Showing papers in "Wound Repair and Regeneration in 2007"
TL;DR: It is suggested that topical zinc therapy is underappreciated even though clinical evidence emphasizes its importance in autodebridement, anti‐infective action, and promotion of epithelialization.
Abstract: Zinc is an essential trace element in the human body and its importance in health and disease is appreciated. It serves as a cofactor in numerous transcription factors and enzyme systems including zinc-dependent matrix metalloproteinases that augment autodebridement and keratinocyte migration during wound repair. Zinc confers resistance to epithelial apoptosis through cytoprotection against reactive oxygen species and bacterial toxins possibly through antioxidant activity of the cysteine-rich metallothioneins. Zinc deficiency of hereditary or dietary cause can lead to pathological changes and delayed wound healing. Oral zinc supplementation may be beneficial in treating zinc-deficient leg ulcer patients, but its therapeutic place in surgical patients needs further clarification. Topical administration of zinc appears to be superior to oral therapy due to its action in reducing superinfections and necrotic material via enhanced local defense systems and collagenolytic activity, and the sustained release of zinc ions that stimulates epithelialization of wounds in normozincemic individuals. Zinc oxide in paste bandages (Unna boot) protects and soothes inflamed peri-ulcer skin. Zinc is transported through the skin from these formulations, although the systemic effects seem insignificant. We present here the first comprehensive account of zinc in wound management in relation to current concepts of wound bed preparation and the wound-healing cascade. This review article suggests that topical zinc therapy is underappreciated even though clinical evidence emphasizes its importance in autodebridement, anti-infective action, and promotion of epithelialization.
496 citations
TL;DR: Caution should be exercised in using silver‐based dressings in clean superficial wounds such as donor sites and superficial burns and also when cultured cells are being applied to wounds.
Abstract: Over the past decade, a variety of advanced silver-based dressings have been developed There are considerable variations in the structure, composition, and silver content of these new preparations In the present study, we examined five commercially available silver-based dressings (Acticoatt, Aquacel s Ag, Contreet s Foam, PolyMem s Silver, Urgotul s SSD) We assessed their cytotoxicity in a monolayer cell culture, a tissue explant culture model, and a mouse excisional wound model The results showed that Acticoatt, Aquacel s Ag, and Contreet s Foam, when pretreated with specific solutes, were likely to produce the most significant cytotoxic effects on both cultured keratinocytes and fibroblasts, while PolyMem s Silver and Urgotul s SSD demonstrated the least cytotoxicity The cytotoxicity correlated with the silver released from the dressings as measured by silver concentration in the culture medium In the tissue explant culture model, in which the epidermal cell proliferation was evaluated, all silver dressings resulted in a significant delay of reepithelialization In the mouse excisional wound model, Acticoatt and Contreet s Foam indicated a strong inhibition of wound reepithelialization on the postwounding-day 7 These findings may, in part, explain the clinical observations of delayed wound healing or inhibition of wound epithelialization after the use of certain topical silver dressings Caution should be exercised in using silverbased dressings in clean superficial wounds such as donor sites and superficial burns and also when cultured cells are being applied to wounds The use of silver as an antimicrobial agent has a long history 1 Its recent resurgence follows from Moyer’s use of silver nitrate solution in patients with burns 2 Solutions gave way to cream formulations but it is now silver-containing dressings that provide the widest range of silverbased wound care products 3,4 Despite the ever increasing number of commercially available silver-based dressings, there is a distinct lack of comparative data on their clinical effectiveness 5 What is known is that silver can be effective against a wide range of microorganisms, including aerobic, anaerobic, Gram-negative and Gram-positive bacteria, yeast, fungi, and viruses The antimicrobial effect of silver can be explained by various mechanisms: silver interferes with the respiratory chain in the cytochromes of microbacteria; additionally, silver ions also interfere with components of the microbial electron transport system, bind DNA, and inhibit DNA replication 6,7 Dressings are designed to have more controlled and prolonged release of silver during the entire wear-time when compared with the cream formulations This allows dressings to be changed less frequently, thereby reducing risk of nosocomial infection, cost of care, further tissue damage, and patient discomfort Many factors affect the clinical performance of a dressing The amount of silver content, the chemical, and physical forms of the silver, silver distribution, and even the affinity for moisture all participate in a dressing’s capability to exert a significant antimicrobial effect Marked differences exist in a variety of silver dressing products These products can be categorized as: (i) silver-delivery dressings such as Acticoatt (Smith & Nephew, Hull, UK) and Urgotul s SSD (Laboratory URGD, Chenove, France), which have silver content coated (on the surface) or impregnated into the dressing material They deliver silver to the wound site after direct contact; (ii) silver-containing dressings such as Aquacel s Ag (Cenvatec, Deeside, UK), Contreet s Foam (Coloplast, Humlebaek, Denmark), and PolyMem s Silver
342 citations
TL;DR: Enhanced understanding of bone marrow derived stem cells may help develop novel therapies for difficult cutaneous conditions such as non‐healing chronic wounds and hypertrophic scarring as well as engineering cutaneous substitutes.
Abstract: Optimum healing of a cutaneous wound requires a well-orchestrated integration of the complex biological and molecular events of cell migration and proliferation, and of extracellular matrix deposition and remodeling. Several studies in recent years suggest that bone marrow derived stem cells such as mesenchymal stem cells, progenitor cells such as endothelial progenitor cells and fibrocytes may be involved in these processes, contributing to skin cells or releasing regulatory cytokines. Stem/progenitor cells may be mobilized to leave the bone marrow, home to injured tissues and participate in the repair and regeneration. Direct injection of bone marrow derived mesenchymal stem cells or endothelial progenitor cells into injured tissues shows improved repair through mechanisms of differentiation and/or release of paracrine factors. Enhanced understanding of these cells may help develop novel therapies for difficult cutaneous conditions such as non-healing chronic wounds and hypertrophic scarring as well as engineering cutaneous substitutes.
