Interstitial collagenase is expressed by keratinocytes that are actively involved in reepithelialization in blistering skin disease

Gene Expression Linked to Reepithelialization of Human Skin Wounds

Our understanding of the regulatory processes of reepithelialization during wound healing is incomplete. In an attempt to map the genes involved in epidermal regeneration and differentiation, we measured gene expression in formalin-fixed, paraffin-embedded standardized epidermal wounds induced by the suction-blister technique with associated nonwounded skin using NanoString technology. The transcripts of 139 selected genes involved in clotting, immune response to tissue injury, signaling pathways, cell adhesion and proliferation, extracellular matrix remodeling, zinc transport and keratinocyte differentiation were evaluated. We identified 22 upregulated differentially expressed genes (DEGs) in descending order of fold change (MMP1, MMP3, IL6, CXCL8, SERPINE1, IL1B, PTGS2, HBEGF, CXCL5, CXCL2, TIMP1, CYR61, CXCL1, MMP12, MMP9, HGF, CTGF, ITGB3, MT2A, FGF7, COL4A1 and PLAUR). The expression of the most upregulated gene, MMP1, correlated strongly with MMP3 followed by IL6 and IL1B. rhIL-1β, but not rhIL-6, exposure of cultured normal human epidermal keratinocytes and normal human dermal fibroblasts increased both MMP1 mRNA and MMP-1 protein levels, as well as TIMP1 mRNA levels. The increased TIMP1 in wounds was validated by immunohistochemistry. The six downregulated DEGs (COL7A1, MMP28, SLC39A2, FLG1, KRT10 and FLG2) were associated with epidermal maturation. KLK8 showed the strongest correlation with MKI67 mRNA levels and is a potential biomarker for keratinocyte proliferation. The observed gene expression changes correlate well with the current knowledge of physiological reepithelialization. Thus, the gene expression panel described in this paper could be used in patients with impaired healing to identify possible therapeutic targets.

A Scoping Review of the Role of Metalloproteinases in the Pathogenesis of Autoimmune Pemphigus and Pemphigoid

Pemphigus and pemphigoid diseases are potentially life-threatening autoimmune blistering disorders that are characterized by intraepithelial and subepithelial blister formation, respectively. In both disease groups, skin and/or mucosal blistering develop as a result of a disruption of intercellular adhesion (pemphigus) and cell-extracellular matrix (ECM) adhesion (pemphigoid). Given that metalloproteinases can target cell adhesion molecules, the purpose of the present study was to investigate the role of these enzymes in the pathogenesis of these bullous dermatoses. Studies examining MMPs (matrix metalloproteinases) and the ADAM (a disintegrin and metalloproteinase) family of proteases in pemphigus and pemphigoid were selected from articles published in the repository of the National Library of Medicine (MEDLINE/PubMed) and bioRxiv. Multiple phases of screening were conducted, and relevant data were extracted and tabulated, with 29 articles included in the final qualitative analysis. The majority of the literature investigated the role of specific components of the MMP family primarily in bullous pemphigoid (BP) whereas studies that focused on pemphigus were rarer. The most commonly studied metalloproteinase was MMP-9 followed by MMP-2; other MMPs included MMP-1, MMP-3, MMP-8, MMP-12 and MMP-13. Molecules related to MMPs were also included, namely, ADAM5, 8, 10, 15, 17, together with TIMP-1 and TIMP-3. The results demonstrated that ADAM10 and MMP-9 activity is necessary for blister formation in experimental models of pemphigus vulgaris (PV) and BP, respectively. The data linking MMPs to the pathogenesis of experimental BP were relatively strong but the evidence for involvement of metalloproteinases in PV was more tentative. These molecules represent potential candidates for the development of mechanism-based treatments of these blistering diseases.

Spatial expression of metallothionein, matrix metalloproteinase-1 and Ki-67 in human epidermal wounds treated with zinc and determined by quantitative immunohistochemistry: A randomised double-blind trial

Reepithelialisation is fundamental to wound healing, but our current understanding largely relies on cellular and animal studies. The aim of the present randomised double-blind three-arm controlled trial was to correlate genuine epidermal wound healing with key proteins and topical zinc treatment in humans. Sixty wounds were produced using deroofed suction blisters in 30 healthy volunteers and randomised to topical zinc sulphate (n = 20), placebo (n = 20), or control (n = 20) treatment for 4 days. All wounds with perilesional skin were processed for automatic immunostaining of paraffin tissue sections with monoclonal antibodies against Ki-67, metallothionein (MT) and matrix metalloproteinase (MMP)-1. Protein expression was quantified by automated digital image analysis. Epidermal Ki-67 and MT labelling indices were increased in keratinocytes in the neoepidermis (∼1.1 mm) and at the wound edge (0.5 mm) compared to normal skin. Increased MMP-1 immunostaining was restricted to the neoepidermis. MT was robustly upregulated in the upper dermis of the wounds. Zinc treatment enhanced MMP-1 expression beneath the neoepidermis via paracrine mechanisms and MT under the neoepidermis and in the nonepithelialised wound bed via direct actions of zinc as indicated by the induction of MT2A mRNA but not MMP-1 mRNA in cultured normal human dermal fibroblasts by zinc sulphate. The present human study demonstrates that quantitative immunohistochemistry can identify proteins involved in reepithelialisation and actions of external compounds. Increased dermal MT expression may contribute to the anti-inflammatory activities of zinc and increased MMP-1 levels to promote keratinocyte migration.

Skin Stem Cells, Their Niche and Tissue Engineering Approach for Skin Regeneration

Skin is the main organ that covers the human body and acts as a protective barrier between the human body and the environment. Skin tissue as a stem cell source can be used for transplantation in therapeutic application in terms of its properties such as abundant, easy to access, high plasticity and high ability to regenerate. The immunological profile of these cells makes it a suitable resource for autologous and allogeneic applications. The lack of major histo-compatibility complex 1 is also advantageous in its use. Epidermal stem cells are the main stem cells in the skin and are suitable cells in tissue engineering studies for their important role in wound repair. In the last 30 years, many studies have been conducted to develop substitutions that mimic human skin. Stem cell-based skin substitutions have been developed to be used in clinical applications, to support the healing of acute and chronic wounds and as test systems for dermatological and pharmacological applications. In this chapter, tissue specific properties of epidermal stem cells, composition of their niche, regenerative approaches and repair of tissue degeneration have been examined.

Evaluation of the temporary effect of physical vapor deposition silver coating on resistance to infection in transdermal skin and bone integrated pylon with deep porosity

Periprosthetic infection via skin-implant interface is a leading cause of failures and revisions in direct skeletal attachment of limb prostheses. Implants with deep porosity fabricated with skin and bone integrated pylons (SBIP) technology allow for skin ingrowth through the implant's structure creating natural barrier against infection. However, until the skin cells remodel in all pores of the implant, additional care is required to prevent from entering bacteria to the still nonoccupied pores. Temporary silver coating was evaluated in this work as a means to provide protection from infection immediately after implantation followed by dissolution of silver layer in few weeks. A sputtering coating with 1 µm thickness was selected to be sufficient for fighting infection until the deep ingrowth of skin in the porous structure of the pylon is completed. In vitro study showed less bacterial (Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa) growth on silver coated tablets compared to the control group. Analysis of cellular density of MG-63 cells, fibroblasts, and mesenchymal stem cells (MSCs) showed that silver coating did not inhibit the cell growth on the implants and did not affect cellular functional activity. The in vivo study did not show any postoperative complications during the 6-month observation period in the model of above-knee amputation in rabbits when SBIP implants, either silver-coated or untreated were inserted into the bone residuum. Three-phase scintigraphy demonstrated angiogenesis in the pores of the pylons. The findings suggest that a silver coating with well-chosen specifications can increase the safety of porous implants for direct skeletal attachment. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 169-177, 2019.

