the treatment of persistent non-healing wounds is among the most difficult clinical issues. We studied 20 samples of normal human skin, 10 specimens from patients with acute trauma, and 9 samples from the patients with chronic wounds that did not heal within 2 months. Using multicolor flow cytometry, we found that the resident T lymphocytes (CD3++ and CD3++) are able to locally produce biologically active substances, normalize human skin homeostasis, thus promoting the wound healing. The data obtained indicate that the blood contains mainly +T lymphocytes (p 0.001), while the +T cells detected in wounds represent a population similar to skin cells. We found no difference in the ratio of resident T cells in chronic and acute wounds, and healthy epithelium. Accordingly, non-healing of wounds and chronic clinical course may be caused by dysfunction of T cells. CD69 regulates T cell secretion of growth factors, IFN, IL-17 and IL-22. The relative number of CD69-expressing T cells from the patients with acute wounds was significantly increased, if compared with cells from normal epidermis and chronic wounds (10.5%2.3, 7.6%1.24, and 3.0%1.05, respectively. p 0.001). The number of cells with the CD3++CD69+ phenotype did not differ significantly between all three groups under comparison. Dysregulation of T cell-mediated healing in chronic wounds is caused by reduced production of IGF-1 by resident CD3++T lymphocytes (1.7%0.9 (p 0.001), and CD3++ (0.44%0.02, p 0.001) compared to CD3++T cells derived from acute wounds (13.6%5.6) and CD3++ (8.9%3.1). The + and + T cells isolated from non-healing chronic wounds did not respond to mitogenic stimuli, unlike the cells obtained from acute wounds and healthy skin. In vitro analysis of cytokine secretion by the CD69-deficient dermal T cells showed a lower spontaneous secretion of IL-22 (4.56%2.3 and 23.9%1.05 and 10.6%1.24, respectively; p 0.001) and IL-2 (0.9%0.08 and 22.6%2.5 and 3.9%1.0, and respectively; p 0.01). When analyzing the number of resident skin T cells secreting IL-17, we obtained the following differences for healthy skin (1.4%0.08), acute wounds (11.3%3.2) and chronic wounds (31.7%11.8), thus showing a significant intergroup difference (p 0.001). T lymphocytes in chronic wounds exhibit some functional disorders and are not able to produce biologically active substances that promote physiological tissue regeneration. The results suggest a role of resident T cells in human skin in wound healing processes and provide new insights into the pathogenesis of chronic wounds.

Diabetes is a leading chronic illness in the modern world and 19-34% develop chronic diabetic foot ulcers (DFUs) in their lifetime, often necessitating amputation. The reduction in tissue growth factors and resulting imbalance between proteolytic enzymes and their inhibitors, along with systemic factors impairing healing appear particularly important in chronic wounds. Growth factors applied topically have thus been suggested to be a non-invasive, safe, and cost-effective adjunct to improve wound healing and prevent complications.Comprehensive database searches of MEDLINE via PubMed, EMBASE, Cochrane, and ClinicalTrials.gov were performed to identify clinical evidence and ongoing trials. The risk of bias analysis included randomized controlled trials (RCTs) was performed using the Cochrane Risk of Bias 2.0 tool. We included randomized controlled trials that compared the use of a topical biologic growth factor-containing regimen to any other regimen. Primary outcomes of interest were time to wound closure, healing rate, and time. Secondary outcomes included the incidence of adverse events such as infection.A total of 41 trials from 1992-2020 were included in this review, with a total recorded 3,112 patients. Platelet-derived growth factors (PDGF) in the form of becaplermin gel are likely to reduce the time of closure, increase the incidence of wound closure, and complete wound healing. Human umbilical cord-related treatments, dehydrated human amnion and chorion allograft (dHACA), and hypothermically stored amniotic membrane (HSAM), consistently increased the rates and incidence of complete ulcer healing while reducing ulcer size and time to complete ulcer healing. Fibroblast growth factor-1 (FGF1) showed only a slight benefit in multiple studies regarding increasing complete ulcer healing rates and incidence while reducing ulcer size and time to complete ulcer healing, with a few studies showing no statistical difference from placebo. Platelet-rich fibrin (PRF) is consistent in reducing the time to complete ulcer healing and increasing wound healing rate but may not reduce ulcer size or increase the incidence of complete ulcer healing.Targeting the wound healing pathway via the extrinsic administration of growth factors is a promising option to augment wound healing in diabetic patients. Growth factors have also shown promise in specific subgroups of patients who are at risk of significantly impaired wound healing such as those with a history of secondary infection and vasculopathy. As diabetes impairs multiple stages of wound healing, combining growth factors in diabetic wound care may prove to be an area of interest. Evidence from this systematic literature review suggests that topical adjuncts probably reduce time to wound closure, reduce healing time, and increase the healing rate in patients with chronic DFUs.

