Wound closure is fundamental to maintaining tissue homeostasis; a plethora of processes and signals must be coordinated, and gap junctions play a critical role. Some tissues exhibit privileged healing, such as buccal mucosa, repairing more rapidly, but gap junction connexin dynamics during wound healing in such tissues have not been investigated. To determine connexin changes during this rapid healing process, incisional wounds were made in the cheeks of mice and microscopically observed. We discovered that buccal mucosa wound edge keratinocytes do not form a thin tongue of migratory cells like epidermis; instead, a wedge of cells rapidly moves into the wound. The dorsal surfaces of opposing sides of the wounds then touch and join in a “V,” which subsequently fills up with cells to form a “delta” that remodels into a flat sheet. Immunostaining showed that connexin26, connexin30, and connexin43 are expressed at significantly higher levels in the buccal mucosa than the epidermis and that, unlike the skin, all three are rapidly down-regulated at the wound edge within 6 hours of wounding. This rapid down-regulation of all three connexins may in part underlie the rapid healing of the buccal mucosa.

Burn injury progression has not been well characterized at the cellular level. To define burn injury progression in terms of cell death, histopathologic spatiotemporal relationships of cellular necrosis and apoptosis were investigated in a validated porcine model of vertical burn injury progression. Cell necrosis was identified by high mobility group box 1 protein and apoptosis by Caspase 3a staining of tissue samples taken 1 hour, 24 hours, and 7 days postburn. Level of endothelial cell necrosis at 1 hour was predictive of level of apoptosis at 24 hours (Pearson's r = 0.87) and of level of tissue necrosis at 7 days (Pearson's r = 0.87). Furthermore, endothelial cell necrosis was deeper than interstitial cell necrosis at 1 hour (p < 0.001). Endothelial cell necrosis at 1 hour divided the zone of injury progression (Jackson's zone of stasis) into an upper subzone with necrotic endothelial cells and initially viable adnexal and interstitial cells at 1 hour that progressed to necrosis by 24 hours and a lower zone with initially viable endothelial cells at 1 hour but necrosis and apoptosis of all cell types by 24 hours. Importantly, this spatiotemporal series of events and rapid progression resembles myocardial infarction and stroke and implicates mechanisms of these injuries, ischemia, ischemia reperfusion, and programmed cell death in burn progression.

Negative-pressure wound therapy (NPWT) has significantly improved healing rates and patient comfort since its inception. However, a considerable number of questions have been raised regarding its mechanisms of action. Many health care workers and researchers have attempted to clarify the role of NPWT in wound healing. The purpose of this perspective article is to assemble some of the concepts that have been put forward in order to propose an integrated view of the mechanisms involved in NPWT. Particular emphasis will be placed on mechanically induced tissue deformations and their involvement in some of the key processes of wound healing, including nutrient and oxygen transport, blood vessel formation, and cellular proliferation and differentiation, mainly of myofibroblasts.

Adipose tissue–derived stem cells (ASCs) are gaining increasing consideration in tissue repair therapeutic application. Recent evidence indicates that ASCs enhance skin repair in animal models of impaired wound healing. To assess the therapeutic activity of autologous vs. allogeneic ASCs in the treatment of diabetic ulcers, we functionally characterized diabetic ASCs and investigated their potential to promote wound healing with respect to nondiabetic ones. Adipose tissue–derived cells from streptozotocin-induced type 1 diabetic mice were analyzed either freshly isolated as stromal vascular fraction (SVF), or following a single passage of culture (ASCs). Diabetic ASCs showed decreased proliferative potential and migration. Expression of surface markers was altered in diabetic SVF and cultured ASCs, with a reduction in stem cell marker-positive cells. ASCs from diabetic mice released lower amounts of hepatocyte growth factor, vascular endothelial growth factor (VEGF)-A, and insulin-like growth factor-1, growth factors playing important roles in skin repair. Accordingly, the supernatant of diabetic ASCs manifested reduced capability to promote keratinocyte and fibroblast proliferation and migration. Therapeutic potential of diabetic SVF administered to wounds of diabetic mice was blunted as compared with cells isolated from nondiabetic mice. Our data indicate that diabetes alters ASC intrinsic properties and impairs their function, thus affecting therapeutic potential in the autologous treatment for diabetic ulcers.

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.

