Localization of tenascin in human skin wounds--an immunohistochemical study

Dating Skin Lesions of Forensic Interest by Immunohistochemistry and Immunofluorescence Techniques: A Scoping Literature Review

Wound age estimation is a significant issue in forensic pathology. Although various methods have been evaluated, no gold standard system or model has been proposed, and accurate injury time estimation is still challenging. The distinction between vital skin wounds-i.e., ante-mortem lesions-and skin alterations that occur after death is a crucial goal in forensic pathology. Once the vitality of the wound has been confirmed, the assessment of the post-trauma interval (PTI) is also fundamental in establishing the causal relationship between the traumatic event and death. The most frequently used techniques in research studies are biochemistry, molecular biology, and immunohistochemistry (IHC). Biochemical methods take advantage of the chemical and physical techniques. A systematic literature search of studies started on 18 February 2023. The search was conducted in the main databases for biomedical literature, i.e., PubMed and Scopus, for papers published between 1973 and 2022, focusing on different techniques of immunohistochemistry and immunofluorescence (IF) for estimating the PTI of skin wounds. The present study involves a comprehensive and structured analysis of the existing literature to provide a detailed and comprehensive overview of the different IHC techniques used to date skin lesions, synthesize the available evidence, critically evaluate the methodologies, and eventually draw meaningful conclusions about the reliability and effectiveness of the different markers that have been discovered and used in wound age estimation.

The basement membrane in epidermal polarity, stemness, and regeneration

The epidermis is a specialized epithelium that constitutes the outermost layer of the skin, and it provides a protective barrier against environmental assaults. Primarily consisting of multilayered keratinocytes, the epidermis is continuously renewed by proliferation of stem cells and the differentiation of their progeny, which undergo terminal differentiation as they leave the basal layer and move upward toward the surface, where they die and slough off. Basal keratinocytes rest on a basement membrane at the dermal-epidermal junction that is composed of specific extracellular matrix proteins organized into interactive and mechanically supportive networks. Firm attachment of basal keratinocytes, and their dynamic regulation via focal adhesions and hemidesmosomes, is essential for maintaining major skin processes, such as self-renewal, barrier function, and resistance to physical and chemical stresses. The adhesive integrin receptors expressed by epidermal cells serve structural, signaling, and mechanosensory roles that are critical for epidermal cell anchorage and tissue homeostasis. More specifically, the basement membrane components play key roles in preserving the stem cell pool, and establishing cell polarity cues enabling asymmetric cell divisions, which result in the transition from a proliferative basal cell layer to suprabasal cells committed to terminal differentiation. Finally, through a well-regulated sequence of synthesis and remodeling, the components of the dermal-epidermal junction play an essential role in regeneration of the epidermis during skin healing. Here too, they provide biological and mechanical signals that are essential to the restoration of barrier function.

Forensic Impact of the Omics Science Involved in the Wound: A Systematic Review

Background: In forensic autopsies, examining the wounds is one of the most critical aspects to clarify the causal relationship between the cause of death and the wounds observed on the corpse. However, on many occasions, it is difficult to differentiate antemortem injuries from post-mortem injuries, mainly when they occur very close to the moment of death. At present, various studies try to find biomarkers and clarify the molecular mechanisms involved in a wound due to the high variability of conditions in which they occur, thus being one of the most challenging problems in forensic pathology. This review aimed to study the omics data to determine the main lines of investigation emerging in the diagnosis of vital injuries, time of appearance, estimation of the age and vitality of the wound, and its possible contributions to the forensic field.

Methods: A systematic review of the human wound concerning forensic science was carried out by following PRISMA guidelines.

Results: This study sheds light on the role of omics research during the process of wounding, identifying different cytokines and other inflammatory mediators, as well as cells involved in the specific stage of the wound healing process, show great use in estimating the age of a wound. On the other hand, the expression levels of skin enzymes, proteins, metal ions, and other biomarkers play an essential role in differentiating vital and post-mortem wounds. More recent studies have begun to analyze and quantify mRNA from different genes that encode proteins that participate in the inflammation phase of a wound and miRNAs related to various cellular processes.

Conclusions: This study sheds light on the role of research in the molecular characterization of vital wounds, heralding a promising future for molecular characterization of wounds in the field of forensic pathology, opening up an important new area of research.

Systematic Review Registration: URL: https://www.crd.york.ac.uk/prospero/#myprospero, Identifier: CRD42021286623.

