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Chronic wounds are a common and costly health issue affecting millions of individuals in the United States, particularly those with underlying conditions such as diabetes, venous insufficiency, and peripheral artery disease. When standard treatments fail, advanced wound care therapies, such as skin substitutes, are often applied. However, the clinical effectiveness, indications, and comparative benefits of these therapies have not been well established. In this study, we report on the usage of both acellular and cellular, single and bilayer, natural and synthetic, dermal, and epidermal skin substitutes in a VA hospital system. We performed a retrospective chart review to understand the ordering and usage patterns of advanced wound therapies for patients with chronic wounds at the VA Northern California Health Care System. We examined types of products being recommended, categories of users recommending the products, indications for orders, and rate of repeated orders. Neuropathic, venous, or pressure ulcers were the main indications for using advanced wound matrices. Only 15.6% of patients for whom the matrices were ordered had supporting laboratory tests. Exactly 34.3% of the ordered matrices were not applied. And the use of wound matrices resulted in increased costs per patient visit of $1018-$3450. Our study sheds light on the usage patterns of these therapies in a VA healthcare facility and highlights the need for more robust evidence-based studies to determine the true benefits, efficacy, and cost-effectiveness of these innovative treatment options., (© 2024 The Authors. Wound Repair and Regeneration published by Wiley Periodicals LLC on behalf of The Wound Healing Society.)

In wound healing, individual cells' behaviors coordinate movement toward the wound center to restore small or large barrier defects. The migration of epithelial cells as a continuous sheet structure is one of the most important processes by which the skin barrier is restored. How such multicellular and tissue level movement is initiated upon injury, coordinated during healing, and stopped when wounds healed has been a research focus for decades. When skin is wounded, the compromised epithelial barrier generates endogenous electric fields (EFs), produced by ion channels and maintained by cell junctions. These EFs are present across wounds, with the cathodal pole at the wound center. Epithelial cells detect minute EFs and migrate directionally in response to electrical signals. It has long been postulated that the naturally occurring EFs facilitate wound healing by guiding cell migration. It is not until recently that experimental evidence has shown that large epithelial sheets of keratinocytes or corneal epithelial cells respond to applied EFs by collective directional migration. Although some of the mechanisms of the collective cell migration are similar to those used by isolated cells, there are unique mechanisms that govern the coordinated movement of the cohesive sheet. We will review the understanding of wound EFs and how epithelial cells and other cells important to wound healing respond to the electric signals individually as well as collectively. Mounting evidence suggests that wound bioelectrical signaling is an important mechanism in healing. Critical understanding and proper exploitation of this mechanism will be important for better wound healing and regeneration., (Copyright © 2022 Cold Spring Harbor Laboratory Press; all rights reserved.)

Non-healing wounds are a major medical challenge, affecting over 6.5 million people in the US alone, with associated healthcare costs of about $16 billion annually. They can result in prolonged hospitalizations, work loss, disability, poor quality of life, and in diabetic patients with foot ulcers, amputation of the affected limb in 25% of patients. Though chronic ulcers may arise from different underlying diseases, the unifying feature is chronic infection, driving persistent inflammation that prolongs the healing process. One of the most frequently cultured or genetically identified pathogens in skin wounds is Pseudomonas aeruginosa. This species avidly forms biofilms in the wound that impede bacterial eradication by the host's immune mechanisms and limit efficacy of systemic antibiotics. Thus, non-antibiotic approaches to limit the growth and biofilm formation of this wound pathogen would be an advance in the treatment of chronic wounds. Prior work has demonstrated that the growth of other microbial species can be modulated by catecholamine agonists and antagonists of the adrenergic receptors (ARs). Here, we demonstrate that not only can the growth of this common wound pathogen be modulated by catecholamines, but also that the beta-AR antagonists can significantly decrease their growth, and importantly, limit their ability to form biofilms. These findings suggest that beta adrenergic antagonists may have a therapeutic role in the treatment of chronic skin wounds., (© 2022 Federation of American Societies for Experimental Biology.)

Skin is innervated by a multitude of sensory nerves that are important to the function of this barrier tissue in homeostasis and injury. The role of innervation and neuromediators has been previously reviewed so here we focus on the role of the transient receptor potential cation channel, subfamily V member 1 (TRPV1) in wound healing, with the intent of targeting it in treatment of non-healing wounds. TRPV1 structure and function as well as the outcomes of TRPV1-targeted therapies utilized in several diseases and tissues are summarized. In skin, keratinocytes, sebocytes, nociceptors, and several immune cells express TRPV1, making it an attractive focus area for treating wounds. Many intrinsic and extrinsic factors confound the function and targeting of TRPV1 and may lead to adverse or off-target effects. Therefore, a better understanding of what is known about the role of TRPV1 in skin and wound healing will inform future therapies to treat impaired and chronic wounds to improve healing.

Diabetic foot ulcers are a major health care concern with limited effective therapies. Mesenchymal stem cell (MSC)-based therapies are promising treatment options due to their beneficial effects of immunomodulation, angiogenesis, and other paracrine effects. We investigated whether a bioengineered scaffold device containing hypoxia-preconditioned, allogeneic human MSCs combined with the beta-adrenergic antagonist timolol could improve impaired wound healing in diabetic mice. Different iterations were tested to optimize the primary wound outcome, which was percent of wound epithelialization. MSC preconditioned in 1 μM timolol at 1% oxygen (hypoxia) seeded at a density of 2.5 × 10 5  cells/cm 2 on Integra Matrix Wound Scaffold (MSC/T/H/S) applied to wounds and combined with daily topical timolol applications at 2.9 mM resulted in optimal wound epithelialization 65.6% (24.9% ± 13.0% with MSC/T/H/S vs 41.2% ± 20.1%, in control). Systemic absorption of timolol was below the HPLC limit of quantification, suggesting that with the 7-day treatment, accumulative steady-state timolol concentration is minimal. In the early inflammation stage of healing, the MSC/T/H/S treatment increased CCL2 expression, lowered the pro-inflammatory cytokines IL-1B and IL6 levels, decreased neutrophils by 44.8%, and shifted the macrophage ratio of M2/M1 to 1.9 in the wound, demonstrating an anti-inflammatory benefit. Importantly, expression of the endothelial marker CD31 was increased by 2.5-fold with this treatment. Overall, the combination device successfully improved wound healing and reduced the wound inflammatory response in the diabetic mouse model, suggesting that it could be translated to a therapy for patients with diabetic chronic wounds., (© 2020 The Authors. STEM CELLS TRANSLATIONAL MEDICINE published by Wiley Periodicals LLC on behalf of AlphaMed Press.)