Biofilms play an important role in the development and pathogenesis of many chronic infections. Oral biofilms, more commonly known as dental plaque, are a primary cause of oral diseases including caries, gingivitis, and periodontitis. Oral biofilms are commonly studied as model biofilm systems as they are easily accessible; thus, biofilm research in oral diseases is advanced with details of biofilm formation and bacterial interactions being well elucidated. In contrast, wound research has relatively recently directed attention to the role biofilms have in chronic wounds. This review discusses the biofilms in periodontal disease and chronic wounds with comparisons focusing on biofilm detection, biofilm formation, the immune response to biofilms, bacterial interaction, and quorum sensing. Current treatment modalities used by both fields and future therapies are also discussed.

Impaired wound healing represents an enormous clinical and financial problem for companion animals and humans alike. Unfortunately, most models used to study healing rely on rodents, which have significant differences in the healing and scarring process and rarely develop complications. In order to better simulate impaired healing, the model should strive to reproduce the natural processes of healing and delayed healing. Wounds on the limbs of horses display similarities to wounds in humans in their epithelialization/contraction ratio, genetic influence as well as dysregulated cytokine profile and the spontaneous development of fibroproliferative disorders. Veterinarians have access to advanced wound therapies that are often identical to those provided to human patients. Wound research in large animals has resulted in new wound models as well as a better understanding of the physiology, immunology, and local environmental impact on both normal and aberrant wound healing. One such model reproduces the naturally occurring fibroproliferative disorder of horses known as exuberant granulation tissue. Comparisons between the normally healing and impaired wounds provide insight into the repair process and can facilitate product development. A better understanding of the wound healing physiopathology based on clinically accurate animal models should lead to the development of novel therapies thereby improving outcomes in both human and veterinary patients.

Despite intensive research efforts into understanding the pathophysiology of both chronic wounds and scar formation, and the development of wound care strategies to target both healing extremes, problematic wounds in human health care remain a formidable challenge. Although valuable fundamental information regarding the pathophysiology of problematic wounds can be gained from in vitro investigations and in vivo studies performed in laboratory animal models, the lack of concordance with human pathophysiology has been cited as a major impediment to translational research in human wound care. Therefore, the identification of superior clinical models for both chronic wounds and scarring disorders should be a high priority for scientists who work in the field of human wound healing research. To be successful, translational wound healing research should function as an intellectual ecosystem in which information flows from basic science researchers using in vitro and in vivo models to clinicians and back again from the clinical investigators to the basic scientists. Integral to the efficiency of this process is the incorporation of models which can accurately predict clinical success. The aim of this review is to describe the potential advantages and limitations of using clinical companion animals (primarily dogs and cats) as translational models for cutaneous wound healing research by describing comparative aspects of wound healing in these species, common acute and chronic cutaneous wounds in clinical canine and feline patients, and the infrastructure that currently exists in veterinary medicine which may facilitate translational studies and simultaneously benefit both veterinary and human wound care patients.

Veterinarians and veterinary medicine have been integral to the development of stem cell therapies. The contributions of large animal experimental models to the development and refinement of modern hematopoietic stem cell transplantation were noted nearly five decades ago. More recent advances in adult stem cell/regenerative cell therapies continue to expand knowledge of the basic biology and clinical applications of stem cells. A relatively liberal legal and ethical regulation of stem cell research in veterinary medicine has facilitated the development and in some instances clinical translation of a variety of cell-based therapies involving hematopoietic stem cells and mesenchymal stem cells, as well as other adult regenerative cells and recently embryonic stem cells and induced pluripotent stem cells. In fact, many of the pioneering developments in these fields of stem cell research have been achieved through collaborations of veterinary and human scientists. This review aims to provide an overview of the contribution of large animal veterinary models in advancing stem cell therapies for both human and clinical veterinary applications. Moreover, in the context of the “One Health Initiative,” the role veterinary patients may play in the future evolution of stem cell therapies for both human and animal patients will be explored.

Venous ulcers are related to dysfunctions in extracellular matrix. Both matrix metalloproteinases (MMP) and neutrophil gelatinase-associated lipocalin (NGAL) could play a role in the healing process in patients with chronic venous ulcers. We evaluated the role of MMP-9 and NGAL in the healing process in venous ulceration. We performed an open-label, parallel groups, single clinical center study. Patients with chronic venous leg ulcers represented the test group (Group I), whereas patients without chronic ulcers represented the control group (Group II). In Group I plasma and wound fluid samples were collected at the time of admission, at the time of the surgery, and at the follow-up, while ulcer tissues were taken at the time of the surgery. In Group II, plasma and wound fluid were collected at admission and at the time of the surgery, whereas skin tissues were collected at the time of the surgery. Enzyme-linked immunosorbent assay test was used to evaluate the levels of MMP-9 and NGAL in plasma and wound fluid, whereas Western blot analysis was performed to estimate the expression of MMP-9 and NGAL in tissues. Enzyme-linked immunosorbent assay tests revealed significantly higher levels of MMP-9 and NGAL in both plasma and wound fluid of patients with ulcers compared to patients without ulcers (p < 0.01). Moreover, Western blot analysis documented an increased expression of MMP-9 and NGAL in biopsy tissue of patients with ulcers compared to patients without ulcers (p < 0.01). In conclusion MMP-9 and NGAL may correlate with the clinical course of venous ulcers.