Gene signatures associated with barrier dysfunction and infection in oral lichen planus identified by analysis of transcriptomic data

Oral lichen planus (OLP) is one of the most prevalent oral mucosal diseases, but there is no cure for OLP yet. The aim of this study was to gain insights into the role of barrier dysfunction and infection in OLP pathogenesis through analysis of transcriptome datasets available in public databases. Two transcriptome datasets were downloaded from the Gene Expression Omnibus database and analyzed as whole and as partial sets after removing outliers. Differentially expressed genes (DEGs) upregulated in the dataset of OLP versus healthy epithelium were significantly enriched in epidermal development, keratinocyte differentiation, keratinization, responses to bacterial infection, and innate immune response. In contrast, the upregulated DEGs in the dataset of the mucosa predominantly reflected chemotaxis of immune cells and inflammatory/immune responses. Forty-three DEGs overlapping in the two datasets were identified after removing outliers from each dataset. The overlapping DEGs included genes associated with hyperkeratosis (upregulated LCE3E and TMEM45A), wound healing (upregulated KRT17, IL36G, TNC, and TGFBI), barrier defects (downregulated FRAS1 and BCL11A), and response to infection (upregulated IL36G, ADAP2, DFNA5, RFTN1, LITAF, and TMEM173). Immunohistochemical examination of IL-36γ, a protein encoded by one of the DEGs IL36G, in control (n = 7) and OLP (n = 25) tissues confirmed the increased expression of IL-36γ in OLP. Collectively, we identified gene signatures associated with hyperkeratosis, wound healing, barrier defects, and response to infection in OLP. IL-36γ, a cytokine involved in both wound repair and antimicrobial defense, may be a possible therapeutic target in OLP.

Extracellular matrix contribution to skin wound re-epithelialization

The ability of skin to act as a barrier is primarily determined by cells that maintain the continuity and integrity of skin and restore it after injury. Cutaneous wound healing in adult mammals is a complex multi-step process that involves overlapping stages of blood clot formation, inflammation, re-epithelialization, granulation tissue formation, neovascularization, and remodeling. Under favorable conditions, epidermal regeneration begins within hours after injury and takes several days until the epithelial surface is intact due to reorganization of the basement membrane. Regeneration relies on numerous signaling cues and on multiple cellular processes that take place both within the epidermis and in other participating tissues. A variety of modulators are involved, including growth factors, cytokines, matrix metalloproteinases, cellular receptors, and extracellular matrix components. Here we focus on the involvement of the extracellular matrix proteins that impact epidermal regeneration during wound healing.

Tenascins in fibrotic disorders-from bench to bedside

Although fibrosis is becoming increasingly recognized as a major cause of morbidity and mortality in chronic inflammatory diseases, available treatment strategies are limited. Tenascins constitute a family of matricellular proteins, primarily modulating interactions of cells with other matrix components and growth factors. Data obtained from tenascin C deficient mice show important roles of this molecule in several models of fibrosis. Moreover there is growing evidence that tenascin C has a strong impact on chronic inflammation, myofibroblast differentiation and recruitment. Tenascin C as well as tenascin X has furthermore been shown to affect TGF-β activation and signaling. Taken together these data suggest that these proteins might be important factors in fibrosis development and make them attractive both as biological markers and as targets for therapeutical intervention. So far most clinical research in fibrosis has been focused on tenascin C. This review aims at summarizing our up-to-date knowledge on the involvement of tenascin C in the pathogenesis of fibrotic disorders.

Infrared LED light therapy influences the expression of fibronectin and tenascin in skin wounds of malnourished rats--a preliminary study

The aim of this investigation was to evaluate the effect of infrared (λ 846±20nm) LED irradiation on the expression profile of the extracellular matrix protein components, tenascin and fibronectin on skin wounds induced in well nourished and malnourished rats. Eighteen albino rats (21 days old) were randomly divided into a well-nourished group (standard diet) and a malnourished group (regional basic diet). After receiving the diet for 70 days, skin wounds were created and the animals were subdivided into three groups: well-nourished control (n=6), malnourished control (n=6), and malnourished+LED irradiated (λ 846±20nm, 100mW, 4J/cm(2)) (n=6). The animals were sacrificed 3 and 7 days after injury and histological sections were immunostained for both proteins. They were examined for the presence, intensity, distribution and pattern of immunolabeling. At 3 days, the distribution of tenascin was shown to be greater in the wound bed of malnourished animals compared to the well-nourished group. The intensity and distribution of tenascin was shown to be lower in the malnourished LED irradiated group compared to the malnourished control. There was a significant difference regarding the presence of fibronectin in the malnourished and well-nourished groups after 7 days (p=0.03). The intensity of fibronectin was slight (100%) in the irradiated group and moderate to intense in the malnourished control group. The results of the present study indicate that infrared LED irradiation modulates positively the expression of tenascin and particularly fibronectin.