Mechanisms of Acantholysis in Pemphigus: Mechanical or Inflammatory?

Pemphigus is a rare autoimmune disease, involving the skin and mucous epithelia, characterized by flaccid blisters and erosions. Histologically, the basic abnormality in all forms of pemphigus is the separation of keratinocytes from one another, a process known as acantholysis. There is direct evidence that autoantibodies against desmoglein, a transmembrane desmosomal component, are critical in its pathogenesis, but the exact mechanism that induces acantholysis is yet unknown. Actually, different studies suggest three possible mechanisms: sterical impedance, intracellular signalling and apoptosis. Understanding these processes should show new therapeutic perspective.

Connective tissue response to fractionated thermo-ablative Erbium: YAG skin laser treatment

Indications for and prevalence of laser therapies with a fractionated laser beam have risen significantly. However, as of yet, little is known about the underlying molecular changes, especially with respect to dermal extracellular-matrix remodelling, wound healing and inflammation. This study aimed at the investigation of the connective tissue response of sun-damaged skin following fractionated laser treatment. Seven patients received a laser therapy on the lateral side of the neck of wrinkles grade III-IV (Glogau scale) using a fractionated thermo-ablative erbium yttrium aluminium garnet (Er:YAG) laser (2940 nm, BURANE XL; Quantel Derma, Erlangen, Germany). Skin biopsies were taken at baseline from untreated skin, 1 and 6 weeks after laser intervention to investigate hyaluronan (HA), collagen-I (Coll-I) and collagen-III (Coll-III) remodelling as well as alteration of matrix metalloproteinase 1 expression (MMP-1). To address this issue, HA synthesizing (HA synthetases, HAS) and degrading (hyaluronidases, HYAL) enzymes were measured at mRNA-level using a real-time PCR. Furthermore, immunohistochemical staining for HA was performed by using the HA binding protein (HAbP) and for Coll-I, Coll-III and MMP-1 by using monoclonal antibodies. The degree of inflammation was correlated descriptively. Our findings were that at the two examined read out points, HAS and HYAL showed a slight response alluding to HA synthesis under minimal signs of inflammatory reaction. Concordantly, although to a varying degree, an increase in the HA content of the skin after laser treatment could be detected by immunhistochemistry. During remodelling, Coll-I, Coll-III and MMP-1 showed a cyclic course with a peak after 1 week. Conclusively, our results indicate a light alteration of the HA metabolism towards synthesis and a transient collagen neogenesis caused by a single fractionated thermo-ablative laser skin intervention. Clinical improvement might be attributed to synergistic effects between collagen neogenesis and the water binding capacities of HA and its influence on skin contraction and remodelling.

Glu-Trp-ONa or its acylated analogue (R-Glu-Trp-ONa) administration enhances the wound healing in the model of chronic skin wounds in rabbits

The management of chronic skin wounds represents a major therapeutic challenge. The synthesized dipeptide (Glu-Trp-ONa) and its acylated analogue (R-Glu-Trp-ONa) were assessed in the model of nonhealing dermal wounds in rabbits in relation to their healing properties in wound closure. Following wound modeling, the rabbits received a course of intraperitoneal injections of Glu-Trp-ONa or R-Glu-Trp-ONa. Phosphate-buffered saline and Solcoseryl® were applied as negative and positive control agents, respectively. An injection of Glu-Trp-ONa and R-Glu-Trp-ONa decreased the period of wound healing in animals in comparison to the control and Solcoseryl-treated groups. Acylation of Glu-Trp-ONa proved to be beneficial as related to the healing properties of the dipeptide. Subsequent zymography analyses showed that the applied peptides decreased the proteolytic activity of matrix metalloproteinases MMP-9, MMP-8, and MMP-2 in the early inflammatory phase and reversely increased the activity of MMP-9, MMP-8, and MMP-1 in the remodeling phase. Histological analyses of the wound sections (hematoxylin-eosin, Mallory's staining) confirmed the enhanced formation of granulation tissue and re-epithelialization in the experimental groups. By administering the peptides, wound closures increased significantly through the modulation of the MMPs' activity, indicating their role in wound healing.

Cdc42 inhibits ERK-mediated collagenase-1 (MMP-1) expression in collagen-activated human keratinocytes

Following injury, keratinocytes switch gene expression programs from the one that promotes differentiation to the one that supports migration. A common feature of human wounds and ulcerations of any form is the expression of matrix metalloproteinase 1 (MMP-1; collagenase-1) by leading-edge basal keratinocytes migrating across the dermal or provisional matrix. Induction of MMP-1 occurs by signaling from the α2β1 integrin in contact with dermal fibrillar type I collagen, and the activity of MMP-1 is required for human keratinocytes to migrate on collagen. Thus, MMP-1 serves a critical role in the repair of damaged human skin. Here, we evaluated the mechanisms controlling MMP-1 expression in primary human keratinocytes from neonatal foreskin and adult female skin. Our results demonstrate that shortly following contact with type I collagen extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase were markedly activated, whereas c-Jun N-terminal kinase (JNK) phosphorylation remained at basal levels. ERK inhibition markedly blocked collagen-stimulated MMP-1 expression in keratinocytes. In contrast, inhibiting p38 or JNK pathways had no effect on MMP-1 production. Moreover, investigating the role of Rho GTPases revealed that Cdc42 attenuates MMP-1 expression by suppressing ERK activity. Thus, our data indicate that injured keratinocytes induce MMP-1 expression through ERK activation, and this process is negatively regulated by Cdc42 activity.

New insights into procathepsin D in pathological and physiological conditions

Procathepsin D is a major glycoprotein that is secreted from numerous types of cancer cells including breast, lung and prostrate carcinomas. It affects multiple stages of tumorigenesis that include proliferation, invasion, metastasis and apoptosis. Previous studies showed that the mitogenic effect of procathepsin D on cancer cells was mediated through its propeptide or activation peptide. Recent studies have also implicated the possible use of procathepsin D/activation peptide as a marker of cancer progression. Considering the broad range of functions of procathepsin D, the present review summarizes the three major potentials of procathepsin D-cancer progression, tumor marker and wound healing.

Procathepsin D and cancer: From molecular biology to clinical applications

Procathepsin D (pCD) is overexpressed and secreted by cells of various tumor types including breast and lung carcinomas. pCD affects multiple features of tumor cells including proliferation, invasion, metastases and apoptosis. Several laboratories have previously shown that the mitogenic effect of pCD on cancer cells is mediated via its propeptide part (APpCD). However, the exact mechanism of how pCD affects cancer cells has not been identified. Recent observations have also revealed the possible use of pCD/APpcD as a marker of cancer progression. The purpose of this review is to summarize the three major potentials of pCD-tumor marker, potential drug, and screening agent.

Nexus between epidermolysis bullosa and transcriptional regulation by thyroid hormone in epidermal keratinocytes

Abstract Thyroid hormone, T3, through the interaction of its receptor with the recognition sequences in the DNA, regulates gene expression. This regulation includes the promoter activity of keratin genes. The receptor shares coregulators with other members of the nuclear receptor family, including RXR. Intending to define the transcriptional effects of thyroid hormones in keratinocytes, we used Affymetrix microarrays to comprehensively compare the genes expressed in T3-treated and untreated human epidermal keratinocytes. The transcriptomes were compared at 1, 4, 24, 48, and 72 hours. Surprisingly, T3 induced only 9 and suppressed 28 genes, much fewer than expected. Significantly, genes associated with epidermolysis bullosa, a set of inherited blistering skin diseases, were found statistically highly overrepresented among the suppressed genes. These genes include Integrin beta4, Plectin, Collagen XVII, MMP1, MMP3, and MMP14. The data imply that in keratinocytes T3 could suppresses the remodeling by, attachment to, and production of extracellular matrix. The results suggest that topical treatment with T3 may be effective for alleviation of symptoms in patients with epidermolysis bullosa.

