The dynamics of inflammatory cytokines in the healing process of mouse skin wound: a preliminary study for possible wound age determination

Inflammatory inert poly(ethylene glycol)--protein wound dressing improves healing responses in partial- and full-thickness wounds

In this study, a novel soft hydrogel system based on the poly(ethylene glycol)-protein conjugates was evaluated as an occlusive wound dressing material. The hydrogel material, referred by the name of BioAquacare, contains up to 96% of the liquid and is formulated with phosphate-buffered saline and safe preservative to control bacterial load in the open wounds. Performance of the BioAquacare as a wound dressing material was assessed in partial- and full-thickness wounds in pigs. Wound analysis comprised macroscopic determination of the wound size, histological examination of the healing tissues and biochemical characterisation of wound exudates. The wounds treated with BioAquacare healed without any signs of inflammation, skin irritation, oedema or erythema. Cellular composition of the reepithelialised wounds was very similar to that of the normal skin, with a well-developed stratum corneum and epithelial layer. It was observed that BioAquacare plays the role of a liquid compartment, which provides pronounced hydration effect and helps maintain a natural moist environment of the healing tissues. BioAquacare showed relatively low protein-absorbing activity, absorbing predominantly low-molecular-weight molecules, including interleukin (IL)-1beta, IL-6, transforming growth factor-beta1 and products of haemoglobin degradation. It is concluded that application of the moist BioAquacare dressing promotes fast reepithelialisation by creating favourable environment for keratinocytes proliferation and it also reduces scarring. The results show that BioAquacare can be considered as a safe, biocompatible and inflammatory inert wound dressing material.

Timing of skin wounds

Wound examination is indispensable in forensic practice. It is always necessary to determine wound vitality or wound age to correctly evaluate the relationship between death and any wounds. Thus, the determination of wound vitality or wound age is a classic but still modern theme in forensic pathology. Skin wound healing is a primitive but well orchestrated biological phenomena consisting of three sequential phases, inflammation, proliferation, and maturation. Many biological substances are involved in the process of wound repair, and this short and simplified overview of wound healing can be adopted to determine wound vitality or wound age in forensic medicine. With the development of immunohistochemistry and chemical analyses, the scientific field of wound age determination has advanced progressively during recent years. In particular, it has been demonstrated that collagens, cytokines, and growth factors are useful candidates and markers for the determination of wound vitality or age. In this review article, some interesting and instructive results are presented, contributing to the future practice of every forensic pathologist.

The autocrine TNFalpha signalling loop in keratinocytes requires atypical PKC species and NF-kappaB activation but is independent of cholesterol-enriched membrane microdomains

Tumor necrosis factor alpha (TNFalpha) is involved in the pathogenesis of many inflammatory skin diseases. Epidermal keratinocytes produce and respond to TNFalpha via the cognate type 1 receptor (TNFR1). Little is known about regulation of TNFalpha signalling in this cell type. In this study, we report that in keratinocytes TNFalpha upregulates its own mRNA synthesis in an autocrine manner. This response peaks at approximately 1h of stimulation with TNFalpha but sustained elevated levels of TNFalpha mRNA are observed for up to 24h after stimulation and are dependent on the presence of the soluble cytokine. This autocrine response is mediated by the signalling cascade comprising TNFR1, atypical protein kinase C (aPKC) species and the transcription factor NF-kappaB, but is not dependent on the integrity of cholesterol-enriched membrane microdomains (lipid rafts). TNFalpha-stimulated keratinocytes produced the membrane-bound form of TNFalpha. It is conceivable that the described autocrine signalling loop contributes to the proinflammatory TNFalpha effect in the skin. The discovery of the crucial roles of aPKC and NF-kappaB might have consequences for the development of more selective anti-TNFalpha therapies for inflammatory skin diseases.

Time-course changes in the expression of heme oxygenase-1 in human subcutaneous hemorrhage

To determine the time-course of human subcutaneous hemorrhage, heme oxygenase (HO)-1 expression and macrophage infiltration were observed using an immunohistochemical technique and semiquantitative analysis. The number of immunoreactive cells and the number of all infiltrating cells of each microscopic field were counted, and the ratio of the former to the latter was calculated as the positive cells ratio. An increase in the HO-1-positive cells ratio was observed starting at 3 h after injury, and the maximum ratio was observed 3 days after injury. The pattern of the increase in the macrophage ratio was similar to that of the HO-1-positive cells ratio in the early period after injury. Observation of serial sections revealed that the expression of HO-1 in the cells corresponded to the localization of macrophage. The present results suggest that the determination of HO-1 expression, as derived from macrophages, might be useful for the estimation of the time-course of subcutaneous hemorrhage.

Absence of IL-1 Receptor Antagonist Impaired Wound Healing along with Aberrant NF-κB Activation and a Reciprocal Suppression of TGF-β Signal Pathway