Background: Diabetic foot ulcers (DFUs) are the most common cause of leg amputations and their management is extremely challenging. Despite many advances and expensive therapies, there has been little success in improving outcomes of DFUs. In prior work our laboratory has examined the effects of beta-adrenergic antagonists (βAAs) on skin and skin-derived cells. We have shown that βAAs enhance the rate of keratinocyte migration, promote angiogenesis, and hasten wound healing in scratch wounds in vitro, in animal wound models, and in anecdotally reported cases of chronic wounds that healed successfully after topical application of the βAA timolol. Thus, we propose to test timolol directly on DFUs to determine if it improves healing above the current standard of care (SOC). This study will examine the efficacy and safety of topically applied beta-antagonist Timoptic-XE® (timolol maleate ophthalmic gel forming solution) in subjects with DFUs., Methods/design: This is a phase two, randomized, double-blinded, controlled, and parallel-group clinical trial with two treatment arms, SOC plus topical Timoptic-XE® and SOC plus a non-biologically active gel (hydrogel, as placebo drug). Study subjects with a DFU will be selected from the Veterans Affairs Northern California Health Care System (VANCHCS). Study duration is up to 31 weeks, with three phases (screening phase for two weeks, active phase for up to 12 weeks, with an additional second consecutive confirmatory visit after 2 weeks, and follow-up phase comprising monthly visits for 4 months). Subjects will apply daily either the topical study drug or the placebo on the foot ulcer for 12 weeks or until healed, whichever comes first. Measurements of wound size and other data will be collected at baseline, followed by weekly visits for 12 weeks, and then a monthly follow-up period., Discussion: This is a clinical translation study, moving the investigators' pre-clinical laboratory research into a translational study in which we will analyze clinical outcomes to assess for safety and estimate the efficacy of a topical beta-antagonist in healing of DFUs. The results from this trial may establish new treatment paradigms and safety profile for DFU treatment., Trial Registration: ClinicalTrials.gov, NCT03282981. Registered on June 14th, 2018.

Therapeutic applications for mesenchymal stem/stromal cells (MSCs) are growing; however, the successful implementation of these therapies requires the development of appropriate MSC delivery systems. Hydrogels are ideally suited to cultivate MSCs but tuning hydrogel properties to match their specific in vivo applications remains a challenge. Thus, further characterization of how hydrogel-based delivery vehicles broadly influence MSC function and fate will help lead to the next generation of more intelligently designed delivery vehicles. To date, few attempts have been made to comprehensively characterize hydrogel impact on the MSC transcriptome. Herein, we have synthesized cell-degradable hydrogels based on bio-inert poly(ethylene glycol) tethered with specific integrin-binding small molecules and have characterized their resulting effect on the MSC transcriptome when compared with 2D cultured and untethered 3D hydrogel cultured MSCs. The 3D culture systems resulted in alterations in the MSC transcriptome, as is evident by the differential expression of genes related to extracellular matrix production, glycosylation, metabolism, signal transduction, gene epigenetic regulation, and development. For example, genes important for osteogenic differentiation were upregulated in 3D hydrogel cultures, and the expression of these genes could be partially suppressed by tethering an integrin-binding RGD peptide within the hydrogel. Highlighting the utility of tunable hydrogels, when applied to ex vivo human wounds the RGD-tethered hydrogel was able to support wound re-epithelialization, possibly due to its ability to increase PDGF expression and decrease IL-6 expression. These results will aid in future hydrogel design for a broad range of applications., (©AlphaMed Press 2019.)

Chronic wounds exhibit persistent inflammation with markedly delayed healing. The significant burden of chronic wounds, which are often resistant to standard therapy, prompts further research on novel therapies. Since the interleukin-17 family has been implicated as a group of proinflammatory cytokines in immune-mediated diseases in the gut and connective tissue, as well as inflammatory skin conditions, we consider here if it may contribute to the pathogenesis of chronic wounds. In this review, we discuss the interleukin-17 family's signaling pathways and role in tissue repair. A PubMed review of the English literature on interleukin-17, wound healing, chronic wounds, and inflammatory skin conditions was conducted. Interleukin-17 family signaling is reviewed in the context of tissue repair, and preclinical and clinical studies examining its role in the skin and other organ systems are critically reviewed. The published work supports a pathologic role for interleukin-17 family members in chronic wounds, though this needs to be more conclusively proven. Clinical studies using monoclonal interleukin-17 antibodies to improve healing of chronic skin wounds have not yet been performed, and only a few studies have examined interleukin-17 family expression in chronic skin wounds. Furthermore, different interleukin-17 family members could be playing selective roles in the repair process. These studies suggest a therapeutic role for targeting interleukin-17A to promote wound healing; therefore, interleukin-17A may be a target worthy of pursuing in the near future., Competing Interests: The authors declare that they have no conflicts of interest., (Copyright © 2019 Yasmin Hadian et al.)

The prevalence of infection in chronic wounds is well documented in the literature but not optimally studied due to the drawbacks of current methodologies. Here, we describe a tractable and simplified ex vivo human skin model of infection that addresses the critical drawbacks of high costs and limited translatability. Wounds were generated from excised abdominal skin from cosmetic procedures and cultured, inoculated with Staphylococcus aureus strain UAMS-1, or under aseptic conditions. After three days, the infected wounds exhibited biofilm formation and significantly impaired reepithelialization compared to the control. Additionally, promigratory and proreparative genes were significantly downregulated, while proinflammatory genes were significantly upregulated, demonstrating molecular characterizations of impaired healing as in chronic wounds. This model allows for a simplified and versatile tool for the study of wound infection and subsequent development of novel therapies., (© 2019 by the Wound Healing Society.)

In a scenario involving a nuclear detonation during war or a terrorist attack, acute radiation exposure combined with thermal and blast effects results in severe skin injury. Although the cutaneous injury in such a scenario may not be lethal, it may lead to inflammation, delayed wound healing and loss of the skin barrier, resulting in an increased risk of infection. In this study, we tested the potential use of timolol, a beta-adrenergic receptor antagonist, to improve epidermal wound closure after combined burn and radiation injury using an ex vivo human skin culture model. Daily application of 10 μ M timolol after combined injury (burn and 10 Gy ex vivo irradiation) increased wound epithelialization by 5-20%. In addition, exposure to 10 Gy significantly suppressed epidermal keratinocyte proliferation by 46% at 48 h postirradiation. Similar to what has been observed in a thermal burn injury, the enzyme phenylethanolamine N-methyltransferase (PNMT), which generates epinephrine, was elevated in the combined thermal burn and radiation wounds. This likely resulted in elevated tissue levels of this catecholamine, which has been shown to delay healing. Thus, with the addition of timolol to the wound to block the binding of locally generated epinephrine to the beta-adrenergic receptor, healing is improved. This work suggests that by antagonizing local epinephrine action within the wound, a beta-adrenergic receptor antagonist such as timolol may be a useful adjunctive treatment to improve healing in the combined burn and radiation injury.

Diabetes mellitus (DM) is a significant international health concern affecting more than 387 million individuals. A diabetic person has a 25% lifetime risk of developing a diabetic foot ulcer (DFU), leading to limb amputation in up to one in six DFU patients. Low-level light therapy (LLLT) uses low-power lasers or light-emitting diodes to alter cellular function and molecular pathways, and may be a promising treatment for DFU. The goal of this systematic review is to examine whether the clinical use of LLLT is effective in the healing of DFU at 12 and 20 weeks in comparison with the standard of care, and to provide evidence-based recommendation and future clinical guidelines for the treatment of DFU using LLLT. On September 30, 2015, we searched PubMed, EMBASE, CINAHL, and Web of Science databases using the following terms: "diabetic foot" AND "low level light therapy," OR "light emitting diode," OR "phototherapy," OR "laser." The relevant articles that met the following criteria were selected for inclusion: randomized control trials (RCTs) that investigated the use of LLLT for treatment of DFU. Four RCTs involving 131 participants were suitable for inclusion based upon our criteria. The clinical trials used sham irriadiation, low dose, or nontherapeutic LLLT as placebo or control in comparison to LLLT. The endpoints included ulcer size and time to complete healing with follow-up ranging from 2 to 16 weeks. Each article was assigned a level of evidence (LOE) and graded according to the Oxford Center for Evidence-based Medicine Levels of Evidence Grades of Recommendation criteria. Limitations of reviewed RCTs include a small sample size (N < 100), unclear allocation concealment, lack of screening phase to exclude rapid healers, unclear inclusion/exclusion criteria, short (<30 days) follow-up period, and unclear treatment settings (wavelength and treatment time). However, all reviewed RCTs demonstrated therapeutic outcomes with no adverse events using LLLT for treatment of DFU. This systematic review reports that LLLT has significant potential to become a portable, minimally invasive, easy-to-use, and cost effective modality for treatment of DFU. To enthusiastically recommend LLLT for treatment of DFU, additional studies with comparable laser parameters, screening period to exclude rapid healers, larger sample sizes and longer follow-up periods are required. We envision future stringent RCTs may validate LLLT for treatment of DFU. Systematic review registration number: PROSPERO CRD42015029825., (© 2016 by the Wound Healing Society.)