272 citations
TL;DR: The modified histologic scoring system described here was found to be reliable and reproducible and a transient fibrinous crust forms in the abdomen but not in the vagina 4–7 days after wounding.
Abstract: We aimed to compare the histologic characteristics of vaginal vs. abdominal surgical wound healing in the rabbit. Bilateral 6 mm full-thickness circular segments were excised from the vagina and abdominal skin in 34 New Zealand white female rabbits. Animals were euthanized on the day of and 4, 7, 10, 14, 21, 28, and 35 days after wounding, and their wounds were evaluated using a modified scoring system. The inter- and intraobserver agreements of the scoring system were good (weighted kappa 0.63 and 0.71, respectively). A transient fibrinous crust was evident in 75% of the abdominal and in none of the vaginal wound specimens on days 4-7 after wounding (p=0.01). Acute inflammation peaked at day 4 in both the vaginal and abdominal wounds, while chronic inflammation peaked at days 4-7 and 14-21 in the abdomen and vagina, respectively. Both neovascularization and the amount of granulation tissue peaked at days 4 and 7 in the vagina and abdomen, respectively. Maturation of granulation tissue and collagen deposition increased persistently in both tissues until postwounding day 35. Reepithelialization increased after wounding, and was completed by day 14 in both tissues. The surgical wound-healing process in both the vagina and abdomen includes transient acute and chronic inflammation, fibroblast proliferation, and neovascularization, as well as progressive maturation of granulation tissue, reepithelialization, and collagen deposition. A transient fibrinous crust forms in the abdomen but not in the vagina 4-7 days after wounding. The modified histologic scoring system described here was found to be reliable and reproducible.
205 citations
TL;DR: The results suggest that splinted db/db mice may be the most appropriate model for studying diabetic wound‐healing interventions as they demonstrate the most significant impairment in wound healing.
Abstract: The pathophysiology of diabetic wound healing and the identification of new agents to improve clinical outcomes continue to be areas of intense research. There currently exist more than 10 different murine models of diabetes. The degree to which wound healing is impaired in these different mouse models has never been directly compared. We determined whether differences in wound impairment exist between diabetic models in order to elucidate which model would be the best to evaluate new treatment strategies. Three well-accepted mouse models of diabetes were used in this study: db/db, Akita, and streptozocin (STZ)-induced C57BL/6J. Using an excisional model of wound healing, we demonstrated that db/db mice exhibit severe impairments in wound healing compared with STZ and Akita mice. Excisional wounds in db/db mice show a statistically significant delay in wound closure, decreased granulation tissue formation, decreased wound bed vascularity, and markedly diminished proliferation compared with STZ, Akita, and control mice. There was no difference in the rate of epithelialization of the full-thickness wounds between the diabetic or control mice. Our results suggest that splinted db/db mice may be the most appropriate model for studying diabetic wound-healing interventions as they demonstrate the most significant impairment in wound healing. This study utilized a novel model of wound healing developed in our laboratory that stents wounds open using silicone splints to minimize the effects of wound contraction. As such, it was not possible to directly compare the results of this study with other studies that did not use this wound model.
201 citations
TL;DR: The significance of the proposed studies is that these novel natural antifibrotics will mimic the effect of glucocorticoids on collagen synthesis during fibrogenesis without the unwanted side effects of these steroids.
Abstract: Transforming-growth factor-beta (TGF-beta) is a pleiotrophic growth factor that is synthesized by many cells in the body. This growth factor is chemotactic for fibroblasts, stimulates fibroblast proliferation, and increases the synthesis of a number of extracellular matrix proteins including collagens. The TGF-beta activator protein is a transacting factor, which binds to the TGF-beta element in the distal promoter of the COL1A1 collagen gene and induces transcription of this gene. Although transient TGF-beta 1 activity participates in repair and regeneration of tissues, persistent TGF-beta 1 function affects excessive fibrosis and ultimately scarring of both skin and internal organs. Scarring of internal organ (e.g., liver and lung) results in a loss of function and ultimately death may occur. The central issue of this review is that phosphorothioate double-stranded decoys or other decoys decrease procollagen gene expression, procollagen synthesis, and collagen during fibrogenesis. The rationale is that the decoys containing the TGF-beta element or other gene transcription regulatory CIS-elements bind the transacting proteins preventing the latter from binding to the CIS-element in the 5'-flanking region of the natural gene resulting in transcription inhibition. We will, in part, focus on aspects involved in TGF-beta 1-induced fibrosis that occur during fibrogenesis and the use of the dsTGF-beta element containing oligodeoxynucleotide decoys to control excessive collagen synthesis, and deposition resulting from persistent TGF-beta. In our model of regulation of collagen synthesis, these double-stranded oligo decoys act as promoter competitors, binding to the activator protein either in the cytoplasm or in the nucleus. The significance of the proposed studies is that these novel natural antifibrotics will mimic the effect of glucocorticoids on collagen synthesis during fibrogenesis without the unwanted side effects of these steroids. Based on our previous studies on the molecular mechanisms by which glucocorticoids selectively decrease collagen synthesis, designed phosphorothioate oligodeoxynucleotides resistant to nuclease action will mimic the effects of glucocorticoids at the molecular, cellular, and in vivo levels of collagen synthesis. However, the glucocorticoids significantly inhibit noncollagen protein synthesis. Both the single-stranded and double-stranded oligodeoxynucleotide specifically decrease collagen synthesis without an inhibitory effect on noncollagen protein synthesis. In this review, we will specifically ask if TGF-beta-induced collagen synthesis is inhibited in cell culture and in vivo by using the double-stranded oligodeoxynucleotide decoys, will this inhibit fibrogenesis and ultimately scarring?
169 citations
TL;DR: Sustained expression of Hif‐1α in leptin receptor‐deficient diabetic wounds restores expression of factors involved in cell proliferation and migration, enhances angiogenesis, and significantly accelerates wound healing.