Although enhanced expression of IL-1 family proteins, including IL-1alpha, IL-1beta, and IL-1 receptor antagonist (IL-1ra) during wound healing has been observed, the pathophysiological roles of these factors, particularly IL-1ra, still remain elusive. We explored skin wound-healing processes in IL-1ra-deficient mice. Compared to wild-type (WT) mice, IL-1ra-deficient mice exhibited impaired wound healing, as evidenced by attenuated collagen deposition and delayed neovascularization. In contrast, neutrophil recruitment was significantly exaggerated, with the augmented expression of IL-1s, TNF-alpha, and CXC chemokines, MIP-2 and KC, in IL-1ra-deficient mice compared with WT mice. Because the transcription of these proinflammatory cytokines and CXC chemokines requires the activation of NF-kappaB, a major target of IL-1- and TNF-alpha-mediated signal pathway, we examined the activation states of NF-kappaB. Nuclear translocation of NF-kappaB p65 was significantly enhanced and prolonged in IL-1ra-deficient mice, compared to that in WT mice. The cross-talk between NF-kappaB and TGF-beta-mediated signals has been proposed based on in vitro observations. Indeed, compared to WT mice, the amounts of total and phosphorylated Smad2 and Smad3 were decreased with a reciprocal increase in the amount of Smad7 in skin wound sites of IL-1ra-deficient mice. Moreover, the gene expression of vascular endothelial growth factor, a target gene of TGF-beta1, was decreased in IL-1ra-deficient mice. Thus, the absence of IL-1ra may suppress TGF-beta-mediated signaling pathway, which is crucial for collagen deposition and vascular endothelial growth factor-mediated neovascularization in wound healing.

Response of mouse skin to tattooing: use of SKH-1 mice as a surrogate model for human tattooing

Tattooing is a popular cosmetic practice involving more than 45 million US citizens. Since the toxicology of tattoo inks and pigments used to formulate tattoo inks has not been reported, we studied the immunological impact of tattooing and determined recovery time from this trauma. SKH-1 hairless mice were tattooed using commercial tattoo inks or suspensions of titanium dioxide, cadmium sulfide, or iron oxide, and sacrificed at 0.5, 1, 3, 4, 7, or 14 days post-tattooing. Histological evaluation revealed dermal hemorrhage at 0.5 and 1 day. Acute inflammation and epidermal necrosis were initiated at 0.5 day decreasing in incidence by day 14. Dermal necrosis and epidermal hyperplasia were prominent by day 3, reducing in severity by day 14. Chronic active inflammation persisted in all tattooed mice from day 3 to 14 post-tattooing. Inguinal and axillary lymph nodes were pigmented, the inguinal being most reactive as evidenced by lymphoid hyperplasia and polymorphonuclear infiltration. Cutaneous nuclear protein concentrations of nuclear factor-kappa B were elevated between 0.5 and 4 days. Inflammatory and proliferative biomarkers, cyclooxygenase-1, cyclooxygenase-2, and ornithine decarboxylase protein levels were elevated between 0.5 and 4 days in the skin and decreased to control levels by day 14. Interleukin-1 beta and interleukin-10 were elevated in the lymph nodes but suppressed in the tattooed skin, with maximal suppression occurring between days 0.5 and 4. These data demonstrate that mice substantially recover from the tattooing insult by 14 days, leaving behind pigment in the dermis and the regional lymph nodes. The response seen in mice is similar to acute injury seen in humans, suggesting that the murine model might be a suitable surrogate for investigating the toxicological and phototoxicological properties of ingredients used in tattooing.

Cytokine gene expression in a murine wound healing model

Inflammatory mediators have been shown to play a major role in the complex series of co-ordinated events that occur in wound healing responses following injury. However, to date most of the studies carried out have addressed the expression, interactions and role of only one or two cytokines that are thought to be involved in wound repair. This study has evaluated, in murine skin samples taken at 0, 3, 12, 18, 24, 48, 72, 120 and 168 h post-wounding, the expression of a wide range of cytokines with potential for a role in wound repair. Various techniques (reverse transcription polymerase chain reaction (RT-PCR), bioassays and ELISA) were used to evaluate cytokine expression in these samples at both the mRNA and protein expressions level. Semi-quantitative analysis using RT-PCR revealed that IL-1beta, IP10, bFGF, and TGFbeta3 up-regulated in wounded samples, compared to non-injured control samples. Expression of mRNA for other cytokines and inflammatory mediators, IL-1alpha, IL-6, TGFbeta1, TNFalpha, MIP-1alpha, MIP-2, JE, KC, PDGFalpha and PDGFbeta, were found to be down-regulated in injured adult murine samples compared to normal control samples. Interestingly we failed to find evidence of mRNA expression for the cytokines IL-2, IL-4, IL-12, GM-CSF, IFNgamma and RANTES, in both non-injured and injured samples. These observations were also generally supported by the results obtained using bioassays for IL-1 and IL-6 and ELISA for IL-1alpha, IL-1beta, IL-6, TNFalpha, and IFNgamma.

Early increase in TNF-alpha-containing mast cells in skin lesions

We have evaluated the numbers and immunohistochemical positivity for tumor necrosis factor (TNF) alpha of the mast cells in (a) 40 skin samples collected at autopsy from subjects who had survived for a few seconds to 1 h, (b) 10 samples of post-mortem skin lesions and (c) 10 surgical biopsies of healthy skin. Sections were treated with fluoresceinated avidin, to tag mast cell granules, followed by indirect immunohistochemistry for TNF-alpha with polyclonal primary and rhodaminated secondary antibodies. We could confirm a progressive increase in mast cell numbers, which became significant 1 h after trauma. More important, the fraction of mast cells positive for TNF-alpha increased progressively in the same time period and became significantly higher than controls in specimens collected more than 15 min after trauma. Samples from post-mortem lesions had significantly fewer mast cells and fewer TNF-alpha-positive cells than any other group of samples. The results suggest that mast cells are quickly recruited to an injured site in response to trauma and upregulate their TNF-alpha content, which can play an early role in directing tissue response to injury. The forensic pathologist can take advantage from this behavior of mast cells for the evaluation of the timing of early vital lesions.

