Iron and 8-isoprostane levels in acute and chronic wounds

Construction of Iron-Scavenging Hydrogel via Thiol-Ene Click Chemistry for Antibiotic-Free Treatment of Bacterial Wound Infection

Bacteria, especially drug-resistant strains, can quickly cause wound infections, leading to delayed healing and fatal risk in clinics. With the growing need for alternative antibacterial approaches that rely less on antibiotics or eliminate their use altogether, a novel antibacterial hydrogel named Ovtgel is developed. Ovtgel is formulated by chemically crosslinking thiol-modified ovotransferrin (Ovt), a member of the transferrin family found in egg white, with olefin-modified agarose through thiol-ene click chemistry. Ovt is designed to sequester ferric ions essential for bacterial survival and protect wound tissues from damages caused by the reactive oxygen species (ROS) generated in Fenton reactions. Experimental data have shown that Ovtgel significantly enhances wound healing by inhibiting bacterial growth and shielding tissues from ROS-induced harms. Unlike traditional antibiotics, Ovtgel targets essential trace elements required for bacterial survival in the host environment, preventing the development of drug resistance in pathogenic bacteria. Ovtgel exhibits excellent biocompatibility due to the homology of Ovt to mammalian transferrin. This hydrogel has the potential to serve as an effective antibiotic-free solution for combating bacterial infections.

Pseudomonas aeruginosa Activates Quorum Sensing, Antioxidant Enzymes and Type VI Secretion in Response to Oxidative Stress to Initiate Biofilm Formation and Wound Chronicity

Pseudomonas aeruginosa (PA) is an opportunistic pathogen frequently isolated from cutaneous chronic wounds. How PA, in the presence of oxidative stress (OS), colonizes chronic wounds and forms a biofilm is still unknown. The purpose of this study is to investigate the changes in gene expression seen when PA is challenged with the high levels of OS present in chronic wounds. We used a biofilm-forming PA strain isolated from the chronic wounds of our murine model (RPA) and performed a qPCR to obtain gene expression patterns as RPA developed a biofilm in vitro in the presence of high levels of OS, and then compared the findings in vivo, in our mouse model of chronic wounds. We found that the planktonic bacteria under OS conditions overexpressed quorum sensing genes that are important for the bacteria to communicate with each other, antioxidant stress genes important to reduce OS in the microenvironment for survival, biofilm formation genes and virulence genes. Additionally, we performed RNAseq in vivo and identified the activation of novel genes/pathways of the Type VI Secretion System (T6SS) involved in RPA pathogenicity. In conclusion, RPA appears to survive the high OS microenvironment in chronic wounds and colonizes these wounds by turning on virulence, biofilm-forming and survival genes. These findings reveal pathways that may be promising targets for new therapies aimed at disrupting PA-containing biofilms immediately after debridement to facilitate the treatment of chronic human wounds.

The application of synthetic antibacterial minerals to combat topical infections: exploring a mouse model of MRSA infection

The development of new antibiotics has stalled, and novel strategies are needed as we enter the age of antibiotic resistance. Certain naturally occurring clays have been shown to be effective in killing antibiotic resistant bacteria. However, these natural clays are too variable to be used in clinical settings. Our study shows that synthetic antibacterial minerals exhibit potent antibacterial activity against topical MRSA infections and increase the rate of wound closure relative to controls. The antibacterial minerals maintain a redox cycle between Fe2+/Fe3+ and the surfaces of pyrite minerals, which act as a semiconductor and produce reactive oxygen species (ROS), while smectite minerals act as a cation exchange reservoir. Acidic conditions are maintained throughout the application of the hydrated minerals and can mitigate the alkaline pH conditions observed in chronic non-healing wounds. These results provide evidence for the strategy of 'iron overload' to combat antibiotic resistant infections through the maintained release of Fe2+ and generation of ROS via distinct geochemical reactions that can break the chronic wound damage cycle.

Topical Iron Chelator Therapy: Current Status and Future Prospects

Systemic iron chelation therapy has long been used for iron overload, providing a role in returning iron levels to proper homeostatic concentrations. Recently, topical iron chelation therapy has emerged as a potential strategy for treating skin damage. This narrative review explores the current status and future prospects of topical iron chelation therapy for treating ultraviolet (UV) and non-UV skin damage, as well as its potential application in wound healing. The review was conducted through a literature search across PubMed, Web of Science, and EMBASE databases, spanning publications from 1990 to 2023. The selection of articles was focused on primary research studies, either experimental or clinical, that explored the implications and formulations of topical iron chelators used alone or in conjunction with another therapeutic agent. The search strategy employed a combination of terms, including "topical iron chelation", "topical deferoxamine", "UV", "wound healing", "skin inflammation", "radiation-induced fibrosis", and "skin cancer". Relevant studies, including methods, intervention strategies, measured outcomes, and findings, are summarized. The review also considered the potential challenges in translating research findings into clinical practice. Results indicate that topical iron chelators, such as deferoxamine, are effective in mitigating UV-induced skin damage, reducing tumorigenesis, and decreasing oxidative damage. In addition, the use of these agents in radiation-induced fibrosis has been shown to significantly increase skin elasticity and reduce dermal fibrosis. Several studies also highlight the use of topical iron chelators in difficult-to-treat chronic wounds, such as diabetic neuropathic ulcers and sickle cell ulcers. In conclusion, topical iron chelation therapy represents a novel and promising approach for skin protection and wound healing. Its potential makes it a promising area of future research.

Keratose Self-Cross-Linked Wound Dressing for Iron Sequestration in Chronic Wounds

Chronic wound diseases affect a large part of the world population, and therefore, novel treatments are becoming fundamental. People with chronic wounds show high iron and protease levels due to genetic disorders or other comorbidities. Since it was demonstrated that iron plays an important role in chronic wounds, being responsible for oxidative processes (ROS generation), while metalloproteinases prevent wound healing by literally "eating" the growing skin, it is crucial to design an appropriate wound dressing. In this paper, a novel bioactive dressing for binding iron in chronic wounds has been produced. Wool-derived keratose wound dressing in the form of films has been prepared by casting an aqueous solution of keratoses. These films are water-soluble; therefore, in order to increase their stability, they have been made insoluble through a thermal cross-link treatment. Fourier transform infrared (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analyzer (TGA) analyses clarified the structure and the properties of the keratose wound dressing films. The capability of this new biomaterial in iron sequestration has been investigated by testing the adsorption of Fe3+ by inductively coupled plasma-optical emission spectrometry (ICP-OES). The results suggest that the keratose cross-linked films can adsorb a large amount of iron (about 85% of the average amount usually present in chronic wounds) following pseudo-second-order kinetics and an intraparticle diffusion model, thus opening new perspectives in chronic wound care. Furthermore, the QSAR Toolbox was applied for conducting in silico tests and for predicting the chemical behavior of the C-Ker-film. All of the data suggest that the keratose bioactive dressing can significantly contribute to wound healing by mechanisms such as iron depletion, acting as a radical scavenger, diminishing the proteolytic damage, acting as a substrate in place of skin, and, finally, promoting tissue regeneration.