Abstract: Impaired wound healing in diabetic patients is associated with deficiencies in the production of factors involved in cell proliferation and migration, such as vascular endothelial growth factor. However, it remains unclear how the transcriptional regulation of the genes encoding these factors is affected by the diabetic environment. Hypoxia-inducible factor-1alpha (Hif-1alpha), the regulatory subunit of the Hif-1 transcription factor, plays an important role in activating many of these genes. Therefore, we tested whether Hif-1alpha function is impaired in the diabetic wound environment and whether restoring Hif-1 function improves wound healing. Here, we show that Hif-1alpha protein levels are dramatically reduced in wounds of leptin receptor-deficient diabetic mice compared with nondiabetic littermates. Reduction in Hif-1alpha levels results in decreased DNA-binding activity and in decreased expression of several Hif-1 target genes, including vascular endothelial growth factor, heme oxygenase-1, and inducible nitric oxide synthase. Furthermore, we demonstrate that sustained expression of Hif-1alpha in leptin receptor-deficient diabetic wounds restores expression of these factors, enhances angiogenesis, and significantly accelerates wound healing. Taken together, these results suggest that Hif-1alpha function plays a significant role in wound healing and reduced levels of Hif-1alpha may contribute to impaired healing.
167 citations
TL;DR: The results suggest that in healing burn wounds, fibrocytes could regulate the activities of local fibroblasts.
Abstract: Wound healing requires an elaborate interplay between numerous cell types that orchestrate a series of regulated and overlapping events. Fibrocytes are a unique leukocyte subpopulation implicated in this process. One role proposed for these cells in wound healing is to synthesize extracellular matrix. Interestingly, using mass spectrometry to quantify hydroxyproline, we discovered that the capacity of fibrocytes from normal subjects or from burn patients to produce collagen is much less than that of dermal fibroblasts. Therefore, we investigated whether fibrocytes could play an indirect, regulatory, role in the healing of burn wounds by affecting the functions of dermal fibroblasts. Dermal fibroblasts treated with medium conditioned by burn patient fibrocytes, but not by those derived from normal subjects, showed an increase in cell proliferation and migration. Using confocal microscopy, flow cytometry, and immunoblotting, we found the level of alpha-smooth muscle actin (alpha-SMA) expression to be increased in these treated dermal fibroblasts, which also showed an enhanced ability to contract collagen lattices. To determine whether these effects could be attributed to transforming growth factor beta (TGF-beta1) or to connective tissue growth factor (CTGF), we measured total TGF-beta1 levels in the conditioned medium by an enzyme-linked immunosorbtion assay and assessed levels of CTGF mRNA and protein in fibroblasts and fibrocytes by reverse transcription-polymerase chain reaction and Western blotting. The results showed significantly higher levels of TGF-beta1 and CTGF produced by burn patient fibrocytes. In addition, the application of a TGF-beta1 neutralizing antibody significantly reduced the effect of burn patient fibrocyte medium on dermal fibroblast proliferation, migration, and collagen lattice contraction. Our results suggest that in healing burn wounds, fibrocytes could regulate the activities of local fibroblasts.
164 citations
TL;DR: The systemic response to injury appears to influence the local healing process whereby increases in Th2 and possibly Th3 cytokines such as IL‐2, IL‐4 and IL‐10 and TGF‐β are present in the circulating lymphocytes in these fibrotic conditions.
Abstract: Hypertrophic scar and keloids are fibroproliferative disorders of the skin which occur often unpredictably, following trauma and inflammation that compromise cosmesis and function and commonly recur following surgical attempts for improvement. Despite decades of research in these fibrotic conditions, current non-surgical methods of treatment are slow, inconvenient and often only partially effective. Fibroblasts from these conditions are activated to produce extracellular matrix proteins such as collagen I and III, proteoglycans such as versican and biglycan and growth factors, including transforming growth factor-beta and insulin like growth factor I. However, more consistently these cells produce less remodeling enzymes including collagenase and other matrix metalloproteinases, as well as the small proteoglycan decorin which is important for normal collagen fibrillogenesis. Recently, the systemic response to injury appears to influence the local healing process whereby increases in Th2 and possibly Th3 cytokines such as IL-2, IL-4 and IL-10 and TGF-beta are present in the circulating lymphocytes in these fibrotic conditions. Finally, unique bone marrow derived cells including mesenchymal and endothelial stem cells as well as fibrocytes appear to traffic into healing wounds and influence the healing tissue. On this background, clinicians are faced with patients who require treatment and the pathophysiologic basis as currently understood is reviewed for a number of emerging modalities.
154 citations
TL;DR: AM transplantation seems to function as a safe substrate, promoting proper epithelialization while suppressing excessive fibrosis, and may be considered to be an alternative method for treating chronic leg ulcers.
Abstract: Amniotic membrane (AM), the most internal placental membrane, has unique properties including antiadhesive effects, bacteriostatic, wound protection and pain-reduction properties, as well as epithelialization initialization capacities. Furthermore, AM is widely available and less costly than other bioengineered skin substitutes. In a prospective pilot study, we evaluated the safety, feasibility, and the effects on healing of AM graft in 15 patients with chronic venous leg ulcers. AM grafts were prepared from placentas harvested during cesarean section. All grafted AM had adhered to the wound bed 7 days after being applied with a 100% engraftment rate. The percentage of granulation tissue increased significantly (from 17% on day 0 to 69% on day 14, p<0.0001), along with a significant decrease of fibrinous slough (from 36% at day 0 to 16% at day 14, p<0.001). A significant clinical response occurred in 12 patients (80%) including complete healing (20%) in three during the 3-month follow-up period. The ulcer surface area decreased significantly from a mean value (+/- standard deviation) of 4.59 +/- 2.49 cm(2) at baseline to 2.91+/-2.01 cm(2) on day 30 (p<0.001). All patients experienced a significant reduction of ulcer-related pain rapidly after AM transplantation. No adverse events were recorded. AM transplantation seems to function as a safe substrate, promoting proper epithelialization while suppressing excessive fibrosis. Further advantages of biotherapy with AM are its easy and low-cost production, and that it can be applied as an ambulatory treatment without immobilization. AM transplantation may thus be considered to be an alternative method for treating chronic leg ulcers.