Wound-healing defect of CD18(-/-) mice due to a decrease in TGF-beta1 and myofibroblast differentiation

We studied the mechanisms underlying the severely impaired wound healing associated with human leukocyte-adhesion deficiency syndrome-1 (LAD1) using a murine disease model. In CD18(-/-) mice, healing of full-thickness wounds was severely delayed during granulation-tissue contraction, a phase where myofibroblasts play a major role. Interestingly, expression levels of myofibroblast markers alpha-smooth muscle actin and ED-A fibronectin were substantially reduced in wounds of CD18(-/-) mice, suggesting an impaired myofibroblast differentiation. TGF-beta signalling was clearly involved since TGF-beta1 and TGF-beta receptor type-II protein levels were decreased, while TGF-beta(1) injections into wound margins fully re-established wound closure. Since, in CD18(-/-) mice, defective migration leads to a severe reduction of neutrophils in wounds, infiltrating macrophages might not phagocytose apoptotic CD18(-/-) neutrophils. Macrophages would thus be lacking their main stimulus to secrete TGF-beta1. Indeed, in neutrophil-macrophage cocultures, lack of CD18 on either cell type leads to dramatically reduced TGF-beta1 release by macrophages due to defective adhesion to, and subsequent impaired phagocytic clearance of, neutrophils. Our data demonstrates that the paracrine secretion of growth factors is essential for cellular differentiation in wound healing.

Forensic application of VEGF expression to skin wound age determination

An immunohistochemical study combined with morphometry was carried out to examine the time-dependent expression of vascular endothelial growth factor (VEGF) using 53 human skin wounds with different wound ages (groups I: 0-12 h, II: 1-4 days, III: 7-14 days and IV: 17-21 days). In the human wound specimens aged 4-12 h, neutrophils recruited at the wound showed no positive signals for VEGF. With an increase in wound ages of > or =7 days, granulation tissue and angiogenesis were observed, with the migration of macrophages and fibroblasts of which the cytoplasm expressed VEGF-positive reactions. Morphometrically, the average VEGF-positive ratio was highest in group III, followed by that of group IV. In groups III and IV, 13 out of 26 wound samples had VEGF-positive ratios of more than 50%. However, all of the wound samples in groups I and II showed VEGF-positive ratios of less than 50%. With regard to the practical applicability and forensic validity, these observations suggest that a VEGF-positive ratio of more than 50% possibly indicates a wound age of 7 days or more.

Effects of Tumor Necrosis Factor-α (TNFα) in Epidermal Keratinocytes Revealed Using Global Transcriptional Profiling

Identification of tumor necrosis factor-alpha (TNF alpha) as the key agent in inflammatory disorders, e.g. rheumatoid arthritis, Crohn's disease, and psoriasis, led to TNF alpha-targeting therapies, which, although avoiding many of the side-effects of previous drugs, nonetheless causes other side-effects, including secondary infections and cancer. By controlling gene expression, TNF alpha orchestrates the cutaneous responses to environmental damage and inflammation. To define TNF alpha action in epidermis, we compared the transcriptional profiles of normal human keratinocytes untreated and treated with TNF alpha for 1, 4, 24, and 48 h by using oligonucleotide microarrays. We found that TNF alpha regulates not only immune and inflammatory responses but also tissue remodeling, cell motility, cell cycle, and apoptosis. Specifically, TNF alpha regulates innate immunity and inflammation by inducing a characteristic large set of chemokines, including newly identified TNF alpha targets, that attract neutrophils, macrophages, and skin-specific memory T-cells. This implicates TNF alpha in the pathogenesis of psoriasis, fixed drug eruption, atopic and allergic contact dermatitis. TNF alpha promotes tissue repair by inducing basement membrane components and collagen-degrading proteases. Unexpectedly, TNF alpha induces actin cytoskeleton regulators and integrins, enhancing keratinocyte motility and attachment, effects not previously associated with TNF alpha. Also unanticipated was the influence of TNF alpha upon keratinocyte cell fate by regulating cell-cycle and apoptosis-associated genes. Therefore, TNF alpha initiates not only the initiation of inflammation and responses to injury, but also the subsequent epidermal repair. The results provide new insights into the harmful and beneficial TNF alpha effects and define the mechanisms and genes that achieve these outcomes, both of which are important for TNF alpha-targeted therapies.

Albumin as a marker of plasma transudation in experimental skin lesions

Liquid chromatography measurements of albumin levels were obtained for experimental incision wounds, excoriations, and heat and freezing injuries of different ages. Hemoglobin levels in tissue specimens were measured and an equivalent amount of blood-related albumin was subtracted from the analysis results. In specimens taken immediately after death, the mean albumin level as compared to control skin was increased by about 2-fold in freezing injuries aged 60 min. In all other lesions, the same increase was observed even after 30 min. The mean albumin level was about 3-fold as compared with the control skin in excoriations aged 30 min, heat and freezing injuries aged 4 h, and incision wounds aged 12 h. An approximately 5-fold increase was seen in heat and freezing injuries aged 1 and 2 weeks. A marked decrease occurred in mean albumin levels in all lesions aged 4 weeks. An increase in albumin in wounds and excoriations was demonstrable also in specimens taken 3 days postmortem. Postmortem hypostasis resulted in a 1.1 to 1.4-fold increase in mean albumin levels in wounds and excoriations inflicted 1 min postmortem.