Toll-like receptors (TLRs) are considered to be the first responders in the defense against invading pathogens. TLR engagement by ligands triggers inflammatory responses in injury and trauma, and thus can impair or contribute to the healing process, depending on TLRs' expression pattern, cellular localization, signaling, and deployment of inflammatory responses. Understanding these attributes could improve therapeutic strategies for treating chronic wounds.

Background/purpose: Wound healing is a complex process that involves multiple intercellular and intracellular processes and extracellular interactions. Explanted human skin has been used as a model for the re-epithelialization phase of human wound healing. The currently used standard technique uses a circular punch biopsy tool to make the initial wound. Despite its wide use, the geometry of round wounds makes it difficult to measure them reliably., Methods: Our group has designed a linear wounding tool, and compared the variability in ex vivo human linear and circular wounds., Results: An F test for differences in variances demonstrated that the linear wounds provided a population of wound size measurements that was 50% less variable than that obtained from a group of matched circular wounds. This reduction in variability would provide substantial advantages for the linear wound technique over the circular wound punch technique, by reducing the sample sizes required for comparative studies of factors that alter healing., Conclusion: This linear wounding tool thus provides a method for wounding that is standardized, provides minimal error in wound gap measurements, and is easily reproducible. We demonstrate its utility in an ex vivo model for the controlled investigation of human skin wounds., (© 2011 John Wiley & Sons A/S.)

Catecholamines are present in saliva, but their influence on oral epithelium is not understood. Because psychological stress increases salivary catecholamines and impairs oral mucosal wound healing, we sought to determine if epithelial adrenergic signaling could link these two findings. We found that cultured human oral keratinocytes (HOK) express the α(2B)- and β(2)-adrenergic receptors (ARs). Exposure of HOK to either epinephrine or the β-AR agonist, isoproterenol, reduced migratory speed and decreased in vitro scratch wound healing. Incubation with the β-AR antagonist timolol reversed the catecholamine-induced effects, indicating that the observed response is mediated by β-AR. Epinephrine treatment decreased phosphorylation of the mitogen-activated protein kinases (MAPK) ERK1/2 and p38; these decreases were also reversed with timolol. Cultured HOK express enzymes of the epinephrine synthetic pathway, and generate epinephrine. These findings demonstrate that stress-induced elevations of salivary catecholamines signal through MAPK pathways, and result in impaired oral keratinocyte migration required for healing.

Many facets of wound healing under redox control require a delicate balance between oxidative stress and antioxidants. While the normal physiology of wound healing depends on low levels of reactive oxygen species and oxidative stress, an overexposure to oxidative stress leads to impaired wound healing. Antioxidants are postulated to help control wound oxidative stress and thereby accelerate wound healing. Many antioxidants are available over the counter or by prescription, but only one, Medihoney®, has been specifically FDA approved for wound healing. Here we review the existing evidence for the use of antioxidants for wound healing, with a review of the pertinent animal and clinical studies. Natural products and naturally derived antioxidants are becoming more popular, and we specifically review the evidence for the use of naturally derived antioxidants in wound healing. Antioxidant therapy for wound healing is promising, but only few animal studies and even fewer clinical studies are available. Because only few products have undergone FDA approval, the consumer is advised to scrutinize them for purity and contaminants prior to use, and this may require direct contact with the companies that sell them. As a field of science, the use of antioxidants for wound healing is in its infancy, and future studies will better elucidate the role of antioxidants in wound healing., (Copyright © 2011 S. Karger AG, Basel.)

Toll-like receptor-2 (TLR2) is a pivotal pathogen recognition receptor that has a key role in inflammation, diabetes, and injury. Hyperglycemia, inflammation, and oxidative stress induce TLR2-myeloid differentiation factor-88 (MyD88) expression and signaling, and are major pathophysiological mechanisms in the impaired diabetic wound-healing process. The aim of the study was to examine the contribution of TLR2-MyD88 expression and signaling to the prolonged inflammation observed in diabetic wounds. Diabetes was induced in male C57BL/6J and TLR2(-/-) mice using streptozotocin (STZ) with matching nondiabetic mice as control. In addition, nonobese diabetic (NOD) mice were used to represent the spontaneous type 1 diabetes condition. After 2 weeks of persistent hyperglycemia in the mice, full-thickness excision wounds were made on the backs aseptically. Total RNA and protein were subjected to real-time PCR and western blot analyses. Wound sizes were measured using digital planimetry. TLR2 mRNA and protein expression increased significantly in wounds of C57BL/6J+STZ and NOD mice (P<0.05) compared with nondiabetic C57BL/6J mice. MyD88 expression, interleukin receptor-associated kinase-1 phosphorylation, and nuclear factor-κ B (NF-κB) activation were increased in diabetic wounds compared with nondiabetic wounds. Wounds of TLR2(-/-)+STZ mice showed less oxidative stress, decreased MyD88 signaling, NF-κB activation, and cytokine secretion. The wound closure was significant in TLR2(-/-)+ STZ mice compared with C57BL/6J+STZ mice. Collectively, our findings show that increased TLR2 mRNA and protein expression, signaling, and activation contribute to the prolonged inflammation in the diabetic wounds and that absence of TLR2 may result in decreased inflammation and improved wound healing.

