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

Advanced glycation of type I collagen and fibronectin modifies periodontal cell behavior

BACKGROUND

Advanced glycation end products (AGEs) have been linked to pathogenic mechanisms of diabetes mellitus. However, little is known about the contribution of protein glycation to periodontal disease in patients with diabetes. Therefore, this study investigated whether glycation of type I collagen (COLI) and fibronectin (FN) modified the behavior of human gingival fibroblasts (hGFs) and periodontal ligament fibroblasts (hPDLs).

METHODS

Procedures for rapid in vitro glycation of COLI and FN used methylglyoxal (MG). Formation of AGEs was analyzed by changes in protein migration using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting with antibodies specific for MG-glycated proteins. Experiments then characterized the effects of glycated FN and COLI on the behavior of hGFs and hPDLs.

RESULTS

MG glycated COLI and FN in <6 hours. Confirming the specificity of the reactions, antibodies specific for MG-induced AGEs reacted with glycated FN and COLI but not with control proteins. In cell culture experiments, glycated FN was significantly less efficient in supporting the attachment of hGFs and hPDLs (P <0.05). Moreover, the morphologic parameters, including length, area, perimeter, and shape factor, were altered (P <0.001) for cells on both glycated proteins. Finally, cell migration was reduced on glycated FN and COLI (P <0.001).

CONCLUSIONS

MG treatment efficiently glycated COLI and FN, providing a new tool to study the effects of diabetes on periodontal disease. The substantial effects of glycated COLI and FN on hGF and hPDL behavior indicated that protein glycation contributed to the pathogenesis and altered periodontal wound healing observed in patients with diabetes.

The effects of mitral regurgitation alone are sufficient for leaflet remodeling

BACKGROUND

Although chronic mitral regurgitation results in adverse left ventricular remodeling, its effect on the mitral valve leaflets per se is unknown. In a chronic ovine model, we tested whether isolated mitral regurgitation alone was sufficient to remodel the anterior mitral leaflet.

METHODS AND RESULTS

Twenty-nine sheep were randomized to either control (CTRL, n=11) or experimental (HOLE, n=18) groups. In HOLE, a 2.8- to 4.8-mm diameter hole was punched in the middle scallop of the posterior mitral leaflet to create "pure" mitral regurgitation. At 12 weeks, the anterior mitral leaflet was analyzed immunohistochemically to assess markers of collagen and elastin synthesis as well as matrix metalloproteinases and proteoglycans. A semiquantitative grading scale for characteristics such as intensity and delineation of stain between layers was used to quantify differences between HOLE and CTRL specimens across the heterogeneous leaflet structure. At 12 weeks, mitral regurgitation grade was greater in HOLE versus CTRL (3.0+/-0.8 versus 0.4+/-0.4, P<0.001). In HOLE anterior mitral leaflet, saffron-staining collagen (Movat) decreased, consistent with an increase in matrix metalloproteases throughout the leaflet. Type III collagen expression was increased in the midleaflet and free edge and expression of prolyl-4-hydroxylase (indicating collagen synthesis) was increased in the spongiosa layer. The proteoglycan decorin, also involved in collagen fibrillogenesis, was increased compared with CTRL (all P</=0.05).

CONCLUSIONS

In HOLE anterior mitral leaflet, the increased expression of proteins related to collagen synthesis and matrix degradation suggests active matrix turnover. These are the first observations showing that regurgitation alone can stimulate mitral leaflet remodeling. Such leaflet remodeling needs to be considered in reparative surgical techniques.

Calmodulin-like protein upregulates myosin-10 in human keratinocytes and is regulated during epidermal wound healing in vivo

Epidermal wound healing is required for normal skin barrier function. Cell motility is a key factor in the ability of keratinocytes to heal epithelial damage. Calmodulin-like protein (CLP) is an epithelial-specific Ca(2+)-binding protein that is regulated during terminal keratinocyte differentiation. CLP is a specific light chain of unconventional myosin-10 (Myo10) and its expression increases filopodial length, filopodial number, and Myo10-dependent cell motility in vitro. However, the effects of CLP expression on keratinocyte motility are unknown. Here we used cultured human keratinocytes to study the role of CLP in regulating Myo10 and the effects of Myo10 and CLP on cell migration. CLP and Myo10 expression were correlated in vitro and required for keratinocyte motility in wound-healing assays. We examined the localization of CLP in wounded skin by immunohistochemistry and found an upregulation and peripheral localization of CLP in the basal and suprabasal cells adjacent to and immediately over the wound bed in vivo. The results suggest that increased CLP expression and CLP-mediated Myo10 function are important for skin differentiation and wound reepithelialization.

Accelerated re-epithelialization in Dpr2-deficient mice is associated with enhanced response to TGFβ signaling

Members of the Dapper (Dpr)/Dact protein family are involved in the regulation of distinct signaling pathways, including TGFβ/Nodal, canonical and noncanonical Wnt pathways. Three Dpr genes, Dpr1, Dpr2 and Dpr3, are expressed in mouse embryos and in many adult tissues; however, their in vivo functions have not been reported. In this study, we generated Dpr2-deficient mice using a gene-knockout approach. Homozygous Dpr2 knockout (Dpr2–/–) embryos developed normally and postnatal Dpr2–/– mice grew to adulthood without obvious morphological or behavioral defects. We found that Dpr2 was expressed highly in epidermal keratinocytes and in hair follicles of adult mice, and that Dpr2 deficiency resulted in accelerated re-epithelialization during cutaneous wound healing. Furthermore, we demonstrated that loss of Dpr2 function enhanced the responses of keratinocytes to TGFβ stimulation, and that TGFβ signals promoted adhesion to fibronectin and migration of keratinocytes, by regulating the expression of specific integrin genes. Thus, Dpr2 plays an inhibitory role in the re-epithelialization of adult skin wounds by attenuating TGFβ signaling.