Interleukin 6 Indirectly Induces Keratinocyte Migration

IL-6-deficient transgenic mice (IL-6 KO) display significantly delayed cutaneous wound healing. To further elucidate the role of IL-6 in skin wound healing, epidermal keratinocyte and dermal fibroblast cells were isolated from neonatal IL-6 KO mice and treated with rmIL-6. It was found that rmIL-6 alone did not significantly modulate the proliferation or migration of cultured IL-6 KO keratinocytes. rmIL-6, however, significantly induced the migration of IL-6 KO keratinocytes (up to 5-fold) when co-cultured with dermal fibroblasts. Culture supernatants from IL-6-treated fibroblasts were also found to induce the migration of keratinocytes to a similar degree. Genomics analysis of treated fibroblasts indicated that rmIL-6 does not induce any known soluble keratinocyte migratory factors. rmIL-6 treatment of fibroblast, however, induced a rapid and sustained phosphorylation of STAT3 protein. These data indicate that IL-6 could influence wound healing by inducing keratinocyte migration through the production of a soluble fibroblast-derived factor, and its activity may be associated with STAT3 activation.

The gene expression of cytokines and chemokines induced by tourniquet shock in mice

Traumatic shock is one of the major fields in forensic pathology, but its mechanism remains elusive from the pathophysiological aspects. Tourniquet shock has been established as one of the animal models of traumatic shock, and we examined the gene expression of cytokines and chemokines in the lung and liver in tourniquet shock using mice. Tourniquet was conducted by the application of elastic bands with five turns at both the thighs as high as possible for 2 h, followed by reperfusion. In this procedure, more than 90% mice died within 48 h after reperfusion. Serum hepatic transaminase and hematocrit values significantly increased at 2 h after reperfusion, and their elevation was still evident after 10 h. Histopathologically, hemorrhages, congestion and leukocyte recruitment were observed in the lung and liver specimens after 6 h of reperfusion. Immunohistochemical analysis with anti-myeloperoxidase antibody demonstrated a massive neutrophil infiltration in the lung and liver at 2 h or more after reperfusion. RT-PCR analyses demonstrated that the gene expression of interleukin-1beta, tumor necrosis factor-alpha, monocytes chemoattractant protein-1, macrophage inflammatory protein (MIP)-1alpha, MIP-2, KC and vascular endothelial adhesion molecule-1 was most enhanced in the lung and liver at 2 h after reperfusion. Thus, the gene expression of cytokines and chemokines is presumed to be closely related with the onset of tourniquet shock. From the forensic aspects, these cytokines and chemokines are considered to be useful markers for the early diagnosis of tourniquet shock.

Essential involvement of IL-6 in the skin wound-healing process as evidenced by delayed wound healing in IL-6-deficient mice

To clarify interleukin (IL)-6 roles in wound healing, we prepared skin excisions in wild-type (WT) and IL-6-deficient BALB/c [knockout (KO)] mice. In WT mice, the wound area was reduced to 50% of original size at 6 days after injury. Microscopically, leukocyte infiltration was evident at wound sites. Furthermore, the re-epithelialization rate was approximately 80% at 6 days after injury with increases in angiogenesis and hydroxyproline contents. The gene expression of IL-1, chemokines, adhesion molecules, transforming growth factor-beta1, and vascular endothelial growth factor was enhanced at the wound sites. In contrast, the enhanced expression of these genes was significantly reduced in KO mice. Moreover, in KO mice, the reduction of wound area was delayed with attenuated leukocyte infiltration, re-epithelialization, angiogenesis, and collagen accumulation. Finally, the administration of a neutralizing anti-IL-6 monoclonal antibody significantly delayed wound closure in WT mice. These observations suggest that IL-6 has crucial roles in wound healing, probably by regulating leukocyte infiltration, angiogenesis, and collagen accumulation.

Intraarticular inflammatory cytokines in acute anterior cruciate ligament injured knee

To understand the dynamics of the intraarticular acute inflammatory phase of an anterior cruciate ligament (ACL) injured knee, we analyzed the level of inflammatory cytokines (TNF-alpha, IL-1beta, IL-6, IL-8, IL-1ra, and IL-10) in joint fluid samples aspirated from 34 knees following an acute ACL injury. The samples were divided into the following five groups according to the duration from injury to aspiration: within 24 h (n=5), 2-3 days (n=14), 4-6 days (n=5), 7-9 days (n=5), 10-14 days (n=4), and 15-21 days (n=3). For comparison, 7 samples were also aspirated from 4 patients with osteoarthritis and 3 with postmenisectomy hydrops (chronic arthritis group). The highest levels of inflammatory cytokines were detected in the ACL-injury group within 24 h of the injury, and the levels decreased thereafter. While there were several patterns of decrease, nearly all of the inflammatory cytokines decreased to the level of that in the chronic arthritis group within 1 week. These dynamics are similar to those reported for inflammatory cytokines in wound fluid during wound healing, and suggest that the intraarticular healing process also progresses in ACL injured knees.

Effects of staphylococci on cytokine production from human keratinocytes

BACKGROUND

Staphylococcus skin infection is characterized by the infiltration of numerous neutrophils within the epidermis; however, the precise mechanism of epidermal infiltration of neutrophils during skin infection with staphylococci is not well understood and the factors regulating the neutrophil recruitment are yet to be determined.

OBJECTIVES

We investigated the effects of staphylococci on cytokine production from keratinocytes, specifically to elucidate the mechanisms of neutrophil infiltration within the epidermis in cutaneous microbial infection.

METHODS

Cytokine production from human keratinocytes was examined after stimulation with heat-killed Staphylococcus aureus, S. epidermidis and S. intermedius.