Wound healing disturbances that occur in chronic diabetic wounds result in various complications and cause a significant burden. With the increasing prevalence of diabetes mellitus, it is estimated that the numbers of chronic diabetic wounds and their complications will also continue to increase. One of the latest managements using growth factors for chronic diabetic wounds gives satisfactory results, but their use is still limited because of the high costs. This study aims to explore the effectiveness of using topical insulin as a cheaper and effective alternative therapy in chronic diabetic wounds. The method of this study is a literature review sourced from Google Scholar and ProQuest search engine. Eight articles were obtained that are relevant to be discussed in this study. According to studies conducted so far, topical insulin can improve wound healing through the modulation of inflammation and insulin signaling pathways. In conclusion, there is improved wound healing in diabetic chronic wounds patients that were given topical insulin. Therefore topical insulin should be considered as part of chronic diabetic wounds management.
 Keywords: wound healing; chronic diabetic wounds; growth factors; topical insulin

Macrophage phenotypic switching from pro-inflammatory M1 to pro-regenerative M2 is impaired in chronic diabetic wounds, leading to excessive reactive oxygen species (ROS) production, poor angiogenesis, and decreased collagen deposition, thereby affecting the healing cascade. Development of multifunctional biomaterial with bioactive compounds to modulate the immune microenvironment and combat ROS, with the potential to facilitate angiogenesis and increase collagen deposition. Here, a novel combination therapy of silk DOPA-crisaborole conjugate (SDC, angiogenic and anti-inflammatory) and eugenol (Eu, antioxidant) has been devised to promote chronic wound healing. The core-shell electrospun fibrous mat has been fabricated with Eu in a polycaprolactone core (PCL-Eu) and SDC in a dextran shell (Dex-SDC), collectively termed Dex-SDC/PCL-Eu. In response to the acidic environment of chronic wounds, the dynamic benzoxaborole-catechol complex between crisaborole and silk DOPA cleaves, releasing crisaborole, while the matrix degradation of Dex-SDC/PCL-Eu over time enables the controlled release of Eu for 12 days. The initial release of crisaborole promotes polarization of M1 macrophages to M2 phenotype by significantly upregulating anti-inflammatory cytokine IL-10 and downregulating pro-inflammatory cytokine IL-6 gene expression in Dex-SDC/PCL-Eu-treated THP-1 cells compared to control. Subsequently, the sustained release of Eu mitigates oxidative damage. Dex-SDC/PCL-Eu fibers facilitate in vitro adhesion, migration, and proliferation of fibroblasts and endothelial cells as well as enhance endothelial tube formation. In the diabetic rat model, the Dex-SDC/PCL-Eu fibers reduce inflammatory granulation tissue and ulceration, while promoting neovascularization, complete re-epithelialization, and well-organized dermis and epidermis formation with uniform collagen deposition. Thus, the developed multifunctional Dex-SDC/PCL-Eu fibrous mat accelerates full-thickness skin wound healing and holds promise for the treatment of chronic diabetic wounds.

Current standard of care dressings are unsatisfactorily inefficacious for the treatment of chronic wounds. Chronic inflammation is the primary cause of the long-term incurable nature of chronic wounds. Herein, an absorbable nanofibrous hydrogel is developed for synergistic modulation of the inflammation microenvironment to accelerate chronic diabetic wound healing. The electrospun thioether grafted hyaluronic acid nanofibers (FHHA-S/Fe) are able to form a nanofibrous hydrogel in situ on the wound bed. This hydrogel degrades and is absorbed gradually within 3 days. The grafted thioethers on HHA can scavenge the reactive oxygen species quickly in the early inflammation phase to relieve the inflammation reactions. Additionally, the HHA itself is able to promote the transformation of the gathered M1 macrophages to the M2 phenotype, thus synergistically accelerating the wound healing phase transition from inflammation to proliferation and remodeling. On the chronic diabetic wound model, the average remaining wound area after FHHA-S/Fe treatment is much smaller than both that of FHHA/Fe without grafted thioethers and the control group, especially in the early wound healing stage. Therefore, this facile dressing strategy with intrinsic dual modulation mechanisms of the wound inflammation microenvironment may act as an effective and safe treatment strategy for chronic wound management.

Skin wounds greatly affect the global healthcare system, creating a substantial burden on the economy and society. Moreover, the situation is exacerbated by low healing rates, which in fact are overestimated in reports. Cutaneous wounds are generally classified into acute and chronic. The immune response plays an important role during acute wound healing. The activation of immune cells and factors initiate the inflammatory process, facilitate wound cleansing and promote subsequent tissue healing. However, dysregulation of the immune system during the wound healing process leads to persistent inflammation and delayed healing, which ultimately result in chronic wounds. The microenvironment of a chronic wound is characterized by high quantities of pro-inflammatory macrophages, overexpression of inflammatory mediators such as TNF-α and IL-1β, increased activity of matrix metalloproteinases and abundance of reactive oxygen species. Moreover, chronic wounds are frequently complicated by bacterial biofilms, which perpetuate the inflammatory phase. Continuous inflammation and microbial biofilms make it very difficult for the chronic wounds to heal. In this review, we discuss the role of innate and adaptive immunity in the pathogenesis of acute and chronic wounds. Furthermore, we review the latest immunomodulatory therapeutic strategies, including modifying macrophage phenotype, regulating miRNA expression and targeting pro- and anti-inflammatory factors to improve wound healing.