Differential effects of epsilon-aminocaproic acid and aprotinin on matrix metalloproteinase release in patients following cardiopulmonary bypass

This study examined whether differential effects of 2 agents commonly used for hemostatic purposes during cardiac surgery, aprotinin and epsilon-aminocaproic acid (EACA), exist with respect to elevations in proinflammatory interleukins (ILs) and matrix metalloproteinases (MMPs) in patients undergoing coronary artery bypass surgery. Sixty patients were prospectively randomized to receive either aprotinin (1 x 10 KIU; n = 30) or EACA (5 g IV; n = 30), and blood samples were obtained for IL and MMP levels just before induction of anesthesia (Baseline), 10 minutes after separation from cardiopulmonary bypass (Post), and 6 hours after surgery (6 hours). IL-6 was increased at Post in the EACA group and increased further at 6 hours. In the aprotinin group, IL-6 was significantly increased only at 6 hours. MMP subtypes associated with inflammation, MMP-8, and MMP-9 were increased in the EACA group at Post and remained elevated at 6 hours. Thus, differential effects on IL and MMP release occurred between aprotinin and EACA, indicative of different mechanisms of action independent of hemostatic effects.

Human matrix metalloproteinases: characteristics and pathologic role in altering mesangial homeostasis

Matrix metalloproteinases are zinc dependent endopeptidases belonging to the M10 family of the metalloproteinase superfamily. They are ubiquitous enzymes, structurally and functionally related, with a high degree of sequence homology. They are primarily involved in extracellular matrix (ECM) turn-over and cell migration through their expanding repertoire of substrate affinities. Twenty three different forms of human MMPs have been described to be arranged in eight distinct structural classes. Their interactions with tissue inhibitors of metalloproteinases (TIMPs), and other indigenous inhibitors have been well documented. This manuscript reviews pertinent information available on matrix metalloproteinases and TIMPs in the literature. Light chain-mediated glomerular injury represents an excellent example of how metalloproteinases participate in altering mesangial homeostasis. Investigations regarding these conditions have shown that the physico-chemical characteristics of the light chains govern the pattern of renal damage that will ensue with the mesangium representing the critical site where pathological alterations are centered. The mesangium is either replaced or expanded depending on the light chains involved in the pathologic process.

Areca nut extract represses migration and differentiation while activating matrix metalloproteinase-9 of normal gingival epithelial cells

BACKGROUND AND OBJECTIVE

Areca (betel) chewing is associated with an increase in the incidence of periodontal diseases. Aberrations in matrix metalloproteinase (MMP) expression have been reported to be associated with periodontal disease. This study investigated the effects of areca nut extract on MMP activity and the phenotype of human gingival epithelial cells.

MATERIAL AND METHODS

Reverse transcription-polymerase chain reaction, western blotting and gelatin zymography were used to assay MMPs. Cell viability, mobility and detachment assays were performed to characterize the phenotypic impact. Confocal microscopy was employed to evaluate cell aggregation and the distribution of E-cadherin and F-actin.

RESULTS

Treatment of gingival epithelial cells with 10 microg/mL of areca nut extract reduced its cell viability. Treatment with 5 and 10 microg/mL of areca nut extract for 24 h activated MMP-9 but not MMP-2 in gingival epithelial cells. This activation could be nuclear factor-kappaB dependent and was abrogated by 10 microM curcumin. Areca nut extract also reduced the migration and detachment of gingival epithelial cells. The differentiated cell-cell contact of gingival epithelial cells was markedly impaired by areca nut extract. This was accompanied by a disruption of distribution of E-cadherin and F-actin.

CONCLUSION

The areca nut extract-mediated activation of MMP-9 in gingival epithelial cells could signify a potential periodontal pathogenesis in areca chewers. The areca nut extract-mediated inhibition of cell viability and migration, together with the changed aggregation in gingival epithelial cells, suggests that impairment of the re-epithelization underlies the process and this, in turn, might exacerbate gingival inflammation.

Fibronectin fragmentation is a feature of periodontal disease sites and diabetic foot and leg wounds and modifies cell behavior

BACKGROUND

Fibronectin (FN) undergoes fragmentation in periodontal disease sites and in poorly healing diabetic wounds. The biologic effects of FN fragments on wound healing remain unresolved. This study characterized the pattern of FN fragmentation and its effects on cellular behavior compared to intact FN.

METHODS

Polyclonal antibodies were raised against FN and three defined recombinant segments of FN and used to analyze gingival crevicular fluid from periodontal disease sites in systemically healthy subjects and in subjects with diabetes, as well as chronic leg and foot wound exudates from subjects with diabetes. Subsequently, the behavior of human gingival fibroblasts (hGFs) and HT1080 reference cells were analyzed by measuring cell attachment, migration, and chemotaxis in the presence of intact FN or recombinant FN fragments.

RESULTS

FN fragmentation was evident in fluids from periodontal disease sites and diabetic leg and foot wounds. However, no fragmentation pattern distinguished systemically healthy subjects from subjects with diabetes. hGFs and HT1080 cells required significantly higher concentrations of FN fragments to achieve attachment comparable to intact FN. Cells cultured on FN fragments also were morphologically different from cells cultured on full-length FN. Migration was reduced for hGFs cultured on FN fragments relative to full-length FN. In contrast, FN fragments increased HT1080 fibrosarcoma cell migration over intact FN.

CONCLUSIONS

FN fragmentation is a prominent feature of periodontal and chronic leg and foot wounds in diabetes. Furthermore, cell culture assays confirmed the hypothesis that exposure to defined FN fragments significantly alters cell behavior.

Genomic survey of candidate stress-response genes in the estuarine anemone Nematostella vectensis

Salt marshes are challenging habitats due to natural variability in key environmental parameters including temperature, salinity, ultraviolet light, oxygen, sulfides, and reactive oxygen species. Compounding this natural variation, salt marshes are often heavily impacted by anthropogenic insults including eutrophication, toxic contamination, and coastal development that alter tidal and freshwater inputs. Commensurate with this environmental variability, estuarine animals generally exhibit broader physiological tolerances than freshwater, marine, or terrestrial species. One factor that determines an organism's physiological tolerance is its ability to upregulate "stress-response genes" in reaction to particular stressors. Comparative studies on diverse organisms have identified a number of evolutionarily conserved genes involved in responding to abiotic and biotic stressors. We used homology-based scans to survey the sequenced genome of Nematostella vectensis, the starlet sea anemone, an estuarine specialist, to identify genes involved in the response to three kinds of insult-physiochemical insults, pathogens, and injury. Many components of the stress-response networks identified in triploblastic animals have clear orthologs in the sea anemone, meaning that they must predate the cnidarian-triploblast split (e.g., xenobiotic receptors, biotransformative genes, ATP-dependent transporters, and genes involved in responding to reactive oxygen species, toxic metals, osmotic shock, thermal stress, pathogen exposure, and wounding). However, in some instances, stress-response genes known from triploblasts appear to be absent from the Nematostella genome (e.g., many metal-complexing genes). This is the first comprehensive examination of the genomic stress-response repertoire of an estuarine animal and a member of the phylum Cnidaria. The molecular markers of stress response identified in Nematostella may prove useful in monitoring estuary health and evaluating coastal conservation efforts. These data may also inform conservation efforts on other cnidarians, such as the reef-building corals.