Background: Stress, both acute and chronic, can impair cutaneous wound repair, which has previously been mechanistically ascribed to stress-induced elevations of cortisol. Here we aimed to examine an alternate explanation that the stress-induced hormone epinephrine directly impairs keratinocyte motility and wound re-epithelialization. Burn wounds are examined as a prototype of a high-stress, high-epinephrine, wound environment. Because keratinocytes express the beta2-adrenergic receptor (beta2AR), another study objective was to determine whether beta2AR antagonists could block epinephrine effects on healing and improve wound repair., Methods and Findings: Migratory rates of normal human keratinocytes exposed to physiologically relevant levels of epinephrine were measured. To determine the role of the receptor, keratinocytes derived from animals in which the beta2AR had been genetically deleted were similarly examined. The rate of healing of burn wounds generated in excised human skin in high and low epinephrine environments was measured. We utilized an in vivo burn wound model in animals with implanted pumps to deliver beta2AR active drugs to study how these alter healing in vivo. Immunocytochemistry and immunoblotting were used to examine the up-regulation of catecholamine synthetic enzymes in burned tissue, and immunoassay for epinephrine determined the levels of this catecholamine in affected tissue and in the circulation. When epinephrine levels in the culture medium are elevated to the range found in burn-stressed animals, the migratory rate of both cultured human and murine keratinocytes is impaired (reduced by 76%, 95% confidence interval [CI] 56%-95% in humans, p < 0.001, and by 36%, 95% CI 24%-49% in mice, p = 0.001), and wound re-epithelialization in explanted burned human skin is delayed (by 23%, 95% CI 10%-36%, p = 0.001), as compared to cells or tissues incubated in medium without added epinephrine. This impairment is reversed by beta2AR antagonists, is absent in murine keratinocytes that are genetically depleted of the beta2AR, and is reproduced by incubation of keratinocytes with other beta2AR-specific agonists. Activation of the beta2AR in cultured keratinocytes signals the down-regulation of the AKT pathway, accompanied by a stabilization of the actin cytoskeleton and an increase in focal adhesion formation, resulting in a nonmigratory phenotype. Burn wound injury in excised human skin also rapidly up-regulates the intra-epithelial expression of the epinephrine synthesizing enzyme phenylethanolamine-N-methyltransferase, and tissue levels of epinephrine rise dramatically (15-fold) in the burn wounded tissue (values of epinephrine expressed as pg/ug protein +/- standard error of the mean: unburned control, 0.6 +/- 0.36; immediately postburn, 9.6 +/- 1.58; 2 h postburn, 3.1 +/- 1.08; 24 h post-burn, 6.7 +/- 0.94). Finally, using an animal burn wound model (20% body surface in mice), we found that systemic treatment with betaAR antagonists results in a significant increase (44%, 95% CI 27%-61%, p < 0.00000001) in the rate of burn wound re-epithelialization., Conclusions: This work demonstrates an alternate pathway by which stress can impair healing: by stress-induced elevation of epinephrine levels resulting in activation of the keratinocyte beta2AR and the impairment of cell motility and wound re-epithelialization. Furthermore, since the burn wound locally generates epinephrine in response to wounding, epinephrine levels are locally, as well as systemically, elevated, and wound healing is impacted by these dual mechanisms. Treatment with beta adrenergic antagonists significantly improves the rate of burn wound re-epithelialization. This work suggests that specific beta2AR antagonists may be apt, near-term translational therapeutic targets for enhancing burn wound healing, and may provide a novel, low-cost, safe approach to improving skin wound repair in the stressed individual.

Adrenergic receptors and their downstream effector molecules are expressed in all cell types in the skin, and it is only recently that functionality of the catecholamine agonist activated signaling in the cutaneous repair process has been revealed. In addition to responding to systemic elevations in catecholamines (as in stress situations) or to pharmacologically administered adrenergic agonists, epidermal keratinocytes themselves can synthesize catecholamine ligands. They also respond to these systemic or self-generated agonists via receptor mediated signaling, resulting in altered migration, and changes in wound re-epithelialization. Endothelial cells, inflammatory cells, dermal fibroblasts, and mesenchymal stem cells, all cells that contribute to the wound repair process, express multiple subtypes of adrenergic receptors and exhibit responses that can be either contribute or impair healing-and occasionally, depending on the species and assay conditions, results can be conflicting. There is still much to be uncovered regarding how this self-contained autocrine and paracrine signaling system contributes to cutaneous wound repair.

Neutrophil influx is an early inflammatory response that is essential for the clearance of bacteria and cellular debris during cutaneous wounding. A non-invasive real-time fluorescence imaging technique was developed to examine the kinetics of enhanced green fluorescence protein-polymorphonuclear leukocyte (EGFP-PMN) influx within a wound. We hypothesized that infection or systemic availability would directly regulate the dynamics of EGFP-PMN recruitment and the efficiency of wound closure. Neutrophil recruitment increased dramatically over the first 24 hours from 10(6) at 4 hours up to a maximum of 5 x 10(6) EGFP-PMNs at 18 hours. A high rate of EGFP-PMN turnover was evidenced by approximately 80% decrease in EGFP signal within 6 hours. In response to wound colonization by Staphylococcus aureus or injection of GM-CSF, systemic PMNs increased twofold above saline control. This correlated with an increase in EGFP-PMN recruitment up to approximately 10(7) within the wound. Despite this effect by these distinct inflammatory drivers, wound closure occurred at a rate similar to the saline-treated control group. In summary, a non-invasive fluorescence-based imaging approach combined with genetic labeling of neutrophils provides a dynamic inner view of inflammation and the kinetics of neutrophil infiltration into the wounded skin over extended durations.

Purpose: Beta-adrenergic receptor (AR) antagonists are frequently prescribed ophthalmic drugs, yet previous investigations into how catecholamines affect corneal wound healing have yielded conflicting, Results: With the use of an integrated pharmacologic and genetic approach, the authors investigated how the beta-AR impacts corneal epithelial healing., Methods: Migratory rates of cultured adult murine corneal epithelial (AMCE) cells and in vivo corneal wound healing were examined in beta2-AR(+/+) and beta2-AR(-/-) mice. Signaling pathways were evaluated by immunoblotting. results. The beta-AR agonist isoproterenol decreased AMCE cell migratory speed to 70% of untreated controls, and this was correlated with a 0.60-fold decrease in levels of activated phospho-ERK (P-ERK). Treatment with the beta-AR antagonist (timolol) increased speed 33% and increased P-ERK 2.4-fold (P < 0.05). The same treatment protocols had no effect on AMCE cells derived from beta2-AR(-/-) mice; all treatment groups showed statistically equivalent migratory speeds and ERK phosphorylation. In beta2-AR(+/+) animals, the beta-AR agonist (isoproterenol) delayed the rate of in vivo corneal wound healing by 79%, whereas beta-AR antagonist (timolol) treatment increased the rate of healing by 16% (P < 0.05) compared with saline-treated controls. In contrast, in the beta2-AR(-/-) mice, all treatment groups demonstrated equivalent rates of wound healing. Additionally, murine corneal epithelial cell expressed the catecholamine-synthesizing enzyme tyrosine hydroxylase and detectable levels of epinephrine (184.5 pg/mg protein)., Conclusions: The authors provide evidence of an endogenous autocrine catecholamine signaling pathway dependent on an intact beta2-AR for the modulation of corneal epithelial wound repair.

Beta2 adrenergic receptors were identified in keratinocytes more than 30 years ago, but their function in the epidermis continues to be elucidated. Abnormalities in their expression, signaling pathway, or in the generation of endogenous catecholamine agonists by keratinocytes have been implicated in the pathogenesis of cutaneous diseases such as atopic dermatitis, vitiligo, and psoriasis. New studies also indicate that the beta2AR also modulates keratinocyte migration, and thus can function to regulate wound reepithelialization. This review focuses on the function of these receptors in keratinocytes and their contribution to cutaneous physiology and disease.

An optimal system for monitoring in vivo corneal wound healing is inexpensive, has utility for wounding and imaging, and is able to provide previews before photography. We outline such an imaging system that takes advantage of a consumer digital camera and an LED-based light source for fluorescein excitation. Using FVB/NJ mice, 2mm diameter, circular, axial corneal epithelial defects were created using a crescent blade. The corneal wounds were imaged every four hours until healed using a Nikon Coolpix 5400 camera attached to a Nikon SMZ-10A stereomicroscope, using the illumination from a 16 LED 464nm flashlight. The wound area was calculated, and the linear regressions of the linear phase of wound healing were compared using the F-test. The slopes of the linear regressions for the 6 trials of 4 mice/trial had an average of -52.95microm/h (SEM=0.55microm/h) and were statistically equivalent (p>0.05). The mean of the R(2) values for the linear regressions was 0.9546 (SEM=0.0121). The equivalent linear regressions and R(2)>0.90 suggest that the imaging system could precisely monitor the wound healing of multiple trials and of animals within each trial, respectively. Using a consumer digital camera and LED-based illumination, we have established a system that is economical, is used in both wounding and imaging, is operated by a single person, and is able to provide real-time previews to monitor corneal wound healing precisely.