Dual-Function Hydrogel Dressings with a Dynamic Exchange of Iron Ions and an Antibiotic Drug for Treatment of Infected Wounds

Bacterial infection is a major problem with diabetic wounds that may result in nonhealing chronic ulcers. Here, we report an approach to antibacterial hydrogel dressings for enhanced treatment of infected skin wounds. A fibrous hydrogel was derived from cellulose nanocrystals that were modified with dopamine and cross-linked with gelatin. The hydrogel was loaded with gentamicin, an antibiotic drug. Enhanced antibacterial hydrogel performance resulted from (i) a highly specific sequestration of Fe³⁺ ions (much needed by bacteria) from the wound exudate and (ii) a dynamic exchange between gentamicin released from the hydrogel and Fe³⁺ ions withdrawn from the wound exudate. Such exchange was possible due to the high value of the binding constant of Fe³⁺ ions to dopamine. The hydrogel did not affect the metabolic activity of skin-related cells and showed enhanced antibacterial performance against common wound pathogens such as S. aureus and P. aeruginosa. Furthermore, it promoted healing of infected diabetic wounds due to a synergistic antibacterial effect providing the dynamic exchange between Fe³⁺ ions and gentamicin. This work provides a strategy for the design of dual-function wound dressings, with both starving and killing bacteria and enhanced wound healing performance.

Emerging ROS-Modulating Technologies for Augmentation of the Wound Healing Process

Reactive oxygen species (ROS) is considered a double-edged sword. The slightly elevated level of ROS helps in wound healing by inhibiting microbial infection. In contrast, excessive ROS levels in the wound site show deleterious effects on wound healing by extending the inflammation phase. Understanding the ROS-mediated molecular and biomolecular mechanisms and their effect on cellular homeostasis and inflammation thus substantially improves the possibility of exogenously augmenting and manipulating wound healing with the emerging antioxidant therapeutics. This review comprehensively delves into the relationship between ROS and critical phases of wound healing and the processes underpinning antioxidant therapies. The manuscript also discusses cutting-edge antioxidant therapeutics that act via ROS scavenging to enhance chronic wound healing.

Relevance of NLRP3 Inflammasome-Related Pathways in the Pathology of Diabetic Wound Healing and Possible Therapeutic Targets

Wound healing is a major secondary complication in type 2 diabetes, which results in significant disability and mortality, imposing a significant clinical and social burden. Sustained activation of the Nod-like receptor protein (NLRP) inflammasome in wounds is responsible for excessive inflammatory responses and aggravates wound damage. The activation of the NLRP3 inflammasome is regulated by a two-step process: the priming/licensing (signal 1) step involved in transcription and posttranslation and the protein complex assembly (signal 2) step triggered by danger molecules. This review focuses on the advances made in understanding the pathophysiological mechanisms underlying wound healing in the diabetic microenvironment. Simultaneously, this review summarizes the molecular mechanisms of the main regulatory pathways associated with signal 1 and signal 2, which trigger the NLRP3 inflammasome complex assembly in the development of diabetic wounds (DW). Activation of the NLRP3 inflammasome-related pathway, involving the disturbance in Nrf2 and the NF-κB/NLRP3 inflammasome, TLR receptor-mediated activation of the NF-κB/NLRP3 inflammasome, and various stimuli inducing NLRP3 inflammasome assembly play a pivotal role in DW healing. Furthermore, therapeutics targeting the NLRP3 inflammasome-related pathways may promote angiogenesis, reprogram immune cells, and improve DW healing.

Time- and Spectrally-Resolved Photoluminescence Study of Alloyed CdxZn1-xSeyS1-y/ZnS Quantum Dots and Their Nanocomposites with SPIONs in Living Cells

Magnetic-luminescent composites based on semiconductor quantum dots (QDs) and superparamagnetic iron oxide nanoparticles (SPIONs) can serve as a platform combining visualization and therapy. Here, we report the construction of QD-SPION nanocomposites based on synthesized SPIONs and alloyed QDs (CdxZn1−xSeyS1−y)/ZnS solubilized with L-cysteine molecules. The study of the spectral-luminescence characteristics, the kinetics of luminescence decay show the composite’s stability in a solution. After incubation with HeLa cells, QDs, SPIONs, and their composites form clusters on the cell surface and associate with endosomes inside the cells. Component-wise analysis of the photoluminescence decay of cell-associated QDs/SPIONs provides information about their localization and aggregate status.

Wound fluid sampling methods for proteomic studies: A scoping review

Understanding why some wounds are hard to heal is important for improving care and developing more effective treatments. The method of sample collection used is an integral step in the research process and thus may affect the results obtained. The primary objective of this study was to summarise and map the methods currently used to sample wound fluid for protein profiling and analysis. Eligible studies were those that used a sampling method to collect wound fluid from any human wound for analysis of proteins. A search for eligible studies was performed using MEDLINE, Embase and CINAHL Plus in May 2020. All references were screened for eligibility by one reviewer, followed by discussion and consensus with a second reviewer. Quantitative data were mapped and visualised using appropriate software and summarised via a narrative summary. After screening, 280 studies were included in this review. The most commonly used group of wound fluid collection methods were vacuum, drainage or use of other external devices, with surgical wounds being the most common sample source. Other frequently used collection methods were extraction from absorbent materials, collection beneath an occlusive dressing and direct collection of wound fluid. This scoping review highlights the variety of methods used for wound fluid collection. Many studies had small sample sizes and short sample collection periods; these weaknesses have hampered the discovery and validation of novel biomarkers. Future research should aim to assess the reproducibility and feasibility of sampling and analytical methods for use in larger longitudinal studies.

