Evidence of oxidative stress in chronic venous ulcers

Nanocrystalline Silver Layer of Knitted Polyester Outperforms Other Silver-Containing Wound Dressings in an In Vitro Wound Model

Background Silver possesses cytotoxic properties against many microorganisms and is regularly used in wound care. Current evidence supporting the use of one type of silver-containing wound dressing (SCWD) is insufficient. Materials and methods To examine the ability of selected SCWDs to inhibit the growth of two strains of bacteria (Escherichia coli and Staphylococcus aureus) commonly found in wounds, an in vitro wound model was used. Bacteria were applied to the surface of nutrient agar, and a piece of each SCWD was applied to the bacteria. The plates were incubated at 37°C overnight. The zone of inhibition (ZI) around each SCWD was measured in cm2. Results The mean ZI for Acticoat Flex-3 on E. coli was 1.59 ± 0.15 cm2, which was significantly greater than that observed for Aquacel Ag (p<0.001), Mepilex Ag (p<0.0001), Mepitel Ag (p<0.001), Optifoam (p<0.0001), and Tegaderm Alginate Ag (p<0.01), but statistically indistinguishable from Maxorb II Ag. The mean ZI on S. aureus was 1.21 ± 0.16 cm2, which was greater than Aquacel Ag (p<0.05), Mepilex (p<0.0001), Optifoam (p<0.0001), and Tegaderm Alginate Ag (p<0.05), but statistically indistinguishable from Maxorb II Ag or Mepitel Ag. Conclusion Of the SCWDs tested, Acticoat Flex-3 demonstrated the most robust antimicrobial effect. Herein, we show that Acticoat Flex-3 may provide the most wound protection against bacterial infection. In conclusion, these data provide clinicians with additional independent evidence to inform their clinical practice on the use of specific wound dressings.

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.

Antioxidant Silk Fibroin Composite Hydrogel for Rapid Healing of Diabetic Wound

Wound healing is a complex process requiring multiple biological pathways and chemical responses to be activated and synchronized to recover tissue integrity. In normal physiological circumstances, the epidermal barrier restoration process through new tissue formation is highly efficient. However, increased production of reactive oxygen species, attack of pathogenic microorganisms, and high glucose level delay the normal healing process in diabetic patients. The successful treatment of diabetic wounds requires efficient strategies to control oxidative stress, promoting angiogenesis, re-epithelialization, and collagen deposition. In this study, we developed a composite hydrogel for rapid wound healing in diabetic condition by the amalgamation of hypolipidemic property of silk fibroin (SF), antioxidant property of melanin and therapeutic effect of berberine. Studies have revealed that cross-linked mesoporous morphology of hydrogel matrix facilitates slow release of berberine to impart long-term therapeutic effects at wound site. The composite hydrogel formulation is biocompatible, stimulates effective migration of fibroblast cells, and control oxidative stress under in vitro conditions. The hydrogel served as scaffold for tissue re-epithelialization and promotes wound repair in diabetic type I Wistar rat model. This study demonstrates the ability of berberine- loaded SF-melanin composite hydrogel (SFCH) as a potential dressing formulation for wound healing in diabetic conditions. This article is protected by copyright. All rights reserved.

Coactivity of Mast Cells and Stem Cells on Angiogenesis and Antioxidants' Potentials at Inflammation, Proliferation, and Tissue Remodeling Phases of Wound

Background  Reactive oxygen species cause serious damage to the physiological function of tissues. Determination of total antioxidant capacity of skin tissue is one of the determinants of damaged tissue function. Mast cells (MCs) are one of the groups of cells that are invited to the site of injury. The healing process begins with the rapid release of various types of MCs' intermediate factors at the site of injury. Bone marrow mesenchymal stem cell (BMMSC) production and secretion have been shown to regenerate the skin. The aim of this research was to evaluate the wound-healing and antioxidant effects of BMMSCs per MCs.

Methods  Fifty-four albino Wistar male rats were divided into three groups: (1) nonsurgery, (2) surgery, and (3) surgery + BMMSCs. Groups 2 and 3 were operated with a 3 × 8 cm flap and in group 3, cell injections (7 × 10 ⁹ cell injection at the time of surgery) were performed. After days 4, 7, and 15, percentage of the surviving tissue, histological characteristics, superoxide dismutase (SOD) activity, and amount of malondialdehyde (MDA) were measured in the groups. For results, Graph Pad Prism 8 software was used, and data were analyzed and compared by analysis of variance and Tukey test.

Results  BMMSCs' application decreased the amount of MDA, increased SOD activity and survival rate of the flaps, and improved the histological characteristics.

Conclusion  This study revealed the protective effects BMMSCs alongside MCs against oxidative stress on the survival of the flaps. However, for clinical use, more research is needed to determine its benefits.