RESULTS

Interleukin (IL)-6 and IL-8 were detected in the culture supernatants by enzyme-linked immunosorbent assay but IL-1beta, monocyte chemotactic protein-1 and tumour necrosis factor-alpha were not. IL-6 and IL-8 mRNAs were also confirmed by reverse transcription-polymerase chain reaction in the keratinocytes stimulated with killed staphylococci for 1, 3, 6, 10 and 24 h.

CONCLUSIONS

These results could explain the epidermal infiltration of neutrophils in cutaneous infection with staphylococci, suggesting that the analysis of cytokines might add valuable information for the pathogenesis of cutaneous infection with Staphylococcus species.

Time-dependent immunohistochemical detection of proinflammatory cytokines (IL-1beta, IL-6, TNF-alpha) in human skin wounds

The proinflammatory cytokines interleukin-1beta (IL-1beta), interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-alpha) hold important functions in the early and late courses of inflammation, trauma and wound healing. In the present study, human skin wounds due to sharp force (n = 105) were collected during surgery and autopsy. The wound age mainly varied from several minutes to 5 h, some specimens aged up to 6 weeks. Control specimens from uninjured skin were available in each case. After preparation of cryostat sections, immunohistochemistry was performed according to the APAAP technique, using monoclonal and polyclonal antibodies. The results were evaluated semiquantitatively. All markers were weakly expressed in normal human skin constitutively. However, the staining pattern changed significantly in vital wounds concerning epidermal layers, subepidermal cells, vessels and sweat glands. IL-1beta and IL-6 showed enhanced expression after 15 and 20 min at the earliest (increase of epidermal reactivity). After 30-60 and 60-90 min, respectively, marked expression was observed with these markers. Similar alterations were detectable with TNF-alpha after 15 and 60-90 min. The reactivity of all three markers persisted over several hours, then decreased to basal levels again and sometimes reappeared after days and in granulation tissue. Leukocytes reacting with IL-1beta and IL-6 appeared after approximately 2 h.

CONCLUSION

proinflammatory cytokines can serve as a useful tool for the estimation of vitality and wound age, in particular in the early post-traumatic interval prior to leukocyte reaction. Autolysis did not play a role in the samples investigated (postmortem interval up to 8 days). Problems could sometimes rise from constitutive expression. Therefore, it is recommended to examine control samples from the same individual and to compare the reactivity with wound specimens.

Immunohistochemical study of basic fibroblast growth factor and vascular endothelial growth factor expression for age determination of cutaneous wounds

The authors investigated the expression of basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) during skin wound healing using immunohistochemical techniques. After a full-thickness incision was made on the dorsal skin, mice were killed 0.5, 1, 3, 8, 24, 72, 144, or 240 hours after incision, and the wound was excised. To evaluate the influences of postmortem degeneration, cutaneous wound excision was performed 1 to 5 days after the mice were killed. The excised wounds were stained by the conventional streptoavidin-biotinylated peroxidase complex method, using specific antibodies, and the ratio of the number of positive cells to total cells was determined. Expression of bFGF was detected in the nuclei of epidermal cells and fibroblasts in the early 0.5- to 1-hour phases and the late 24- to 144-hour phases. Expression of VEGF was detected in the cytoplasm of epidermal cells in the 24- to 144-hour phases. Immunoreactivity of both cytokines was detected 1 day post mortem and was especially well preserved in the fibroblasts. Time-dependent expression of both factors suggested that they would be useful markers for the determination of wound age. However, bFGF should be superior to VEGF because of its earlier expression and because of its more persistent expression in dermal fibroblasts with increasing postmortem interval.

Accelerated wound healing in tumor necrosis factor receptor p55-deficient mice with reduced leukocyte infiltration

To clarify biological roles of tumor necrosis factor receptor p55 (TNF-Rp55) -mediated signals in wound healing, skin excisions were prepared in BALB/c (WT) and TNF-Rp55-deficient (KO) mice. In WT mice, the wound area was reduced to 50% of the original area 6 days after injury, with angiogenesis and collagen accumulation. Histopathologically, reepithelialization rate was approximately 80% 6 days. Myeloperoxidase activity and macrophage recruitment were the most evident 1 and 6 days after injury, respectively. Gene expression of adhesion molecules, interleukin 1alpha (IL-1alpha), IL-1beta, monocyte chemoattractant protein 1, macrophage inflammatory protein 1alpha (MIP-1alpha), MIP-2, transforming growth factor beta1 (TGF-beta1) connective tissue growth factor (CTGF), vascular endothelial growth factor (VEGF), Flt-1, and Flk-1 was enhanced at the wound site. In KO mice, an enhancement in angiogenesis, collagen content, and reepithelialization was accelerated with the increased gene expression of TGF-beta1, CTGF, VEGF, Flt-1, and Flk-1 at the wound sites, resulting in accelerated wound healing compared with WT mice. In contrast, leukocyte infiltration, mRNA expression of adhesion molecules, and cytokines were significantly reduced in KO mice. These observations suggest that TNF-Rp55-mediated signals have some role in promoting leukocyte infiltration at the wound site and negatively affect wound healing, probably by reducing angiogenesis and collagen accumulation.

Interleukin-8 and tumor necrosis factor alpha production in human epidermal keratinocytes induced by Trichophyton mentagrophytes

Production of interleukin-8 (IL-8) and tumor necrosis factor alpha (TNF-alpha) was confirmed by enzyme-linked immunosorbent assay in a medium where human epidermal keratinocytes were cocultured with Trichophyton mentagrophytes for 1 to 12 h. IL-8 and TNF-alpha mRNAs were also detected in the keratinocytes cocultured with T. mentagrophytes.