ROS-Scavenging Therapeutic Hydrogels for Modulation of the Inflammatory Response

Although reactive oxygen species (ROS) are essential for cellular processes, excessive ROS could be a major cause of various inflammatory diseases because of the oxidation of proteins, DNA, and membrane lipids. It has recently been suggested that the amount of ROS could thus be regulated to treat such physiological disorders. A ROS-scavenging hydrogel is a promising candidate for therapeutic applications because of its high biocompatibility, 3D matrix, and ability to be modified. Approaches to conferring antioxidant properties to normal hydrogels include embedding ROS-scavenging catalytic nanoparticles, modifying hydrogel polymer chains with ROS-adsorbing organic moieties, and incorporating ROS-labile linkers in polymer backbones. Such therapeutic hydrogels can be used for wound healing, cardiovascular diseases, bone repair, ocular diseases, and neurodegenerative disorders. ROS-scavenging hydrogels could eliminate oxidative stress, accelerate the regeneration process, and show synergetic effects with other drugs or therapeutic molecules. In this review, the mechanisms by which ROS are generated and scavenged in the body are outlined, and the effects of high levels of ROS and the resulting oxidative stress on inflammatory diseases are described. Next, the mechanism of ROS scavenging by hydrogels is explained depending on the ROS-scavenging agents embedded within the hydrogel. Lastly, the recent achievements in the development of ROS-scavenging hydrogels to treat various inflammation-associated diseases are presented.

Arginase Signalling as a Key Player in Chronic Wound Pathophysiology and Healing

Arginase (ARG) represents an important evolutionarily conserved enzyme that is expressed by multiple cell types in the skin. Arg acts as the mediator of the last step of the urea cycle, thus providing protection against excessive ammonia under homeostatic conditions through the production of L-ornithine and urea. L-ornithine represents the intersection point between the ARG-dependent pathways and the urea cycle, therefore contributing to cell detoxification, proliferation and collagen production. The ARG pathways help balance pro- and anti-inflammatory responses in the context of wound healing. However, local and systemic dysfunctionalities of the ARG pathways have been shown to contribute to the hindrance of the healing process and the occurrence of chronic wounds. This review discusses the functions of ARG in macrophages and fibroblasts while detailing the deleterious implications of a malfunctioning ARG enzyme in chronic skin conditions such as leg ulcers. The review also highlights how ARG links with the microbiota and how this impacts on infected chronic wounds. Lastly, the review depicts chronic wound treatments targeting the ARG pathway, alongside future diagnosis and treatment perspectives.

The senescence-associated secretory phenotype: Fueling a wound that never heals

Wound healing is impaired with advanced age and certain chronic conditions, such as diabetes and obesity. Moreover, common cancer treatments, including chemotherapy and radiation, can cause unintended tissue damage and impair wound healing. Available wound care treatments are not always effective, as some wounds fail to heal or recur after treatment. Hence, a more thorough understanding of the pathophysiology of chronic, nonhealing wounds may offer new ideas for the development of effective wound care treatments. Cancers are sometimes referred to as wounds that never heal, sharing mechanisms similar to wound healing. We describe in this review how cellular senescence and the senescence-associated secretory phenotype (SASP) contribute to chronic wounds versus cancer.

From wound response to repair - lessons from C. elegans

As a result of evolution, the ability to repair wounds allows organisms to combat environment insults. Although the general process of wound healing at the tissue level has been described for decades, the detailed molecular mechanisms regarding the early wound response and rapid wound repair at the cellular level remain little understood. Caenorhabditis elegans is a model organism widely used in the field of development, neuroscience, programmed cell death etc. The nematode skin is composed of a large epidermis associated with a transparent extracellular cuticle, which likely has a robust capacity for epidermal repair. Yet, until the last decades, relatively few studies had directly analyzed the wound response and repair process. Here we review recent findings in how C. elegans epidermis responds to wounding and initiates early actin-polymerization-based wound closure as well as later membrane repair. We also discussed some remained outstanding questions for future study.

Sex-Specific Genetically Predicted Iron Status in relation to 12 Vascular Diseases: A Mendelian Randomization Study in the UK Biobank

Background

Iron overload has been implicated in the pathogenesis of varicose veins (VVs). However, the association of serum iron status with other vascular diseases (VDs) is not well understood, which might be a potential target for VD prevention. This study was aimed at investigating the causal associations between iron status and VDs using the Mendelian randomization (MR) method.

Methods

A two-sample MR was designed to investigate whether iron status was associated with VDs, based on iron data from a published genome-wide association study meta-analysis of 48,972 subjects of European descent and VD data obtained from the UK Biobank, including 361,194 British subjects (167,020 males and 194,174 females). We further explored whether there was sex difference in the associations between genetically predicted iron status and VDs.

Results

The results demonstrated that iron status had a significant causal effect on VVs of lower extremities (P < 0.001) and a potential effect on coronary atherosclerosis (P < 0.05 for serum iron, ferritin, and transferrin saturation, respectively), but not on other VDs. Furthermore, higher iron status exerted a detrimental effect on VVs of lower extremities in both genders (P < 0.05) and a protective effect on male patients with coronary atherosclerosis (P < 0.05 for serum iron, ferritin, and transferrin saturation, respectively).

Conclusions

This MR study provides robust evidence that higher iron status increases the risk of VVs of lower extremities, whereas it reduces the incidence of coronary atherosclerosis in the male population, which indicates that iron has divergent effects on vascular pathology.

Prophylactic treatment with transdermal deferoxamine mitigates radiation-induced skin fibrosis

Radiation therapy can result in pathological fibrosis of healthy soft tissue. The iron chelator deferoxamine (DFO) has been shown to improve skin vascularization when injected into radiated tissue prior to fat grafting. Here, we evaluated whether topical DFO administration using a transdermal drug delivery system prior to and immediately following irradiation (IR) can mitigate the chronic effects of radiation damage to the skin. CD-1 nude immunodeficient mice were split into four experimental groups: (1) IR alone (IR only), (2) DFO treatment for two weeks after recovery from IR (DFO post-IR), (3) DFO prophylaxis with treatment through and post-IR (DFO ppx), or (4) no irradiation or DFO (No IR). Immediately following IR, reactive oxygen species and apoptotic markers were significantly decreased and laser doppler analysis revealed significantly improved skin perfusion in mice receiving prophylactic DFO. Six weeks following IR, mice in the DFO post-IR and DFO ppx groups had improved skin perfusion and increased vascularization. DFO-treated groups also had evidence of reduced dermal thickness and collagen fiber network organization akin to non-irradiated skin. Thus, transdermal delivery of DFO improves tissue perfusion and mitigates chronic radiation-induced skin fibrosis, highlighting a potential role for DFO in the treatment of oncological patients.