Reactive oxygen species-degradable polythioketal urethane foam dressings to promote porcine skin wound repair

Porous, resorbable biomaterials can serve as temporary scaffolds that support cell infiltration, tissue formation, and remodeling of nonhealing skin wounds. Synthetic biomaterials are less expensive to manufacture than biologic dressings and can achieve a broader range of physiochemical properties, but opportunities remain to tailor these materials for ideal host immune and regenerative responses. Polyesters are a well-established class of synthetic biomaterials; however, acidic degradation products released by their hydrolysis can cause poorly controlled autocatalytic degradation. Here, we systemically explored reactive oxygen species (ROS)-degradable polythioketal (PTK) urethane (UR) foams with varied hydrophilicity for skin wound healing. The most hydrophilic PTK-UR variant, with seven ethylene glycol (EG7) repeats flanking each side of a thioketal bond, exhibited the highest ROS reactivity and promoted optimal tissue infiltration, extracellular matrix (ECM) deposition, and reepithelialization in porcine skin wounds. EG7 induced lower foreign body response, greater recruitment of regenerative immune cell populations, and resolution of type 1 inflammation compared to more hydrophobic PTK-UR scaffolds. Porcine wounds treated with EG7 PTK-UR foams had greater ECM production, vascularization, and resolution of proinflammatory immune cells compared to polyester UR foam-based NovoSorb Biodegradable Temporizing Matrix (BTM)-treated wounds and greater early vascular perfusion and similar wound resurfacing relative to clinical gold standard Integra Bilayer Wound Matrix (BWM). In a porcine ischemic flap excisional wound model, EG7 PTK-UR treatment led to higher wound healing scores driven by lower inflammation and higher reepithelialization compared to NovoSorb BTM. PTK-UR foams warrant further investigation as synthetic biomaterials for wound healing applications.

Extracellular vesicles from hair follicle-derived mesenchymal stromal cells: isolation, characterization and therapeutic potential for chronic wound healing

BACKGROUND

Mesenchymal stromal cells (MSCs) and their extracellular vesicles (MSC-EVs) have demonstrated to elicit immunomodulatory and pro-regenerative properties that are beneficial for the treatment of chronic wounds. Thanks to different mediators, MSC-EVs have shown to play an important role in the proliferation, migration and cell survival of different skin cell populations. However, there is still a big bid to achieve the most effective, suitable and available source of MSC-EVs.

METHODS

We isolated, characterized and compared medium-large EVs (m-lEVs) and small EVs (sEVs) obtained from hair follicle-derived MSCs (HF-MSCs) against the gold standard in regenerative medicine, EVs isolated from adipose tissue-derived MSCs (AT-MSCs).

RESULTS

We demonstrated that HF-EVs, as well as AT-EVs, expressed typical MSC-EVs markers (CD9, CD44, CD63, CD81 and CD105) among other different functional markers. We showed that both cell types were able to increase human dermal fibroblasts (HDFs) proliferation and migration. Moreover, both MSC-EVs were able to increase angiogenesis in human umbilical vein endothelial cells (HUVECs) and protect HDFs exposed to a hyperglycemic environment from oxidative stress and cytotoxicity.

CONCLUSIONS

Taken together, HF-EVs demonstrated to exhibit comparable potential to that of AT-EVs as promising candidates in the treatment of chronic wounds.

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.

A Review of Recent Advances in Flexible Wearable Sensors for Wound Detection Based on Optical and Electrical Sensing

Chronic wounds that are difficult to heal can cause persistent physical pain and significant medical costs for millions of patients each year. However, traditional wound care methods based on passive bandages cannot accurately assess the wound and may cause secondary damage during frequent replacement. With advances in materials science and smart sensing technology, flexible wearable sensors for wound condition assessment have been developed that can accurately detect physiological markers in wounds and provide the necessary information for treatment decisions. The sensors can implement the sensing of biochemical markers and physical parameters that can reflect the infection and healing process of the wound, as well as transmit vital physiological information to the mobile device through optical or electrical signals. Most reviews focused on the applicability of flexible composites in the wound environment or drug delivery devices. This paper summarizes typical biochemical markers and physical parameters in wounds and their physiological significance, reviews recent advances in flexible wearable sensors for wound detection based on optical and electrical sensing principles in the last 5 years, and discusses the challenges faced and future development. This paper provides a comprehensive overview for researchers in the development of flexible wearable sensors for wound detection.

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.

Compendium of Conventional and Targeted Drug Delivery Formulation Used for the Treatment and Management of the Wound Healing

Wound healing is a complex and dynamic phenomenon that involves the restoration of normal physiology and functioning of injured tissue. The process of wound healing is primarily regulated by various cytokines, inflammatory mediators, and growth factors at the molecular level. Any intervention in the normal wound healing process leads to further tissue damage, which in turn leads to delayed wound healing. Several natural, synthetic drugs and their combinations were used to restored and accelerate the wound healing process. However, the conventional delivery carriers were not much effective, and thus, nowadays, nanocarriers are gaining much popularity since they are playing a pivotal role in drug delivery. Since nanocarriers have their own applicability and benefits (enhance the bioavailability, site-specific targeting) so, they can accelerate wound healing more efficiently. This review briefly discussed about the various events that take place during the wound healing process with emphasis on various natural, synthetic, and combination drug therapy used for accelerating wound healing and the role of nanotechnology-based approaches in chronic wound healing.

Optically activated and interrogated plasmonic hydrogels for applications in wound healing

We disclose the use of hybrid materials featuring Au/Ag core/shell nanorods in porous chitosan/polyvinyl alcohol scaffolds for applications in tissue engineering and wound healing. The combination of Au and Ag in a single construct provides synergistic opportunities for optical activation of functions as near infrared laser tissue bonding, and remote interrogation to return parameters of prognostic relevance in wound healing monitoring. In particular, the bimetallic component ensures optical tunability, enhanced shelf life and photothermal stability, serves as a reservoir of germicidal silver cations, and changes in near-infrared and visible color according to the environmental level of oxidative stress. At the same time, the polymeric blend is ideal to bind connective tissue upon photothermal activation, and to support fabrication processes that provide high porosity, such as electrospinning, thus putting all the premises for cellular repopulation and antimicrobial protection.