154 citations
TL;DR: An agent‐based model capable of reproducing qualitatively much of the literature data on skin wound healing, including changes in relevant cell populations and their key effector cytokines, is developed and found that these therapies would have similar effects regardless of the initial assumption of the derangement that underlies DFU.
Abstract: Inflammation and wound healing are inextricably linked and complex processes, and are deranged in the setting of chronic, nonhealing diabetic foot ulcers (DFU). An ideal therapy for DFU should both suppress excessive inflammation while enhancing healing. We reasoned that biological simulation would clarify mechanisms and help refine therapeutic approaches to DFU. We developed an agent-based model (ABM) capable of reproducing qualitatively much of the literature data on skin wound healing, including changes in relevant cell populations (macrophages, neutrophils, fibroblasts) and their key effector cytokines (tumor necrosis factor-alpha [TNF], interleukin [IL]-1beta, IL-10, and transforming growth factor [TGF]-beta1). In this simulation, a normal healing response results in tissue damage that first increases (due to wound-induced inflammation) and then decreases as the collagen levels increase. Studies by others suggest that diabetes and DFU are characterized by elevated TNF and reduced TGF-beta1, although which of these changes is a cause and which one is an effect is unclear. Accordingly, we simulated the genesis of DFU in two ways, either by (1) increasing the rate of TNF production fourfold or (2) by decreasing the rate of TGF-beta1 production 67% based on prior literature. Both manipulations resulted in increased inflammation (elevated neutrophils, TNF, and tissue damage) and delayed healing (reduced TGF-beta1 and collagen). Our ABM reproduced the therapeutic effect of platelet-derived growth factor/platelet releasate treatment as well as DFU debridement. We next simulated the expected effect of administering (1) a neutralizing anti-TNF antibody, (2) an agent that would increase the activation of endogenous latent TGF-beta1, or (3) latent TGF-beta1 (which has a longer half-life than active TGF-beta1), and found that these therapies would have similar effects regardless of the initial assumption of the derangement that underlies DFU (elevated TNF vs. reduced TGF-beta1). In silico methods may elucidate mechanisms of and suggest therapies for aberrant skin healing.
TL;DR: If biopsies do not contribute significantly to patient management, their use should be discouraged in clinically noninfected wounds, and independent predictors of healing, such as wound surface microbial diversity and density, could identify patients likely to have an unfavorable outcome and to whom resources should be targeted.
Abstract: This study determined whether comprehensive microbiological analysis offered real predictive value in terms of healing outcome, and assessed the clinical usefulness of surface swabs vs. tissue biopsies for clinically noninfected leg wounds. The wound microflora of 70 patients with chronic venous leg ulcers was quantified after sampling by swabbing and biopsy. A highly significant association between wound surface area at 4 weeks and eventual healing at 6 months was found (p 0.1). A significant association between healing and bacterial diversity in the wound as assessed by swab (p=0.023) was demonstrated. Furthermore, the bacterial density of wound surface area by swab (CFU/mL; p=0.018) or biopsy (CFU/g tissue; p=0.038) were shown to be independent predictors of nonhealing. Logistic regression showed that microbiological analysis of biopsies provided no additional prognostic information when compared with analysis of the surface microflora (p=0.27). Hence, if biopsies do not contribute significantly to patient management, their use should be discouraged in clinically noninfected wounds. Furthermore, independent predictors of healing, such as wound surface microbial diversity and density, could identify patients likely to have an unfavorable outcome and to whom resources should be targeted.
TL;DR: The synthetic CS‐HP sECM films mimic the chemistry and biology of heparan sulfate proteoglycans, and may have clinical potential for topical delivery of growth factors to patients with compromised wound healing.
Abstract: We describe synthetic extracellular matrix (sECM) hydrogel films composed of co-crosslinked thiolated derivatives of chondroitin 6-sulfate (CS) and heparin (HP) for controlled-release delivery of basic fibroblast growth factor (bFGF) to full-thickness wounds in genetically diabetic (db/db) mice. In this model for chronic wound repair, full-thickness wounds were treated with CS, CS-bFGF, or CS-HP-bFGF films. At 2 and 4 weeks postinjury, wound closure and formation of the new epidermis and dermis were determined. Both CS and CS-HP hydrogel films accelerated wound repair, even without bFGF. Addition of bFGF to CS films showed partial dose-dependent acceleration of wound repair. Importantly, addition of bFGF to co-crosslinked CS-HP sECM films showed a dramatic bFGF dose-dependent acceleration of wound healing, as well as improved dermis formation and vascularization. Compared with 27% wound closure in 2 weeks in the controls, 89% wound closure was observed for mice treated with the CS-HP-bFGF films. The synthetic CS-HP sECM films mimic the chemistry and biology of heparan sulfate proteoglycans, and may have clinical potential for topical delivery of growth factors to patients with compromised wound healing.
TL;DR: It is concluded that topical application of BM‐derived SPCs may represent an effective strategy for the treatment of chronic diabetic wounds through indirect mechanisms which lead to enhanced vascularization rather than through direct participation and incorporation into tissue.