Ozonated Oils and Cutaneous Wound Healing

Wound tissue repair is a complex and dynamic process of restoring cellular structures and tissue layers. Improvement in this process is necessary to effectively treat several pathologies characterized by a chronic delayed wound closure, such as in diabetes, and the investigation of new approaches aimed to ameliorate the wound healing process is under continuous evolution. Recently, the usage of vegetable matrices in the form of ozonated oils has been proposed, and several researchers have shown positive effects on wound healing, due to the bactericidal, antiviral, and antifungal properties of these ozonated oils. In the present review, we intend to summarize the actual state of the art of the topical usage of ozonated oil in cutaneous wounds with special emphasis to the importance of the ozonated degree of the oil.

Redox dysregulation in the pathogenesis of chronic venous ulceration

In chronic venous ulcers (CVUs), which account for up to 75% of leg ulcers, the inflammatory stage of wound healing fails to down-regulate, preventing progression to proliferation, remodeling and eventual epithelialisation. The roles of reactive oxygen species (ROS) in the oxidative burst and pathogen killing are well known, but ROS also have important functions in extra-cellular and intra-cellular signalling. Iron deposition, resulting from venous reflux, primes macrophages towards a persistent inflammatory response, with ongoing stimulation by bacteria potentially playing a role. Generation of excessive ROS by activated inflammatory cells causes tissue destruction and disintegration of the dermis, and then at later stages, a failure to heal. Here, we review the evidence for ROS in CVU formation and in normal and delayed healing. We also discuss how ROS modulation might be used to influence the healing of these complex wounds, which cause long-term morbidity and are associated with a significant financial burden to healthcare systems.

Does localized iron loss in venous disease lead to systemic iron deficiency? A descriptive pilot study

Haemosiderin deposition in the legs of patients with venous leg ulcers is well established, and several theories suggest this stored iron has a role in disease pathophysiology. In this novel pilot study of patients with chronic venous leg ulcers, we aimed to establish the relationship between wound fluid iron levels, serum iron parameters and healing. Fifteen patients with venous ulcers were included in the study. Blood samples were taken for full blood count and iron studies, while simultaneously wound fluid was obtained from the wound surface using filter paper. Wound areas were measured at initial and 4 week (+/- 2 day) follow-up visits. We found a positive correlation between wound fluid and serum iron (correlation co-efficient 0.27) and those with the lowest wound fluid iron level were also anemic. No association was found between initial wound area and wound fluid iron level but the largest wound areas were found in patients with anemia. Only 38% of patients demonstrated a reduction in wound area during the 4 week study, and 80% of those were not anemic or iron deficient. Conversely in those patients whose wounds did not reduce in size 88% were anemic or iron deficient. These findings demonstrate a previously unrecognized phenomenon of systemic iron store depletion secondary to leaching out of the body in wound exudate. In addition, these results suggest a high prevalence of anemia in patients with chronic venous ulcers, though whether this is cause or effect requires further research. Our findings also suggest that patients with venous ulcers have a high prevalence of iron deficiency and anemia, which appears to be often undiagnosed, and that diagnostic criteria for iron deficiency in patients with chronic wounds need to be revised to reflect the effect of chronic inflammation on iron metabolism.

Tissue Iron Promotes Wound Repair via M2 Macrophage Polarization and the Chemokine (C-C Motif) Ligands 17 and 22

Macrophages are important for effective iron recycling and erythropoiesis, but they also play a crucial role in wound healing, orchestrating tissue repair. Recently, we demonstrated a significant accumulation of iron in healing wounds and a requirement of iron for effective repair. Herein, we sought to determine the influence of iron on macrophage function in the context of wound healing. Interestingly, wound macrophages extensively sequestered iron throughout healing, associated with a prohealing M2 phenotype. In delayed healing diabetic mouse wounds, both macrophage polarization and iron sequestration were impaired. In vitro studies revealed that iron promotes differentiation, while skewing macrophages toward a hypersecretory M2-like polarization state. These macrophages produced high levels of chemokine (C-C motif) ligands 17 and 22, promoting wound reepithelialization and extracellular matrix deposition in a human ex vivo wound healing model. Together, these findings reveal a novel, unappreciated role for iron in modulating macrophage behavior to promote subsequent wound repair. These findings support therapeutic evaluation of iron use to promote wound healing in the clinic.

An overview of the relationship between anaemia, iron, and venous leg ulcers

The factors preventing healing in venous leg ulcers are still not fully understood. Iron-mediated tissue damage has been hypothesised, yet anecdotally anaemia is also thought to have a negative effect on wound healing. This article summarises the current evidence for these theories and their likely effects in the context of venous ulceration. A comprehensive search of the literature was conducted. Studies suggest that a number of forms of iron including haemosiderin and ferritin are implicated in progression of venous disease, ulcer formation, and impaired healing, which is thought to be primarily free radical mediated. There is a paucity of evidence for the role of iron deficiency and anaemia on ulcer healing; however, there is likely to be a highly complex interplay between the damaging effects of iron on local tissues and the negative effects of anaemia-mediated tissue hypoxia. Studies looking at options to increase local oxygen delivery such as topical haemoglobin suggest that this may have an impact on some aspects of healing, but findings are generally inconclusive. There is growing evidence that locally elevated iron levels may have a detrimental effect on ulcer healing and formation; however, more robust research is needed.

Iron and iron-dependent reactive oxygen species in the regulation of macrophages and fibroblasts in non-healing chronic wounds

Chronic wounds pose a stern challenge to health care systems with growing incidence especially in the aged population. In the presence of increased iron concentrations, recruitment of monocytes from the circulation and activation towards ROS and RNS releasing M1 macrophages together with the persistence of senescent fibroblasts at the wound site are significantly enhanced. This unrestrained activation of pro-inflammatory macrophages and senescent fibroblasts has increasingly been acknowledged as main driver causing non-healing wounds. In a metaphor, macrophages act like stage directors of wound healing, resident fibroblasts constitute main actors and increased iron concentrations are decisive parts of the libretto, and - if dysregulated - are responsible for the development of non-healing wounds. This review will focus on recent cellular and molecular findings from chronic venous leg ulcers and diabetic non-healing wounds both constituting the most common pathologies often resulting in limb amputations of patients. This not only causes tremendous suffering and loss of life quality, but is also associated with an increase in mortality and a major socio-economic burden. Despite recent advances, the underlying molecular mechanisms are not completely understood. Overwhelming evidence shows that reactive oxygen species and the transition metal and trace element iron at pathological concentrations are crucially involved in a complex interplay between cells of different histogenetic origin and their extracellular niche environment. This interplay depends on a variety of cellular, non-cellular biochemical and cell biological mechanisms. Here, we will highlight recent progress in the field of iron-dependent regulation of macrophages and fibroblasts and related pathologies linked to non-healing chronic wounds.