Protease levels are significantly altered in pediatric burn wounds

Burn wounds contain high levels of protease activity due to the need to remodel the damaged extracellular matrix proteins. While necessary, excessive protease activity can lead to improper wound healing and is associated with increased contraction and fibrosis. No studies to date have investigated the expression changes of all the collagenases and elastases in burn wounds. The present study compares gene expression changes and changes in collagenase and elastase activity between burn wound eschar and normal skin in a pediatric population. Deidentified pediatric tissues were used for these experiments. Burn wound tissue was excised as part of normal standard care within a week from injury; normal skin was removed during elective plastic surgery procedures. RNA-sequencing was performed and significant results were confirmed with qRT-PCR. Activity assays showed a significant increase in both collagenase and elastase activity in the burn wound tissue compared to the normal skin. Western blotting and substrate zymography of tissue homogenates evaluated the results at the protein levels. Four elastases and three collagenases were determined to be significantly upregulated in the wound tissues by both RNA-sequencing and qRT-PCR. Cathepsin V was the only protease that was significantly downregulated. All but one metalloproteinase studied was significantly upregulated. None of the serine proteases were significantly altered in the wound tissues. In conclusion, matrix metalloproteinases appear to be the most highly elevated proteases after a pediatric burn wound injury, at least within the first 3-7 days. The data warrant further investigation into the effects of MMPs on burn wound healing.

Exosome laden oxygen releasing antioxidant and antibacterial cryogel wound dressing OxOBand alleviate diabetic and infectious wound healing

Lack of oxygen, reduced vascularization, elevated oxidative stress, and infection are critical clinical hallmarks of non-healing chronic diabetic wounds. Therefore, delivering oxygen, inducing angiogenesis, and management of oxidative stress and infection may provide newer and improved therapeutic avenues for better clinical outcomes in diabetic wound healing. Here, we report the development and evaluation of an exosome laden oxygen releasing antioxidant wound dressing OxOBand to promote wound closure and skin regeneration in diabetic wounds. OxOBand is composed of antioxidant polyurethane (PUAO), as highly porous cryogels with sustained oxygen releasing properties and supplemented with adipose-derived stem cells (ADSCs) exosomes. Exosomes engulfed by the cells enhanced the migration of human keratinocytes and fibroblasts and increased the survival of human neuroblastoma cells under hyperglycemic conditions. OxOBand facilitated faster wound closure, enhanced collagen deposition, faster re-epithelialization, increased neo-vascularization, and decreased oxidative stress within two weeks as compared to untreated diabetic control wounds. The dressing promoted the development of mature epithelial structures with hair follicles and epidermal morphology similar to that of healthy skin. In clinically challenging infected diabetic wounds, these dressings prevented infection and ulceration, improved wound healing with increased collagen deposition, and re-epithelialization. Altogether, OxOBand is a remarkably newer treatment strategy for enhanced diabetic wound healing and may lead to novel therapeutic interventions for the treatment of diabetic ulcers.

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.

Conceptual Model of Biofilm Antibiotic Tolerance That Integrates Phenomena of Diffusion, Metabolism, Gene Expression, and Physiology

Transcriptomic, metabolomic, physiological, and computational modeling approaches were integrated to gain insight into the mechanisms of antibiotic tolerance in an in vitro biofilm system. Pseudomonas aeruginosa biofilms were grown in drip flow reactors on a medium composed to mimic the exudate from a chronic wound. After 4 days, the biofilm was 114 μm thick with 9.45 log₁₀ CFU cm^-2 These biofilms exhibited tolerance, relative to exponential-phase planktonic cells, to subsequent treatment with ciprofloxacin. The specific growth rate of the biofilm was estimated via elemental balances to be approximately 0.37 h^-1 and with a reaction-diffusion model to be 0.32 h^-1, or one-third of the maximum specific growth rate for planktonic cells. Global analysis of gene expression indicated lower transcription of ribosomal genes and genes for other anabolic functions in biofilms than in exponential-phase planktonic cells and revealed the induction of multiple stress responses in biofilm cells, including those associated with growth arrest, zinc limitation, hypoxia, and acyl-homoserine lactone quorum sensing. Metabolic pathways for phenazine biosynthesis and denitrification were transcriptionally activated in biofilms. A customized reaction-diffusion model predicted that steep oxygen concentration gradients will form when these biofilms are thicker than about 40 μm. Mutant strains that were deficient in Psl polysaccharide synthesis, the stringent response, the stationary-phase response, and the membrane stress response exhibited increased ciprofloxacin susceptibility when cultured in biofilms. These results support a sequence of phenomena leading to biofilm antibiotic tolerance, involving oxygen limitation, electron acceptor starvation and growth arrest, induction of associated stress responses, and differentiation into protected cell states.IMPORTANCE Bacteria in biofilms are protected from killing by antibiotics, and this reduced susceptibility contributes to the persistence of infections such as those in the cystic fibrosis lung and chronic wounds. A generalized conceptual model of biofilm antimicrobial tolerance with the following mechanistic steps is proposed: (i) establishment of concentration gradients in metabolic substrates and products; (ii) active biological responses to these changes in the local chemical microenvironment; (iii) entry of biofilm cells into a spectrum of states involving alternative metabolisms, stress responses, slow growth, cessation of growth, or dormancy (all prior to antibiotic treatment); (iv) adaptive responses to antibiotic exposure; and (v) reduced susceptibility of microbial cells to antimicrobial challenges in some of the physiological states accessed through these changes.