Abstract: The direct application of bone marrow (BM) can accelerate the healing of chronic wounds. We hypothesized that this effect is due to the presence of stromal progenitor cells (SPCs) found within whole BM preparations. To test this hypothesis, we isolated adult murine SPCs from whole BM and examined their ability to enhance impaired wound healing compared with ficoll separated BM cells in the diabetic (db/db) mouse model. SPCs significantly enhanced reepithelialization, granulation tissue formation, and neovascularization compared with control wounds treated with BM or PBS alone. Higher frequencies of donor SPC cells compared with donor BM cells were observed in treated wounds at 7 days. Transdifferentiation into GFP-positive mature endothelial cells was not observed. These observations suggest that SPCs improve wound healing through indirect mechanisms which lead to enhanced vascularization rather than through direct participation and incorporation into tissue. We conclude that topical application of BM-derived SPCs may represent an effective strategy for the treatment of chronic diabetic wounds.
TL;DR: The full‐skin substitute has a greater potential to stimulate wound healing than epidermal or dermal substitutes and is required to trigger the release of dermal‐derived inflammatory/angiogenic mediators from skin substitutes.
Abstract: Full-skin substitutes, epidermal substitutes, and dermal substitutes are currently being used to heal deep burns and chronic ulcers. In this study, we investigated which wound-healing mediators are released from these constructs and whether keratinocyte–fibroblast interactions are involved. Autologous skin substitutes were constructed from human keratinocytes, fibroblasts, and acellular donor dermis. Full-thickness skin was used to represent an autograft. Secretion of woundhealing mediators was investigated by means of protein array, enzyme-linked immunosorbent assay, neutralizing antibodies, and conditioned culture supernatants. Full-skin substitutes and autografts produce high amounts of inflammatory/ angiogenic mediators (IL-6, CCL2, CXCL1, CXCL8, and sST2). Epidermal and dermal substitutes produced less of these proteins. Epidermal-derived proinflammatory cytokines interleukin-1a (IL-1a) and tumor necrosis factor-a (TNF-a) were found to mediate synergistically the secretion of these wound-healing mediators (with the exception of sST2) from fibroblasts in dermal substitutes. The secretion of proinflammatory cytokines (IL-1a, TNF-a), chemokine/mitogen (CCL5) and angiogenic factor (vascular endothelial growth factor) by epidermal substitutes and tissue remodeling factors (tissue inhibitor of metalloproteinase-2, hepatocyte growth factor) by dermal substitutes was not influenced by keratinocyte–fibroblast interactions. The full-skin substitute has a greater potential to stimulate wound healing than epidermal or dermal substitutes. Both epidermalderived IL-1a and TNF-a are required to trigger the release of dermal-derived inflammatory/angiogenic mediators from skin substitutes. Skin tissue engineering is rapidly moving from fundamental research to clinical applications. The benefits of living keratinocytes in the epidermal compartment and/or living fibroblasts in the dermal compartment above an acellular dressing have now been widely accepted: living skin substitutes secrete a cocktail of cytokines, chemokines, and growth factors that promote wound healing (by stimulating angiogenesis, granulation tissue formation, and epithelialization) as well as providing an immediate cover for the wound. 1,2
TL;DR: It is demonstrated here that low‐power lasers are capable of activating latent TGF‐β1 and ‐β3 in vitro and, further, that it is capable of “priming” these complexes, making them more amenable to physiological activation present in the healing milieu.
Abstract: The term Laser "Photobiomodulation" was coined to encompass the pleiotropic effects of low-power lasers on biological processes. The purpose of this study was to investigate whether transforming growth factor (TGF)-\beta had a role in mediating the biological effects of low-power far-infrared laser irradiation. We assayed for in vitro activation using various biological forms of cell-secreted, recombinant, and serum latent TGF-\beta using the p3TP reporter and enzyme-linked immunosorbent assays. We demonstrate here that low-power lasers are capable of activating latent TGF-\beta1 and -\beta3 in vitro and, further, that it is capable of "priming" these complexes, making them more amenable to physiological activation present in the healing milieu. Using an in vivo oral tooth extraction-healing model, we observed an increased TGF-\beta1, but not \beta3, expression by immunohistochemistry immediately following laser irradiation while TGF-\beta3 expression was increased after 14 days, concomitant with an increased inflammatory infiltrate. All comparisons were performed between laser-irradiated wounds and nonirradiated wounds in each subject essentially using them as their own control (paired T-test p<0.05). Low-power laser irradiation is capable of activating the latent TGF-\beta1 complex in vitro and its expression pattern in vivo suggests that TGF-play a central role in mediating the accelerated healing response.
TL;DR: Results indicate that the dressing material has a significant effect on cell response following negative pressure wound therapy, and the ability to support cell growth, stimulate chemotaxis, and proliferation without increasing apoptosis may provide an insight into the mechanisms of action of V.A.C.C., NPWT.
Abstract: Vacuum Assisted Closure brand Negative Pressure Wound Therapy (V.A.C. NPWT) has been shown to be an effective therapeutic option for the treatment of recalcitrant wounds; however, the mechanism of action at the cellular level remains to be elucidated. Here, we examined the effects of negative pressure wound therapy, manifolded with two different dressings, on fibroblast viability, chemotactic signaling, and proliferation in a fibrin clot matrix. Fibroblasts were grown in a three-dimensional fibrin matrix and were treated for 48 hours with either V.A.C. NPWT and GranuFoam Dressing, or with gauze under suction, or as static controls without negative pressure or dressings. Cells treated by gauze under suction showed significantly greater cell death and stimulated less migration and proliferation than static and V.A.C. NPWT-treated cells (p<0.05). Apoptosis was also significantly higher in gauze under suction than in static treatments. These results indicate that the dressing material has a significant effect on cell response following negative pressure wound therapy. The ability to support cell growth, stimulate chemotaxis, and proliferation without increasing apoptosis may provide an insight into the mechanisms of action of V.A.C. NPWT.
TL;DR: The diverse actions of LPA and S1P on many types of cells involved in the wound healing process are highlighted, with special emphasis on their regulation of fibroblasts.