Allograft airway fibrosis in the pulmonary milieu: a disorder of tissue remodeling

Obliterative bronchiolitis (OB) is thought to be a form of chronic allograft rejection. However, immunosuppressive therapy is not effective once fibrosis has developed. We hypothesize that disordered tissue remodeling is a mechanism for the pathogenesis of OB. We examined allograft airway fibrosis in an intrapulmonary tracheal transplant model of OB. Allograft airways were completely obliterated at day 21 by fibrotic tissue; however, tissue remodeling continued thereafter, as demonstrated by the change of collagen deposition density, shift from type I to type III collagen, shift from fibroblasts to myofibroblasts and shift of expression profiles and activities of matrix metalloproteinases (MMPs). We then used a broad-spectrum MMP inhibitor, SC080, to attempt to manipulate tissue remodeling. Administration of the MMP inhibitor from day 0 to day 28 reduced airway obliteration, without inhibiting T-cell activation. MMP inhibition from day 14 to day 28 showed similar effects on airway obliteration. MMP inhibition from day 21 to day 35 did not reverse the airway obliteration, but significantly reduced the collagen deposition, type III collagen and myofibroblasts in the lumen. We conclude that tissue remodeling plays a critical role in the development and maintenance of fibrosis after transplantation.

Fibronectin, vitronectin, and collagen I induce chemotaxis and haptotaxis of human and rabbit mesenchymal stem cells in a standardized transmembrane assay

The mesenchymal stem cell (MSC) is a critical element in tissue repair and regeneration. Its ability to differentiate into multiple connective tissue cell types and to self-renew has made it a prime candidate in regenerative medicine strategies. Currently, the environmental cues responsible for in situ recruitment and control of MSC distribution at repair sites are not entirely revealed and in particular the role of extracellular matrix (ECM) proteins as motogenic factors has not been studied. Here we have used a standardized transmembrane chemotaxis assay to assess the chemotactic and haptotactic potential of fibronectin, vitronectin, and collagen type 1 on MSCs from both rabbit and human origin. The use of both cell types was based in part on the widespread use of rabbit models for musculoskeletal-related tissue engineering and repair models and their unknown correspondence to human in terms of MSC migration. The optimized assay yielded a greatly increased chemotactic response toward known factors such as platelet-derived growth factor-BB (PDGF)-BB compared to previous studies. Our primary finding was that all three ECM proteins tested (fibronectin, vitronectin, and collagen I) induced significant motogenic activity, in both soluble and insoluble forms, for both rabbit and human MSCs. These results suggest that ECM proteins could play roles as significant as cytokines in the recruitment of pluripotential repair cells wound and tissue repair sites. Furthermore, designed ECM coatings of scaffolds or implants could provide a new tool to control both cell influx and outflux from the scaffold post-implantation. Finally, the similarity of motogenic behavior of both rabbit and human cells suggests the rabbit is a reliable model for assessing MSC recruitment in repair and regeneration strategies.

Myocardial Matrix Remodeling and the Matrix Metalloproteinases: Influence on Cardiac Form and Function

It is now becoming apparent that dynamic changes occur within the interstitium that directly contribute to adverse myocardial remodeling following myocardial infarction (MI), with hypertensive heart disease and with intrinsic myocardial disease such as cardiomyopathy. Furthermore, a family of matrix proteases, the matrix metalloproteinases (MMPs) and the tissue inhibitors of MMPs (TIMPs), has been recognized to play an important role in matrix remodeling in these cardiac disease states. The purpose of this review is fivefold: 1) to examine and redefine the myocardial matrix as a critical and dynamic entity with respect to the remodeling process encountered with MI, hypertension, or cardiomyopathic disease; 2) present the remarkable progress that has been made with respect to MMP/TIMP biology and how it relates to myocardial matrix remodeling; 3) to evaluate critical translational/clinical studies that have provided a cause-effect relationship between alterations in MMP/TIMP regulation and myocardial matrix remodeling; 4) to provide a critical review and analysis of current diagnostic, prognostic, and pharmacological approaches that utilized our basic understanding of MMP/TIMPs in the context of cardiac disease; and 5) most importantly, to dispel the historical belief that the myocardial matrix is a passive structure and supplant this belief that the regulation of matrix protease pathways such as the MMPs and TIMPs will likely yield a new avenue of diagnostic and therapeutic strategies for myocardial remodeling and the progression to heart failure.

Inhibition of MMP-2 gelatinolysis by targeting exodomain-substrate interactions

MMP-2 (matrix metalloproteinase 2) contains a CBD (collagen-binding domain), which is essential for positioning gelatin substrate molecules relative to the catalytic site for cleavage. Deletion of the CBD or disruption of CBD-mediated gelatin binding inhibits gelatinolysis by MMP-2. To identify CBD-binding sites on type I collagen and collagen peptides with the capacity to compete CBD binding of gelatin and thereby inhibit gelatinolysis by MMP-2, we screened a one-bead one-peptide combinatorial peptide library with recombinant CBD as bait. Analyses of sequences from the CBD-binding peptides pointed to residues 715-721 in human alpha1(I) collagen chain as a binding site for CBD. A peptide (P713) including this collagen segment was synthesized for analyses. In SPR (surface plasmon resonance) assays, the CBD and MMP-2(E404A), a catalytically inactive MMP-2 mutant, both bound immobilized P713 in a concentration-dependent manner, but not a scrambled control peptide. Furthermore, P713 competed gelatin binding by the CBD and MMP-2(E404A). In control assays, neither of the non-collagen binding alkylated CBD or MMP-2 with deletion of CBD (MMP-2DeltaCBD) bound P713. Consistent with the exodomain functions of the CBD, P713 inhibited approximately 90% of the MMP-2 gelatin cleavage, but less than 20% of the MMP-2 activity on a peptide substrate (NFF-1) which does not require the CBD for cleavage. Confirming the specificity of the inhibition, P713 did not alter MMP-2DeltaCBD or MMP-8 activities. These experiments identified a CBD-binding site on type I collagen and demonstrated that a corresponding synthetic peptide can inhibit hydrolysis of type I and IV collagens by competing CBD-mediated gelatin binding to MMP-2.