Cell salvage in acute and chronic wounds: a potential treatment strategy. Experimental data and early clinical results

On 9 May 2018, the authors took part in a closed panel discussion on the impact of cell salvage in acute and chronic wounds. The goal was to deliberate the possible use of plurogel micelle matrix (PMM) as a new treatment strategy for wound healing and the authors openly shared their experiences, thoughts, experimental data and early clinical results. The outcome of the panel discussion has been abridged in this paper. The cell membrane consists of a lipid bilayer, which provides a diffusion barrier separating the inside of a cell from its environment. Cell membrane injury can result in acute cellular necrosis when defects are too large and cannot be resealed. There is a potential hazard to the body when these dying cells release endogenous alarm signals referred to as 'damage (or danger) associated molecular patterns' (DAMPs), which trigger the innate immune system and modulate inflammation. Cell salvage by membrane resealing is a promising target to ensure the survival of the individual cell and prevention of further tissue degeneration by inflammatory processes. Non-ionic surfactants such as poloxamers, poloxamines and PMM have the potential to resuscitate cells by inserting themselves into damaged membranes and stabilising the unstable portions of the lipid bilayers. The amphiphilic properties of these molecules are amenable to insertion into cell wall defects and so can play a crucial, reparative role. This new approach to cell rescue or salvage has gained increasing interest as several clinical conditions have been linked to cell membrane injury via oxidative stress-mediated lipid peroxidation or thermal disruption. The repair of the cell membrane is an important step in salvaging cells from necrosis to prevent further tissue degeneration by inflammatory processes. This is applicable to acute burns and chronic wounds such as diabetic foot ulcers (DFUs), chronic venous leg ulcers (VLUs), and pressure ulcers (PUs). Experimental data shows that PMM is biocompatible and able to insert itself into damaged membranes, salvaging their barrier function and aiding cell survival. Moreover, the six case studies presented in this paper reveal the potential of this treatment strategy.

A Viable Lyopreserved Amniotic Membrane Modulates Diabetic Wound Microenvironment and Accelerates Wound Closure

Objective: Wound healing is a complex process involving the dynamic interplay of various types of cells and bioactive factors. Impaired wound healing is characterized by a loss in synchronization of the process, resulting in non-healing chronic wounds. Human amniotic membrane (AM) has been shown to be effective in the management of chronic wounds. Recently, a viable lyopreserved AM (VLAM) has been developed. The VLAM retains the structural, molecular, and functional properties of fresh AM with the advantage of a long shelf life for living tissue at ambient temperatures. The objective of this study was to evaluate the effects of VLAM on the impaired wound microenvironment and wound closure in db/db mice.

Approach: VLAM or saline gel (control) was applied weekly to 7-mm excisional wounds in diabetic (db/db) mice. Wound appearance and size were assessed weekly. Inflammation and redox state in wounds were tested by cytokine gene and protein expression, and by catalase and glutathione peroxidase activities, respectively. Wound tissue granulation and neovascularization were assessed histologically.

Results: Diabetic wounds treated with VLAM closed faster than control wounds. On an average, VLAM-treated wounds closed 4 days faster than the control wounds, with a significantly faster rate of closure at days 7 and 14 as compared with control wounds. The faster closure correlated with a decrease in the expression of proinflammatory factors and oxidative stress, and an increase in angiogenesis and dermal thickness.

Innovation: Effects of VLAM on a chronic wound microenvironment and underlying molecular mechanisms were investigated for the first time.

Conclusion: VLAM accelerates wound closure in db/db mice by decreasing inflammation and oxidative stress and supporting wound tissue granulation, neovascularization, and re-epithelialization.

Exudates absorption and proteases trapping in venous leg ulcers

OBJECTIVE

In venous leg ulcer (VLU), the impaired healing has been shown to be associated with excessive levels of protease activities such as matrix metalloproteinases (MMPs) and elastases found in exudates. The present study focused on exudates absorption and proteases trapping capacity of a new generation of polyacrylate superabsorbent, Tegaderm superabsorber (TS), compared with a traditional dressing such as Zetuvit.

METHOD

We studied the proteases implicated in VLU (MMP-1, MMP-2, MMP-9 and PMN elastase). Absorption was tested using an artificial exudate like fluid, over 30 minutes. The protein trapping ability was obtained using ELISA assays (enzyme-linked immunosorbent assay) to determine the amount retained by the dressings from spiked fluid samples.

RESULTS

TS had a higher exudate absorption capacity (72.8±1.7%) compared with the standard dressing (36.5±1.6%), and was also able to trap and retain proteases while the standard dressing released them. The difference was shown to be much larger for MMP-2 and PMN elastase.

CONCLUSION

In our knowledge, this is the first comparative in vitro study evaluating absorption capacity as well as protease trapping capacity of a polyacrylate dressing for the four most implicated proteases in VLU. TS could be an appropriate alternative to improve the management of VLU by trapping MMPs and PMN elastse with a particularly high affinity for MMP-2 and PMN elastase.