Abstract: The bioactive lysophospholipids, primarily lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P), are recent additions to the list of potent mediators of tissue repair and wound healing. In this review, we highlight the diverse actions of LPA and S1P on many types of cells involved in the wound healing process, with special emphasis on their regulation of fibroblasts. The effects of LPA and S1P are principally mediated via specific cell surface receptors. Important signaling pathways downstream of these receptors and the importance of TGFbeta and S1P cross-talk for wound healing are also discussed. Moreover, specific agonists and antagonists of the lysophospholipid receptors may be useful for the treatment of wounds and abnormal wound healing.
TL;DR: The cause‐and‐effect relationships between chronic venous insufficiency and venous ulcers are discussed, focusing particularly on the biological processes that lead from the underlying disease condition to overt ulceration.
Abstract: Venous ulceration represents the most prevalent form of difficult-to-heal wounds and these problematic wounds require a significant amount of healthcare resources for their treatment. In order to develop effective treatment regimens a clearer understanding of the underlying pathological processes that lead to skin breakdown is required. However, to date, most of these studies have tended to focus on describing the pathology of already-established ulcers. By bringing together relevant aspects of diverse disciplines such as inflammation, cardiovascular, and connective tissue biology, we aim to provide an insight into how circulatory abnormalities that are caused by the underlying disease etiology can induce local tissue inflammation resulting in tissue breakdown. Initially this results in internal tissue damage but if the underlying disease is not treated, the internal tissue damage can worsen and lead to open ulceration. This article discusses the cause-and-effect relationships between chronic venous insufficiency and venous ulceration, focusing particularly on the biological processes that lead from the underlying disease condition to overt ulceration. Available evidence also suggests that formation of pressure, diabetic foot and arterial ulcers, and ulcers as results of blood disorders, is also likely to share some of the same biological processes as venous ulcers.
TL;DR: The HS model in the rabbit ear is a highly reliable, responsive, and practical model for studying scar tissue behavior and it is suggested that the degree and the duration of occlusion are most important for reducing scar tissue formation.
Abstract: Hypertrophic scarring poses a clinically relevant problem as it can be cosmetically disfiguring and functionally debilitating. A lack of animal models has hindered an understanding of the pathogenesis and development of new treatment strategies therefore has largely been empiric. Our group has developed a unique hypertrophic scar (HS) model in the rabbit ear. The model has been reproducible, quantifiable, and measurable over a time period of 1 month. We describe the development as well as the reliability and responsiveness of this model to different therapeutic agents, such as TGF-beta blockade, silicone occlusion, and application of collagen-synthesis inhibitors. Moreover, it has given insights into the mechanism of action of silicone sheeting occlusive treatment and ultimately suggests that the epidermis plays a critical role in the development of HS. Additionally, we will present new data supporting the importance of the epidermis and further clarify the mechanism of action of silicone sheeting. When a semi-occlusive polyurethane film was left in place for an additional time period, scar formation was reduced. HSs of this model covered with silicone sheets and five layers of Tegaderm showed a significant scar reduction by 80% compared with wounds with only one layer of Tegaderm. The HS model in the rabbit ear is a highly reliable, responsive, and practical model for studying scar tissue behavior. Furthermore, our data suggest that the degree and the duration of occlusion are most important for reducing scar tissue formation.
TL;DR: The Duroc/Yorkshire model has been used in this article for the study of hypertrophic scarring after burns and it has been shown that the red DuroC pig does make thick scar.
Abstract: Hypertrophic scarring after burns is an unsolved problem and remains as devastating today as it was in the 40s and it may be that the main reason for this is the lack of an accepted, useful animal model. The female, red Duroc pig was described as a model of hypertrophic scarring nearly 30 years ago but then vanished from the literature. This seemed strange since the authors reported that 12 of 12 pigs developed thick scar. In the mid 90s we explored the model and found that, indeed, the red Duroc pig does make thick scar. Other authors have established that the Yorkshire pig does not heal in this fashion so there is the possibility of a same species control. We have continued to explore the Duroc/Yorkshire model and herein describe our experiences. Is it a perfect model of hypertrophic scarring? No. Is it a useful model of hypertrophic scarring? Time will tell. We have now obtained gene expression data from the Duroc/Yorkshire model and analysis is underway.
TL;DR: Postoperative administration of bFGF inhibited hypertrophic scarring and widening of remaining scars without any serious side effects.
Abstract: In order to identify a means to reduce scar formation of the skin after incision, this study examined the effect of local administration of basic fibroblast growth factor (bFGF) in humans. bFGF was administered to a sutured wound immediately after an operation. The drug was injected once into the dermis of the margins of wounds using a 27G needle or rinsing after performing dermostitches. The lengths of the treated wounds varied from 1 to 32 cm, and the subjects were 2-86 years old. Sutured wounds after excision of skin tumors from the face, trunk, and limbs and sutured wounds such as those at the donor sites of full-thickness skin grafts were treated with low-dose bFGF injections (0.1 microg/cm wound; Group 2), high-dose bFGF injections (1 microg/cm wound; Group 3), and rinsed with high-dose bFGF (1 microg/cm wound; Group 4). No patient treated with bFGF had hypertrophic scars, while some patients had hypertrophic or very wide scars in the control group (Group 1), and the ratios of minimum scarring of Group 2 (p<0.001), Group 3 (p<0.0001), and Group 4 (p<0.0001) were statistically significantly higher than those of Group 1. Postoperative administration of bFGF inhibited hypertrophic scarring and widening of remaining scars without any serious side effects.
TL;DR: It is suggested that the antifibrotic effects of PGE2 during keloid formation are potentially diminished due to aberrant paracrine fibroblast signaling.