Tenascin-C is increased in atherothrombotic stroke patients and has an anti-inflammatory effect in the human carotid artery

Tenascin-C (Tn-C) is an endogenous ligand of toll-like receptor-4 (TLR-4); a key signalling molecule associated with chronic inflammatory conditions. Both Tn-C and TLR-4 are increased in unstable human atheroma, but their effects on local inflammatory conditions have not been investigated. The aim of the present study was to investigate the association and functional implications of Tn-C/TLR-4 signalling in large artery atherosclerotic stroke. Plasma Tn-C was measured by ELISA and found to be higher in recent stroke patients (n = 336; median 12.77 µg/mL, inter-quartile range 10.23-15.74 µg/mL) than in controls (n = 321; median 11.31 µg/mL, inter-quartile range 8.89-13.90 µg/mL), P < 0.001. Plasma Tn-C was also independently positively associated with stroke (odds ratio for highest Tn-C quartile 2.27, 95% confidence interval 1.37-3.76). Assessment of Tn-C associated chronic cytokine secretion was performed in vitro using paired, human, macroscopically disease matched, carotid atheroma tissue biopsies obtained from five patients undergoing carotid endarterectomy. A 4-day incubation with specific Tn-C blocking antibodies (Abs) increased secretion of TLR-4-associated cytokines, interleukin (IL)-8, IL-1β, tumour necrosis factor and C-C motif chemokine (CCL)3 and expression of TLR-4 in the tissue. These results suggest with Tn-C blockade another endogenous TLR-4 ligand upregulates TLR-4 expression and subsequent cytokine secretion. Titration of the Tn-C Abs also dose dependently increased secretion of IL-6, IL-8, IL-1β, and CCL3 in mixed, healthy, primary vascular cell culture. In summary, circulating concentrations of Tn-C are higher in patients with a recent history of atherosclerotic stroke and may play an anti-inflammatory role by reducing pro-inflammatory cytokine release from atheroma.

The newcomer in the integrin family: integrin α9 in biology and cancer

Integrins are heterodimeric transmembrane receptors regulating cell-cell and cell-extracellular matrix interactions. Of the 24 integrin heterodimers identified in humans, α9β1 integrin is one of the least studied. α9, together with α4, comprise a more recent evolutionary sub-family of integrins that is only found in vertebrates. Since α9 was thought to have similar functions as α4, due to many shared ligands, it was a rather overlooked integrin until recently, when its importance for survival after birth was highlighted upon investigation of the α9 knockout mouse. α9β1 is expressed on a wide variety of cell types, interacts with many ligands for example fibronectin, tenascin-C and ADAM12, and has been shown to have important functions in processes such as cell adhesion and migration, lung development, lymphatic and venous valve development, and in wound healing. This has sparked an interest to investigate α9β1-mediated signaling and its regulation. This review gives an overview of the recent progress in α9β1-mediated biological and pathological processes, and discusses its potential as a target for cancer diagnosis and therapy.

The role of tenascin-C in tissue injury and tumorigenesis

The extracellular matrix molecule tenascin-C is highly expressed during embryonic development, tissue repair and in pathological situations such as chronic inflammation and cancer. Tenascin-C interacts with several other extracellular matrix molecules and cell-surface receptors, thus affecting tissue architecture, tissue resilience and cell responses. Tenascin-C modulates cell migration, proliferation and cellular signaling through induction of pro-inflammatory cytokines and oncogenic signaling molecules amongst other mechanisms. Given the causal role of inflammation in cancer progression, common mechanisms might be controlled by tenascin-C during both events. Drugs targeting the expression or function of tenascin-C or the tenascin-C protein itself are currently being developed and some drugs have already reached advanced clinical trials. This generates hope that increased knowledge about tenascin-C will further improve management of diseases with high tenascin-C expression such as chronic inflammation, heart failure, artheriosclerosis and cancer.

The role of tenascin-C in tissue injury and tumorigenesis

The extracellular matrix molecule tenascin-C is highly expressed during embryonic development, tissue repair and in pathological situations such as chronic inflammation and cancer. Tenascin-C interacts with several other extracellular matrix molecules and cell-surface receptors, thus affecting tissue architecture, tissue resilience and cell responses. Tenascin-C modulates cell migration, proliferation and cellular signaling through induction of pro-inflammatory cytokines and oncogenic signaling molecules amongst other mechanisms. Given the causal role of inflammation in cancer progression, common mechanisms might be controlled by tenascin-C during both events. Drugs targeting the expression or function of tenascin-C or the tenascin-C protein itself are currently being developed and some drugs have already reached advanced clinical trials. This generates hope that increased knowledge about tenascin-C will further improve management of diseases with high tenascin-C expression such as chronic inflammation, heart failure, artheriosclerosis and cancer.