Keratinocyte expression of MMP3 enhances differentiation and prevents tumor establishment

Matrix metalloproteinase (MMP)-3 is induced by multiple cell types in the skin during processes involved in both normal and pathological tissue remodeling. We previously demonstrated that MMP3-null animals have an increased sensitivity to the development of squamous cell carcinoma, suggesting that overall, MMP3 has a protective role in squamous cell carcinoma. However, not all cellular responses affected by a loss of MMP3 are tumor-protective, and tumor expression of MMP3 is co-incident with an invasive tumor phenotype. Transgenic mice were generated with MMP3 targeted to keratinocytes to examine the biological role of tumor-produced MMP3. Overexpression of MMP3 reduced tumor multiplicity in response to chemically induced squamous cell carcinoma. Vascular density was increased with MMP3 overexpression; however, other cellular processes, including tumor growth and leukocyte infiltration, were unaffected. In accordance with the change in tumor multiplicity, SP-1 murine papilloma cell lines that were generated to stably express MMP3 lost the capacity to establish palpable tumors following orthotopic injection into immunocompromised mice. Analysis of epidermal biopsies taken at 1 to 2 weeks postinjection revealed that these MMP3-expressing Sp-1 lines had reduced levels of proliferation and pronounced differentiation. These same cells demonstrated an increased ability to differentiate in vitro, an effect that was inhibited by broad-spectrum MMP and selective MMP3 inhibition. These studies suggest that keratinocyte expression of MMP3 promotes cellular differentiation, impeding tumor establishment during tumorigenesis.

Metalloproteinases and their inhibitors: regulators of wound healing

Wound healing is a dynamic process that involves a coordinated response of many cell types representing distinct tissue compartments and is fundamentally similar among tissue types. Among the many gene products that are essential for restoration of normal tissue architecture, several members of the matrix metalloproteinase (MMP) family function as positive and, at times, negative regulators of repair processes. MMPs were initially thought to only function in the resolution phase of wound healing, particularly during scar resorption; however, recent evidence suggests that they also influence other wound-healing responses, such as inflammation and re-epithelialization. In this review, we discuss what is currently known about the function of MMPs in wound healing and will provide suggestions for future research directions.

Procathepsin D secreted by HaCaT keratinocyte cells - A novel regulator of keratinocyte growth

Procathepsin D (pCD), the precursor form of lysosomal aspartic protease, is overexpressed and secreted by various carcinomas. The fact that secreted pCD plays an essential role in progression of cancer has been established. In this study, we describe substantial secretion of pCD by the human keratinocyte cell line HaCaT, under serum-free conditions. Moreover, exogenous addition of purified pCD enhanced the proliferation of HaCaT cells. The proliferative effect of pCD was inhibited by a monoclonal antibody against the activation peptide (AP) of pCD. Treatment of HaCaT cells with pCD or AP led to the secretion of a set of cytokines that might promote the growth of cells in a paracrine manner. The role of secreted pCD and its mechanism of action were studied in a scratch wound model and the presence of pCD and AP enhanced regeneration, while this effect was reversed by the addition of anti-AP antibody. Expression and secretion of pCD was upregulated in HaCaT cells exposed to various stress conditions. Taken together, our results strongly suggest that the secretion of pCD is not only linked to cancer cells but also plays a role in normal physiological conditions like wound healing and tissue remodeling.

Hypoxia induces epidermal keratinocyte matrix metalloproteinase-9 secretion via the protein kinase C pathway

Hypoxia promotes keratinocyte migration on wound bed connective tissues and is a profound biological signal that transforms a basal keratinocyte, destined to differentiate, into a motile cell that is essential for re-epithelialization. In this study, we examined the effect of hypoxia on keratinocyte-derived collagenases associated with keratinocyte migration. Cells plated on various connective tissue matrices under normoxic and hypoxic conditions, demonstrated a two-fold increase in the 92 kDa, type IV collagenase (MMP-9) when examined by quantitative zymography and ELISA. Western blotting and ELISA demonstrated a two-fold increase in tissue inhibitor of metalloproteinase (TIMP-1), an enzyme that binds to MMP-9 and inhibits its activity. The hypoxia-induced increase in cell motility could be inhibited by a neutralizing antibody to MMP-9. Northern blotting demonstrated that MMP-9 and TIMP-1 mRNA increased 2.5- to 4-fold, 2-12 h after the cells were made hypoxic. The hypoxia-induced changes in MMP-9 and TIMP-1 were inhibited by staurosporine and bisindolylmaleimide, inhibitors of protein kinase C (PKC), but not by inhibitors of tyrosine phosphorylation and the mitogen-activated protein kinase pathway. Inhibition of PKC also inhibited hypoxia-induced keratinocyte migration on type I collagen. These data provide evidence that hypoxia-induced keratinocyte migration is mediated by increased cellular secretion of MMP-9 via the PKC pathway.

Use of an in vitro model of tissue-engineered human skin to study keratinocyte attachment and migration in the process of reepithelialization

To produce a stable epidermis, keratinocytes need to be firmly attached to the basement membrane. However, following wounding, keratinocytes are required to develop a migratory phenotype in order to reepithelialize the wound. To investigate some of the issues underlying reepithelialization, we have developed a three-dimensional in vitro model of tissue-engineered skin, comprising sterilized human dermis seeded with human keratinocytes and dermal fibroblasts. Using this model, we have shown that the inclusion of fibroblasts within the model increases the stability of keratinocyte attachment. We have also demonstrated that keratinocyte migration occurs most effectively in the absence of a basement membrane and following the inclusion of fibroblasts in the model. In addition, subjecting the keratinocyte layer to mechanical trauma induces a migratory phenotype. We conclude that this three-dimensional in vitro wound model can be used to increase our understanding of the factors that enhance keratinocyte migration and hence wound healing in vivo.

Molecular events in tendinopathy: a role for metalloproteases

Disorganized, haphazard ineffective healing is a constant feature of chronic tendinopathy. Normal tendon is composed mostly of type I collagen. Tendinopathic tendons, conversely, have a greater proportion of type III collagen, which is associated with tendon rupture. Matrix metalloproteinases (MMPs) are involved in remodelling of the extracellular matrix (ECM) of tendons, because they are either up- or down-regulated in tendinopathy. A balance between MMPs and tissue inhibitors of metalloproteinases is required to maintain tendon homeostasis. The mechanism of activation of MMPs is poorly understood, and their precise role in tendinopathy is unclear.

The inhibition of MAPK pathway is correlated with down-regulation of MMP-9 secretion induced by TNF-alpha in human keratinocytes

MMP-9 (92 kDa) is the major gelatinase able to degrade collagen IV, secreted by keratinocytes that are actively involved in wound-healing or tumorigenesis. Since the invasive phenotype of cancers is dependent on MMP-9 expression, it appeared of interest to precisely characterize which signal transduction pathways activated by TNF-alpha are involved in MMP-9 up-regulation induced by TNF-alpha. In HaCaT cells, activation of MMP-9 occurs at the transcriptional level. Inhibition of the MAPK pathway using specific inhibitors of the Ras, Raf, MEK1/2, and Erk1/2 cascade was correlated with a marked inhibition of MMP-9 activity, as determined by gene and protein expression. MAPK pathway activation via TNF-alpha was confirmed by marked AP-1 activation detected in EMSA. Under our experimental conditions, p38 MAPK and SAPK/JNK pathways were not activated. Gene and protein expression of other MMPs that regulate MMP-9, such as MMP-1 and MMP-13, were also up-regulated by TNF-alpha and inhibited by UO126, providing evidence that the MAPK pathway plays a fundamental role in the regulation of MMP-9 secretion by keratinocytes. As TNF-alpha is known to be a main activator of NF-kappaB pathway, the effects of campthothecin and caffeic acid were investigated, such as, TNF-alpha campthothecin up-regulated MMP-9 activity but caffeic acid only weakly inhibited MMP-9 activation induced by TNF-alpha. However, NF-kappaB is activated as shown from immunostaining data, a nuclear staining and higher Western blotting expression of p50 and p65 NF-kappaB subunits were detected after TNF-alpha treatment. A higher specific signal was also detected in EMSA for TNF-alpha-treated cells.