Xanthine Oxidoreductase: A Novel Therapeutic Target for the Treatment of Chronic Wounds?

Significance: Chronic wounds are a major burden to patients and to healthcare systems worldwide. These wounds are difficult to heal and treatment is often lengthy and expensive. This has led to research efforts focussed on the wound environment attempting to understand the underlying pathological mechanisms of impaired wound healing. While some of this research has translated to advancements in wound therapies and implementation of new treatment options, chronic wounds remain a significant challenge to treat. Thus, identification of effective, low-cost, advanced wound therapies that enhance healing rates of these problematic wounds is still essential. Recent Advances and Critical Issues: Xanthine oxidoreductase (XOR), a molybdoflavin enzyme, is emerging as an important source of reactive oxygen species (ROS) in various pathologies, including diabetes and chronic wounds. XOR has recently been shown to be upregulated in chronic wounds, stimulating the overproduction of ROS during dysfunctional wound healing. XOR-induced ROS can amplify and potentiate inflammation in the wound environment further delaying wound closure. Future Directions: The detrimental role of XOR in impaired healing indicates it may be a therapeutic target. Targeted inhibition of XOR has been shown to reduce the expression and activity of this enzyme in diabetic wound models. In turn, this resulted in a significant decrease in ROS levels in the wound environment and improved wound healing. Therefore, repurposing existing XOR inhibitors that are approved for human use may be able to restore homeostasis at the wound site and enable damaged tissue to return to normal healing.

Drug-Porous Silicon Dual Luminescent System for Monitoring and Inhibition of Wound Infection

Wound monitoring and curing is of great importance in biomedical research. This work created a smart bandage that can simultaneously monitor and inhibit wound infection. The main components of the smart bandage are luminescent porous silicon (LuPSi) particles loaded with ciprofloxacin (CIP). This dual luminescent system can undergo accelerated fluorescent color change from red to blue upon the stimulation of reactive oxygen species (ROS) and elevated pH, which are main biomarkers in the infected wound. The mechanism behind the chemical-triggered fluorescent color change was studied in detail. In vitro experiment showed that the ratiometric fluorescent intensity (I_Red/I_Blue) of CIP-LuPSi particles decreased from 10 to 0.03 at pH 7.5 after 24 h, while the value deceased from 10 to 2.15 at pH 7.0. Strong correlation can be also found between the I_Red/I_Blue value and ROS concentration ranging from 0.1 to 10 mM. In addition, the oxidation of LuPSi also simultaneously triggered the release of CIP molecules, which exhibited bacterial inhibition activity. Therefore, the ratiometric fluorescent intensity change at red and blue channels can indicate not only the wound infection status but also the release of antibiotics. In vivo test proved that the smart bandage could distinguish infected wounds from acute wounds, just relying on the naked eyes or a cell phone camera. On the basis of the Si nanotechnology established in this work, theranostic wound care will be realized in future.

Iron-Regulated Phospholipase C Activity Contributes to the Cytolytic Activity and Virulence of Acinetobacter baumannii

Acinetobacter baumannii is an opportunistic Gram-negative pathogen that causes a wide range of infections including pneumonia, septicemia, necrotizing fasciitis and severe wound and urinary tract infections. Analysis of A. baumannii representative strains grown in Chelex 100-treated medium for hemolytic activity demonstrated that this pathogen is increasingly hemolytic to sheep, human and horse erythrocytes, which interestingly contain increasing amounts of phosphatidylcholine in their membranes. Bioinformatic, genetic and functional analyses of 19 A. baumannii isolates showed that the genomes of each strain contained two phosphatidylcholine-specific phospholipase C (PC-PLC) genes, which were named plc1 and plc2. Accordingly, all of these strains were significantly hemolytic to horse erythrocytes and their culture supernatants tested positive for PC-PLC activity. Further analyses showed that the transcriptional expression of plc1 and plc2 and the production of phospholipase and thus hemolytic activity increased when bacteria were cultured under iron-chelation as compared to iron-rich conditions. Testing of the A. baumannii ATCC 19606^Tplc1::aph-FRT and plc2::aph isogenic insertion derivatives showed that these mutants had a significantly reduced PC-PLC activity as compared to the parental strain, while testing of plc1::ermAM/plc2::aph demonstrated that this double PC-PLC isogenic mutant expressed significantly reduced cytolytic and hemolytic activity. Interestingly, only plc1 was shown to contribute significantly to A. baumannii virulence using the Galleria mellonella infection model. Taken together, our data demonstrate that both PLC1 and PLC2, which have diverged from a common ancestor, play a concerted role in hemolytic and cytolytic activities; although PLC1 seems to play a more critical role in the virulence of A. baumannii when tested in an invertebrate model. These activities would provide access to intracellular iron stores this pathogen could use during growth in the infected host.

URIC ACID AND TISSUE REPAIR

Uric acid, a metabolic product of purines, may exert a role in tissue healing. In this review we will explore its role as an alarm initiating the inflammatory process that is necessary for tissue repair, as a scavenger of oxygen free radicals, as a mobilizer of progenitor endothelial cells and as supporter of adaptive immune system.

Reactive oxygen species and bacterial biofilms in diabetic wound healing

Chronic wounds are a common and debilitating complication for the diabetic population. It is challenging to study the development of chronic wounds in human patients; by the time it is clear that a wound is chronic, the early phases of wound healing have passed and can no longer be studied. Because of this limitation, mouse models have been employed to better understand the early phases of chronic wound formation. In the past few years, a series of reports have highlighted the importance of reactive oxygen species and bacterial biofilms in the development of chronic wounds in diabetics. We review these recent findings and discuss mouse models that are being utilized to enhance our understanding of these potentially important contributors to chronic wound formation in diabetic patients.