Reduced migration, altered matrix and enhanced TGFbeta1 signaling are signatures of mouse keratinocytes lacking Sdc1

We have reported previously that syndecan-1 (Sdc1)-null mice show delayed re-epithelialization after skin and corneal wounding. Here, we show that primary keratinocytes obtained from Sdc1-null mice and grown for 3-5 days in culture are more proliferative, more adherent and migrate more slowly than wt keratinocytes. However, the migration rates of Sdc1-null keratinocytes can be restored to wild-type levels by replating Sdc1-null keratinocytes onto tissue culture plates coated with fibronectin and collagen I, laminin (LN)-332 or onto the matrices produced by wild-type cells. Migration rates can also be restored by treating Sdc1-null keratinocytes with antibodies that block alpha6 or alphav integrin function, or with TGFbeta1. Antagonizing either beta1 integrin function using a function-blocking antibody or TGFbeta1 using a neutralizing antibody reduced wild-type keratinocyte migration more than Sdc1-null keratinocyte migration. Cultures of Sdc1-null keratinocytes accumulated less collagen than wild-type cultures but their matrices contained the same amount of LN-332. The Sdc1-null keratinocytes expressed similar total amounts of eight different integrin subunits but showed increased surface expression of alphavbeta6, alphavbeta8, and alpha6beta4 integrins compared with wild-type keratinocytes. Whereas wild-type keratinocytes increased their surface expression of alpha2beta1, alphavbeta6, alphavbeta8, and alpha6beta4 after treatment with TGFbeta1, Sdc1-null keratinocytes did not. Additional data from a dual-reporter assay and quantification of phosphorylated Smad2 show that TGFbeta1 signaling is constitutively elevated in Sdc1-null keratinocytes. Thus, our results identify TGFbeta1 signaling and Sdc1 expression as important factors regulating integrin surface expression, activity and migration in keratinocyte and provide new insight into the functions regulated by Sdc1.

Matrix metalloproteinase activity is necessary for thymosin beta 4 promotion of epithelial cell migration

Studies from our laboratory provide substantial evidence that thymosin beta 4, (Tbeta(4)), an actin-sequestering protein, promotes corneal wound healing through its ability to stimulate epithelial cell migration. Matrix metalloproteinases (MMPs), which are expressed in a wide variety of tissues including the cornea, also play a key role in epithelial cell migration and wound healing. In this study we investigated the role of MMPs in Tbeta(4)-stimulated corneal epithelial cell migration. In Boyden chamber assays, XG076, an inhibitor of the conversion of pro- to active MMPs, had no effect on epithelial cell migration stimulated by exogenous activated MMP-1. However, in in vitro migration assays where the activation of pro-MMPs was blocked, XG076 significantly inhibited cell migration and wound healing in the presence or absence of Tbeta(4). GM6001, a broad-spectrum inhibitor of active MMPs and selective MMP inhibitors, also suppressed Tbeta(4)-stimulated cell migration. Tbeta(4) upregulated MMP-1 gene and protein expression in primary human corneal epithelial cells and in transformed human corneal epithelial cells following scrape wounding. From these results we conclude that MMP catalytic activity is necessary for Tbeta(4) promotion of epithelial cell migration. These novel findings are the first to demonstrate a functional link between the two.

Do low-molecular-weight heparins influence the healing process in colon anastomosis?

Anastomosis leakage is one of the most serious complications of colorectal surgery. A role for extracellular matrix remodelling in the healing process of the colon wall has been recently postulated. Changes in matrix metalloproteinase (MMP) activity in the intestinal wall occurring prior to elective resection and primary anastomosis appear to be responsible for dehiscence leading to anastomosis. Thrombophylaxis using low-molecular-weight heparins is routinely administered to all patients during the perioperative period. However, adverse antiproliferative and proapoptotic effects such as limitation of bioavailability of growth factors and angiogenesis inhibition have been characterized in various cell types as a result of heparin administration. It is also likely that relationships exist between extracellular matrix homeostasis and the coagulation/fibrinolysis system. We hypothesize that subcutaneous administration of LMWHs (low-molecular-weight heparins) may influence matrix metalloproteinase activity in the colon wall and increase the risk of postoperative leakage.

Role of Biomarkers in Incisional Hernias

Incisional hernias represent one of the most common complications of laparotomies. Previous investigations have suggested that a disorder in collagen fiber structure and production level may be an important pathologic cause of abdominal wall hernias. We hypothesized that a cross-examination of multiple extracellular matrix biomarkers might identify underlying defects contributing to the development of hernias. We examined two patient populations: patients with incisional hernias (presenting for hernia repair) and patients with no hernia after previous laparotomy (undergoing a second laparotomy). Patients with previous wound infections, open abdomens, or on steroids were excluded. Fascia samples were obtained from all patients at the time of their second operation and they were studied. Western blots and reverse transcriptase-polymerase chain reaction were used to determine the ratio of type I, III, and IV collagens, as well as matrix metalloproteinase 1 (MMP1) and MMP2 in both groups. Values of P < 0.05 were considered statistically significant. At the protein level, collagen I/III ratio was slightly decreased in patients with incisional hernias compared with those with no hernia, whereas it was significantly decreased at the mRNA transcript level (0.49 vs 1.03, P < 0.01, respectively). The MMP-1 mRNA transcripts were not different in incisional hernia (IH) versus nonincisional hernia, but the MMP-2 level was significantly increased in patients with IH. Reduced collagen I/III and MMP-1/MMP-2 ratios in IH might be consequence of the biological activities between key elements participating in the development of IH after laparotomies. The potential role of MMP-2–specific inhibitors in preventing IH is of significance for future studies.