Immunohistochemical detection of chemokines in human skin wounds and its application to wound age determination

Immunohistochemical studies on the time-dependent expression of the chemokines such as interleukin (IL)-8, monocyte chemoattractant protein (MCP)-1 and macrophage inflammatory protein (MIP)-1alpha were performed on 50 human skin wounds with different wound ages (group I 0-12 h, group II 1-4 days, group III 7-14 days and group IV 17-21 days). In the wound specimens with wound ages between 4 and 12 h, neutrophils mainly showed positive reactions for IL-8, MCP-1 and MIP-1alpha. With increasing wound ages, macrophages and fibroblasts were positively stained with anti-IL-8, MIP-1alpha and MCP-1 antibodies. Morphometrically, there was a similar distribution in the positive ratios of the inflammatory cells among IL-8, MCP-1 and MIP-alpha. The positive ratios of each chemokine were very low in group I and a considerable increase of the positive ratios in each chemokine was observed in group II (mean +/- standard error IL-8: 59.8 +/- 2.1%, MCP-1: 42.4 +/- 3.1% and MIP-1alpha: 50.4 +/- 3.7%). Although the positive ratios for each chemokine gradually decreased according to the wound age, the mean positive ratios in groups III and IV were significantly higher than those in group I. From the forensic aspect, these chemokines are considered useful markers for wound age determination. Thus, ratios of > 50% for IL-8, > 30% for MCP-1 or > 40% for MIP-1alpha indicate a wound age of at least I day. Moreover, the combined investigation of these three chemokines can make wound age determination more objective and accurate.

Interleukin-6 treatment augments cutaneous wound healing in immunosuppressed mice

It has been postulated that the inflammatory response that occurs after cutaneous wounding is a prerequisite for healing and that inflammatory cytokines, such as interleukin-6 (IL-6) are involved in this process. We showed previously that IL-6-deficient mice display delayed wound healing, which could be reversed by administration of a murine IL-6 expression plasmid or recombinant murine IL-6 (rMuIL-6). In the present study, we observed that delayed cutaneous wound healing, which occurs as a result of glucocorticoid-induced immunosuppression, can also be reversed by rMuIL-6, as evidenced by epithelialization, granulation tissue formation, and wound closure. In vehicle control mice, rMuIL-6 did not augment healing but rather delayed the process. Immunochemical studies indicated that the expression of matrix metalloproteinase-10 (MMP-10) was increased in dexamethasone-treated mice and that rMuIL-6 treatment reduced its expression, indicating that IL-6 may influence dermal matrix formation and, specifically, collagen synthesis. These results demonstrate that IL-6 can restore abnormal wound repair that occurs in immunodeficiency and suggest its use as a potential therapy.

Keratinocyte-derived growth factors play a role in the formation of hypertrophic scars

In predisposed individuals, wound healing can lead to hypertrophic scar or keloid formation, characterized by an overabundant extracellular matrix. It has recently been shown that hypertrophic scars are accompanied by abnormal keratinocyte differentiation and proliferation, and significantly increased acanthosis, compared with normal scars. This study addressed the question of whether the development of normal and hypertrophic scars is regulated by differences in the growth factor profiles of both the epidermis and the dermis. The presence of interleukin-1alpha (IL-1alpha), IL-1beta, tumour necrosis factor-alpha (TNF-alpha), platelet-derived growth factor (PDGF), transforming growth factor-beta1 (TGF-beta1), and basic fibroblast growth factor (bFGF) was investigated in biopsies taken from breast reduction scars at 3 and 12 months following surgery. The samples were analysed by immunohistological methods and categorized as scars that remained hypertrophic (HH), became normal (HN) or remained normal after 12 months (NN). The epidermal expression of IL-1alpha was significantly increased in NN scars compared with HN and HH scars 3 and 12 months following operation, whereas the dermal expression showed no difference. PDGF was significantly increased in the dermis of normal scars after 3 months and in both the epidermis and the dermis of hypertrophic scars after 12 months. IL-1beta, TNF-alpha, TGF-beta and bFGF showed no differences. It is hypothesized that impaired production of keratinocyte-derived growth factors, such as IL-1alpha, leads to a decrease in the catabolism of the dermal matrix, whereas augmented epidermal PDGF production leads to increased formation of the dermal matrix in hypertrophic scars. These observations support the possibility that the epidermis is involved in preventing the formation of hypertrophic scars.

Impaired cutaneous wound healing in interleukin-6-deficient and immunosuppressed mice

It has been postulated that an inflammatory response after cutaneous wounding is a prerequisite for healing, and inflammatory cytokines, such as interleukin-6 (IL-6), might be intimately involved in this process. IL-6-deficient transgenic mice (IL-6 KO) displayed significantly delayed cutaneous wound healing compared with wild-type control animals, requiring up to threefold longer to heal. This was characterized by minimal epithelial bridge formation, decreased inflammation, and granulation tissue formation. Using electrophoretic mobility shift assays of wound tissue from IL-6 KO mice, decreased AP-1 transcription factor activation was shown compared with wild-type mice 16 h after wounding. In situ hybridization of wound tissue from wild-type mice revealed IL-6 mRNA expression primarily in the epidermis at the leading edge of the wound. Delayed wound healing in IL-6 KO mice was reversed with a single dose of recombinant murine IL-6 or intradermal injection of an expression plasmid containing the full-length murine IL-6 cDNA. Treatment with rmIL-6 also reconstituted wound healing in dexamethasone-treated immunosuppressed mice. The results of this study may indicate a potential use for IL-6 therapeutically where cutaneous wound healing is impaired.