Diabetic wound regeneration using peptide-modified hydrogels to target re-epithelialization

There is a clinical need for new, more effective treatments for chronic wounds in diabetic patients. Lack of epithelial cell migration is a hallmark of nonhealing wounds, and diabetes often involves endothelial dysfunction. Therefore, targeting re-epithelialization, which mainly involves keratinocytes, may improve therapeutic outcomes of current treatments. In this study, we present an integrin-binding prosurvival peptide derived from angiopoietin-1, QHREDGS (glutamine-histidine-arginine-glutamic acid-aspartic acid-glycine-serine), as a therapeutic candidate for diabetic wound treatments by demonstrating its efficacy in promoting the attachment, survival, and collective migration of human primary keratinocytes and the activation of protein kinase B Akt and MAPK_p42/44 The QHREDGS peptide, both as a soluble supplement and when immobilized in a substrate, protected keratinocytes against hydrogen peroxide stress in a dose-dependent manner. Collective migration of both normal and diabetic human keratinocytes was promoted on chitosan-collagen films with the immobilized QHREDGS peptide. The clinical relevance was demonstrated further by assessing the chitosan-collagen hydrogel with immobilized QHREDGS in full-thickness excisional wounds in a db/db diabetic mouse model; QHREDGS showed significantly accelerated and enhanced wound closure compared with a clinically approved collagen wound dressing, peptide-free hydrogel, or blank wound controls. The accelerated wound closure resulted primarily from faster re-epithelialization and increased formation of granulation tissue. There were no observable differences in blood vessel density or size within the wound; however, the total number of blood vessels was greater in the peptide-hydrogel-treated wounds. Together, these findings indicate that QHREDGS is a promising candidate for wound-healing interventions that enhance re-epithelialization and the formation of granulation tissue.

Wound Fluids: A Window Into the Wound Environment?

Wound healing of the skin is a complex biologic process involving temporal interactions between numerous types of cells, extracellular matrix molecules, and soluble factors. The process of repair can be viewed as involving 3 or 4 phases: homeostasis, inflammation, synthesis, and remodeling. These phases occur at different times and differ in their cellular, biochemical, and physiologic requirements. Disruption of one or more of these interactions can significantly interfere with the repair process. Such comorbidities as age, nutrition, immune status, and underlying disease status (eg, diabetes or venous stasis) contribute additional intricacy to the repair process. Because of this complexity, care of chronic wounds remains highly individualized, and it should not come as a surprise that treatment of these wounds as a group with single target therapies have met with only modest success. A major hurdle in the progression toward improved treatment regimens has been the lack of objective biochemical and physiological landmarks that can be used to assess wound status. Collection and biochemical characterization of wound fluids presents the opportunity to noninvasively obtain information reflecting the status of the wound and of specific biomarkers. This review discusses the collection of wound fluid and highlights biomarkers that may be useful to this end.

Olive oil-induced reduction of oxidative damage and inflammation promotes wound healing of pressure ulcers in mice

BACKGROUND

The overproduction of reactive oxygen species (ROS) and exacerbated inflammatory response are the main events that impair healing of pressure ulcers. Therefore, olive oil may be a good alternative to improve the healing of these chronic lesions due to its anti-inflammatory and antioxidant properties.

OBJECTIVE

This study investigated the effect of olive oil administration on wound healing of pressure ulcers in mice.

METHODS

Male Swiss mice were daily treated with olive oil or water until euthanasia. One day after the beginning of treatment, two cycles of ischemia-reperfusion by external application of two magnetic plates were performed in skin to induced pressure ulcer formation.

RESULTS

The olive oil administration accelerated ROS and nitric oxide (NO) synthesis and reduced oxidative damage in proteins and lipids when compared to water group. The inflammatory cell infiltration, gene tumor necrosis factor-α (TNF-α) expression and protein neutrophil elastase expression were reduced by olive oil administration when compared to water group. The re-epithelialization and blood vessel number were higher in the olive oil group than in the water group. The olive oil administration accelerated protein expression of TNF-α, active transforming growth factor-β1 and vascular endothelial growth factor-A when compared to water group. The collagen deposition, myofibroblastic differentiation and wound contraction were accelerated by olive oil administration when compared to water group.

CONCLUSION

Olive oil administration improves cutaneous wound healing of pressure ulcers in mice through the acceleration of the ROS and NO synthesis, which reduces oxidative damage and inflammation and promotes dermal reconstruction and wound closure.

Pathophysiology of wound healing and alterations in venous leg ulcers-review

Venous leg ulcer (VLU) is one of the most common lower extremity ulcerated wound, and is a significant healthcare problem with implications that affect social, economic, and the well-being of a patient. VLU can have debilitating related problems which require weekly medical care and may take months to years to heal. The pathophysiology of VLU is complex, and healing is delayed in many patients due to a persistent inflammatory condition. Patient genetic and environmental factors predispose individuals to chronic venous diseases including VLU. Changes in shear stress affecting the glycocalyx are likely initiating events, leading to activation of adhesion molecules on endothelial cells, and leukocyte activation with attachment and migration into vein wall, microcirculation, and in the interstitial space. Multiple chemokines, cytokines, growth factors, proteases and matrix metalloproteinases are produced. The pathology of VLU involves an imbalance of inflammation, inflammatory modulators, oxidative stress, and proteinase activity. Understanding the cellular and biochemical events that lead to the progression of VLU is critical. With further understanding of inflammatory pathways and potential mechanisms, certain biomarkers could be revealed and studied as both involvement in the pathophysiology of VLU but also as therapeutic targets for VLU healing.

HFE p.C282Y gene variant is associated with varicose veins in Russian population

Recently, the association of polymorphism rs1800562 (p.C282Y) in the hemochromatosis (HFE) gene with the increased risk of venous ulceration was shown. We hypothesized that HFE gene polymorphism might be involved not only in ulceration process, but also in susceptibility to primary varicose veins. We genotyped HFE p.C282Y (rs1800562) and p.H63D (rs1799945) variants in patients with primary varicose veins (n = 463) and in the control group (n = 754). In our study, p.282Y variant (rs1800562 A allele) was significantly associated with the risk of varicose veins (OR 1.79, 95 % CI = 1.11-2.89, P = 0.02). A borderline significant reverse association of p.63D variant (rs1799945 G allele) with venous leg ulcer development was revealed in Russians (OR 0.25, 95 % CI = 0.06-1.00, P = 0.05), but not in the meta-analysis (P = 0.56). We conclude that the HFE gene polymorphism can affect the risk of developing primary varicose veins.