Deep dermal burns can be covered with different kind of materials and techniques; one of them is a polylactide-based temporary skin substitute. The aim of this study was to intraindividually compare its 1-year outcome with the results obtained by use of autologous skin grafts in patients suffering from deep dermal burns. A prospective noninferiority trial was designed in order to assess skin quality and scar formation by use of subjective (Vancouver Scar Scale; Patient and Observer Scar Assessment Scale) and objective (noninvasive cutometry) burn scar assessment tools. All items of the Patient and Observer Scar Assessment Scale, except vascularity, were found to be noninferior in the areas covered with the temporary skin substitute vs. autologous skin. Results of objective scar evaluation showed comparable viscoelastic parameters without reaching noninferiority. Overall, the outcome of deep dermal burns covered with a polylactide-based temporary skin substitute revealed satisfactory results in terms of scar formation and skin quality as compared with autologous skin. This paper supports its use in deep dermal burns, where autologous skin donor sites require either to be reserved for coverage of full-thickness skin defects in severe burns or to be saved for reduction of additional morbidity in selected patient collectives.

We analyzed nitric oxide metabolites (nitrate and nitrite, NOx) and other biomarkers in human wound fluids and correlated these markers with wound healing status (progressing or worsening) based on patient's wound history. Samples were collected pre- and postcleansing from patients with wounds of various etiologies and analyzed for NOx, matrix metalloproteinase activity, and elastase activity. A laboratory method was developed to analyze NOx which can detect at least 5 μM in samples as small as 10 μL. A nitrate-free sample collection device was identified to match the sensitivity of this new assay (most “nitrate-free” products tested contained nitrate levels higher than this detection limit when extracted in such a small volume). The correlation between pre- and postcleansing biomarker values, and the diagnostic potential of the biomarkers to wound progress were analyzed. Fifty wounds provided samples that were suitable for NOx analysis. The pre- and postcleansing values for NOx showed good correlation (r = 0.72); the correlation was not very strong for matrix metalloproteinase and elastase. Data analysis showed that NOx represents the best metabolite to discriminate between worsening and progressing wounds, and suggested that a two cut point diagnostic test using NOx is better than a single cut point test to identify progressing from worsening wounds.

Identifying patients who benefit from hyperoxygenation therapy is important, because treatment is time-consuming and involves high costs and complications (minor). Our objective was to develop a model for predicting therapy outcome based on population of patients with and without diabetes. A retrospective cohort study was carried out in a major hospital in Israel. All 385 patients treated between 1/1/1998 and 1/1/2007 for ischemic nonhealing lower extremities wounds were included. Data on medical history, demographic, transcutaneous oximetry, wounds, treatment, and outcome characteristics were collected. Eight factors were identified to optimally predict wound healing: (1) number of hyperbaric oxygenation treatments (odds ratio [OR] = 1.034, p < 0.001), (2) transcutaneous oximetry values at hyperbaric conditions (OR = 1.001, p = 0.019), (3) wound duration (OR = 0.988, p = 0.022), (4) absence of heart disease (OR = 3.304, p < 0.001), (5) being employed (OR = 3.16, p = 0.008), (6) low socioeconomic status (OR = 2.50, p = 0.004), (7a) good/partial granulation wound appearance (OR = 2.73, p = 0.022), (7b) wounds covered with fibrin (OR = 3.16, p = 0.015), and (8) absence of anemia (OR = 2.13, p = 0.016). The model's sensitivity is 78.7%, specificity is 62.9%, and accuracy is 71.8%. We suggest using our model as an adjunct to patients' clinical evaluation. Also, we recommend initiating hyperoxygenation therapy no later than 2 months after wound appearance.