An essential feature of a healed wound is the restoration of an intact epidermal barrier through wound epithelialization, also known as re-epithelialization. The directed migration of keratinocytes is critical to wound epithelialization and defects in this function are associated with the clinical phenotype of chronic non-healing wounds. A complex balance of signaling factors and surface proteins are expressed and regulated in a temporospatial manner that promote keratinocyte motility and survival to activate wound re-epithelialization. The majority of this review focuses on the mechanisms that regulate keratinocyte migration in the re-epithelialization process. This includes a review of cell attachments via desmosomes, hemidesmosomes, and integrins, the expression of keratins, the role of growth factors, cytokines and chemokines, eicosanoids, oxygen tension, antimicrobial peptides, and matrix metalloproteinases. Also reviewed are recently emerging novel mediators of keratinocyte motility including the role of electric fields, and signaling via the acetylcholine and beta-adrenergic receptors. These multiple regulators impact the ability of keratinocytes to migrate from the wound edge or other epidermal reservoirs to efficiently re-epithelialize a breach in the integrity of the epidermis. New discoveries will continue to uncover the elegant network of events that result in restoration of epidermal integrity and complete the wound repair process.

Wound healing is a complex and well-orchestrated biological process. Corneal epithelial cells (CECs) must respond quickly to trauma to rapidly restore barrier function and protect the eye from noxious agents. They express a high level of beta2-adrenergic receptors but their function is unknown. Here, we report the novel finding that they form part of a regulatory network in the corneal epithelium, capable of modulating corneal epithelial wound repair. Beta-adrenergic receptor agonists delay CEC migration via a protein phosphatase 2A-mediated mechanism and decrease both electric field-directed migration and corneal wound healing. Conversely, beta-adrenergic receptor antagonists accelerate CEC migration, enhance electric field-mediated directional migration, and promote corneal wound repair. We demonstrate that CECs express key enzymes required for epinephrine (beta-adrenergic receptor agonist) synthesis in the cytoplasm and can detect epinephrine in cell extracts. We propose that the mechanism for the pro-motogenic effect of the beta-adrenergic antagonist is blockade of the beta2-adrenergic receptor preventing autocrine catecholamine binding. Further investigation of this network will improve our understanding of one of the most frequently prescribed class of drugs., ((c) 2007 Wiley-Liss, Inc.)

The skin is our primary defense against noxious environmental agents. Upon injury, keratinocytes migrate directionally into the wound bed to initiate re-epithelialization, essential for wound repair and restoration of barrier integrity. Keratinocytes express a high level of beta2-adrenergic receptors (beta2-ARs) that appear to play a role in cutaneous homeostasis as aberrations in either keratinocyte beta2-AR function or density are associated with various skin diseases. Here we report the novel finding that beta-AR antagonists promote wound re-epithelialization in a "chronic" human skin wound-healing model. beta-AR antagonists increase ERK phosphorylation, the rate of keratinocyte migration, electric field-directed migration, and ultimately accelerate human skin wound re-epithelialization. We demonstrate that keratinocytes express two key enzymes required for catecholamine (beta-AR agonist) synthesis, tyrosine hydroxylase and phenylethanolamine-N-methyl transferase, both localized within keratinocyte cytoplasmic vesicles. Finally, we confirm the synthesis of epinephrine by measuring the endogenously synthesized catecholamine in keratinocyte extracts. Previously, we have demonstrated that beta-AR agonists delay wound re-epithelialization. Here we report that the mechanism for the beta-AR antagonist-mediated augmentation of wound repair is due to beta2-AR blockade, preventing the binding of endogenously synthesized epinephrine. Our work describes an endogenous beta-AR mediator network in the skin that can temporally regulate skin wound repair. Further investigation of this network will improve our understanding of both the skin repair process and the multiple modes of action of one of the most frequently prescribed class of drugs, hopefully resulting in a new treatment for chronic wounds.

Dermal fibroblasts are required for skin wound repair; they migrate into the wound bed, proliferate, synthesize extracellular matrix components and contract the wound. Although fibroblasts express beta2-adrenergic receptors (beta2-AR) and cutaneous keratinocytes can synthesize beta-AR agonists (catecholamines), the functional significance of this hormonal mediator network in the skin has not been addressed. Emerging studies from our laboratory demonstrate that beta2-AR activation modulates keratinocyte migration, essential for wound re-epithelialization. Here we describe an investigation of the effects of beta2-AR activation on the dermal component of wound healing. We examined beta2-AR-mediated regulation of biological processes in dermal fibroblasts that are critical for wound repair: migration, proliferation, contractile ability and cytoskeletal conformation. We provide evidence for the activation of at least two divergent beta2-AR-mediated signaling pathways in dermal fibroblasts, a Src-dependent pro-migratory pathway, transduced through the epidermal growth factor receptor and extracellular signal-regulated kinase, and a PKA-dependent pro-proliferative pathway. beta2-AR activation attenuates collagen gel contraction and alters the actin cytoskeleton and focal adhesion distribution through PKA-dependent mechanisms. Our work uncovers a previously unrecognized role for the adrenergic hormonal mediator network in the cutaneous wound repair process. Exploiting these divergent beta2-AR agonist responses in cutaneous cells may generate novel therapeutic approaches for the control of wound healing.

A microneedle array has been fabricated and applied to the measurement of transdermal skin potentials in human subjects. Potential changes were recorded in the vicinity of superficial wounds, confirming the generation of a lateral electric field in human skin. The measured electric field decays with distance from the wound edge, and is directed towards the wound. The measurement of endogenous fields in skin is a prelude to the study of the therapeutic efficacy of applied electric fields to chronic non-healing wounds.

Keratinocytes migrate directionally into the wound bed to initiate re-epithelialization, necessary for wound closure and restoration of barrier function. They solely express the beta2-adrenergic receptor (beta2-AR) subtype of beta-ARs and can also synthesize beta-AR agonists generating a hormonal mediator network in the skin. Emerging studies from our laboratory demonstrate that beta-AR agonists decrease keratinocyte migration via a protein phosphatase (PP) 2A-dependent mechanism. Here we have extended our investigations to observe the effects of beta2-AR activation on keratinocyte polarization, migration, and ERK phosphorylation at the wound edge, cytoskeletal organization, phospho-ERK intracellular localization, proliferation, human skin wound re-epithelialization, wound-induced ERK phosphorylation, and murine skin wound healing. We demonstrate that in keratinocytes, beta2-AR activation is anti-motogenic and anti-mitogenic with both mechanisms being PP2A dependent. beta2-AR activation dramatically alters the organization of the actin cytoskeleton and prevents localization of phospho-ERK to the lamellipodial edge and its colocalization with vinculin. Finally, we demonstrate a beta2-AR-mediated delay in re-epithelialization and decrease in wound-induced epidermal ERK phosphorylation in human skin wounds and a delay in re-epithelialization in murine tail-clip wounds. Our work uncovers novel keratinocyte biology and a previously unrecognized role for the adrenergic hormonal mediator network in the wound repair process.