Serum ferritin is an important inflammatory disease marker, as it is mainly a leakage product from damaged cells

"Serum ferritin" presents a paradox, as the iron storage protein ferritin is not synthesised in serum yet is to be found there. Serum ferritin is also a well known inflammatory marker, but it is unclear whether serum ferritin reflects or causes inflammation, or whether it is involved in an inflammatory cycle. We argue here that serum ferritin arises from damaged cells, and is thus a marker of cellular damage. The protein in serum ferritin is considered benign, but it has lost (i.e. dumped) most of its normal complement of iron which when unliganded is highly toxic. The facts that serum ferritin levels can correlate with both disease and with body iron stores are thus expected on simple chemical kinetic grounds. Serum ferritin levels also correlate with other phenotypic readouts such as erythrocyte morphology. Overall, this systems approach serves to explain a number of apparent paradoxes of serum ferritin, including (i) why it correlates with biomarkers of cell damage, (ii) why it correlates with biomarkers of hydroxyl radical formation (and oxidative stress) and (iii) therefore why it correlates with the presence and/or severity of numerous diseases. This leads to suggestions for how one might exploit the corollaries of the recognition that serum ferritin levels mainly represent a consequence of cell stress and damage.

A novel model of chronic wounds: importance of redox imbalance and biofilm-forming bacteria for establishment of chronicity

Chronic wounds have a large impact on health, affecting ∼6.5 M people and costing ∼$25B/year in the US alone. We previously discovered that a genetically modified mouse model displays impaired healing similar to problematic wounds in humans and that sometimes the wounds become chronic. Here we show how and why these impaired wounds become chronic, describe a way whereby we can drive impaired wounds to chronicity at will and propose that the same processes are involved in chronic wound development in humans. We hypothesize that exacerbated levels of oxidative stress are critical for initiation of chronicity. We show that, very early after injury, wounds with impaired healing contain elevated levels of reactive oxygen and nitrogen species and, much like in humans, these levels increase with age. Moreover, the activity of anti-oxidant enzymes is not elevated, leading to buildup of oxidative stress in the wound environment. To induce chronicity, we exacerbated the redox imbalance by further inhibiting the antioxidant enzymes and by infecting the wounds with biofilm-forming bacteria isolated from the chronic wounds that developed naturally in these mice. These wounds do not re-epithelialize, the granulation tissue lacks vascularization and interstitial collagen fibers, they contain an antibiotic-resistant mixed bioflora with biofilm-forming capacity, and they stay open for several weeks. These findings are highly significant because they show for the first time that chronic wounds can be generated in an animal model effectively and consistently. The availability of such a model will significantly propel the field forward because it can be used to develop strategies to regain redox balance that may result in inhibition of biofilm formation and result in restoration of healthy wound tissue. Furthermore, the model can lead to the understanding of other fundamental mechanisms of chronic wound development that can potentially lead to novel therapies.

Neuroprotectin/protectin D1: endogenous biosynthesis and actions on diabetic macrophages in promoting wound healing and innervation impaired by diabetes

Dysfunction of macrophages (MΦs) in diabetic wounds impairs the healing. MΦs produce anti-inflammatory and pro-resolving neuroprotectin/protectin D1 (NPD1/PD1, 10R,17S-dihydroxy-docosa-4Z,7Z,11E,13E,15Z,19Z-hexaenoic acid); however, little is known about endogenous NPD1 biosynthesis by MΦs and the actions of NPD1 on diabetic MΦ functions in diabetic wound healing. We used an excisional skin wound model of diabetic mice, MΦ depletion, MΦs isolated from diabetic mice, and mass spectrometry-based targeted lipidomics to study the time course progression of NPD1 levels in wounds, the roles of MΦs in NPD1 biosynthesis, and NPD1 action on diabetic MΦ inflammatory activities. We also investigated the healing, innervation, chronic inflammation, and oxidative stress in diabetic wounds treated with NPD1 or NPD1-modulated MΦs from diabetic mice. Injury induced endogenous NPD1 biosynthesis in wounds, but diabetes impeded NPD1 formation. NPD1 was mainly produced by MΦs. NPD1 enhanced wound healing and innervation in diabetic mice and promoted MΦs functions that accelerated these processes. The underlying mechanisms for these actions of NPD1 or NPD1-modulated MΦs involved 1) attenuating MΦ inflammatory activities and chronic inflammation and oxidative stress after acute inflammation in diabetic wound, and 2) increasing MΦ production of IL10 and hepatocyte growth factor. Taken together, NPD1 appears to be a MΦs-produced factor that accelerates diabetic wound healing and promotes MΦ pro-healing functions in diabetic wounds. Decreased NPD1 production in diabetic wound is associated with impaired healing. This study identifies a new molecular target that might be useful in development of more effective therapeutics based on NPD1 and syngeneic diabetic MΦs for treatment of diabetic wounds.

Current development in non-enzymatic lipid peroxidation products, isoprostanoids and isofuranoids, in novel biological samples

Isoprostanoids and isofuranoids are lipid mediators that can be formed from omega-3 and omega-6 polyunsaturated fatty acids (PUFAs). F2-isoprostanes formed from arachidonic acid, especially 15-F2t-isoprostane, are commonly measured in biological tissues for decades as the biomarker for oxidative stress and diseases. Recently, other forms of isoprostanoids derived from adrenic, eicosapentaenoic, and docosahexaenoic acids namely F2-dihomo-isoprostanes, F3-isoprostanes, and F4-neuroprostanes respectively, and isofuranoids including isofurans, dihomo-isofurans, and neurofurans are reported as oxidative damage markers for different metabolisms. The most widely used samples in measuring lipid peroxidation products include but not limited to the blood and urine; other biological fluids, specialized tissues, and cells can also be determined. In this review, measurement of isoprostanoids and isofuranoids in novel biological samples by gas chromatography (GC)-mass spectrometry (MS), GC-MS/MS, liquid chromatography (LC)-MS, and LC-MS/MS will be discussed.

Eicosanoids and Keratinocytes in Wound Healing

Significance: Eicosanoids are biologically active lipid mediators derived from arachidonic acid that are important in injury and inflammatory responses. Cyclooxygenase-1 and cyclooxygenase-2 mediate the production of prostanoids, whereas 5-lipoxygenase mediates the production of leukotrienes and hydroxyeicosatetraenoic acids. These lipid mediators have traditionally been known to recruit cells of the immune system to a site of injury and inflammation. However, they also interact with various cells that are resident to the wound bed, including modulation of keratinocyte activity. Recent Advances: Recent work has identified multiple prostanoid and leukotriene receptors on keratinocytes, indicating that eicosanoids directly interact with them. Recent work also shows that keratinocytes are capable of producing prostanoids and leukotrienes. Critical Issues: Much of the critical work has been performed in cell culture and mouse in vivo models. This has greatly expanded our understanding of the eicosanoid interactions with keratinocytes and wound healing in general. However, few of these in vivo models have been able to critically evaluate keratinocyte migration and re-epithelialization. Future Directions: As research continues in this exciting field, the cellular pathways stimulated by the eicosanoids will become better defined. Future research with excisional wound models in mice and pigs and ex vivo human skin models will better isolate the contribution of eicosanoid-mediated effects on keratinocyte migration and re-epithelialization.