Matrix proteolytic activity during wound healing: modulation by acute ethanol exposure

BACKGROUND

Clinical studies demonstrate that intoxicated patients exhibit an increased incidence of wound healing complications. Previous studies in a murine excisional wound model revealed that acute ethanol exposure impairs the wound healing response, causing decreased angiogenesis and a significant reduction in wound collagen content.

METHODS

Using the same murine model of excisional wounding, we examined the effect of a single dose of ethanol on the overall collagen content and collagen type I and type III mRNA expression, transforming growth factor-beta (TGF-beta) production, and levels of several components of the extracellular matrix proteolytic cascade.

RESULTS

Wounds from ethanol-treated mice exhibited a significant decrease in collagen and in the production of collagen type I mRNA compared with saline controls. Exposure to ethanol also caused significant increase in wound TGF-beta by day 2 after injury (1.69 +/- 0.29 vs 12.34 +/- 3.97 pg/microg protein, p<0.01). In addition, wounds from mice exposed to ethanol had significantly increased levels of active urokinase plasminogen activator at day 7, (205.10 +/- 48.79 vs 642.70 +/- 159.80 pg/microg protein, p<0.001). The level of matrix metalloproteinase-8, a collagen type I proteinase, was 2.2-fold higher in wounds of ethanol-treated mice compared with control at day 7 (p<0.05).

CONCLUSIONS

These studies demonstrate that a single dose of ethanol decreases collagen production, increases the production of TGF-beta and increases levels of matrix degrading enzymes. This alteration in protease balance may partially explain the impaired wound healing that follows acute alcohol intoxication.

Hereditary gingival fibromatosis: characteristics and novel putative pathogenic mechanisms

Hereditary gingival fibromatosis (HGF) is a rare condition that can occur as an isolated disease or as part of a syndrome or chromosomal abnormality. In severe cases, the gingival enlargement may cover the crowns of teeth and cause severe functional and esthetic concerns. Histological and cell culture studies have uncovered some of the molecular and cellular changes associated with HGF. However, the pathogenesis of the disease is still largely unknown. Recent studies about the genetic characteristics of HGF have provided novel clues about the potential pathogenic mechanisms. In particular, mutation in the son-of-sevenless (SOS-1) gene has been associated with one form of the disease. However, HGF displays genetic heterogeneity, and mutations in other genes are also likely involved. This review outlines the current knowledge about the histological, cellular, and genetic characteristics of HGF. In addition, the potential role of the SOS-1 molecule and related novel intracellular signaling pathways in the pathogenesis of HGF will be discussed.

Deletion of Prostaglandin E2 EP2 Receptor Protects against Ultraviolet-Induced Carcinogenesis, but Increases Tumor Aggressiveness

Ultraviolet (UV) light is a complete carcinogen inducing and promoting squamous-cell carcinoma (SCC) of the skin. Recent work has shown that SCC initiation and promotion are enhanced by prostaglandin E2 (PGE2). PGE2 interacts with specific EP receptors to regulate cellular functions. Previous work from our group has shown that the prostaglandin E2 EP2 receptor is a powerful regulator of keratinocyte growth. SKH-1 hairless mice lacking the EP2 receptor were therefore studied to understand how this growth signaling pathway contributes to photocarcinogenesis. Our data indicate that UV-irradiated mice lacking EP2 receptors exhibit decreased proliferation and a poor capacity for epidermal hypertrophy in response to UV injury. In a chronic irradiation model, these animals were protected from tumor formation, developing 50% fewer tumors than wild-type controls. Despite this capacity to protect against tumorigenesis, animals lacking EP2 receptors grew tumors that were larger in size, with a more aggressive phenotype. Further study suggested that this susceptibility may be associated with synthesis of active metalloproteinase enzymes in greater quantities than keratinocytes expressing the EP2 receptor, thereby enhancing the invasive potential of EP2-/- cells.

Effects of applied DC electric field on ligament fibroblast migration and wound healing

Applied electric fields (static and pulsing) are widely used in orthopedic practices to treat nonunions and spine fusions and have been shown to improve ligament healing in vivo. Few studies, however, have addressed the effect of electric fields (EFs) on ligament fibroblast migration and biosynthesis. In the current study, we applied static and pulsing direct current (DC) EFs to calf anterior cruciate ligament (ACL) fibroblasts. ACL fibroblasts demonstrated enhanced migration speed and perpendicular alignment to the applied EFs. The motility of ligament fibroblasts was further modulated on type I collagen. In addition, type I collagen expression increased in ACL fibroblasts after exposure to pulsing EFs. In vitro wound-healing studies showed inhibitory effects of static EFs, which were alleviated with a pulsing EF. Our results demonstrate that applied EFs augment ACL fibroblast migration and biosynthesis and provide potential mechanisms by which EFs may be used for enhancing ligament healing and repair.

Expression of intracellular filament, collagen, and collagenase genes in diabetic and normal skin after injury

Reports have shown differences in gene expression in the skin of diabetic and normal mice both at baseline and after injury. Cluster analysis identified distinct expression patterns within intermediate filaments and extracellular proteins. This report addresses the effect of diabetes and injury on the expression of keratin-associated proteins, keratin complexes, procollagen, and collagenase (matrix metalloproteinase; MMP) genes. At baseline keratin-associated proteins and keratin complexes gene expression was increased in diabetic mice. After surgery, the level of expression for keratin-associated proteins and keratin complexes genes decreased in diabetic mice, but did not change in normal mice. If the expression of a procollagen gene differed between diabetic and normal mice, the expression was lower in diabetic mice. Procollagen gene expression was elevated after skin excision compared with noninjured skin. At baseline, the level of MMP and tissue inhibitor of metalloproteinase gene expression was comparable between mouse strains. With injury, the expression of several MMP genes was increased in both mouse strains, but to higher levels in diabetic mice. At day 7, the level of MMP-9 activity in granulation tissue was elevated. This alteration may contribute to delayed healing in diabetic mice. Therefore, differences in gene expression exist between mouse strains and can assist in understanding of physiological manifestations, including delayed healing, in diabetic mice.