Abstract: Keloid formation has been linked to aberrant fibroblast activity, exacerbated by growth factors and inflammatory mediators. Prostaglandin E2 (PGE2), synthesized from arachidonic acid by cyclooxygenases (COX) and synthases (PGES), acts as both an inflammatory mediator and fibroblast modulator. Although PGE2 has known antifibrotic effects in the lower airway, its role in dermal fibrosis in general, and keloid formation in particular, remains unclear. This study focused on: (1) the effects of PGE2 on keloid fibroblast migration, contraction, and collagen synthesis and (2) endogenous PGE2 synthesis in response interleukin-1beta. PGE2 decreased keloid fibroblast migration and contraction via an EP2/EP4-cAMP mechanism that disrupted actin cytoskeletal dynamics and reversed transforming growth factor-beta1-induced collagen I and III synthesis. Impaired fibroblast PGE2 production has been linked to lower airway fibrosis and recently to keloid formation. Here, we showed that interleukin-1beta stimulation leads to nuclear factor-kappaB translocation to the nucleus, resulting in up-regulation of COX-2 and microsomal PGE2 synthase 1. Up-regulation of COX-2 in, and secretion of PGE2 by keloid fibroblasts are diminished compared with their normal fibroblast counterparts. We suggest that the antifibrotic effects of PGE2 during keloid formation are potentially diminished due to aberrant paracrine fibroblast signaling. Exogenous PGE2 may supplement decreased endogenous levels and inhibit keloid formation or progression.
TL;DR: This review addresses the question of how keratinocyte–fibroblast interaction plays a role in controlling the expression of key extracellular matrix molecules such as matrix metalloproteinases, which are critical in the healing process following any types of insults to the skin.
Abstract: The ability to generate or repair injured tissue is essential to the continuity of human life. As in all other organs, wound healing in the skin is a dynamic process involving tissue response to different types of insults. This process involves a continuous sequence of signals and responses in which platelets, fibroblasts, epithelial, endothelial, and immune cells come together outside their usual domains to orchestrate a very complex event that results in tissue repair. These signals, which are mainly growth factors and cytokines, orchestrate the initiation, continuation, and termination of wound healing. An imbalance in the synthesis and release of these cytokines and growth factors at the wound site, therefore, may result in either retarded wound healing, as is seen in diabetic patients and the elderly population, or overhealing wounds such as fibroproliferative disorders frequently seen following surgical incision, traumatic wounds, and severe electrical and thermal injury. In general, regardless of the site of injury, in any phase of the dynamic healing process, a fine balance between synthesis of extracellular matrix and degradation by a large family of enzymes, known as matrix metalloproteinases, is required for maintaining the structural integrity of healing tissue. The availability of new models such as organotypic co-culture systems have allowed us to gain new insight into the cell-cell interactions at both cellular and molecular levels. Recent evidence indicates that mesenchymal-epithelial interactions play a critical role in regulation of skin homeostasis and this cross-talk is mediated by soluble factors acting as autocrine/paracrine regulators of fibroblast and keratinocyte growth, function, and differentiation. In this review we address the question of how keratinocyte-fibroblast interaction plays a role in controlling the expression of key extracellular matrix molecules such as matrix metalloproteinases, which are critical in the healing process following any types of insults to the skin.
TL;DR: The current evidence base on the use of these silver‐based products on leg ulcers is limited, both in terms of the quantity available and the quality of the evidence.
Abstract: To determine the quantity and quality of current research on the effectiveness of silver-based dressings and topical agents for the treatment of leg ulcers, this paper presents a systematic review of randomized controlled trials (RCTs) looking at the effects of silver-based dressings and topical agents on leg ulcer healing. Electronic databases were searched up to May 2006 for relevant randomized controlled trials. Journals and conference proceedings were also searched. The methodological quality of selected trials was assessed and statistical pooling of the results from similar studies undertaken. Rate of healing, proportion of ulcers completely healed and change in ulcer size were observed. Nine studies were considered eligible for inclusion. These studies varied in terms of the types of leg ulcers treated, interventions used, and outcomes assessed. Studies provided inconsistent evidence regarding the effects of silver-based dressings and topical agents on leg ulcer healing. Studies generally provided poor evidence due to a lack of statistical power, poor study designs, and incomplete reporting. In conclusion, the current evidence base on the use of these silver-based products on leg ulcers is limited, both in terms of the quantity available and the quality of the evidence. This review highlights the need for further, more rigorous research to be carried out before the use of these silver-based interventions in routine leg ulcer management is supported.
TL;DR: It is concluded that M MP‐8 and MMP‐26 are differentially expressed in acute and chronic wounds.
Abstract: Wound healing involves highly controlled events including reepithelialization, neoangiogenesis, and reformation of the stromal compartment. Matrix metalloproteinases (MMPs) are a family of neutral zinc-dependent endopeptidases known to be essential for the wound-healing process. MMP-8 (collagenase-2) is a neutrophil-derived highly effective type I collagenase, recently indicated to be important for acute wound healing. MMP-26 is a more recent and less well-studied member of the MMP family. Our aim was to study the expression of MMP-8 and MMP-26 in human cutaneous wound repair and chronic wounds using histological methods and cell culture. MMP-8 expression was associated with epithelial cells, neutrophils, and other inflammatory cells in chronic human wounds. MMP-26 was prominently expressed in the extracellular compartment of most chronic wounds in close vicinity to the basement membrane area. MMP-26 was also expressed in acute day 1 wounds with declining expression thereafter. In vitro wound experiments showed that both MMP-8 and MMP-26 were expressed by migrating human mucosal keratinocytes. Inhibiting MMP-26 resulted in aberrant keratinocyte migration and proliferation. We conclude that MMP-8 and MMP-26 are differentially expressed in acute and chronic wounds.
TL;DR: The instrument's sensitivity to differences in clinical outcome and responsiveness to change in clinical parameters makes it a useful tool to assess the outcomes of treatment from the patients' perspective.