Regulation of fibroblast migration by tenascin-C

Synthesis of new tissue by fibroblasts is required for tissue rebuilding in response to injury. Fibroblast migration from surrounding healthy tissue into the fibrin-fibronectin provisional matrix deposited upon injury is a key rate-limiting step of this stage of tissue repair. These events must be tightly regulated. Excessive deposition of scar tissue is the major hallmark of fibrotic disease. Tenascin-C is an extracellular matrix glycoprotein that is transiently expressed upon tissue injury, where it is specifically localized to the wound edge, and persistently up-regulated in fibrotic disease. We have shown that full-length tenascin-C promotes fibroblast migration within fibrin-fibronectin matrices and we have mapped the domains within the molecule critical for enhancing migration. We also demonstrated that specific fragments of tenascin-C inhibit fibroblast migration. These results suggest that transient expression of tenascin-C at the wound boundary is key to tissue repair: its induction recruits fibroblasts into the wound and fragments resulting from its breakdown prevent excessive fibroblast infiltration. Our results demonstrate how fibroblast migration in three-dimensional provisional matrices may be differentially regulated by proteolysis of matrix molecules and could explain how persistent expression of tenascin-C contributes to the progression of fibrotic disease.

Modulation of cell-fibronectin matrix interactions during tissue repair

Environmental signals from the extracellular matrix (ECM) are transmitted by cell surface receptors that connect to the actin cytoskeleton and to multiple intracellular signaling pathways. To dissect how the ECM regulates cell functions, we are using a three-dimensional (3D) fibrin-fibronectin matrix, resembling the wound provisional matrix. Fibroblasts adhere to fibronectin in this matrix via concomitant engagement of alpha 5 beta 1 integrin receptors and syndecan-4, a transmembrane proteoglycan. An adhesive phenotype is developed with actin stress fibers and activation of focal adhesion kinase (FAK) and Rho GTPase. Lack of syndecan-4 engagement, as occurs in the presence of the ECM protein tenascin-C, promotes a motile phenotype; FAK and Rho signaling are downregulated and filopodia are extended. Fibronectin matrices have distinct effects on two other receptors: alpha 4 beta 1 and beta v beta 3 integrins. Although alpha 4 beta 1 does not naturally support strong cell interactions with a fibrin-fibronectin matrix, binding is dramatically enhanced by proteolytic cleavage of fibronectin. Conversely, activity of alpha v beta 3 is stimulated by multimeric fibronectin fibrils showing that the organization of fibronectin differentially affects integrin functions. Thus, deposition of additional ECM components, expression of co-receptors for ECM, cleavage of adhesive proteins, and the architecture of the ECM microenvironment are different mechanisms for modulating cell responses to fibronectin matrix.

A histological and immunohistochemical study of tissue reactions to solid poly(ortho ester) in rabbits

In many cases only the temporary presence of a biomaterial is needed in tissue support, augmentation or replacement. In such cases biodegradable materials are better alternatives than biostable ones. At present, biodegradable polymers are widely used in the field of maxillofacial surgery as sutures, fracture fixation devices and as absorbable membranes. The most often used polymers are aliphatic polyesters, such as polyglycolic acid (PGA) and polylactic acid (PLA). Poly(ortho ester) is a surface eroding polymer, which has been under development since 1970, but is used mostly in drug delivery systems in semisolid form. The aim of this study was to evaluate the tissue reactions of solid poly(ortho ester) (POE), histologically and immunohistochemically. Resorption times and the effect of 2 different sterilization methods (gamma radiation and ethylene oxide) upon resorption were also evaluated. Material was implanted into the tibia and subcutaneously into the mandibular ramus area of 24 rabbits. Follow-up times were 1-10, 14 and 24 weeks. Histological studies showed that POE induces a moderate inflammation in soft tissue and in bone. At 24 week follow-up, inflammation was mild in soft tissue and moderate in bone. In immunohistochemical studies, no highly fluorescent layer of tenascin or fibronectin was found adjacent to the implant. Resorption of gamma-sterilized rods was faster than ethylene oxide-sterilized rods. The total resorption time was more than 24 weeks in both groups. Clinically the healing was uneventful and the implants the well tolerated by the living tissue. This encourages these authors to continue studies with this interesting new material to search for the ideal material for bone filling and fracture fixation.