Matrix metalloproteinases and their tissue inhibitors in severely burned children

Severe burns cause not only skin injury but several marked systemic derangements. During wound healing, matrix metalloproteinases (MMPs) and the tissue inhibitors of metalloproteinases play an important role in tissue regeneration and remodeling processes. Therefore, in the present study, we determined the serum levels of MMPs and tissue inhibitor of metalloproteinase-1 in burn patients over time. Serum samples from 12 severely burned children (mean age 7.9 +/- 2.5 years) with >40% total body surface area burns were obtained within 0.5 hours, 3, 7, and 21 days after injury. Pro-MMP-1, MMP-3, MMP-9, and tissue inhibitor of metalloproteinase-1 serum levels were assayed by enzyme-linked immunoassay and compared to normal healthy volunteers. Two-way analysis of variance and Bonferroni's test were used for statistical analysis. Pro-MMP-1 levels in the serum were significantly elevated by the seventh day after burn. MMP-3 and MMP-9 levels showed significant increases by day 3 and 21 compared to normals, respectively. Tissue inhibitor of metalloproteinase-1 levels did not change with time after burn but were significantly higher by 3 days after burn compared to normal serum. In conclusion, changes in MMPs and tissue inhibitor of metalloproteinase-1 occur in burn patients and those changes may be a mechanism beneficial to wound healing.

MMPs and TIMP-1 are differentially expressed between acute murine excisional and laser wounds

BACKGROUND AND OBJECTIVES

Matrix metalloproteinases (MMPs) and their physiological inhibitors, the tissue inhibitors of metalloproteinases (TIMPs) play significant roles in wound repair. The aim of this study was to determine whether MMP and TIMP-1 mRNA is differentially expressed between laser-created and excisional skin wounds.

STUDY DESIGN/MATERIALS AND METHODS

Full-thickness wounds were created on the dorsal surface of Balb/c mice by either excision of the skin or with a CO2 laser. Animals were sacrificed at days 1, 3, 5, 7, 10, and 13, and their wounds processed for RNA isolation or histology and immunohistochemistry.

RESULTS

Northern hybridization for MMP-3, -10, -13, and TIMP-1 mRNA demonstrated higher expression on days 1, 3, and 5 in the laser wounds as compared to the excisional wounds. Histological evaluation revealed a two day delay in the resurfacing of laser wounds as compared to excisional wounds. Immunohistochemistry of Day 5 and 7 excisional and laser wounds showed MMP-3 within the epidermal compartment and the neo-dermis. No remarkable differences were noted in the spatial distribution patterns of MMP-3 between wound types.

CONCLUSIONS

Our findings demonstrate that MMPs and TIMP-1 mRNA expression is higher on days 1-5 post injury in full thickness laser-created wounds than in comparable same day excisional wounds.

The cellular proliferative phase of the wound repair process

The proliferative--or new-tissue formation--phase of wound healing is complex. This article examines the changes that occur to cells during this stage and the effect on the extracellular matrix environment.

Characterization of the living skin equivalent as a model of cutaneous re-epithelialization

The living skin equivalent, a three-dimensional organotypic model, has been widely used to investigate many aspects of cutaneous biology. However, there are relatively few studies assessing how faithfully the skin equivalent reproduces normal skin biology. The skin equivalent was fabricated by seeding human epidermal keratinocytes onto the upper surface of a hydrated collagen lattice populated with human dermal fibroblasts and subsequently raised to the air-liquid interface where keratinocyte stratification and differentiation led to the formation of a tissue which showed many common morphological features to that of normal skin. Histology and immunohistochemical detection of keratinocyte integrins and matrix metalloproteinases (MMPs) were used as cytological markers to assess the accuracy of the model during cutaneous re-epithelialization. Analysis of expression of keratinocyte integrins revealed that whilst there were a number of similarities to normal skin, skin equivalent keratinocytes appeared to be 'activated' and hyper-proliferating. Wounding of the skin equivalent, by complete bisection, induced re-epithelialization from both wound edges within 8-12 h, which completely restored the epidermis within 4 days. This migration, like that in vivo, was associated with nascent expression of MMPs and upregulation of certain integrins. However, whilst integrin expression, was similar to in vivo re-epithelialization, there were subtle differences in the level of expression and distribution of certain integrins.

Proteolytic events of wound-healing--coordinated interactions among matrix metalloproteinases (MMPs), integrins, and extracellular matrix molecules

During wound-healing, cells are required to migrate rapidly into the wound site via a proteolytically generated pathway in the provisional matrix, to produce new extracellular matrix, and, subsequently, to remodel the newly formed tissue matrix during the maturation phase. Two classes of molecules cooperate closely to achieve this goal, namely, the matrix adhesion and signaling receptors, the integrins, and matrix-degrading and -processing enzymes, the matrix metalloproteinases (MMPs). There is now substantial experimental evidence that blocking key molecules of either group will prevent or seriously delay wound-healing. It has been known for some time now that cell adhesion by means of the integrins regulates the expression of MMPs. In addition, certain MMPs can bind to integrins or other receptors on the cell surface involved in enzyme activation, thereby providing a mechanism for localized matrix degradation. By proteolytically modifying the existing matrix molecules, the MMPs can then induce changes in cell behavior and function from a state of rest to migration. During wound repair, the expression of integrins and MMPs is simultaneously up-regulated. This review will focus on those aspects of the extensive knowledge of fibroblast and keratinocyte MMPs and integrins in biological processes that relate to wound-healing.

Topical synthetic inhibitor of matrix metalloproteinases delays epidermal regeneration of human wounds

Matrix metalloproteinases (MMPs) degrade extracellular proteins during epithelialization of wounds. To evaluate the biological significance of MMPs in epidermal healing, the synthetic broad-spectrum MMP inhibitor GM 6001 (also called Galardin and Ilomastat) was applied topically to standardized human wounds. GM 6001 (10 microg/microl) or vehicle alone was applied every second day onto 4 de-roofed 6 mm suction blister wounds on the volar forearm of healthy male volunteers for 12 days. GM 6001 delayed healing by 2-4 days as assessed macroscopically and microscopically. In situ hybridization or immunohistochemistry showed that MMP-1 (interstitial collagenase) was present in and MMP-2 (gelatinase A) close to laterally migrating keratinocytes whereas MMP-9 (gelatinase B) was seen during maturation of new epidermis. MMP-1 was undetectable in blister roofs (normal epidermis) and found in low levels in normal skin. Total MMP-1 activities increased about 100-fold in wounds, independent of treatment, compared to normal skin as analyzed by specific ELISA-based activity assay. By gelatin zymography, MMP-2, but not MMP-9, was detected in blister roofs and wound healing was associated with increased active MMP-2 and latent MMP-9 levels. GM 6001 prevented activation of MMP-2 and increased latent MMP-9 levels. GM 6001 delayed re-appearance of laminin-5, the synthesis of which correlated with epidermal regeneration. Restoration of stratum corneum, measured indirectly by transepidermal water loss, was also impaired (P<0.05) in the GM 6001 group. In conclusion, pharmacological MMP inhibition delayed epidermal regeneration in vivo, suggesting that MMPs are required to restore epidermis after epidermal ablation in humans.