Protease activity as a prognostic factor for wound healing in venous leg ulcers

BACKGROUND

Venous leg ulcers (VLUs) are a common type of complex wound that have a negative impact on people's lives and incur high costs for health services and society. It has been suggested that prolonged high levels of protease activity in the later stages of the healing of chronic wounds may be associated with delayed healing. Protease modulating treatments have been developed which seek to modulate protease activity and thereby promote healing in chronic wounds.

OBJECTIVES

To determine whether protease activity is an independent prognostic factor for the healing of venous leg ulcers.

SEARCH METHODS

In February 2018, we searched the following databases: Cochrane Central Register of Controlled Trials (CENTRAL), Ovid MEDLINE, Ovid Embase and CINAHL.

SELECTION CRITERIA

We included prospective and retrospective longitudinal studies with any follow-up period that recruited people with VLUs and investigated whether protease activity in wound fluid was associated with future healing of VLUs. We included randomised controlled trials (RCTs) analysed as cohort studies, provided interventions were taken into account in the analysis, and case-control studies if there were no available cohort studies. We also included prediction model studies provided they reported separately associations of individual prognostic factors (protease activity) with healing. Studies of any type of protease or combination of proteases were eligible, including proteases from bacteria, and the prognostic factor could be examined as a continuous or categorical variable; any cut-off point was permitted. The primary outcomes were time to healing (survival analysis) and the proportion of people with ulcers completely healed; the secondary outcome was change in ulcer size/rate of wound closure. We extracted unadjusted (simple) and adjusted (multivariable) associations between the prognostic factor and healing.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for inclusion at each stage, and undertook data extraction, assessment of risk of bias and GRADE assessment. We collected association statistics where available. No study reported adjusted analyses: instead we collected unadjusted results or calculated association measures from raw data. We calculated risk ratios when both outcome and prognostic factor were dichotomous variables. When the prognostic factor was reported as continuous data and healing outcomes were dichotomous, we either performed regression analysis or analysed the impact of healing on protease levels, analysing as the standardised mean difference. When both prognostic factor and outcome were continuous data, we reported correlation coefficients or calculated them from individual participant data.We displayed all results on forest plots to give an overall visual representation. We planned to conduct meta-analyses where this was appropriate, otherwise we summarised narratively.

MAIN RESULTS

We included 19 studies comprising 21 cohorts involving 646 participants. Only 11 studies (13 cohorts, 522 participants) had data available for analysis. Of these, five were prospective cohort studies, four were RCTs and two had a type of case-control design. Follow-up time ranged from four to 36 weeks. Studies covered 10 different matrix metalloproteases (MMPs) and two serine proteases (human neutrophil elastase and urokinase-type plasminogen activators). Two studies recorded complete healing as an outcome; other studies recorded partial healing measures. There was clinical and methodological heterogeneity across studies; for example, in the definition of healing, the type of protease and its measurement, the distribution of active and bound protease species, the types of treatment and the reporting of results. Therefore, meta-analysis was not performed. No study had conducted multivariable analyses and all included evidence was of very low certainty because of the lack of adjustment for confounders, the high risk of bias for all studies except one, imprecision around the measures of association and inconsistency in the direction of association. Collectively the research indicated complete uncertainty as to the association between protease activity and VLU healing.

AUTHORS' CONCLUSIONS

This review identified very low validity evidence regarding any association between protease activity and VLU healing and there is complete uncertainty regarding the relationship. The review offers information for both future research and systematic review methodology.

Cell proliferation and migration mechanism of caffeoylserotonin and serotonin via serotonin 2B receptor in human keratinocyte HaCaT cells

Caffeoylserotonin (CaS), one derivative of serotonin (5-HT), is a secondary metabolite produced in pepper fruits with strong antioxidant activities. In this study, we investigated the effect of CaS on proliferation and migration of human keratinocyte HaCaT cells compared to that of 5-HT. CaS enhanced keratinocyte proliferation even under serum deficient condition. This effect of CaS was mediated by serotonin 2B receptor (5-HT2BR) related to the cell proliferation effect of 5-HT. We also confirmed that both CaS and 5-HT induced G1 progression via 5-HT2BR/ERK pathway in HaCaT cells. However, Akt pathway was additionally involved in upregulated expression levels of cyclin D1 and cyclin E induced by CaS by activating 5-HT2BR. Moreover, CaS and 5-HT induced cell migration in HaCaT cells via 5-HT2BR. However, 5-HT regulated cell migration only through ERK/AP-1/MMP9 pathway while additional Akt/NF-κB/MMP9 pathway was involved in the cell migration effect of CaS. These results suggest that CaS can enhance keratinocyte proliferation and migration. It might have potential as a reagent beneficial for wound closing and cell regeneration.

Reactive Oxygen Species and NOX Enzymes Are Emerging as Key Players in Cutaneous Wound Repair

Our understanding of the role of oxygen in cell physiology has evolved from its long-recognized importance as an essential factor in oxidative metabolism to its recognition as an important player in cell signaling. With regard to the latter, oxygen is needed for the generation of reactive oxygen species (ROS), which regulate a number of different cellular functions including differentiation, proliferation, apoptosis, migration, and contraction. Data specifically concerning the role of ROS-dependent signaling in cutaneous wound repair are very limited, especially regarding wound contraction. In this review we provide an overview of the current literature on the role of molecular and reactive oxygen in the physiology of wound repair as well as in the pathophysiology and therapy of chronic wounds, especially under ischemic and hyperglycemic conditions.

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.