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.

Increased postoperative concentrations of tenascin-C in wound fluid

BACKGROUND

Tenascin-C (Tn-C) is the most studied member of a family comprising large oligomeric glycoproteins in the extracellular matrix. The function of Tn-C still is unclear, and the levels of Tn-C in human wound fluid have not been studied.

METHODS

The participants in this study were 24 patients referred for elective major gastrointestinal surgery. Concentrations of Tn-C and procollagen propeptides type 1 and type 3 in serum and wound fluid were measured after surgery.

RESULTS

In wound fluid, Tn-C was present on postoperative day 1, and the concentration increased from day 5 up to day 7.

CONCLUSIONS

The concentration of Tn-C increases postoperatively in wound fluid. The concentration of Tn-C in wound fluid is markedly higher than that of serum. The differences in expression between Tn-C and the procollagen propeptides may reflect different tasks of these extracellular matrix proteins.

Changes in gene expression in response to mechanical strain in human scleral fibroblasts

Scleral fibroblasts are involved in scleral remodeling during axial elongation in myopia. Mechanical load is a potent stimulator of gene expression. This study seeks to identify changes in gene expression of scleral fibroblasts in response to mechanical load and speculate on possible mechanisms of scleral remodeling in the development of myopia. Human scleral fibroblasts (HSFs) were mechanically stretched for 30 min and 24 hr. A gene microarray analysis was used to measure changes in gene expression. A total of 237 genes revealed differential and significant changes in expression (P<0.01) after 30 min of stretching. Of these, 28 unexpressed genes began to be expressed (turned on), while 31 expressed genes were no longer expressed (turned off). After 24 hr, 308 genes showed reproducible changes in expression (P<0.01), while 29 genes were turned on and 17 genes were turned off. After 30 min, 25 genes showed at least a threefold change in expression. These included genes for cell receptors, protein kinases, cell growth/differentiation factors, extracellular matrix (ECM) proteins, lipid metabolism, protein metabolism, transcription factors, binding proteins and water channels. After 24 hr, 21 genes showed at least a threefold change in expression. These included genes for cell receptors, protein kinases, cell growth/differentiation factors, lipid metabolism, ECM proteins, transcription factors, and carbohydrate metabolism. RT-PCR and Southern blotting confirmed the changes in expression of selected genes. In this study we identified a large number of early and late mechanical response genes in HSFs. These changes in gene expression will provide potential candidate genes that might be involved in scleral remodeling during axial elongation in myopia.

Tenascin-C modulates matrix contraction via focal adhesion kinase- and Rho-mediated signaling pathways

A provisional matrix consisting of fibrin and fibronectin (FN) is deposited at sites of tissue damage and repair. This matrix serves as a scaffold for fibroblast migration into the wound where these cells deposit new matrix to replace lost or damaged tissue and eventually contract the matrix to bring the margins of the wound together. Tenascin-C is expressed transiently during wound repair in tissue adjacent to areas of injury and contacts the provisional matrix in vivo. Using a synthetic model of the provisional matrix, we have found that tenascin-C regulates cell responses to a fibrin-FN matrix through modulation of focal adhesion kinase (FAK) and RhoA activation. Cells on fibrin-FN+tenascin-C redistribute their actin to the cell cortex, downregulate focal adhesion formation, and do not assemble a FN matrix. Cells surrounded by a fibrin-FN+tenascin-C matrix are unable to induce matrix contraction. The inhibitory effect of tenascin-C is circumvented by downstream activation of RhoA. FAK is also required for matrix contraction and the absence of FAK cannot be overcome by activation of RhoA. These observations show dual requirements for both FAK and RhoA activities during contraction of a fibrin-FN matrix. The effects of tenascin-C combined with its location around the wound bed suggest that this protein regulates fundamental processes of tissue repair by limiting the extent of matrix deposition and contraction to fibrin-FN-rich matrix in the primary wound area.