Forensic wound examination

Wound examination is of prime importance in forensic pathology, and it is desirable to establish a wound examination system in order to evaluate and record the nature of wound more accurately and objectively. Modern diagnostic techniques and devices as well as advanced cell-biological methods should be introduced as the means for this aim. For example, radiological, endoscopic or magnetic resonance imaging (MRI) examination have been used in addition to examination with the naked eye. In our department, a binocular surgical operating microscope is routinely employed at forensic autopsy, which is useful for elucidating the nature of wound in more detail. It is also necessary to determine whether a wound has vitality, and, if antemortem, how long before death the wound has been sustained. For the determination of wound age including vitality, various biological factors such as cytokines and extracellular matrix components involved in wound healing have been examined by histopathological methods. Our studies have shown that interleukin (IL)-1alpha, IL-1 b, IL-6, IL-10 and tumor necrosis factor-alpha are possibly useful markers for wound age determination as well as cell-biological indicators of vitality. Furthermore, molecular biological techniques have been intended to be applied to wound examination; our experimental study has shown that even mRNA of cytokines mentioned above can be histologically detected by reverse transcriptase-polymerase chain reaction or in situ hybridization. A trial of forensic wound examination from macroscopic to molecular level is discussed.

Expression of adhesion molecules in skin wounds: diagnostic value in legal medicine

The adhesion molecules identified in recent years can help improve the diagnosis of the wound age, especially of injuries with a short survival time. This is also indicative of the vitality of the wounds. The material investigated in the study originated from 465 skin wounds. The samples were taken from human autopsy material, during the surgical treatment of wounds (excision) of patients and from experimental incised wounds of mice. To judge the age of skin wounds the endothelial adhesion molecules were detected in paraffin sections after autoclaving and using the ABC technique. Human skin wounds: strong positive staining was observed of ICAM-1 1.5 h at the earliest and 3.5 days at the latest, for the P-selectin 3 min at the earliest and 7 h at the latest, for the E-selectin 1 h at the earliest and 17 days at the latest and for VCAM-1 3 h at the earliest and 3.5 days at the latest after the time of injury. The L-selectin was expressed constitutively. Mice skin wounds: strong positive immunohistochemical reactions were found as a rule earlier than in human skin wounds. The detection of an increased expression of ICAM-1, VCAM-1 and P- and E-selectins can improve the wound age assessment in injuries with short survival times.

Quantitative analysis of proinflammatory cytokines (IL-1beta, IL-6, TNF-alpha) in human skin wounds

Proinflammatory cytokines play an important role in the mediation of inflammation and trauma. They could be useful for the determination of vitality and wound age. In the present study, 144 human skin wounds due to sharp force were investigated. The material was collected during operations (N=96) and postmortem examinations (N=48). The wound age varied from several seconds or minutes to 9 days. Control skin was available in each individual. The tissue specimens were homogenized and extracted in a solution of PBS and protease inhibitors. Interleukin-1beta (IL-1beta), interleukin-6 (IL-6) and tumour necrosis factor alpha (TNF-alpha) were measured by quantitative ELISA analysis. Statistical evaluation was performed by the t-test using the quotients of levels (wound sample/control skin). In surgical specimens the cytokine levels revealed a clear tendency to increase with wound age. IL-1beta in early skin wounds (</=30 min) and TNF-alpha after a wound age of 1-2 h demonstrated statistically significant changes in comparison with control skin (P<0.05). In autopsy samples with severe traumatization excessive elevation of cytokine levels was observed: IL-1beta, IL-6 and TNF-alpha showed significant increases (P<0.001-0.05) in stab and incised wounds with very short survival times of less than 5 min, but not in possibly supravital injuries. Elevated IL-6 levels persisted in older wounds (>24 h, P<0.05). The quantitative analysis of proinflammatory cytokines in wound extracts can contribute to the determination of vitality and wound age, in particular in the very early post-traumatic interval (classic stab wounds).

Immunohistochemical study on the expression of c-Fos and c-Jun in human skin wounds

An immunohistochemical study on the temporal expression of c-Fos and c-Jun, both of which designate proto-oncogene products, was performed on 60 human skin wounds with different post-infliction intervals. In unwounded skin, c-Fos or c-Jun was immunolocalized at the nuclei of the epidermal cells in the basal layer, hair follicle cells and sweat gland cells. During the early inflammatory phase of wound healing, the nuclei of polymorphonuclear cells (probably neutrophils), mainly infiltrating at the wound site, were labeled with anti-c-Fos or -c-Jun antibody. As the wound age increased, the neutrophils had disappeared at the wound site, and both mononuclear cells (probably macrophages) and spindle-shaped fibroblastic cells, which expressed a c-Fos or c-Jun positive reaction in the nuclei, were mainly observed. Morphometrically, the distribution of the c-Fos-positive ratio was very similar to that of the c-Jun-positive ratio; the positive ratio was considerably increased in wound specimens with a post-infliction interval of > or = 1 day, thus indicating the late inflammatory or proliferative phase. This study showed that c-Fos and c-Jun were closely involved in the inflammatory phase as well as the proliferative phase of the wound healing process.