Microbial alginate dressings show improved binding capacity for pathophysiological factors in chronic wounds compared to commercial alginate dressings of marine origin

Marine alginates are well established in wound management. Compared with different modern wound dressings, marine alginates cannot prove superior effects on wound healing. Alginates from bacteria have never been studied for medical applications so far, although the microbial polymer raises expectations for improved binding of wound factors because of its unique O-acetylation. Due to its possible positive effects on wound healing, alginates from bacteria might be a superior future medical product for clinical use. To prove the binding capacity of microbial alginates to pathophysiological factors in chronic wounds, we processed microbial alginate fibres, produced from fermentation of the soil bacterium Azotobacter vinelandii ATCC 9046, into needle web dressings and compared them with commercial dressings made of marine alginate. Four dressings were assessed: Marine alginate dressings containing either ionic silver or zinc/manganese/calcium, and microbial alginate dressings with and without nanosilver. All dressings were tested in an in vitro approach for influence on chronic wound parameters such as elastase, matrix metalloproteases-2, tumour necrosis factor-α, interleukin-8, and free radical formation. Despite the alginate origin or addition of antimicrobials, all dressings were able to reduce the concentration of the proinflammatory cytokines TNF-α and IL-8. However, microbial alginate was found to bind considerable larger amounts of elastase and matrix metalloproteases-2 in contrast to the marine alginate dressings. The incorporation of zinc, silver or nanosilver into alginate fibres did not improve their binding capacity for proteases or cytokines. The addition of nanosilver slightly enhanced the antioxidant capacity of microbial alginate dressings, whereas the marine alginate dressing containing zinc/manganese/calcium was unable to inhibit the formation of free radicals. The enhanced binding affinity by microbial alginate of Azotobacter vinelandii to pathophysiological factors may be interesting to support optimal conditions for wound healing.

Plasma Oxidative Stress in Patients With Chronic Vascular Cutaneous Ulcers

Oxidative stress is hypothesized to be one of the main causes of the pathophysiologic alterations observed during impaired healing of wounds. In the present study, we aimed to measure systemic levels of free radicals in blood and anti-oxidant (AO) activity in the plasma of patients with chronic ulcers (venous stasis ulcers and arterial insufficiency ulcers) of lower extremities (CULEs). Oxidants and AO activity were measured in eighty-five consecutive patients with CVSUs of the lower extremities as they arrived randomly for routine visits to our ambulatory clinic. Values of oxidant and AO status in patients with CULEs were significantly different from normal. No significant differences in oxidant and AO values were found between patients with arterial ulcers or those with venous ulcers. A significant difference was found in AO values of diabetic patients with chronic venous ulcers compared with non-diabetic patients with chronic venous ulcers. No significant differences were observed when evaluating oxidant/AO values and smoking habits. Precise reasons why the association of diabetes and venous (but not arterial) ulcers was correlated with defective AO status in plasma are not known. Other data were also intriguing: diminished AO activity was observed in female patients, no significant differences in oxidant and values were found between patients with arterial ulcers or those with venous ulcers, no significant correlation was found between age and oxidant, as well as no significant differences were observed when evaluating oxidant/AO values and smoking habits.

Induced oxidative stress management in wounds through phenolic acids engineered fibrous protein: An in vitro assessment using polymorphonuclear (PMN) cells

The present study explores the preparation, characterization and the role of phenolic acid tethered fibrous protein in the management of induced oxidative stress studied under in vitro conditions. In brief, the biomaterial is prepared by engineering the fibrous protein with dihydroxy and trihydroxy phenolic acid moieties and subjected to characterization to ensure the tethering. The resultant biomaterial studied for its efficacy as a free radical scavenger using polymorphonuclear (PMN) cells with induced oxidative stress and also as an agent for cell migration using fibroblasts cells. Results revealed that induced oxidative stress in PMN cells after exposure to UVB radiation managed well with the prepared biomaterial by reducing the levels of superoxide anion, oxygen and hydroxyl radicals. Further, the protein and the phenolic acid interaction supports the cell migration as evidenced from the scratch assay. In conclusion, though phenolic acids are well known for their antimicrobial and antioxidant potential, indenting these acids directly to the wounds is not sensible, but tethering to protein explored the scavenging activity as expected. The present study infers that phenolic acid engineered protein has a significant role in managing the imbalance in the redox state prevailing in wounds and supports the healing at appreciable level.

Effects of a novel NADPH oxidase inhibitor (S42909) on wound healing in an experimental ischemic excisional skin model

Chronic wounds are a serious healthcare problem. As non-healing wounds involve continuous pathologic inflammatory stage, research is focused on anti-inflammatory treatments. Our objective was to analyze the effect of S42909, a potent NADPH oxidase inhibitor activity, with vascular anti-inflammatory properties. An ischemic rabbit ear ulcer model (24 New Zealand white rabbits) was used to evaluate the reepithelialization/contraction areas, anti-/pro-inflammatory cytokines mRNA (TGF-β1/IL-10/IFN-γ/VEGF) by qRT-PCR, collagen I/III deposition, and neovascularization (TGF-β1/VEGF) by morphological and immunohistochemical analyses. Three different doses were administered by gavage for 2 weeks: 10 and 30 mg/kg/d in self-microemulsion drug delivery system (SMEDDS) and 100 mg/kg/d in arabic gum. Each vehicle was used as control. No signs of infection or necrosis were found. Reepithelialization was almost complete whatever the groups reaching 95% at the dose of 100 mg/kg. Wound contraction was significantly reduced in all S42909-treated groups. A significant increase in anti-inflammatory cytokines TGF-β1 mRNA and IL-10 mRNA was observed at the dose of 100 and 30 mg/kg/d, respectively. No changes were observed in pro-inflammatory factors INF-γ and VEGF mRNA. Ischemic skin wound areas had scarce expression of collagen I/III and showed rich glycosaminoglycans content. Treatment increased the collagen deposition and TGF-β1 protein expression and decreased glycosaminoglycan content dose dependently; however, no effect in VEGF was appreciated. Therefore, our results indicate that S42909 improved healing process by dampening excessive inflammation and facilitating collagen deposition without wound contraction phenomena. S42909 might be a promising therapy to treat chronic wounds as venous leg ulcers.