Immunohistochemical detection of fibronectin and tenascin in incised human skin injuries

Immunohistochemical detection of molecules involved in inflammatory reaction can be useful for the diagnosis of vitality in skin wounds. We studied the expression of fibronectin (FN) and tenascin (TN) in 58 human skin wounds (48 vital and 10 postmortem). The age of vital injuries ranged from 3 min to 8 h and postmortem specimens were collected after a postinfliction interval of 15-180 min. One hundred thirty-seven formalin-fixed paraffin-embedded sections (mean: 2.3 sections per case) were stained with each of two monoclonal antibodies against FN and TN using the streptABC technique. A reticular staining for FN in wound edge and dermis was observed in 50% of vital specimens versus 0% in postmortem cases. Immunoreactivity was reduced in 10 autolysed cases. FN positivity exclusively at the injury margin was observed in 39.4% of vital wounds and 10% of postmortem cases. TN was negative in all specimens. Vital and postmortem hemorrhage areas showed positivity for FN and TN. Due to its low sensitivity, immunohistochemical analysis of FN is useful for determining vitality only in a minority of cases. Different factors in everyday practice, including autolysis and technical problems often produce false negative reactions with the result that FN cannot be regarded as a reliable parameter of vitality. Positive reactions (network staining) are more valuable than negativity but are not pathognomonic. Both vital and postmortem hemorrhages show an enhanced positivity for FN and TN, thus impeding the diagnosis.

Effects of BisGMA and TEGDMA on proliferation, migration, and tenascin expression of human fibroblasts and keratinocytes

Previous studies have documented a marked cytotoxic potency of BisGMA and TEGDMA. The purpose of this investigation was to determine if these substances also affect proliferation, migration, and tenascin expression of primary human gingival fibroblasts (HGF) and immortalized human keratinocytes (HaCaT). These parameters play an important role in healing wounds. HGF and HaCaT cultures were incubated with TEGDMA and BisGMA. Cell proliferation (BrdU-assay) and migration (Boyden method) were determined 24 h after incubation. Tenascin expression was investigated four and seven days after treatment. Results were statistically evaluated by ANOVA using the Wilcoxon-Mann-Whitney test (p < 0.05). Proliferation of both cell types was significantly inhibited at concentrations > or = 0.25 mM (TEGDMA) or > or = 0.01 mM (BisGMA). Migration of HaCaT was significantly increased after incubation with BisGMA for 24 h. TEGDMA did not alter migration of HGF and HaCaT. In addition, TEGDMA had no effect on tenascin expression of both cell cultures. After 4 days of incubation, BisGMA (at a concentration of 0.01 mM) significantly reduced tenascin production of HaCaT cultures related to cell number. However, 7 days after treatment, BisGMA significantly increased tenascin expression of HGF and HaCaT cultures. Altogether, our results indicate that BisGMA can affect migration of keratinocytes and alters the expression of the extracellular matrix component tenascin. Thus, BisGMA may significantly influence the healing of injured oral tissues.

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.

Integrin expression during epithelial migration and restratification in the tenascin-C-deficient mouse cornea

In the unwounded cornea, tenascin-C localizes to a short stretch of the basement membrane zone at the corneoscleral junction or limbus. To determine whether the function of the limbus is affected by the absence of tenascin-C, mice possessing a deletion of tenascin-C and strain-matched wild-type mice are used in corneal debridement wounding experiments. The expression of integrins (alpha3, alpha9, and beta4) in the tenascin-C knockout corneas is evaluated by producing polyclonal cytoplasmic domain antipeptide sera and performing immunofluorescence microscopy. In addition, we evaluate the localization of several other proteins involved in wound healing, including fibronectin, laminin beta1, nidogen/entactin, and VCAM-1, in both the tenascin knockout and wild-type mice. There are no differences in healing rate, scarring, or neovascularization after corneal debridement wounds. alpha9 integrin is expressed at the limbal border of unwounded tenascin-C knockout animals and is upregulated during migration only after the larger wounds. At 8 weeks after larger wounds, the localization of alpha9 again becomes restricted to the limbal border. Results show that tenascin-C is not required for development or maintenance of the corneal limbus or for normal re-epithelialization of corneal epithelial cells after debridement wounding.

Differences in cellular infiltrate and extracellular matrix of chronic diabetic and venous ulcers versus acute wounds

In diabetic patients, wound healing is impaired. We studied the pathogenesis behind this clinical observation by characterizing the pattern of deposition of extracellular matrix (ECM) molecules and the cellular infiltrate in chronic (>8 wk) diabetic wounds, compared with chronic venous ulcers and an acute wound healing model. Punch biopsies were obtained from the chronic ulcer margins and control samples were collected from upper leg skin 5, 19, 28 d and 12 and 18 mo postwounding (p.w.). T cells, B cells, plasma cells, granulocytes and macrophages, and the ECM molecules fibronectin (FN), chondroitin sulfate (CS), and tenascin (TN) were visualized using immunohistochemical techniques. Expression of FN, CS, and TN was detected in dermal tissue early in normal wound healing (5-19 d p.w.). Abundant staining was seen 3 mo p.w., returning to prewounding levels after 12-18 mo p.w. In the dermis of chronic diabetic and venous ulcers with a duration of 12 mo or more, a prolonged presence of these ECM molecules was noted. Compared with normal wound healing: (i) the CD4/CD8 ratio in chronic wounds was significantly lower (p < 0.0027) due to a relatively lower number of CD4+ T cells; (ii) a significantly higher number of macrophages was present in the edge of both type of chronic ulcers (p < 0.001 versus day 29 p.w.); and (iii) more B cells and plasma cells were detected in both type of chronic wounds compared with any day in the acute wound healing model (p < 0.04 for CD20+ and p < 0.01 for CD79a+ cells). These data indicate that important differences exist in the cellular infiltrate and ECM expression patterns of acute, healing versus chronic wounds, which may be related to the nonhealing status of chronic wounds.