Proteolytic regulatory mechanisms in the formation of extracellular morphogen gradients

Growth factors are secreted into the extracellular space, where they encounter soluble inhibitors, extracellular matrix glycoproteins and proteoglycans, and proteolytic enzymes that can each modulate the spatial distribution, activity state, and receptor interactions of these signaling molecules. During development, morphogenetic gradients of these growth factors pattern fields of cells responsive to different levels of signaling, creating such structures as the branched pattern of airways and vasculature, and the arrangement of digits in the hand. This review focuses specifically on the roles of proteolytic enzymes and their regulators in the generation of such activity gradients. Evidence from Drosophila developmental pathways provides a detailed understanding of general mechanisms underlying proteolytic control of morphogen gradients, while recent studies of several mammalian growth factors illustrate the relevance of this proteolytic control to human development and disease.

Expression of Endo180 is spatially and temporally regulated during wound healing

AIMS

Interactions of cells with the extracellular matrix are important for normal wound healing and may play a role in scar formation. Remarkably, wound healing in human gingiva does not result in scar formation and serves as a model for wound regeneration. Endo180 (CD280) is a cell surface receptor that has novel functions to regulate cell migration and bind and internalize collagens that are key processes in wound healing. The aim of this study was to examine the expression of Endo180 during gingival wound regeneration.

METHODS AND RESULTS

Biopsies were collected from normal human gingiva and 1-60 days after wounding and expression of Endo180 was analysed by immunostaining. Expression of Endo180 by cultured fibroblasts and keratinocytes was studied by immunoblotting and semiquantitative reverse transcriptase-polymerase chain reaction. In normal gingiva, Endo180 was expressed by basal epithelial cells, fibroblasts, myofibroblasts, pericytes, macrophages and endothelial cells. In wounds, Endo180 expression was spatiotemporally increased in the migrating and differentiating wound epithelium, in subsets of myofibroblasts, pericytes, macrophages and endothelial cells. Growth factors involved in wound healing up-regulated the expression of Endo180 in keratinocytes and fibroblasts.

CONCLUSIONS

The findings suggest that Endo180 plays a role in re-epithelialization and connective tissue remodelling during wound regeneration.

Effect of Fibroblasts on Tracheal Epithelial Regenerationin vitro

Several artificial grafts for covering deficient trachea have been produced through tissue engineering. Recently, our group clinically used an artificial trachea made from collagen sponge for patients with noncircumferential tracheal resection. However, the slowness of epithelial regeneration on the surface of the artificial trachea was confirmed as one particular problem. In this study, we co-cultured tracheal epithelial cells with fibroblasts and examined effects of fibroblasts on epithelial regeneration in vitro. Fibroblasts activated epithelial cell proliferation and migration. In co-culture with fibroblasts, epithelial cells reconstructed pseudostratified epithelium, which was composed of ciliated, goblet, and basal cells. Furthermore, a basement membrane was reconstructed between epithelial cells and fibroblasts, and integrin beta4 was also observed there. Fibroblasts rapidly increased mucin secretion by epithelial cells. These results indicate that stimulatory effects of fibroblasts on epithelial cell migration, proliferation, and differentiation would reduce the time required for covering of epithelial cells on the defect of luminal surface and hasten regeneration of morphologically and functionally normalized epithelium involving the reconstruction of basement membrane.

Matrix metalloproteinase 9 (MMP-9) is upregulated during scarless wound healing in athymic nude mice

Cutaneous wound healing is associated with migratory and remodeling events that require the action of matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs). Differences in their expressions were observed during scar-forming and scar-free skin wound healing. We previously found that athymic nude mice are exceptional among mature mammals in their ability to heal injured skin scarlessly. The present study was undertaken to determine whether the modulation of MMP-2 and MMP-9 expression during scarless healing in nude mice was different from scar-forming animals. Full thickness skin wounds were made into the back of nude, wild-type controls (C57BL/6J), immunodeficient SCID and Rag, thymectomized neonates and adults, and cyclosporin A treated mice. Post-injured skin tissues were harvested at Day 7 and 24 after injury. Quantitative RT-PCR, Western blot, gelatin zymography and immunohistochemical assays were performed. Our results show that MMP-2 protein was high but similarly expressed in all post-injured animals on Day 7 after injury. Late phase (Day 24) of wound repair was characterized by a decrease in mRNA and protein expression and a decrease in gelatinolytic activity of MMP-2 in all post-injured samples. On the contrary, high (p < 0.001) levels of mRNA expression, prominent pro-and active forms of MMP-9 and cells immunopositive for MMP-9 were present exclusively in the post-injured tissues from nude mice on Day 24 after wounding. This data suggest that MMP-9 expression in the remodeling phase of wound healing in nude mice could be a major component of their ability for scar-free healing.

Chronic Matrix Metalloproteinase Inhibition Following Myocardial Infarction in Mice: Differential Effects on Short and Long-Term Survival

Left ventricular (LV) remodeling occurs after myocardial infarction (MI), and the matrix metalloproteinases (MMPs) contribute to adverse LV remodeling after MI. Short-term pharmacological MMP inhibition (MMPi; days to weeks) in animal models of MI have demonstrated a reduction in adverse LV remodeling. However, the long-term effects (months) of MMPi on survival and LV remodeling after MI have not been examined. MI was induced in adult mice (n = 131) and, at 3 days post-MI, assigned to MMPi [MI-MMPi: (s)-2-(4-bromo-biphenyl-4-sulfonylamino)-3-methyl-butyric acid (PD200126), 7.5 mg/day/p.o., n = 64] or untreated (MI-only, n = 67). Unoperated mice (n = 16) served as controls. The median survival in the MI-only group was 5 days, whereas median survival was significantly greater in the MI-MMPi group at 38 days (p < 0.05). However, with prolonged MMPi (>120 days), a significant divergence in the survival curves occurred in which significantly greater mortality was observed with prolonged MMPi (p < 0.05). LV echocardiography at 6 months revealed LV dilation in the MI-only and MI-MMPi groups (154 +/- 14 and 219 +/- 24 microl) compared with control (67 +/- 4 microl, p < 0.05), with a greater degree of dilation in the MI-MMPi group (p < 0.05). MMPi conferred a beneficial effect on survival early post-MI, but prolonged MMPi (>3 months) was associated with higher mortality and adverse LV remodeling. These unique results suggest that an optimal temporal window exists with respect to pharmacological interruption of MMP activity in the post-MI period.