Cutaneous scarring affects up to 100 million people per annum. There is no effective scar reducing/preventing therapeutic developed to date. Interleukin (IL)-10 is an anti-inflammatory and antifibrotic cytokine. In the embryo it is important for scarless wound repair. We investigated the effect on wound healing and scarring of a double deletion of the IL-10 and IL-4 genes in a knockout (KO) mouse model, and also the effect of exogenous addition of recombinant human (rh) IL-10 into rat and human cutaneous incisions. Mouse study: Two incisions were made on the dorsal skin of 20 double IL-4/IL-10 KO mice and 20 wild-type (WT) controls. Rat study: Three concentrations of rhIL-10 were investigated. Four incisions were made on the dorsal skin of 30 rats. Each rat received two concentrations. Each incision receiving a concentration of rhIL-10 was matched with a control incision, which received either placebo or standard care. Human study: Eight concentrations of rhIL-10 were investigated. Four incisions were made on each arm of 175 healthy volunteers. Four incisions received four different concentrations, which were matched with four control incisions that received either standard care or placebo. KO mice healed with poor scar histology and increased inflammation. rhIL-10–treated rat incisions healed with decreased inflammation, better scar histology, and better macroscopic scar appearance. rhIL-10–treated human incisions at low concentrations healed with better macroscopic scar appearance and less red scars. IL-10 is an important cytokine in wound healing and its suppression of inflammation and scarring is demonstrated in mice and rats with a translational effect in humans.

Hypoxia is associated with the dermal wound healing process and hypoxia signaling is presumed to be crucial for normal wound repair. The Siah2 ubiquitin ligase controls the abundance of hypoxia-inducible factor-1 alpha, and loss of Siah2 results in destabilization of hypoxia-inducible factor-1 alpha under hypoxia. Utilizing Siah2^−/− mice we demonstrate that cutaneous wound healing is impaired in these mice. Wounds in Siah2^−/− mice heal slower and are associated with delayed induction of myofibroblast infiltration and reduced collagen deposition. This coincides with delayed angiogenesis and reduced macrophage infiltration into the wounds of Siah2^−/− mice. We furthermore demonstrate that primary Siah2^−/− dermal fibroblasts have reduced migratory capacities and produce less collagen than wild-type fibroblasts. Additionally, Siah2^−/− fibroblasts showed conserved responses to transforming growth factor-β at the receptor level (pSmad 2C activation) but reduced responses downstream. Together, our data show, for the first time, that Siah2 is involved as a positive regulator in the wound healing response. Understanding the role of hypoxia signaling in tissue repair and fibrosis and interference with the hypoxia signaling pathway via regulation of Siah2 may provide new targets for clinical regulation of fibrosis and scarring.

Hypertrophic scars are a significant fibroproliferative disorder complicating deep injuries to the skin. We hypothesize that activated deep dermal fibroblasts are subject to regulation by bone marrow–derived mesenchymal stem cells (BM-MSCs), which leads to the development of excessive fibrosis following deep dermal injury. We found that the expression of fibrotic factors was higher in deep burn wounds compared with superficial burn wounds collected from burn patients with varying depth of skin injury. We characterized deep and superficial dermal fibroblasts, which were cultured from the deep and superficial dermal layers of normal uninjured skin obtained from abdominoplasty patients, and examined the paracrine effects of BM-MSCs on the fibrotic activities of the cells. In vitro, deep dermal fibroblasts were found higher in the messenger RNA (mRNA) levels of type 1 collagen, alpha smooth muscle actin, transforming growth factor beta, stromal cell–derived factor 1, and tissue inhibitor of metalloproteinase 1, an inhibitor of collagenase (matrix metalloproteinase 1). As well, deep dermal fibroblasts had low matrix metalloproteinase 1 mRNA, produced more collagen, and contracted collagen lattices significantly greater than superficial fibroblasts. By co-culturing layered fibroblasts with BM-MSCs in a transwell insert system, BM-MSCs enhanced the fibrotic behavior of deep dermal fibroblasts, which suggests a possible involvement of BM-MSCs in the pathogenesis of hypertrophic scarring.