Stromelysin-2 is upregulated during normal wound repair and is induced by cytokines

Stromelysin-2 is a matrix metalloproteinase that degrades in vitro several protein components relevant to wound repair such as collagens III and IV, gelatin, nidogen, laminin-1, proteoglycans, and elastin. Furthermore, it can activate other matrix metalloproteinases, such as collagenase-1 (matrix metalloproteinase-1) and collagenase-2 (matrix metalloproteinase-8), as well as 92 kDa gelatinase. The aim of this study was to determine in a large variety of wounds (normally healing dermal and mucosal wounds, suction blisters, ex vivo cultures, diabetic, decubitus, rheumatic, and venous ulcers) and keratinocyte cultures, which factors contribute to stromelysin-2 expression and how it is induced in relation to other matrix metalloproteinases. Our results show that stromelysin-2 mRNA and protein are upregulated later (at 3 d) than matrix metalloproteinase-1 in normally healing wounds and ex vivo explants, in which stromelysin-2 is invariably expressed by keratinocytes migrating over dermal matrix. The number of keratinocytes expressing stromelysin-2 was greatest in chronic inflamed diabetic and venous ulcers compared with rheumatoid and decubitus ulcers, six of which had no signal. In keratinocyte cultures, tumor necrosis factor-alpha, epidermal growth factor, and transforming growth factor-beta1 induced stromelysin-2 expression as measured by quantitative reverse transcriptase-polymerase chain reaction, whereas different matrices did not upregulate the mRNA. Immunostaining demonstrated stromal transforming growth factor-beta1 in contact with the stromelysin-2-positive keratinocytes. Our results suggest that stromelysin-2 expression is important for the normal repair process and is upregulated by cytokines rather than cell-matrix interactions. Stromelysin-2 is most likely to participate in the remodeling of the newly formed basement membrane, and is not overexpressed in retarded wound healing.

Urokinase-type plasminogen activator and its receptor synergize to promote pathogenic proteolysis

Urokinase-type plasminogen activator (uPA) is a potent catalyst of extracellular proteolysis, which also binds to a high-affinity plasma membrane receptor (uPAR). Binding of uPA may influence pericellular proteolysis and/or activate intracellular signal transduction. Transgenic mice overexpressing either uPA or uPAR in basal epidermis and hair follicles had no detectable cutaneous alterations. In contrast, bi-transgenic mice overexpressing both uPA and uPAR, obtained by crossing the two transgenic lines, developed extensive alopecia induced by involution of hair follicles, epidermal thickening and sub-epidermal blisters. The phenotype was due to uPA catalytic activity since combined overexpression of uPAR and uPAR-binding but catalytically inactive uPA in the same tissue was not detrimental in another bi-transgenic line. It was accompanied by increased plasmin-generating capacity, up-regulation and activation of matrix metalloproteinases type-2 and -9, and cleavage of uPAR. Thus, combined overexpression of uPA and uPAR acts in synergy to promote pathogenic extracellular proteolysis.

Ras-transfection up-regulated HaCaT cell migration: inhibition by Marimastat

Cell migration is an essential process in physiological and pathological conditions such as wound healing and tumor invasion. This phenomenon involves cell adhesion on the extracellular matrix mediated by integrins, and cell detachment promoted in part by metalloproteinases (MMPs). In the present study, the migration of two HaCaT-ras clones (metastatic or not), was compared with HaCaT cells, and normal human primary cultured keratinocytes. Using colloidal gold migration assay, the migration index on type I and type IV collagen was similar for primary cultured keratinocytes and HaCaT, whereas it was markedly higher for the HaCaT-ras clones. High motility of ras-transfected cells was confirmed from an in vitro wound healing assay. It was not correlated with changes in integrin expression or related to a different adhesion on extracellular matrix. The Marismastat (BB-2516), a MMP inhibitor, inhibited in a dose-dependent effect the migration in both assays, demonstrating the important role of MMPs in the migration process. Under our experimental conditions, MMP-1 activity was not detected in HaCaT and MMP-9 activity was secreted by these cells only after their stimulation by EGF. Here, MMP-2 was the major gelatinolytic activity secreted by all the cells and its secretion was markedly higher for HaCaT-nis clones compared with HaCaT. In addition, Western blotting results confirmed a higher expression of MMP-2 associated with a lower expression of TIMP-2 in HaCaT-ras compared with HaCaT. These results suggest that Ha-ras oncogene could be a stimulating factor of migration and might modified the balance between MMP-2 and TIMP-2 in keratinocyte cell lines.

The PHSRN sequence induces extracellular matrix invasion and accelerates wound healing in obese diabetic mice

The PHSRN sequence of the plasma fibronectin (pFn) cell-binding domain induces human keratinocytes and fibroblasts to invade the naturally serum-free extracellular matrices of sea urchin embryos. The potency of acetylated, amidated PHSRN (Ac-PHSRN-NH(2)) is significantly increased, making it more active on a molar basis than the 120-kDa cell-binding domain of pFn. Arginine is important to this activity because PHSAN and PHSEN are inactive, as is a randomized sequence peptide, Ac-HSPNR-NH(2). One treatment with Ac-PHSRN-NH(2) stimulates reepithelialization and contraction of dermal wounds in healing-impaired, obese diabetic C57BL6/KsJ db/db mice. Wound closure is equally rapid in treated db/db and db/+ mice and may be more rapid than in untreated nondiabetic db/+ littermates. In contrast, treatment with either Ac-HSPNR-NH(2) or normal saline (NS) has no effect. Analysis of sectioned db/db wounds shows that, in contrast to treatment with Ac-HSPNR-NH(2) or NS, a single Ac-PHSRN-NH(2) treatment stimulates keratinocyte and fibroblast migration into wounds, enhances fibroplasia and vascularization in the provisional matrix, and stimulates the formation of prominent fibers that may be associated with wound contraction.

Differential expression of matrix metalloproteinases and their tissue-derived inhibitors in cutaneous wound repair

Wound extracellular matrix is a key regulator of cell adhesion, migration, proliferation, and differentiation during cutaneous repair. The amount and organization of normal wound extracellular matrix are determined by a dynamic balance among overall matrix synthesis, deposition, and degradation. Matrix metalloproteinases (MMPs) are one family of structurally related enzymes that have the collective ability to degrade nearly all extracellular matrix components. The MMPs are broadly categorized into collagenases, gelatinases, stromelysins, and membrane-type MMPs by their substrate specificity. The aim of this study was to characterize the temporal changes in mRNA profiles for rat collagenase [matrix metalloproteinase-1 (MMP-1)], gelatinase A (MMP-2), matrilysin (MMP-7), gelatinase B (MMP-9), and membrane type 1-MMP (MT1-MMP), as well as tissue inhibitor of metalloproteinases-1 (TIMP-1), TIMP-2, and TIMP-3 during the inflammatory, granulation, and early remodeling phases of excisional skin repair. Eight full-thickness skin wounds were made on the backs of each rat (7-mm2 wounds; 16 rats; n = 128 wounds). Two animals at a time were reanesthetized, and all eight wounds on each animal were excised at 12 and 24 hours and at 2, 3, 5, 7, 10, and 14 days after injury. Six wounds from each animal were excised for RNA isolation, whereas two wounds were excised for histology. Controls consisted of nonwounded skin from identical locations in four animals. Total RNA from each time point was isolated and relative mRNA quantitation performed by using reduced-cycle reverse transcription-polymerase chain reaction. Correct polymerase chain reaction product amplification was confirmed by probing the blotted polymerase chain reaction product with a 32P-labeled oligonucleotide specific for a given MMP or TIMP. We demonstrated that the majority of MMP and TIMP mRNA induction and peak expression coincided temporally with the well-characterized inflammatory and granulation stages of repair. In conclusion, there is a distinct pattern of MMP and TIMP expression during normal excisional wound repair.