Annexin I regulates SKCO-15 cell invasion by signaling through formyl peptide receptors

Annexin 1 (AnxA1) is a multifunctional phospholipid-binding protein associated with the development of metastasis in some invasive epithelial malignancies. However, the role of AnxA1 in the migration/invasion of epithelial cells is not known. In this study, experiments were performed to investigate the role of AnxA1 in the invasion of a model epithelial cell line, SKCO-15, derived from colorectal adenocarcinoma. Small interfering RNA-mediated knockdown of AnxA1 expression resulted in a significant reduction in invasion through Matrigel-coated filters. Localization studies revealed a translocation of AnxA1 to the cell surface upon the induction of cell migration, and functional inhibition of cell surface AnxA1 using antiserum (LCO1) significantly reduced cell invasion. Conversely, SKCO-15 cell invasion was increased by approximately 2-fold in the presence of recombinant full-length AnxA1 and the AnxA1 N-terminal-derived peptide mimetic, Ac2-26. Because extracellular AnxA1 has been shown to regulate leukocyte migratory events through interactions with n-formyl peptide receptors (nFPRs), we examined the expression of FPR-1, FPRL-1, and FPRL-2 in SKCO-15 cells by reverse transcriptase-PCR and identified expression of all three receptors in this cell line. Treatment of SKCO-15 cells with AnxA1, Ac2-26, and the classical nFPR agonist, formylmethionylleucylphenylalanine, induced intracellular calcium release consistent with nFPR activation. Furthermore, the nFPR antagonist, Boc2, abrogated the AnxA1 and Ac2-26-induced intracellular calcium release and increase in SKCO-15 cell invasion. Together, these results support an autocrine/paracrine role for membrane AnxA1 in stimulating SKCO-15 cell migration through nFPR activation. The findings in this study suggest that activation of nFPRs stimulates epithelial cell motility important in the development of metastasis as well as wound healing.

Functional basis for the overlap in ligand interactions and substrate specificities of matrix metalloproteinases-9 and -2

The MMPs (matrix metalloproteinases) MMP-9 and -2 each possess a unique CBD (collagen-binding domain) containing three fibronectin type II-like modules. The present experiments investigated whether the contributions to ligand interactions and enzymatic activities by the CBD of MMP-9 (CBD-9) corresponded to those of CBD in MMP-2 (CBD-2). The interactions of recombinant CBD-9 with a series of collagen types and extracellular matrix molecules were characterized by protein-protein binding assays. CBD-9 bound native and denatured type I, II, III, IV and V collagen, as well as Matrigel and laminin, with apparent K(d) values of (0.1-6.8)x10(-7) M, which were similar to the K(d) values for CBD-2 [(0.2-3.7)x10(-7) M]. However, CBD-9 bound neither native nor denatured type VI collagen. We also generated two modified MMPs, MMP-9(E402A) and MMP-2(E404A), by site-specific mutations in the active sites to obtain enzymes with intact ligand binding, but abrogated catalytic properties. In subsequent competitive binding assays, CBD-9 and MMP-9(E402A) inhibited the interactions of MMP-2(E404A) and, conversely, CBD-2 and MMP-2(E404A) competed with MMP-9(E402A) binding to native and denatured type I collagens, pointing to shared binding sites. Importantly, the capacity of CBD-9 to disrupt the MMP-9 and MMP-2 binding of collagen translated to inhibition of the gelatinolytic activity of the enzymes. Collectively, these results emphasize the essential contribution of CBD-9 to MMP-9 substrate binding and gelatinolysis, and demonstrate that the CBDs of MMP-9 and MMP-2 bind the same or closely positioned sites on type I collagen.

Human gingival fibroblast integrin subunit expression on titanium implant surfaces

BACKGROUND

Implant surface characteristics have been shown to modify cell behavior and regulate integrin expression. Integrin expression and resultant integrin-mediated cellular activity are essential components of tissue healing and homeostasis. Although both osseous and soft tissue healing around dental implants are critical to clinical success, there is limited information available on the effect of implant surfaces on integrin expression in soft tissues. Therefore, the aim of this study was to examine integrin expression for gingival fibroblasts on titanium surfaces and the influence of titanium surface roughness on integrin expression and cell morphology.

METHODS

Human gingival fibroblasts were cultured on smooth (polished) and rough (sand-blasted acid-etched) titanium surfaces and a cell culture plastic (control) surface. To analyze integrin expression, total RNA was isolated from experimental and control cells, and levels of integrin subunit mRNA were assessed by reverse transcription-polymerase chain reaction (RT-PCR) using primers specific for the alpha2, alpha4, alpha5, alpha(v), and beta1 integrin subunits and aldolase (internal control). PCR products were analyzed by polyacrylamide gel electrophoresis (PAGE), confirmed via DNA sequencing, and quantified using computer-assisted densitometry. The expression of the integrin subunits was analyzed at the protein level using flow cytometry, as well as fluorescence and confocal laser microscopy. Cell morphology was evaluated using scanning electron microscopy (SEM).

RESULTS

Our experiments demonstrated cellular expression of the alpha2, alpha4, alpha5, alpha(v), and beta1 integrin subunits at both mRNA and protein levels on all surfaces. In addition, the alpha4 and beta1 mRNA levels were significantly increased on smooth titanium relative to plastic surfaces (P <.05) with intermediate mRNA levels found on the rough titanium surfaces. The smooth titanium surfaces exhibited a flat monolayer of cells, while rough titanium surfaces showed cells orienting themselves along surface irregularities.

CONCLUSIONS

These results demonstrate the presence of multiple integrin subunits in human gingival fibroblasts grown in contact with titanium implant surfaces and that titanium surface roughness alters cellular morphology but appears to have limited effects on integrin expression. This study provides insight into the complicated cellular and molecular events occurring at the implant surface that may be critical to optimizing the soft tissue interactions with the soft tissue-implant interface.