Chronic wounds present a significant challenge, because there are few available treatment options for timely healing. Topical negative pressure devices have been used in a number of different types of wounds, including chronic wounds. They are believed to hasten wound healing by (1) maintaining a moist environment, (2) removing wound exudates, (3) increasing local blood flow, (4) increasing granulation tissue formation, (5) applying mechanical pressure to promote wound closure, and (6) reducing bacterial loads in the wound. Multiple nonrandomized, noncontrolled studies have reported that the use of these devices results in faster healing times and more successful closures. Five small randomized, controlled trials have also shown favorable outcomes with the use of topical negative pressure devices compared with conventional treatment. Adverse effects include discomfort, pain, and excessive tissue growth into the dressing. Complications are limited if the device is used properly. In light of the current treatment options, topical negative pressure devices may be considered useful as adjuvant therapy for chronic wounds; however, there is inadequate definitive evidence that wound healing is substantially better with these devices than with traditional therapy.

Dermal fibroblasts actively contribute to wound healing by migrating to the wound, synthesizing extracellular matrices, and generating mechanical forces within the wound to initiate wound contraction. Fibroblast-seeded collagen gels provide an in vitro model to study wound contraction. The authors are evaluating the role of the adrenergic signaling system in cutaneous wound repair and recently found that beta2-adrenergic receptor (beta2-AR) activation markedly decreases keratinocyte migration, an essential step in wound reepithelialization. Because the beta2-ARs are also expressed on dermal fibroblasts, a study was initiated to determine the effects of beta-adrenergic agonists on dermal fibroblast-mediated collagen gel contraction. A beta-agonist (isoproterenol) delayed gel contraction in a dose-dependent manner. A beta2-AR specific antagonist (ICI 118,551) prevented the delay, indicating that the beta2-AR alone mediated the delay. The active cyclic adenosine monophosphate (cAMP) analog also delayed collagen gel contraction, whereas an inactive cAMP analog partially prevented the delay, suggesting that the mechanism for beta-AR agonist-mediated delay was partly cAMP-dependent. Identifying and characterizing agents that modulate wound contraction improves understanding of the wound healing process and could result in novel therapeutic strategies for preventing unwanted wound contraction in burn and trauma patients.

Understanding the mechanisms that regulate cell migration is important for devising novel therapies to control metastasis or enhance wound healing. Previously, we demonstrated that beta2-adrenergic receptor (beta2-AR) activation in keratinocytes inhibited their migration by decreasing the phosphorylation of a critical promigratory signaling component, the extracellular signal-related kinase (ERK). Here we demonstrate that beta2-AR-induced inhibition of migration is mediated by the activation of the serine/threonine phosphatase PP2A. Pretreating human keratinocytes with the PP2A inhibitor, okadaic acid, prevented the beta2-AR-induced inhibition of migration, either as isolated cells or as a confluent sheet of cells repairing an in vitro "wound" and also prevented the beta2-AR-induced reduction in ERK phosphorylation. Similar results were obtained with human corneal epithelial cells. In keratinocytes, immunoprecipitation studies revealed that beta2-AR activation resulted in the rapid association of beta2-AR with PP2A as well as a 37% increase in association of PP2A with ERK2. Finally, beta2-AR activation resulted in a rapid and transient 2-fold increase in PP2A activity. Thus, we provide the first evidence that beta2-AR activation in keratinocytes modulates migration via a novel pathway utilizing PP2A to alter the promigratory signaling cascade. Exploiting this pathway may result in novel therapeutic approaches for control of epithelial cell migration.

Wounding skin generates an endogenous electric field of 100-200 mV/mm in the immediate vicinity of the wound. When keratinocytes are exposed to direct current electric fields of this magnitude, they exhibit galvanotaxis, or directional migration toward the cathode, suggesting that wound-generated electric fields provide migrational cues that contribute to wound healing. Because melanocytes must also migrate into the healing wound to repigment it, their motility in response to electric fields of physiologic magnitude was examined. Human skin-derived melanocytes, either exposed to 100 mV/mm direct current electric fields or nonexposed controls, both exhibited motility rates of 9 micro m/hour, significantly (three- to five-fold) lower than the motility rates of keratinocytes under identical conditions. However, in sharp contrast to keratinocytes, melanocytes exhibited no directional migration in the electric field. Additionally, neither the number of primary dendrites per cell, nor the orientation of the dendrites with respect to the field vector, nor the average length of the dendrites was significantly different in melanocytes exposed to the electric field as compared to nonexposed controls. Thus, in marked contrast to keratinocytes, human skin-derived melanocytes do not respond to direct current electric fields of physiologic magnitude with either directional migration or reorientation of dendrites. This may account for the delay in repigmentation that often accompanies wound reepithelialization.

After an epithelium is wounded, multiple soluble and extracellular matrix-associated signals induce a repair response. An often-overlooked signal is the endogenous electrical field established in the vicinity of the wound immediately upon disruption of epithelial integrity. Previous studies have detected lateral electric fields of approximately 42 mV mm-1 near bovine corneal wounds. In addition, electric fields on the order of 100-200 mV mm-1 have been measured lateral to wounds in mammalian epidermis. Here we report the migratory response of human corneal epithelial cells to DC electric fields of similar, physiologic magnitude. Our findings demonstrate that in a 100 mV mm-1 DC field, corneal epithelial cells demonstrate directed migration towards the cathode. The migratory speed and distances traversed by cultured human corneal epithelial cells is remarkably similar to those of cultured skin-derived keratinocytes under similar conditions; however, corneal epithelial cells demonstrate a more rapid directional response to the field than keratinocytes. These findings suggest that endogenous, wound-induced electric fields present in the cornea play an important role in human corneal wound healing, by orienting the directional response of migratory cells so that they efficiently re-epithelialize the wounded area.

BackgroundBurns are severe injuries often associated with impaired wound healing. Impaired healing is caused by multiple factors, including dysregulated inflammatory responses at the wound site. Interestingly, montelukast, an antagonist for cysteinyl leukotrienes and U.S. Food and Drug Administration approved for treatment of asthma and allergy, was previously shown to enhance healing in excision wounds and to modulate local inflammation.MethodsIn this study, the authors examined the effect of montelukast on wound healing in a mouse model of scald burn injury. Burn wound tissues isolated from montelukast- and vehicle-treated mice at various times after burn injury were analyzed for wound areas ( n = 34 to 36), reepithelialization ( n = 14), inflammation ( n = 8 to 9), and immune cell infiltration ( n = 3 to 6) and proliferation ( n = 7 to 8).ResultsIn contrast to previously described beneficial effects in excision wounds, this study shows that montelukast delays burn wound healing by impairing the proliferation of keratinocytes and endothelial cells. This occurs largely independently of inflammatory responses at the wound site, suggesting that montelukast impairs specifically the proliferative phase of wound healing in burns. Wound healing rates in mice in which leukotrienes are not produced were not affected by montelukast.ConclusionMontelukast delays wound healing mainly by reducing the proliferation of local cells after burn injury.Clinical relevance statementAlthough additional and clinical studies are necessary, our study suggests that burn patients who are on montelukast may exhibit delayed healing, necessitating extra observation.

A combination product of human mesenchymal stem/stromal cells (MSCs) embedded in an extracellular matrix scaffold and preconditioned with hypoxia and the beta-adrenergic receptor antagonist, timolol, combined with sustained timolol application post implantation, has shown promising results for improving wound healing in a diabetic mouse model. In the present study, we extend those findings to the more translatable large animal porcine wound model and show that the combined treatment promotes wound reepithelialization in these excisional wounds by 40.2% and increases the CD31 immunostaining marker of angiogenesis compared with the matrix control, while maintaining an accumulated timolol plasma concentration below the clinically safe level of 0.3 ng/mL after the 15-day course of topical application. Human GAPDH was not elevated in the day 15 wounds treated with MSC-containing device relative to wounds treated with matrix alone, indicating that the xenografted human MSCs in the treatment do not persist in these immune-competent animals after 15 days. The work demonstrates the efficacy and safety of the combined treatment for improving healing in the clinically relevant porcine wound model.