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.

Oxidative stress and antioxidant strategies in dermatology

Oxidative stress results from a prooxidant-antioxidant imbalance, leading to cellular damage. It is mediated by free radicals, such as reactive oxygen species or reactive nitrogen species, that are generated during physiological aerobic metabolism and pathological inflammatory processes. Skin serves as a protective organ that plays an important role in defending both external and internal toxic stimuli and maintaining homeostasis. It is becoming increasingly evident that oxidative stress is involved in numerous skin diseases and that antioxidative strategies can serve as effective and easy methods for improving these conditions. Herein, we review dysregulated antioxidant systems and antioxidative therapeutic strategies in dermatology.

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.

The Role of Hydrogen Peroxide and Other Reactive Oxygen Species in Wound Healing

Wound healing is a complex physiological process important for tissue homeostasis. An acute injury initiates massive cell migration, proliferation and differentiation, synthesis of extracellular matrix components, scar formation and remodelling. Blood flow and tissue oxygenation are parts of the complex regulation of healing. Higher organisms utilize molecular oxygen as a terminal oxidant. This way of gaining energy for vital processes such as healing leads to the production of a number of oxygen compounds that may have a defensive or informatory role. They may be harmful when present in high concentrations. Both the lack and the excess of reactive oxygen species may influence healing negatively.

Modulation of ROS levels in fibroblasts by altering mitochondria regulates the process of wound healing

Mitochondria are the major source of reactive oxygen species (ROS) in fibroblasts which are thought to be crucial regulators of wound healing with a potential to affect the expression of nuclear genes involved in this process. ROS generated by mitochondria are involved in all stages of tissue repair process but the regulation of ROS-generating system in fibroblasts still remains poorly understood. The purpose of this study was to better understand molecular mechanisms of how the regulation of ROS levels generated by mitochondria may influence the process of wound repair. Cybrid model system of mtDNA variations was used to study the functional consequences of altered ROS levels on wound healing responses in a uniform nuclear background of cultured ρ(0) fibroblasts. Mitochondrial ROS in cybrids were modulated by antioxidants that quench ROS to examine their ability to close the wound. Real-time PCR arrays were used to investigate whether ROS generated by specific mtDNA variants have the ability to alter expression of some key nuclear-encoded genes central to the wound healing response and oxidative stress. Our data suggest levels of mitochondrial ROS affect expression of some nuclear encoded genes central to wound healing response and oxidative stress and modulation of mitochondrial ROS by antioxidants positively affects in vitro process of wound closure. Thus, regulation of mitochondrial ROS-generating system in fibroblasts can be used as effective natural redox-based strategy to help treat non-healing wounds.

Periodic Exposure of Keratinocytes to Cold Physical Plasma: An In Vitro Model for Redox-Related Diseases of the Skin

Oxidative stress illustrates an imbalance between radical formation and removal. Frequent redox stress is critically involved in many human pathologies including cancer, psoriasis, and chronic wounds. However, reactive species pursue a dual role being involved in signaling on the one hand and oxidative damage on the other. Using a HaCaT keratinocyte cell culture model, we investigated redox regulation and inflammation to periodic, low-dose oxidative stress after two, six, eight, ten, and twelve weeks. Chronic redox stress was generated by recurrent incubation with cold physical plasma-treated cell culture medium. Using transcriptome microarray technology, we identified both acute ROS-stress responses as well as numerous adaptions after several weeks of redox challenge. We determined a differential expression (2-fold, FDR < 0.01, p < 0.05) of 260 genes that function in inflammation and redox homeostasis, such as cytokines (e.g., IL-6, IL-8, and IL-10), growth factors (e.g., CSF2, FGF, and IGF-2), and antioxidant enzymes (e.g., HMOX, NQO1, GPX, and PRDX). Apoptotic signaling was affected rather modestly, especially in p53 downstream targets (e.g., BCL2, BBC3, and GADD45). Strikingly, the cell-protective heat shock protein HSP27 was strongly upregulated (p < 0.001). These results suggested cellular adaptions to frequent redox stress and may help to better understand the inflammatory responses in redox-related diseases.