Abstract: To develop and validate a disease-specific quality of life (QoL) measure, based on the conceptual model of the SKINDEX-29 for patients with a chronic venous leg ulcer (VLU), in-depth interviews, and focus groups of patients (n=36) with VLU were used to generate VLU-specific items. These items were added to selected SKINDEX-29 items that were adapted for use in VLU. Further samples of VLU patients were used for item reduction (n=124) and to assess the psychometric properties of the new tool (n=120). The final VLU-QoL contained 34 items: 17 items adapted from the SKINDEX-29 and 17 VLU-specific items. Factor analysis of the items confirmed the existence of three hypothesized domains: Activities (12 items), Psychological (12 items), and Symptom Distress (10 items). Reliability in terms of internal consistency and test-retest reliability was found to be good. The measure was also found to be valid and responsive to clinical change. The VLU-QoL has good psychometric properties. The instrument's sensitivity to differences in clinical outcome and responsiveness to change in clinical parameters makes it a useful tool to assess the outcomes of treatment from the patients' perspective.
TL;DR: The results may challenge the traditional concept that adipose tissue plays a negative role in wound healing and may offer direct evidence for encouraging the retention of adipOSE tissue in autologous skin grafting for skin wounds.
Abstract: The main function of adipose tissue has been considered as storage of triglycerides. Adipose tissue was considered harmful for healing extensive and deep burns because of poor circulation and easy liquefaction in wound beds, which offer an excellent culture medium for bacteria. However, these traditional concepts have been challenged with the discovery of the endocrine function of adipose tissue. To investigate the effects of adipose tissue extract on wound healing, we created four 3.0 x 2.5 cm full-thickness wounds on each side of the back of male Wu Zhi Shan minipigs (n=6), for eight wounds in each animal. The wounds were randomly divided to receive normal saline (0.5 mL; controls), adipose tissue extract (1.5 g), basic fibroblast growth factor (50 U/cm(2)), and epidermal growth factor (50 U/cm(2)). Reduction in wound area and wound volume was accelerated with adipose tissue treatment as compared with growth factor or control treatment. The thickness of the regenerated epidermis and the number of new vascular nets were markedly increased in adipose tissue-treated wounds. Biopsy of adipose tissue-treated wounds showed enhanced expression of proliferation cell nuclear antigen (PCNA) and Factor VIII-related antigen, which indicated active cell differentiation and proliferation. In vitro study in rat tissue showed adipose tissue extracts stimulating skin growth. Bacteriology results showed no significant differences in amount or type of bacteria, whatever the treatment. These results may challenge the traditional concept that adipose tissue plays a negative role in wound healing and may offer direct evidence for encouraging the retention of adipose tissue in autologous skin grafting for skin wounds.
TL;DR: Experiments using human adipose‐derived stem cells and dermal fibroblasts cultured in media containing various concentrations of DF and fetal bovine serum suggested that for some cell types, DF‐contained growth factors that are not obtained from SPRP could be used to supplement or substitute for serum in culture media.
Abstract: Wound fluids, human serum from platelet-poor and platelet-rich plasma (SPPP and SPRP), contain various soluble factors involved in cell growth and proliferation. Levels of cytokines, chemokines, and matrix metalloproteinases (MMPs) in drainage fluids (DFs) harvested from subcutaneous wounds, punctured fluids (PF) from seroma, and SPPP were measured. SPPP and SPRP from four healthy volunteers were also subjected to the analysis. Biochemical profiles of DF reflected the sequential stages of wound healing. Early-phase DF contained high concentrations of basic fibroblast growth factor and platelet-derived growth factor and EGF. The levels of keratinocyte growth factor, interleukin-6, and MMP-8 in DF peaked on days 2-3, while vascular endothelial growth factor, hepatocyte growth factor, interleukin-8, and MMP-1 increased over time during days 0-6. Punctured fluids contained high levels of TGF-beta1, keratinocyte growth factor, vascular endothelial growth factor, hepatocyte growth factor, and MMP-1. Experiments using human adipose-derived stem cells and dermal fibroblasts cultured in media containing various concentrations of DF and fetal bovine serum suggested that for some cell types, DF-contained growth factors that are not obtained from SPRP could be used to supplement or substitute for serum in culture media. SPRP and DF are economical ready-made mixtures of serum and autologous soluble factors, and may be differentially useful for regenerative therapies.
TL;DR: Observations about the role of neuropeptides in cutaneous repair, neuronal modulation of repair processes at two extremes of abnormal wound healing, chronic non‐healing ulcers in type II diabetes mellitus and hypertrophic scars in deep partial thickness wounds, may provide therapeutic targets.
Abstract: Healed partial thickness wounds including burns and donor sites cause hypertrophic scar formation and patient discomfort. For many patients with hypertrophic scars, pruritis is the most distressing symptom, which leads to wound excoriation and chronic wound formation. In spite of the clinical significance of abnormal innervation in scars, the nervous system has been largely ignored in the pathophysiology of hypertrophic scars. Evidence that neuropeptides contribute to inflammatory responses to injury include inflammatory cell chemotaxis, cytokine and growth factor production. The neuropeptide substance P, which is released from nerve endings after injury, induces inflammation and mediates angiogenesis, keratinocyte proliferation, and fibrogenesis. Substance P activity is tightly regulated by neutral endopeptidase (NEP), a membrane bound metallopeptidase that degrades substance P at the cell membrane. Altered substance P levels may contribute to impaired cutaneous healing responses associated with diabetes mellitus or hypertrophic scar formation. Topical application of exogenous substance P or an NEP inhibitor enhances wound closure kinetics in diabetic murine wounds suggesting that diabetic wounds have insufficient substance P levels to promote a neuroinflammatory response necessary for normal wound repair. Conversely, increased nerve numbers and neuropeptide levels with reduced NEP levels in human and porcine hypertrophic scar samples suggest that excessive neuropeptide activity induces exuberant inflammation in hypertrophic scars. Given these observations about the role of neuropeptides in cutaneous repair, neuronal modulation of repair processes at two extremes of abnormal wound healing, chronic non-healing ulcers in type II diabetes mellitus and hypertrophic scars in deep partial thickness wounds, may provide therapeutic targets.