Re-epithelialization of wounds is a critical element of wound closure. Growth factors have been used in combination with conventional wound management to promote closure, but the method of delivery has been limited to the topical application of ointment formulations. Cytoactive factors delivered in this way have short resident times in wounds and have met with limited success. Here, we demonstrate that methods used to covalently immobilize proteins on synthetic materials can be extended to immobilize cytoactive factors such as the epidermal growth factor (EGF) onto the wound beds of genetically diabetic mice that exhibit impaired healing. Full-thickness splinted excisional wounds were created in diabetic (db/db) mice with a well-defined silicone splint to limit wound contracture. Wound surfaces were treated with a reducing agent to expose sulfhydryl groups and subsequently treated with EGF modified with a heterobifunctional crosslinker. This allowed for the covalent immobilization of the EGF to the wound surface. The conjugation chemistry was validated in vitro and in vivo. In a separate group of mice, wounds were topically treated twice daily with soluble EGF. The mice were evaluated over 11 days for wound closure. This covalent immobilization strategy resulted in EGF being retained on the wound surface for 2 days and significantly increased epithelial wound closure by 20% compared to wounds treated with topical EGF or topical vehicle. Covalent immobilization was not only therapeutically effective but also delivered a markedly reduced load of growth factor to the wound surface compared to topical application (when only 180 ng of EGF was immobilized onto the wound surface in comparison with 7200 ng of topically applied EGF over a period of 11 days). No adverse effects were observed in treated wounds. Results obtained provide proof of concept for the effectiveness of covalent immobilization in the treatment of dysregulated wounds. The covalent immobilization of cytoactive factors represents a potentially transformative approach to the management of difficult chronic wounds.

Keratinocyte migration into skin wounds is the step of the healing process that correlates with the wound closure rate. Keratinocyte migration, and wound epithelialization are decreased when beta 2-adrenergic receptors (B2AR) are activated by 1 μM epinephrine/adrenaline, resulting in delayed wound healing in human and mouse skin. In the present study, we found paradoxically, that in a subset of keratinocyte strains exposure to low concentrations of epinephrine (0.1 nM) increased, rather than decreased, their migratory rate. We find that both the alpha- and the beta-adrenergic receptors are expressed in human keratinocytes, and expression of alpha-2 AR subtypes demonstrated for the first time. Therefore, we tested if the alpha-AR could be modulating the increased migratory response observed in these cell strains. By using specific inhibitors to alpha-AR, we demonstrated that blocking A2B-AR could reverse the rapid cell migration induced by the 0.1 nM epinephrine. Phosphorylation of ERK was elevated after 1-10 minutes of the low epinephrine treatment and the A2B-AR inhibitor blocked the ERK phosphorylation. The results suggest that both the A2B-AR and B2AR mediate keratinocyte migration, in which with a low level of epinephrine treatment, A2B-AR could alter the B2AR signals and regulate the migration rate.

BackgroundSkin fibrosis is a significant global health problem that affects over 100 million people annually and has a profoundly negative impact on quality of life. Characterized by excessive fibroblast proliferation and collagen deposition, skin fibrosis underlies a wide spectrum of dermatologic conditions ranging from pathologic scars secondary to injury (e.g., burns, surgery, trauma) to immune-mediated diseases. Effective anti-scarring therapeutics remain an unmet need, underscoring the importance of developing novel approaches to treat and prevent skin fibrosis. Our in vitro data show that light emitting diode-red light (LED-RL) can modulate key cellular and molecular processes involved in skin fibrosis. In two phase I clinical trials (STARS 1 and STARS 2), we demonstrated the safety and tolerability of LED-RL at fluences of 160 J/cm2 up to 480 J/cm2 on normal human skin.Methods/designCURES (Cutaneous Understanding of Red-light Efficacy on Scarring) is a dose-ranging, randomized, parallel group, split-face, single-blind, mock-controlled phase II study to evaluate the efficacy of LED-RL to limit post-surgical skin fibrosis in subjects undergoing elective mini-facelift surgery. Thirty subjects will be randomly allocated to three treatment groups to receive LED-RL phototherapy or temperature-matched mock irradiation (control) to either periauricular incision site at fluences of 160 J/cm2, 320 J/cm2, or 480 J/cm2. Starting one week post-surgery (postoperative days 4-8), treatments will be administered three times weekly for three consecutive weeks, followed by efficacy assessments at 30 days, 3 months, and 6 months. The primary endpoint is the difference in scar pliability between LED-RL-treated and control sites as determined by skin elasticity and induration measurements. Secondary outcomes include clinical and photographic evaluations of scars, 3D skin imaging analysis, histological and molecular analyses, and adverse events.DiscussionLED-RL is a therapeutic modality of increasing importance in dermatology, and has the potential to limit skin fibrosis clinically by decreasing dermal fibroblast activity and collagen production. The administration of LED-RL phototherapy in the early postoperative period may optimize wound healing and prevent excessive scarring. The results from this study may change the current treatment paradigm for fibrotic skin diseases and help to pioneer LED-RL as a safe, non-invasive, cost-effective, portable, at-home therapy for scars.Trial registrationClinicalTrials.gov, NCT03795116 . Registered on 20 December 2018.

Chronic wounds exhibit persistent inflammation with markedly delayed healing. The significant burden of chronic wounds, which are often resistant to standard therapy, prompts further research on novel therapies. Since the interleukin-17 family has been implicated as a group of proinflammatory cytokines in immune-mediated diseases in the gut and connective tissue, as well as inflammatory skin conditions, we consider here if it may contribute to the pathogenesis of chronic wounds. In this review, we discuss the interleukin-17 family's signaling pathways and role in tissue repair. A PubMed review of the English literature on interleukin-17, wound healing, chronic wounds, and inflammatory skin conditions was conducted. Interleukin-17 family signaling is reviewed in the context of tissue repair, and preclinical and clinical studies examining its role in the skin and other organ systems are critically reviewed. The published work supports a pathologic role for interleukin-17 family members in chronic wounds, though this needs to be more conclusively proven. Clinical studies using monoclonal interleukin-17 antibodies to improve healing of chronic skin wounds have not yet been performed, and only a few studies have examined interleukin-17 family expression in chronic skin wounds. Furthermore, different interleukin-17 family members could be playing selective roles in the repair process. These studies suggest a therapeutic role for targeting interleukin-17A to promote wound healing; therefore, interleukin-17A may be a target worthy of pursuing in the near future.