Stress responses in the opportunistic pathogen Acinetobacter baumannii

Acinetobacter baumannii causes a wide range of severe infections among compromised and injured patients worldwide. The relevance of these infections are, in part, due to the ability of this pathogen to sense and react to environmental and host stress signals, allowing it to persist and disseminate in medical settings and the human host. This review summarizes current knowledge on the roles that environmental and cellular stressors play in the ability of A. baumannii to resist nutrient deprivation, oxidative and nitrosative injury, and even the presence of the commonly used antiseptic ethanol, which could serve as a nutrient- and virulence-enhancing signal rather than just being a convenient disinfectant. Emerging experimental evidence supports the role of some of these responses in the pathogenesis of the infections A. baumannii causes in humans and its capacity to resist antibiotics and host response effectors.

Adipose-derived stem cells and keratinocytes in a chronic wound cell culture model: the role of hydroxyectoine

Chronic wounds represent a major socio-economic problem in developed countries today. Wound healing is a complex biological process. It requires a well-orchestrated interaction of mediators, resident cells and infiltrating cells. In this context, mesenchymal stem cells and keratinocytes play a crucial role in tissue regeneration. In chronic wounds these processes are disturbed and cell viability is reduced. Hydroxyectoine (HyEc) is a membrane protecting osmolyte with protein and macromolecule stabilising properties. Adipose-derived stem cells (ASC) and keratinocytes were cultured with chronic wound fluid (CWF) and treated with HyEc. Proliferation was investigated using MTT test and migration was examined with transwell-migration assay and scratch assay. Gene expression changes of basic fibroblast growth factor (b-FGF), vascular endothelial growth factor (VEGF), matrix metalloproteinases-2 (MMP-2) and MMP-9 were analysed by quantitative real-time polymerase chain reaction (qRT-PCR). CWF significantly inhibited proliferation and migration of keratinocytes. Addition of HyEc did not affect these results. Proliferation capacity of ASC was not influenced by CWF whereas migration was significantly enhanced. HyEc significantly reduced ASC migration. Expression of b-FGF, VEGF, MMP-2 and MMP-9 in ASC, and b-FGF, VEGF and MMP-9 in keratinocytes was strongly induced by chronic wound fluid. HyEc enhanced CWF induced gene expression of VEGF in ASC and MMP-9 in keratinocytes. CWF negatively impaired keratinocyte function, which was not influenced by HyEc. ASC migration was stimulated by CWF, whereas HyEc significantly inhibited migration of ASC. CWF induced gene expression of VEGF in ASC and MMP-9 in keratinocytes was enhanced by HyEc, which might partly be explained by an RNA stabilising effect of HyEc.

Wound Fluid in Diabetic Foot Ulceration

Valid and reproducible sampling techniques as well as processing protocols are required for the assessment of biomarkers and mediators contained in wound exudate. Moreover, the ideal technique should be easy to use even in daily clinical routine. This is challenging since wound fluid represents an inhomogeneous mixture of different exogenous and endogenous sources. Analyzing wound fluid, however, may facilitate clinical decision making. Many techniques for obtaining wound fluid have been described. There is very little validation data, and the array of different techniques appears confusing. Structuring and new standards are needed to avoid wound fluid sampling yielding an “undefined soup.” A lot of wound fluid parameters have been analyzed, although none of them have made its way into clinical practice. Nevertheless, basic principles of wound healing have been established from wound fluid analysis. With adequate techniques suitable for daily practice, basic research might foster our clinical understanding of wound healing with implications for new therapies. So far, research has mainly concentrated on analyzing available sample material with respect to either a wide variety of analytes or comparing acute with chronic wound exudate. Clinical endpoints such as healing or wound infection as well as longitudinal data may indeed be more valuable for clinical practice, enabling the discovery of meaningful biomarkers using a suitable technique.

Neutrophil activity in chronic venous leg ulcers--a target for therapy?

Chronic venous leg ulcers (CVLUs) affect approximately 600,000 people annually in the United States and accrue yearly treatment costs of US $2.5-5 billion. As the population ages, demands on health care resources for CVLU treatments are predicted to drastically increase because the incidence of CVLUs is highest in those ≥65 years of age. Furthermore, regardless of current standards of care, healing complications and high recurrence rates prevail. Thus, it is critical that factors leading to or exacerbating CVLUs be discerned and more effective, adjuvant, evidence-based treatment strategies be utilized. Previous studies have suggested that CVLUs' pathogenesis is related to the prolonged presence of high numbers of activated neutrophils secreting proteases in the wound bed that destroy growth factors, receptors, and the extracellular matrix that are essential for healing. These events are believed to contribute to a chronically inflamed wound that fails to heal. Therefore, the purpose of this project was to review studies from the past 15 years (1996-2011) that characterized neutrophil activity in the microenvironment of human CVLUs for new evidence that could explicate the proposed relationship between excessive, sustained neutrophil activity and CVLUs. We also appraised the strength of evidence for current and potential therapeutics that target excessive neutrophil activity.

Expression of Reactive Oxygen Species during Wound Healing of Vocal Folds in a Rat Model

Objectives:

Previous studies have indicated that although normal wound healing requires low levels of reactive oxygen species (ROS), excessive amounts of ROS impair wound healing. In injured vocal folds, this excess may result in dysphonia due to scarring that is difficult to treat. However, the expression of ROS during vocal fold wound healing has yet to be investigated. In this study, we assessed the expression and localization of ROS in injured vocal folds by immunohistochemical analysis.

Methods:

Vocal folds of Sprague-Dawley rats were unilaterally injured by stripping the mucosa under transoral endoscopy. The larynges were harvested at specific time points after injury and were immunohistochemically examined for 4-hydroxy-2-nonenal (4-HNE), an ROS marker, and for the presence of inflammatory cells.

Results:

We found that 4-HNE–immunopositive cells were significantly increased in the lamina propria of the injured vocal folds as compared to the normal vocal folds on postinjury days 1 and 3. More than half of the 4-HNE–immunopositive cells were also immunopositive for a macrophage- and granulocyte-specific antibody.

Conclusions:

This study suggests that a large amount of ROS is produced during early-phase wound healing, until postinjury day 3, and that this period may be crucial for regulating ROS levels. The results also suggest that inflammatory cells may contribute to ROS generation.