The effect of muscle flap transposition to the fracture site on TNFalpha levels during fracture healing

The trauma and sepsis that follow open fractures and wounds may lead to the production of various cytokines. Understanding wound healing requires a direct knowledge of the specific cytokines and the respective wound fluid levels that are present at the wound site. An animal model was designed that mimics the open fracture and the clinical repair of the human, high-energy open fracture. Canine right tibiae were fractured with a penetrating, captive-bolt device, then repaired in a standard clinical fashion using an interlocking intramedullary nail. Before primary wound closure, microdialysis probes were placed at the fracture site and in a muscle located at a contralateral site. Canines received one of the following experimental protocols: (1) tibial fracture (n = 5); (2) tibial fracture plus Staphylococcus aureus inoculation at the fracture site (n = 5); and (3) tibial fracture, S. aureus inoculation, and a rotational gastrocnemius muscle flap (n = 5). Microdialysis fluid samples were collected intermittently for 7 days. Tumor necrosis factor alpha (TNFalpha) levels at the fracture site were significantly elevated 3 to 34-fold (p<0.02), as compared with respective serum levels at all time points for all treatment groups. Fracture site TNFalpha levels were elevated (p<0.02) in days 1 through 6, as compared with the baseline and contralateral in all treatment groups. At days 1 through 6, the TNFalpha levels of the muscle flap group fracture site were significantly decreased by approximately 50 percent (p<0.05), as compared with the fractures without muscle flaps and regardless of additional S. aureus inoculation. On day 7, fracture site TNFalpha levels in all animal groups were similar, yet remained well above those of baseline TNFalpha. These results demonstrate that S. aureus does not further elevate TNFalpha levels in the presence of an open fracture and that a muscle flap reduces pro-inflammatory TNFalpha levels during early wound healing. This experimental model allows for the characterization of specific biological signals and cellular pathways that are influenced by bacterial infection and surgical closure. These data provide a scientific framework on which to judge or validate therapeutic regimens for open-fracture wound healing.

Immunohistochemical study on Fas and Fas ligand in skin wound healing

An immunohistochemical study on the expression of Fas and Fas ligand (Fas L) was performed in order to examine the role of apoptosis through Fas-Fas L in mouse skin wound healing. After a 1-cm-long incision in the central dorsum skin, mice were sacrificed at intervals ranging from 0.5 to 240 h, followed by the sampling of wound margin. The expression of Fas and Fas L in the wound margins and in uninjured skin controls was studied using frozen sections. In uninjured skin controls, a very weak expression of Fas and Fas L was detected immunohistochemically in hair follicles, sebaceous glands and epidermal cells. In wounded specimens, polymorphonuclear cells and inflammatory mononuclear ones (round-shaped and spindle-shaped types) were evident. A single immunostaining showed that Fas or Fas L was detectable in inflammatory mononuclear cells involved in the skin wound healing process. Double immunostaining for Fas and Fas L revealed that inflammatory mononuclear cells co-expressed both antigens. In situ TUNEL combined with immunostaining showed that the inflammatory mononuclear cells expressing Fas or Fas L and the polymorphonuclear cells were TUNEL-stained, although neither Fas nor Fas L was detected in the polymorphonuclear cells. The number of TUNEL-positive, inflammatory mononuclear cells expressing Fas or Fas L per 0.01 x 0.01 cm2 was counted. The average number of 10 randomly selected microscope fields reached a peak at the fibro-proliferative phase of wound healing. These results indicate that apoptosis through Fas and Fas L may play an important role for reducing the cellularity during skin wound healing in mice.

Regulatory role of endogenous interleukin-10 in cutaneous inflammatory response of murine wound healing

This study investigated the role of endogenous interleukin (IL)-10 in cutaneous wound healing. Both IL-10 mRNA and protein were detectable in murine incised wounds for 10 days after injury. The IL-10 protein level peaked 3 h after incision, returned to the normal level by 24 h, but increased again to another peak at 72 h. In situ hybridization studies and immunostaining revealed that epidermal cells and infiltrating mononuclear cells were the major source of IL-10. Neutralizing antibody studies demonstrated that IL-10 inhibited the infiltration of neutrophils and macrophages toward the site of injury. IL-10 also inhibited overexpression of C-C chemokines (monocyte chemoattractant protein-1, macrophage inflammatory protein-1alpha) and proinflammatory cytokines (IL-1beta, IL-6, tumor necrosis factor-alpha) in vivo. These results suggest that IL-10 may play an important regulatory role in the phase-specific infiltration of neutrophils and macrophages as well as the cytokine production in the inflammatory response of cutaneous wound healing.

Changes of the interleukin-6 levels in skin at different sites after thermal injury

OBJECTIVE

To delineate the regulation of IL-6 production in unburned skin adjacent to a burn in an animal model.

METHODS

In C57BL/6 mice, at 15, 30, and 60 minutes after a 20% full-thickness burn, skin was removed from various sites. Control samples were obtained from unburned mice. Normal skins were incubated with tumor necrosis factor-alpha (TNF-alpha), interleukin-1 alpha (IL-1alpha), IL-1 beta, and IL-6. Unburned skin specimens were incubated with anti-TNF-alpha and IL-1alpha antibodies. Cytokine levels were measured by enzyme-linked immunosorbent assay.

RESULTS

The burn increased the IL-6 levels at 30 minutes (p < 0.05) and the IL-1alpha levels at 15 and 60 minutes in the unburned skin. TNF-alpha, IL-1alpha, and IL-1beta increased IL-6 production in normal skin (p < 0.05). Anti-IL-1alpha antibody decreased IL-6 production in the unburned skin (p < 0.05).

CONCLUSIONS

IL-1alpha modulates IL-6 production in unburned skin after injury. IL-6 and IL-1alpha might contribute to the alterations after a burn.