Tenascin-C expression in normal, inflamed, and scarred human corneas

AIMS/BACKGROUND

In adult tissues the expression of tenascin-cytotactin (TN-C), an extracellular matrix glycoprotein, is limited to tumours and regions of continuous renewal. It is also transiently expressed in cutaneous and corneal wound healing. There are limited data regarding its expression in inflammation and scarring of the adult human cornea. In this study, TN-C expression patterns in normal, inflamed, and scarred human corneas have been examined.

METHODS

Penetrating keratoplasty specimens were selected from cases of herpes simplex keratitis, herpes zoster ophthalmicus, rheumatoid arthritis ulceration, bacterial keratitis, rosacea keratitis, interstitial keratitis, and previous surgery so as to encompass varying degrees of active and chronic inflammation and scarring. TN-C in these and in normal corneas was immunodetected using TN2, a monoclonal antibody to human TN-C.

RESULTS

There was no TN2 immunopositivity in normal corneas except at the corneoscleral interface. In pathological corneas, TN2 immunopositivity was localised in and around regions of active inflammation, fibrosis, and neovascularisation. TN2 positivity was less in acute inflammation than in active chronic inflammation. Mature, avascular scar tissue and epithelial downgrowth were TN2 negative.

CONCLUSION

These results indicate that in the adult human cornea, TN-C expression is induced in regions of inflammation, fibrosis, and neovascularisation, but that expression is absent in mature, avascular scar tissue. This suggests a role for this glycoprotein in inflammation, healing, and extracellular matrix reorganisation of the cornea.

Human epidermal keratinocytes are a source of tenascin-C during wound healing

Tenascin-C is a large hexameric extracellular matrix glycoprotein that is expressed in a temporally and spatially restricted pattern associated with stromal-epithelial interactions. In adult human skin, the expression level of tenascin-C is low, but tenascin-C is abundantly present in the dermal compartment during embryogenesis and wound healing and in skin tumors. Herein we have investigated the cellular source of tenascin-C production in human skin, both in vivo and in vitro, by using immunohistochemistry, mRNA in situ hybridization, western blotting, and an enzyme-linked immunosorbent assay. In addition we studied the cell-matrix interaction between epidermal keratinocytes and purified tenascin-C. By using in vitro culture models, we found that keratinocytes not only synthesize and secrete tenascin-C but can also deposit tenascin-C in de-epidermized dermis in a pattern that is very similar to that in vivo. In vivo, during wound healing of normal human skin, we found tenascin-C extracellularly in the wound bed and also in a granular pattern within the neo-epidermis. By mRNA in situ hybridization, we could identify the basal migrated keratinocytes as the main source of tenascin-C in the early phase of wound healing. In the granulation phase, tenascin-C expression by the keratinocytes is downregulated. Cultured keratinocytes were found to adhere poorly to tenascin-C, and those that did adhere retained a rounded morphology. We conclude that human keratinocytes are a major source of tenascin-C during the early phase of wound healing, and we hypothesize that tenascin-C is unlikely to be an adhesive substrate for migrating keratinocytes.

Upregulation of alpha 9 integrin and tenascin during epithelial regeneration after debridement in the cornea