Cellular responses to egg-oil (charismon©)

Egg-oil (Charismon©) is known for its beneficial action in wound healing and other skin irritancies and its antibacterial activity. The physiological basis for these actions has been investigated using cells in culture: HaCaT-cells (immortalized human keratinocytes), human endothelial cells in culture (HUVEC), peripheral blood mononuclear lymphocytes (PBML) and a full thickness human skin model (FTSM). Emphasis was on the influence of egg-oil on cell migration and IL-8 production in HaCaT cells, respiration, mitochondrial membrane potential, reactive oxygen (ROS) production and proliferation in HUVEC and HaCaT cells, cytokine and interleukin production in PBML and UV-light induced damage of FTSM. IL-8 production by HaCaT cells is stimulated by egg-oil whilst in phythemagglutin in-activated PBMLs production of the interleukins IL-2, IL-6, IL-10 and IFN-γ and TFN-α is reduced. ROS-production after H(2)O(2) stimulation first is enhanced but later on reduced. Respiration becomes activated due to partial uncoupling of the mitochondrial respiratory chain and proliferation of HaCaT and HUVEC is reduced. Recovery of human epidermis cells in FTSM after UV-irradiation is strongly supported by egg-oil. These results support the view that egg-oil acts through reduction of inflammatory processes and ROS production. Both these processes are equally important in cellular aging as in healing of chronic wounds.

Pathogenesis of skin ulcers: lessons from the Mycobacterium ulcerans and Leishmania spp. pathogens

Skin ulcers are most commonly due to circulatory or metabolic disorders and are a major public health concern. In developed countries, chronic wounds affect more than 1 % of the population and their incidence is expected to follow those observed for diabetes and obesity. In tropical and subtropical countries, an additional issue is the occurrence of ulcers of infectious origins with diverse etiologies. While the severity of cutaneous Leishmaniasis correlates with protective immune responses, Buruli ulcers caused by Mycobacterium ulcerans develop in the absence of major inflammation. Based on these two examples, this review aims to demonstrate how studies on microorganism-provoked wounds can provide insight into the molecular mechanisms controlling skin integrity. We highlight the potential interest of a mouse model of non-inflammatory skin ulceration caused by intradermal injection of mycolactone, an original lipid toxin with ulcerative and immunosuppressive properties produced by M. ulcerans.

Generating and reversing chronic wounds in diabetic mice by manipulating wound redox parameters

By 2025, more than 500 M people worldwide will suffer from diabetes; 125 M will develop foot ulcer(s) and 20 M will undergo an amputation, creating a major health problem. Understanding how these wounds become chronic will provide insights to reverse chronicity. We hypothesized that oxidative stress (OS) in wounds is a critical component for generation of chronicity. We used the db/db mouse model of impaired healing and inhibited, at time of injury, two major antioxidant enzymes, catalase and glutathione peroxidase, creating high OS in the wounds. This was necessary and sufficient to trigger wounds to become chronic. The wounds initially contained a polymicrobial community that with time selected for specific biofilm-forming bacteria. To reverse chronicity we treated the wounds with the antioxidants α-tocopherol and N-acetylcysteine and found that OS was highly reduced, biofilms had increased sensitivity to antibiotics, and granulation tissue was formed with proper collagen deposition and remodeling. We show for the first time generation of chronic wounds in which biofilm develops spontaneously, illustrating importance of early and continued redox imbalance coupled with the presence of biofilm in development of wound chronicity. This model will help decipher additional mechanisms and potentially better diagnosis of chronicity and treatment of human chronic wounds.

Review and update on new horizon in the management of venous ulcers

Chronic venous ulcers (CVUs) contribute to functional deficits and are a source of significant morbidity among the affected population. In addition, they directly impact the quality of life of patients and are a significant economic burden on the health care system. In this review, we critically evaluate the current strategies for treating CVUs that have emerged within the last decade and outlined a suggested algorithm for treating patients with this difficult condition.

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.

Influence of secretory leukocyte protease inhibitor-based peptides on elastase activity and their incorporation in hyaluronic acid hydrogels for chronic wound therapy

Chronic nonhealing skin wounds, such as leg ulcers and pressure sores, represent a major clinical problem and a financial burden for the health care systems. Chronic wounds are characterized by prolonged inflammatory phase that results in high levels of elastase, reactive oxygen species (ROS), and diminished growth factor activity. Under normal physiological conditions, elastase is a powerful host defence and its activity is regulated by endogenous inhibitors. The unrestrained elastase activity in chronic wounds may be tuned by exogenous active materials that inhibit elastase. Secretory leucocyte protease inhibitor, SLPI, is a potent endogenous inhibitor of elastase. Peptide fragments, KRCCPDTCGIKCL (Pep4) and KRMMPDTMGIKML (Pep4M), selected from SLPI primary structure were studied as potential elastase inhibitors. Kinetic studies performed for human neutrophil elastase (HNE) and porcine pancreatic elastase (PPE) in presence of these peptides revealed that both behave as uncompetitive and noncompetitive inhibitors of HNE and PPE, respectively. The influence of ROS and albumin on Pep4 and Pep4M inhibitory activity toward elastase reveals that this mixture increases the inhibitory activity of both peptides. These peptides were incorporated in hyaluronic acid hydrogels to evaluate the possibility of being used as active compounds in a drug delivery system. Assessment of HNE and PPE activity in the presence of these hydrogels formulations revealed a considerable decrease in enzyme activity. Although, only moderated elastase inhibition was observed, these peptides represent potential candidates for chronic wound applications, as there is no need for complete elastase inhibition in the normal wound healing process.

Acute or chronic? What's the difference?

Acute and chronic wounds heal and behave differently. An understanding of these differences is imperative to the practitioner in providing and planning appropriate wound care and management. The purpose of this article is to present some of the major differences and enable the practitioner in developing and modifying an appropriate plan of care to enhance healing and manage patient expectations.

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.