Matrix metalloproteinases in repair

During repair, many different matrix metalloproteinases are produced by multiple cell types residing in various compartments within the wound environment. This diversity of enzymes, coupled with discreet cellular expression, implies that different matrix metalloproteinases serve different functions, acting on a variety of substrates, during wound healing. With few exceptions, however, the actual function and spectrum of functions of matrix metalloproteinases in vivo is not known. Even with the advent of genetically defined animal models, few studies have rigorously addressed the substrates and role of matrix metalloproteinases in wound repair. Before we can understand the role of matrix metalloproteinases in ulceration and disease, we need to determine the function these enzymes serve in normal tissues and repair.

Impaired wound contraction in stromelysin-1-deficient mice

OBJECTIVE

To determine whether the deletion of stromelysin-1, a single metalloproteinase gene product, will alter the time course and quality of dermal wound repair in mice.

SUMMARY BACKGROUND DATA

After dermal injury, a highly coordinated program of events is initiated by formation of a fibrin clot, followed by migration of keratinocytes, contraction of the dermis, recruitment of inflammatory macrophages, formation of granulation tissue with angiogenesis, and finally tissue remodeling. Matrix metalloproteinases are rapidly induced in the dermis and granulation tissue and at the leading edge of the epidermis in the healing wounds.

METHODS

Incisional and circular full-thickness wounds 2 to 10 mm were made in the dermis of stromelysin-1-deficient and wild-type mice. The wounds were analyzed for rate of cellular migration and epithelialization. The wound contraction was examined by immunohistochemical staining for alpha-smooth muscle actin and fluorescent staining for fibrillar actin.

RESULTS

Independent of the age of the animal, excisional wounds in stromelysin-1-deficient mice failed to contract and healed more slowly than those in wild-type mice. Cellular migration and epithelialization were unaffected in the stromelysin-1-deficient animals. The functional defect in these mice is failure of contraction during the first phase of healing because of inadequate organization of actin-rich stromal fibroblasts.

CONCLUSIONS

Excisional dermal wound healing is impaired in mice with a targeted deletion in the stromelysin-1 gene. Incisional wound healing is not affected. These data implicate stromelysin-1 proteolysis during early wound contraction and indicate that stromelysin-1 is crucial for the organization of a multicellular actin network.

Differential expression of tissue inhibitors of metalloproteinases (TIMP-1, -2, -3, and -4) in normal and aberrant wound healing

Wound healing is characterized by hemostasis, re-epithelialization, granulation tissue formation, and remodeling of the extracellular matrix. Matrix metalloproteinases and their specific inhibitors, TIMPs, contribute to these events. We investigated a total of 47 samples of normally healing wounds, chronic venous ulcers, ulcerative vasculitis, and suction blisters using immunohistochemistry and in situ hybridization, to clarify the role of TIMPs in normal and aberrant wound repair. Expression of TIMP-1 and -3 mRNAs was found in proliferating keratinocytes in 3- to 5-day-old normally healing wounds, whereas no epidermal expression was detected in chronic ulcers. However, TIMP-3 protein was found in the proliferating epidermis in 20 of 24 samples representing both full-thickness acute and chronic wounds. TIMP-1 and TIMP-3 also were abundantly expressed by spindle-shaped, fibroblast-like, and plump, macrophage-like stromal cells, as well as by endothelial cells. In normally healing wounds, TIMP-2 protein localized under the migrating epithelial tip and to the stromal tissue under the eschar more frequently than in chronic ulcers. Occasional staining for TIMP-4 protein was detected in stromal cells of chronic ulcers near blood vessels. Our results indicate that TIMP-1 and TIMP-3 may be involved both in the regeneration of the epidermis by stabilizing the basement membrane zone and in the regulation of stromal remodeling and angiogenesis of the wound bed. Lack of TIMP-2 near the migrating epithelial wound edges might contribute to uncontrolled activity of MMP-2 in chronic ulcers. We conclude also that TIMPs are temporally and spatially tightly regulated and that the imbalance between metalloproteinases and TIMPs-1, -2, and -3 may lead to delayed wound healing.

Role of matrix metalloproteinases and their inhibition in cutaneous wound healing and allergic contact hypersensitivity

Normal wounds can heal by secondary intention (epidermal migration to cover a denuded surface) or by approximation of the wound edges (e.g., suturing). In healing by secondary intention, epidermis-derived MMPs are important. Keratinocyte migration begins within 3-6 hr post injury, as basal cells detach from underlying basal lamina and encounter a dermal substratum rich in type I collagen. Cell contact with type I collagen in vitro stimulates collagenase-1 expression, which is mediated by the alpha 2 beta 1 integrin, the major keratinocyte collagen-binding receptor. Collagenase-1 activity alone is necessary and sufficient for keratinocyte migration over a collagen subsurface. Stromelysins-1 and -2 are also found in the epidermis of normal acute wounds. Stromelysin-2 co-localizes with collagenase-1 and may facilitate cell migration over non-collagenous matrices of the dermis. In contrast, stromelysin-1 is expressed by keratinocytes behind the migrating front and which remain on basal lamina, i.e., the proliferative cell population. Studies with stromelysin-1-deficient mice that suggest this MMP plays a role in keratinocyte detachment from underlying basement membrane to initiate cell migration. In chronic ulcers, MMP levels are markedly elevated, in contrast to their precise temporal and spatial expression in acute wounds. Both collagenase-1 and stromelysin-1 are found in fibroblasts underlying the nonhealing epithelium, and stromelysin-1 expression is especially prominent. Two key questions underlie the use of MMP inhibitors and wound healing: (1) will these agents impair normal reepithelialization in wounds that heal by secondary intention; and (2) can MMP inhibitors be effective therapy for chronic ulcers? The answer to neither is known. Batimastat and marimastat appear not to interfere with normal wound healing, but only in sutured surgical wounds, a situation in which MMP expression has practically no role. We also show the first example of an in vivo immune response, contact hypersensitivity, which is dependent upon MMP activity. Using gene-deficient mice, we demonstrate that stromylysin-1 (MMP-3) is required for sensitization, whereas gelatinase B (MMP-9) is required for timely resolution of the reaction to antigenic challenge.

A partial catalog of proteins secreted by epidermal keratinocytes in culture

Proteins secreted by epidermal keratinocytes are known to engage in functions other than those directly associated with barrier formation. We have used a previously published culture model to collect proteins secreted by adult human epidermal keratinocytes. Electrophoresis and microsequencing allowed us to identify 20 proteins. The list of proteins includes those known to be produced by keratinocytes (beta-2 microglobulin, betaIG-H3, calgranulin A, cathepsin B and D, E-cadherin, gelatinase B, gelsolin, interstitial collagenase, laminin B2t, plasminogen activator inhibitor-1, protein 14-3-3epsilon, SCC antigen, stratifin, and translationally controlled tumor protein) as well as those not previously known to be secreted by keratinocytes (epididymis secretory protein, maspin, and anti-neoplastic urinary protein). In addition, two proteins were identified that are not known to be secreted (glutathione-S-transferase and heat shock protein 27/28 kDa). The varied nature of the proteins identified suggests that epidermal keratinocytes have physiologic functions that have yet to be identified.