Stratified epithelia are exposed to abrasive forces and are required to respond rapidly to injury to minimize fluid loss and the risk for microbial infection. Healing involves a cell migratory phase to reestablish barrier function and cell proliferation to restratify the epithelium. Cell migration during re-epithelialization involves cell sliding, termed sheet movement, during which cells retain their cell-cell junctions while dynamically altering their shape and cell-substrate interactions to permit movement across the exposed wound bed. Proteins of the integrin family of receptor molecules modulate cell shape, cell migration, and signal transduction in many cell types. In epithelial cells, integrins of the beta 1 family have been implicated in regulating cell proliferation and differentiation, alpha 9 beta b1 is one of the newer members of the integrin beta family and has been recently shown to function as a tenascin receptor. Although little is known about its function in vivo, studies in developing mouse cornea and eyelid suggest that it may play a role in epithelial differentiation. Using a debridement wound model in the mouse cornea, we show in this study that (a) in response to small debridement wounds that close without cell proliferation, alpha 9 integrin protein and mRNA are not induced during migration but are induced during restratification, (b) larger debridement wounds that require cell proliferation to generate the cells necessary for sheet movement result in a dramatic induction of alpha 9 protein and its mRNA during both migration and restratification, and (c) tenascin, an alpha 9 beta 1 ligand, accumulates beneath epithelial cells during restratification but not during cell migration. Therefore, alpha 9 integrin protein production and tenascin accumulation are dynamically regulated in response to corneal epithelial injury.

Tenascin and fibronectin expression in healing human myocardial scars

Fibronectin and tenascin are matrix proteins known to be present in early experimental wound healing. As only limited data are available regarding early matrix changes in human myocardial infarction, the presence of tenascin and fibronectin was studied in human myocardial infarctions of different post-infarction times (6 h to 17 years), using immunohistochemistry. In normal myocardium, fibronectin immunostaining was found in the subendothelial space in vessels. Tenascin was not present in normal myocardium. While fibronectin was demonstrated in the ischaemic cardiomyocytes within 1 day, tenascin was found 4-6 days post-infarction and was located at the margin of the area of infarction. Tenascin expression then shifted from the margin to the centre of the area of infarction, where it could be found 2-3 weeks post-infarction. More than 4 weeks post-infarction, the scar tissue consisted of collagen fibres, with sparse (myo)fibroblasts. By that time, both tenascin and fibronectin expression had disappeared. Another interesting observation in this study was the presence of tenascin, but not fibronectin, surrounding vacuolated glycogen-rich cells, or so-called hibernating cardiomyocytes.

Immunolocalisation of tenascin-C in focal reactive overgrowths of oral mucosa

Focal reactive overgrowths of oral mucosa were investigated in the following groups: gingival pyogenic granuloma, fibrous epulis, calcifying fibrous epulis, peripheral giant cell granuloma, giant cell fibroma, fibroepithelial polyp and denture-related fibrous hyperplasia (n = 8 for each group). We hypothesised that immunoreactivity to tenascin-C, a functional protein associated with connective tissue organisation and cell migration, would be differentially distributed in individual lesions and between lesion groups. Staining patterns for giant cell fibromas and fibroepithelial polyps were similar to those reported for normal mucosa. By contrast, additional staining was observed in the other lesion groups, although immunoreactivity was variable and not specific to each lesion group. Strong immunoreactivity was observed around blood vessels lined with plump endothelial cells and in regions where keratinocytes were migrating over ulcerated surfaces. Interlacing collagenous fascicles could be either strongly or weakly immunoreactive, with either fibrillar or diffuse staining. Localised staining was observed around, but not within, areas of calcification.

Tenascin expression during wound healing in human skin

In adult human skin, the expression of the extracellular matrix glycoprotein tenascin is limited. Under hyperproliferative conditions such as psoriasis and epidermal tumours, dermal tenascin expression is strongly upregulated. The aim of this study was to investigate the pattern and kinetics of tenascin expression in human skin during wound healing and to address the question of whether keratinocytes can directly interact with tenascin during re-epithelialization. Tenascin expression was investigated in excisional wounds in normal human skin, in explants of normal human skin, and in chronic venous ulcers, using immunohistochemistry. No tenascin staining was found directly underneath the leading edge of the sheet of migrating keratinocytes in the excisional wounds and explants. In the excisional wounds and the ulcers, dermal tenascin was strongly upregulated in areas adjacent to hyperproliferative epidermis. These hyperproliferative areas are located approximately 10-50 cells behind the leading edge, as assessed by staining for the Ki-67 antigen and the proliferating cell nuclear antigen (PCNA). At the later stages of normal wound healing and in the chronic ulcers, tenascin was also detected in the wound bed. In these areas, the dermal-epidermal junction stained positive for laminin but was negative for heparan sulphate. The absence of the latter basement membrane component suggests that the formation of a new basement membrane is not completed in these wounds. These findings suggest that tenascin is not a substrate for migrating keratinocytes; that the rapid induction of tenascin expression in the papillary dermis during wound healing results from interaction with the hyperproliferative epidermis; and that in the later stages of wound healing, keratinocytes can potentially interact with tenascin in the wound bed, because the basement membrane of the neo-epidermis is incomplete.