BackgroundSkin fibrosis is involved in a variety of pathologic conditions ranging from scar formation secondary to surgery or trauma to immune-mediated processes. Skin fibrosis is a significant international health problem with an estimated incidence of greater than 100 million people affected per year worldwide with few effective treatment options available. Preliminary in vitro data generated by our research group suggests that red light can function as a stand-alone treatment for skin fibrosis. To our knowledge, no prior clinical trials have been performed to determine the safety of high-fluence (dose) light-emitting diode-red light (LED-RL) phototherapy. The goal of this study is to evaluate the safety of LED-RL fluences from 160 J/cm(2) up to 640 J/cm(2) in healthy subjects.Methods/designThis is a single-blind, dose escalation, randomized controlled, phase I study to evaluate the safety of high-fluence LED-RL on human skin. The protocol for dose escalation requires subjects be enrolled sequentially in groups of five. Within each group, three subjects will be randomized to LED-RL phototherapy and two subjects randomized to mock therapy. Subjects in group 1 randomized to LED-RL phototherapy will receive the maximum recommended starting dose (160 J/cm(2)). LED-RL dose will be escalated in subsequent groups (320 J/cm(2), 480 J/cm(2) and 640 J/cm(2)). The maximally tolerated dose (MTD) is defined as the dose level below the dose producing unacceptable but reversible toxicity and is considered to be the upper limit of subject tolerance. After either a MTD has been established, or the study endpoint of 640 J/cm(2) has been achieved, an additional 27 LED-RL phototherapy subjects (for a total of 30) and 18 mock therapy subjects (for a total of 20) (determined randomly) will be enrolled. Each subject will receive a total of nine procedures, three times per week for three consecutive weeks.DiscussionThis study may provide important safety information on the effects of high-fluence LED-RL phototherapy on human skin and help facilitate future phase II studies to evaluate the efficacy of high-fluence LED-RL as a potential noninvasive, safe, portable, at-home therapy for treatment of skin fibrosis.Trial registrationClinicalTrials.gov NCT02630303 . Registered on 9 December 2015.

The physiological electric field serves specific biological functions, such as directing cell migration in embryo development, neuronal outgrowth and epithelial wound healing. Applying a direct current electric field to cultured cells in vitro induces directional cell migration, or galvanotaxis. The 2-dimensional galvanotaxis method we demonstrate here is modified with custom-made poly(vinyl chloride) (PVC) chambers, glass surface, platinum electrodes and the use of a motorized stage on which the cells are imaged. The PVC chambers and platinum electrodes exhibit low cytotoxicity and are affordable and re-useable. The glass surface and the motorized microscope stage improve quality of images and allow possible modifications to the glass surface and treatments to the cells. We filmed the galvanotaxis of two non-tumorigenic, SV40-immortalized prostate cell lines, pRNS-1-1 and PNT2. These two cell lines show similar migration speeds and both migrate toward the cathode, but they do show a different degree of directionality in galvanotaxis. The results obtained via this protocol suggest that the pRNS-1-1 and the PNT2 cell lines may have different intrinsic features that govern their directional migratory responses.

Stress-induced hormones can alter the inflammatory response to tissue injury; however, the precise mechanism by which epinephrine influences inflammatory response and wound healing is not well defined. Here we demonstrate that epinephrine alters the neutrophil (polymorphonuclear leukocyte (PMN))-dependent inflammatory response to a cutaneous wound. Using noninvasive real-time imaging of genetically tagged PMNs in a murine skin wound, chronic, epinephrine-mediated stress was modeled by sustained delivery of epinephrine. Prolonged systemic exposure of epinephrine resulted in persistent PMN trafficking to the wound site via an IL-6-mediated mechanism, and this in turn impaired wound repair. Further, we demonstrate that β2-adrenergic receptor-dependent activation of proinflammatory macrophages is critical for epinephrine-mediated IL-6 production. This study expands our current understanding of stress hormone-mediated impairment of wound healing and provides an important mechanistic link to explain how epinephrine stress exacerbates inflammation via increased number and lifetime of PMNs.

Vagus nerve stimulation (VNS) has been approved as a treatment for various conditions, including drug‐resistant epilepsy, migraines, chronic cluster headaches and treatment‐resistant depression. It is known to have anti‐inflammatory, anti‐nociceptive and anti‐adrenergic effects, and its therapeutic potential for diverse pathologies is being investigated. VNS can be achieved through invasive (iVNS) or non‐invasive (niVNS) means, targeting different branches of the vagus nerve. iVNS devices require surgical implantation and have associated risks, while niVNS devices are generally better tolerated and have a better safety profile. Studies have shown that both iVNS and niVNS can reduce inflammation and pain perception in patients with acute and chronic conditions. VNS devices, such as the VNS Therapy System and MicroTransponder Vivistim, have received Food and Drug Administration approval for specific indications. Other niVNS devices, like NEMOS and gammaCore, have shown effectiveness in managing epilepsy, pain and migraines. VNS has also demonstrated potential in autoimmune disorders, such as rheumatoid arthritis and Crohn's disease, as well as neurological disorders like epilepsy and migraines. In addition, VNS has been explored in cardiovascular disorders, including post‐operative atrial fibrillation and myocardial ischemia–reperfusion injury, and has shown positive outcomes. The mechanisms behind VNS's effects include the cholinergic anti‐inflammatory pathway, modulation of cytokines and activation of specialised pro‐resolving mediators. The modulation of inflammation by VNS presents a promising avenue for investigating its potential to improve the healing of chronic wounds. However, more research is needed to understand the specific mechanisms and optimise the use of VNS in wound healing. Ongoing clinical trials may support the use of this modality as an adjunct to improve healing. [ABSTRACT FROM AUTHOR]

Skin wound healing is a complex process requiring the coordinated, temporal orchestration of numerous cell types and biological processes to regenerate damaged tissue. Previous work has demonstrated that a functional β-adrenergic receptor autocrine/paracrine network exists in skin, but the role of β2-adrenergic receptor (β2AR) in wound healing is unknown. A range of in vitro (single-cell migration, immunoblotting, ELISA, enzyme immunoassay), ex vivo (rat aortic ring assay), and in vivo (chick chorioallantoic membrane assay, zebrafish, murine wild-type, and β2AR knockout excisional skin wound models) models were used to demonstrate that blockade or loss of β2AR gene deletion promoted wound repair, a finding that is, to our knowledge, previously unreported. Compared with vehicle-only controls, β2AR antagonism increased angiogenesis, dermal fibroblast function, and re-epithelialization, but had no effect on wound inflammation in vivo. Skin wounds in β2AR knockout mice contracted and re-epithelialized faster in the first few days of wound repair in vivo. β2AR antagonism enhanced cell motility through distinct intracellular signalling mechanisms and increased vascular endothelial growth factor secretion from keratinocytes. β2AR antagonism promoted wound repair processes in the early stages of wound repair, revealing a possible new avenue for therapeutic intervention.

Endogenous electric fields are generated lateral to skin wounds, with the cathodal pole of the field residing in the center of the wound. These fields are thought to be an important mechanism in guiding the migration of keratinocytes and other cells into wounds to effect healing. In this work, human dermal fibroblasts were exposed to direct current electric fields of physiological strength, and their migrational behavior was quantitated. Only random migration of human dermal fibroblasts was observed in direct-current electric fields under conditions that support the directional migration of human epidermal keratinocytes. Additionally, neither the presence of serum nor serum plus additional Mg++ in the experimental medium supported directional migration. Migratory rates of fibroblasts varied depending on the experimental medium used: in serum-containing medium the average velocity was as low as 0.23 mum/min, while in serum-free keratinocyte medium the average velocity was as high as 0.36 mum/min. These studies suggest that dermal fibroblasts do not respond to the endogenous electric field of a wound, and use other migratory cues to direct their movement into the wound bed.

The article presents insights on the potential use of deferoxamine (DFO) as topical treatment for chronic wounds. Topics discussed include the local vasculature characteristics of chronic wounds, the deposition of free iron in chronic wounds, and the effects of DFO on the expression of several cytokines and growth factors.