The lectin Artin M has been shown to accelerate the wound-healing process. The aims of this study were to evaluate the effects of Artin M on wound healing in the palatal mucosa of rats and to investigate the effects of Artin M on transforming growth factor beta (TGF-β) and vascular endothelial growth factor (VEGF) secretion by rat gingival fibroblasts. A surgical wound was created on the palatal mucosa of 72 rats divided into three groups according to treatment: C—Control (nontreated), A—Artin M gel, and V—Vehicle. Eight animals per group were sacrificed at 3, 5, and 7 days postsurgery for histology, immunohistochemistry and determination of the levels of cytokines, and growth factors. Gingival fibroblasts were incubated with 2.5 μg/mL of Artin M for 24, 48, and 72 hours. The expression of VEGF and TGF-β was determined by enzyme-linked immunosorbent assay. Histologically, at day 7, the Artin M group showed earlier reepithelialization, milder inflammatory infiltration, and increased collagen fiber formation, resulting in faster maturation of granular tissue than in the other groups (p < 0.05). Artin M–induced cell proliferation in vivo and promoted a greater expression of TGF-β and VEGF in both experiments (p < 0.05). Artin M was effective in healing oral mucosa wounds in rats and was associated with increased TGF-β and VEGF release, cell proliferation, reepithelialization, and collagen deposition and arrangement of fibers.

Obesity is associated with significant changes in skin combined with metabolic alterations such as insulin resistance. Our aim was to investigate the effects of insulin resistance induced by a high-fat diet on cutaneous wound healing. Male C57BL/6 mice were fed standard chow (SC group) or high-fat chow (HFC group) for 30 weeks. On day 0 (28th week), an excisional wound was performed. After 14 days (30th week), the mice were euthanized. Starting from the 8th week, the HFC group had a higher body weight. The HFC group became intolerant to glucose, resistant to insulin, and presented increased plasma cholesterol and triglyceride levels. The wound area was greater in the HFC group. The inflammatory infiltrate and the amount of “fibroblast-like” cells increased in superficial regions of the lesions in the HFC group. The collagen fibers were more organized and denser in the SC group. Hydroxyproline levels were lower in the HFC group. The nitric oxide synthase-2-positive cells were higher in the HFC group. Lipid peroxidation and protein carbonyl levels were higher in the HFC group. The expression levels of alpha-smooth muscle actin and transforming growth factor-β were higher in the HFC group. These findings support the hypothesis that insulin resistance leads to delayed cutaneous wound healing.

Collagen-based dressings are of great interest in wound care. However, evidence supporting their mechanism of action is scanty. This work provides first results from a preclinical swine model of excisional wounds, elucidating the mechanism of action of a modified collagen gel (MCG) dressing. Following wounding, wound-edge tissue was collected at specific time intervals (3, 7, 14, and 21 days postwounding). On day 7, histological analysis showed significant increase in the length of rete ridges, suggesting improved biomechanical properties of the healing wound tissue. Rapid and transient mounting of inflammation is necessary for efficient healing. MCG significantly accelerated neutrophil and macrophage recruitment to the wound site on day 3 and day 7 with successful resolution of inflammation on day 21. MCG induced monocyte chemotactic protein-1 expression in neutrophil-like human promyelocytic leukemia-60 cells in vitro. In vivo, MCG-treated wound tissue displayed elevated vascular endothelial growth factor expression. Consistently, MCG-treated wounds displayed significantly higher abundance of endothelial cells with increased blood flow to the wound area indicating improved vascularization. This observation was explained by the finding that MCG enhanced proliferation of wound-site endothelial cells. In MCG-treated wound tissue, Masson's trichrome and picrosirius red staining showed higher abundance of collagen and increased collagen type I:III ratio. This work presents first evidence from a preclinical setting explaining how a collagen-based dressing may improve wound closure by targeting multiple key mechanisms. The current findings warrant additional studies to determine whether the responses to the MCG are different from other collagen-based products used in clinical setting.

A gelatinase-based device for fast detection of wound infection was developed. Collective gelatinolytic activity in infected wounds was 23 times higher (p ≤ 0.001) than in noninfected wounds and blisters according to the clinical and microbiological description of the wounds. Enzyme activities of critical wounds showed 12-fold elevated enzyme activities compared with noninfected wounds and blisters. Upon incubation of gelatin-based devices with infected wound fluids, an incubation time of 30 minutes led to a clearly visible dye release. A 32-fold color increase was measured after 60 minutes. Both matrix metalloproteinases and elastases contributed to collective gelatinolytic enzyme activity as shown by zymography and inhibition experiments. The metalloproteinase inhibitor 1,10-phenanthroline (targeting matrix metalloproteinases) and the serine protease inhibitor phenylmethlysulfonyl fluoride (targeting human neutrophil elastase) inhibited gelatinolytic activity in infected wound fluid samples by 11–37% and 60–95%, respectively. Staphylococcus aureus and Pseudomonas aeruginosa, both known for gelatinase production, were isolated in infected wound samples.