Keratinocyte collagenase-1 expression requires an epidermal growth factor receptor autocrine mechanism

In response to cutaneous injury, expression of collagenase-1 is induced in keratinocytes via alpha2beta1 contact with native type I collagen, and enzyme activity is essential for cell migration over this substratum. However, the cellular mechanism(s) mediating integrin signaling remain poorly understood. We demonstrate here that treatment of keratinocytes cultured on type I collagen with epidermal growth factor receptor (EGFR) blocking antibodies or a specific receptor antagonist inhibited cell migration across type I collagen and the matrix-directed stimulation of collagenase-1 production. Additionally, stimulation of collagenase-1 expression by hepatocyte growth factor, transforming growth factor-beta1, and interferon-gamma was blocked by EGFR inhibitors, suggesting a required EGFR autocrine signaling step for enzyme expression. Collagenase-1 mRNA was not detectable in keratinocytes isolated immediately from normal skin, but increased progressively following 2 h of contact with collagen. In contrast, EGFR mRNA was expressed at high steady-state levels in keratinocytes isolated immediately from intact skin but was absent following 2 h cell contact with collagen, suggesting down-regulation following receptor activation. Indeed, tyrosine phosphorylation of the EGFR was evident as early as 10 min following cell contact with collagen. Treatment of keratinocytes cultured on collagen with EGFR antagonist or heparin-binding (HB)-EGF neutralizing antibodies dramatically inhibited the sustained expression (6-24 h) of collagenase-1 mRNA, whereas initial induction by collagen alone (2 h) was unaffected. Finally, expression of collagenase-1 in ex vivo wounded skin and re-epithelialization of partial thickness porcine burn wounds was blocked following treatment with EGFR inhibitors. These results demonstrate that keratinocyte contact with type I collagen is sufficient to induce collagenase-1 expression, whereas sustained enzyme production requires autocrine EGFR activation by HB-EGF as an obligatory intermediate step, thereby maintaining collagenase-1-dependent migration during the re-epithelialization of epidermal wounds.

The prevention and treatment of cutaneous injury secondary to chemical warfare agents. Application of these finding to other dermatologic conditions and wound healing

Chemical warfare agents are easily and inexpensively produced and are therefore potentially accessible to even underdeveloped nations and are a threat to civilian populations as well as advancing troops. Sulfur mustard is by far the most significant chemical warfare agent that produces cutaneous injury. Significant advances over the past few years have been made in understanding the pathophysiology of the lesions produced by sulfur mustard, as well as development of barrier creams and pre and post exposure therapies to moderate the damage and accelerate healing. Not only have these advances improved our understanding of the sulfur mustard injury and the care of the patients, these are potentially numerous applications for these findings in other dermatologic conditions including the treatment of chronic wounds.

Lipodermatosclerosis is characterized by elevated expression and activation of matrix metalloproteinases: implications for venous ulcer formation

Lipodermatosclerosis refers to skin induration of the lower extremities and is associated with patients preceding venous ulcerations. To better understand the pathogenesis of ulcer formation we investigated the expression of matrix metalloproteinases (MMP) and tissue inhibitors of metalloproteinases (TIMP) in lipodermatosclerosis. By preparing biopsies from healthy skin and liposclerotic lesions, MMP-1, MMP-2, MMP-9, TIMP-1, and TIMP-2 were analyzed by using reverse transcriptase-polymerase chain reaction, western blot, zymography, hydrolysis of [3H]labeled collagens, and immunohistochemistry. Our investigations provide evidence that mRNA and protein expression of MMP-1, MMP-2, and TIMP-1 were significantly increased in lipodermatosclerosis, whereas the total amount of MMP-9 and TIMP-2 mRNA and protein was not altered. Western blot of liposclerotic lesions revealed an inactive proMMP-1-TIMP-1 complex, whereas MMP-2 was prominent as an active 66 kDa band. Increased proteolytic activity of MMP-2 could be proven in lesional in comparison with healthy skin by zymography and [3H] collagen degradation. Increased diffuse staining was found for MMP-1 in the epidermis and dermis in comparison with controls. In lipodermatosclerosis, MMP-2 was predominantly localized in the basal and suprabasal layers of the epidermis, in perivascular regions, and in the reticular part of the dermis. Furthermore, MMP-2 was imbalanced by locally reduced expression of TIMP-2 in the basement membrane zone of lesional skin. Our findings indicate lipodermatosclerosis to be characterized by elevated matrix turnover.

Generation of Biologically Active IL-1β by Matrix Metalloproteinases: A Novel Caspase-1-Independent Pathway of IL-1β Processing

Biologic activity of IL-1β requires processing of the inactive precursor, a function generally ascribed to IL-1β-converting enzyme (caspase-1). However, alternative mechanisms of IL-1β activation have been postulated in local inflammatory reactions. Expression of IL-1β and matrix metalloproteinases (MMPs) frequently occurs simultaneously at sites of inflammation. We describe here that stromelysin-1 (MMP-3), as well as the gelatinases A (MMP-2) and B (MMP-9), processes recombinant human IL-1β precursor (pIL-1β) into biologically active forms. Detection of both pIL-1β processing and biologic IL-1β activity demonstrated different processing capacities of the respective MMPs. Conversion of pIL-1β by stromelysin-1 required coincubation for at least 1 h, and biologic activity faded after 8 h to 24 h. Gelatinase A was less effective in processing pIL-1β, requiring at least 24 h of coincubation. In contrast, gelatinase B processed pIL-1β within minutes, resulting in immunoreactive products as well as biologic activity stable for 72 h. In addition, prolonged incubation of mature IL-1β with stromelysin-1, and to a lesser extent also with gelatinases, but not with interstitial collagenase, resulted in the degradation of mature IL-1β. None of the MMPs processed the second isoform of IL-1, IL-1α. The present study indicates a biphasic regulation of IL-1β activity by MMPs: a caspase-1-independent pathway of IL-1β activation and inhibition of IL-1β activity by degrading the mature cytokine. The balance of the respective MMPs and pIL-1β might regulate the long term appearance of IL-1β activity at sites of acute or chronic inflammation.

Induction of matrix metalloproteinases and a collagen-degrading phenotype in fibroblasts and epithelial cells by secreted Porphyromonas gingivalis proteinase

Periodontitis is characterized by advancement of a narrow band of epithelium (1-10 cells wide) through the collagenous periodontal ligament in response to bacterial accumulation and infection. A modulating role by epithelial cells in the progression of periodontitis was hypothesized due to the close proximity of the advancing epithelium to both the etiological bacteria and to the collagen fibers of the ligament. We demonstrate that rat mucosal epithelial cells and human fibroblasts are similarly stimulated to degrade a collagen type I cellular substrate by thiol-dependent activity released by the major periodontal pathogen Porphyromonas gingivalis. A purified, extracellular bacterial thiol-proteinase from P. gingivalis ATCC 33277 stimulated mucosal epithelial cells to upregulate expression of collagenase and stromelysin, and to degrade a collagen type I fibril matrix. Stimulation of the epithelial cells with this purified proteinase was associated with morphological changes in the cells and with accumulation of secreted latent procollagenase throughout the culture medium. Release of active collagenase was minimal and collagen degradation by the epithelial cells was discreet and localized subcellularly suggesting the possibility that activation of secreted procollagenase was cell-associated. We conclude that a collagen-degrading phenotype can be stimulated in relatively quiescent mucosal epithelial cells and fibroblasts by the presence of bacterial proteinase. These experiments suggest roles for the P. gingivalis thiol-proteinase and the epithelial cell in the pathogenesis of periodontal disease and demonstrate the potential for dysregulation of extracellular matrix remodeling events during healing of other bacterially infected wounds.

Matrilysin expression and function in airway epithelium

We report that matrilysin, a matrix metalloproteinase, is constitutively expressed in the epithelium of peribronchial glands and conducting airways in normal lung. Matrilysin expression was increased in airway epithelial cells and was induced in alveolar type II cells in cystic fibrosis. Other metalloproteinases (collagenase-1, stromelysin-1, and 92-kD gelatinase) were not produced by normal or injured lung epithelium. These observations suggest that matrilysin functions in injury-mediated responses of the lung. Indeed, matrilysin expression was increased in migrating airway epithelial cells in wounded human and mouse trachea. In human tissue, epithelial migration was reduced by > 80% by a hydroxamate inhibitor, and in mouse tissue, reepithelialization in trachea from matrilysin-null mice was essentially blocked. In vivo observations and cell culture studies demonstrated that matrilysin was secreted lumenally by lung epithelium, but upon activation or while migrating over wounds, some matrilysin was released basally. The constitutive production of matrilysin in conducting airways, its upregulation after injury, its induction by alveolar epithelium, and its release into both lumenal and matrix compartments suggest that this metalloproteinase serves multiple functions in intact and injured lung, one of which is to facilitate reepithelialization.

Collagenase-1 complexes with alpha2-macroglobulin in the acute and chronic wound environments

The purpose of this study was to examine the appearance and activation of collagenase-1 (MMP-1) in the wound environment. We found that MMP-1 accumulates in the fluid phase of the burn wound environment within 2 d of injury and reaches maximal levels by day 4. Two forms of the enzyme were evident; one that corresponded to proMMP-1 and another that corresponded to a group of high molecular mass (approximately 200 kDa and >200 kDa doublet) MMP-1 containing complexes. ProMMP-1 and MMP-1 containing complexes also occurred in wound fluid from venous stasis ulcers, but neither was detected in mastectomy fluid or in plasma. Levels of the proteinase inhibitor alpha2-macroglobulin in burn fluid and chronic ulcer wound fluid were almost as high as in plasma, and the high molecular mass MMP-1 containing complexes in burn fluid appeared to result from binding between alpha2-macroglobulin and activated MMP-1. These observations provide direct evidence that active MMP-1 in the fluid phase of the wound environment becomes complexed to alpha2-macroglobulin.

Laminin-5 expression is independent of the injury and the microenvironment during reepithelialization of wounds

We examined the expression of laminin-5 and its integrin receptors during reepithelialization of human wounds. We used suction blisters of skin as a model of keratinocyte migration on a basement membrane matrix and mucosal full-thickness wounds as a model in which keratinocytes migrate in a provisional matrix. An animal model, in which human epidermal keratinocytes were injected into the back of athymic mice, was used to follow the deposition of the basement membrane components. In 4-day-old blisters, about 20-50 cells at the leading edge of the migrating tongue showed cytoplasmic laminin-5 immunostaining. Laminin-5 mRNA was detected in 15-30 cells at the leading edge of the migrating epidermis. alpha3beta1 and alpha6beta4 integrins were found in membrane projections of the migrating basal cells and also in suprabasal cell layers, suggesting their combined role in binding laminin-5. In mucosal wounds, laminin-5 was the only basement membrane zone component that was deposited between the clot and the migrating keratinocytes. In the animal model, linear deposition of laminin-5 and alpha6beta4 integrin was already seen on Day 2, whereas the other basement membrane zone components were not yet organized. The results suggest that, regardless of the injury and the microenvironment, laminin-5 plays an essential role in the interaction between wound keratinocytes and the surrounding matrix.

Histopathologic and immunohistochemical features in human skin after exposure to nitrogen and sulfur mustard

N-methyl-2,2'-dichlorodiethylamine (HN2)is a topical chemotherapeutic agent used as therapy for cutaneous T-cell lymphomas (CTCL). Di(2-chloroethyl)sulfide (SM), and less often HN2, have been used as chemical weapons, with the skin being a principle target. The mechanisms by which these chemicals produce their therapeutic and toxic effects in skin, however, are not clearly defined. We exposed human skin explants to two doses of HN2 and SM. At 18 hours after exposure, histopathologic features were compared. In addition, immunohistochemical markers to basement membrane proteins were used to evaluate the effects of both chemicals on the basement membrane zone. Gross vesication was not seen. Pyknotic nuclei with or without dyskeratotic changes within epidermal keratinocytes were present at both doses. These changes varied more between skin specimens than they did between doses. Ballooning degeneration was more marked after SM exposures. Diffuse dermal-epidermal separation was present only at high-dose exposures and did not appear to correlate with the degree of changes locally in the overlying epidermis. Antibodies to laminin-5 showed decreased immunoreactivity after exposure to HN2 and SM. Immunoreactivity for laminin- was decreased to a lesser extent, and immunoreactivity for collagen IV and VII was unchanged. HN2 and SM produce similar histopathologic and immunohistochemical features after cutaneous exposure. These features suggest that part of mechanism of action of HN2 and SM is a direct effect on the basement membrane zone. Understanding the effects of HN2 and SM separate from their effect on DNA may be important in designing therapies and in advancing our understanding of the pathophysiologic changes induced by these chemicals when delivered topically.

Matrix metalloproteinases in skin

Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases collectively capable of degrading essentially all extracellular matrix components. These enzymes can be produced by several different types of cells in skin such as fibroblasts, keratinocytes, macrophages, endothelial cells, mast cells, and eosinophils and their activity can be specifically inhibited by TIMPs (tissue inhibitors of metalloproteinases), which bind to active MMPs with 1:1 stoichiometry. In general, MMPs are not constitutively expressed in skin but are induced temporarily in response to exogenous signals such as various cytokines, growth factors, cell matrix interactions and altered cell-cell contacts. At present, more evidence is accumulating that MMPs play an important role in proteolytic remodeling of extracellular matrix in various physiologic situations, including developmental tissue morphogenesis, tissue repair, and angiogenesis. On the other hand, MMPs play an important pathogenetic role in excessive breakdown of connective tissue components, e.g. in rheumatoid arthritis, osteoarthritis, chronic ulcers, dermal photoageing, and periodontitis, as well as in tumor cell invasion and metastasis. In this review we discuss the role of MMPs and TIMPs in human skin based on new observations on the regulation of the expression of MMPs, on their substrate specificity, and MMP expression in physiologic and pathologic conditions of skin involving matrix remodeling. Furthermore, therapeutic modalities based on regulating MMP activity will be reviewed.

Immunohistochemical studies of basement membrane proteins and proliferation and apoptosis markers in sulfur mustard induced cutaneous lesions in weanling pigs

Sulfur mustard (2,2-dichlorodiethyl sulfide, HD) is a chemical warfare agent that is a threat to both troops and civilians. The focus of HD research has been on intracellular adduct formation leading to apoptosis and/or necrosis in cutaneous lesions. However, there is work which suggests that HD may have a more direct effect on the basement membrane zone. Immunohistochemical staining to desmosomal proteins, cellular fibronectin, laminin 1, laminin 5, collagen IV, collagen VII, p53, Bcl-2, and PCNA was performed on weanling pig skin exposed to vesicating doses of HD, GB3, an antibody to laminin 5, showed a progressive decrease with loss of expression during the time period of clinical vesiculation. The other basement membrane proteins showed no change or inconsistent changes. PCNA, and p53 staining increased in the overlying epidermis in areas of vesiculation without significant necrosis. Bcl-2 positive cells were decreased or absent after exposure. This study implicates laminin 5 as the main basement membrane protein affected acutely by HD exposure. The patterns of staining of PCNA, Bcl-2, and p53 within the epidermis suggest that apoptosis and cellular necrosis both may play a role in cell death secondary to HD.