The Effect of AgK114 on Wound Healing

AgK114 is a newly isolated membrane-associated protein which is expressed on keratinocytes. Its expression is restricted to dermal sheath cells near sebaceous glands in normal skin. However, it is transiently induced by UV exposure or injury stimulation (Tatefuji T. et al., Biol. Pharm. Bull., 27, 1742-1749, 2004). Thus, the expression pattern of AgK114 suggested its potential role in wound healing response. We report here that expression of AgK114 is induced in the initial 24 h at the edge keratinocytes during keratinocyte migration, followed by disappearance once epithelialization is completed in the murine excisional wound model. We also demonstrate that exogenous recombinant mouse AgK114FL promoted wound healing process. Mouse AgK114FL up-regulated pro-matrix-metalloproteinase-9, vascular endothelial growth factor, transforming growth factor-beta, IL-6, and IL-1beta production in the early stage of wound tissue. Moreover, mouse AgK114FL induced the matrix-metalloproteinase-9 activity of wound fibroblasts prepared from impaired skin in the presence of proinflammatory cytokines. These results suggest that the AgK114 participates in the wound response during the healing process, and promotes wound repair.

Differential expression and localization of WNTs in an animal model of skin wound healing

Wound healing is a dynamic process, and a variety of growth factors have a significant impact on the process. Although the WNT family has a multitude of effects on the state of various physiological pathways, the expression and role of WNT in wounded tissue have remained an enigma. The aim of this study was to assess the expression and localization of WNTs in a murine model of wound healing. RNA isolated from full-thickness cutaneous wounds from day 1 to day 21 postwounding were subjected to reverse transcription-polymerase chain reaction, and expression of WNT3, 4, 5a, and 10b were observed. Immunohistochemistry localized WNT10b to regenerating epithelial cells on day 1 and 3, and WNT4 on day 3 and 5. WNT4 also reacted with fibroblast-like cells beneath the epithelium. The cytoplasmic staining of beta-catenin, a WNT signaling molecule, in the epithelial cells indicates an activation of the WNT signaling pathway. Among target genes downstream of the pathway, matrix metalloproteinases (MMPs) degrade and remodel the extracellular matrix during wound healing. Gelatin zymography showed that MMP9 was expressed from day 1 to day 5. MMP-2 was continuously expressed, but maximally up-regulated at day 5. Activation of MMP-2 coincided with expression of membrane-type 1 MMP, suggesting an involvement of WNTs in this proteolytic cascade. Therefore, WNTs may contribute to the process of wound healing in a spatiotemporal manner.

Tetracycline at Subcytotoxic Levels Inhibits Matrix Metalloproteinase-2 and -9 But Does Not Remove the Smear Layer

BACKGROUND

The antibacterial and anticollagenolytic properties of tetracycline (TCN) are valuable in periodontal therapy, and TCN treatment can remove the smear layer following root instrumentation. However, recent reports pointing to cytotoxic effects of several acids prompted this study to define TCN concentrations that are anticollagenolytic and remove the smear layer, but have low cytotoxicity.

METHODS

Human gingival (hGF) and periodontal ligament (hPDL) cells were treated short- (3 minutes) or long-term (24 hours) with TCN to determine concentrations yielding 50% (TD(50)) and 90% (TD(10)) cell survival. Activity assays measured TCN concentrations with half-maximal inhibition (IC(50)) of matrix metalloproteinase- 2 and -9 (MMP-2 and -9). Finally, we analyzed the effects of TCN with high (75 mg/ml) or low (1 mg/ml) cytotoxicity on the smear layer by scanning electron microscopy (SEM).

RESULTS

The TD(50) for TCN after short-term treatment was 4 mg/ml for both hGF and hPDL. Ninety percent of the cells survived 0.2 mg/ml. With long-term treatment, the TD(50) for hGF and hPDL was 70 and 30 microg/ml, respectively, and the TD(10) was 20 and 5 microg/ml. HGF and hPDL recovered from the 3-minute treatment with 1 mg/ml, but not from concentrations exceeding 3 and 9 mg/ml, respectively. The IC(50) was 25 microg/ml for both MMP-2 and MMP-9. Whereas 75 mg/ml TCN removed the smear layer, 1 mg/ml TCN had no effects.

CONCLUSIONS

Tetracycline has significant cytotoxicity on periodontal cells. Since non-cytotoxic concentrations of TCN inhibited MMP-2 and -9 but had no effects on the smear layer, TCN is not recommended for root surface treatment.

Zymographic techniques for the analysis of matrix metalloproteinases and their inhibitors

The balance between matrix metalloproteinases (MMPs) and their inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), is largely responsible for the remodeling of tissues. Deregulation of this balance is a characteristic of extensive tissue degradation in certain degenerative diseases. To analyze the role of MMPs and TIMPs in tissue remodeling under normal and pathological conditions, it is important to have reliable detection methods. This review will focus on zymographical techniques for the analysis of MMPs and TIMPs. MMPs can be analyzed with several zymographical techniques, but substrate zymography is the most commonly used. This technique identifies MMPs by the degradation of their preferential substrate and by their molecular weight. Several substrates that can be used for zymography are described. Reverse zymography, which detects TIMPs by their ability to inhibit MMPs, is also discussed. Finally, in situ zymography is described, which is used to localize MMPs in tissue sections. Common problems encountered during sample preparation, zymography itself and the data analysis are discussed. Hints are given to improve the sensitivity and accuracy of zymographical methods. In conclusion, zymography is a valuable tool for research purposes and for the development of new diagnostic techniques and therapies for pathological conditions such as rheumatoid and osteoarthritis, and tumor progression.

Identification of the novel membrane-associated protein AgK114 on hamster keratinocytes recognized by a monoclonal antibody K114

We have established a monoclonal antibody K114 (mAbK114) against hamster keratinocytes. The mAbK114 recognizes a 50-95 kDa cell-surface protein that is expressed restrictedly in the dermal sheath cells near the bulge area of the hair follicle and in the differentiated sebocytes of the normal adult hamster skin. Upon being cultured in vitro, however, the keratinocytes strongly and transiently expressed this novel K114 antigen (AgK114) in spite of low expression level of AgK114 by the freshly prepared keratinocytes. The cDNA of AgK114 was isolated by expression cloning using mAbK114. Sequence analysis revealed that it had 242 amino acid residues with a signal peptide at the N terminus, potential six N-glycosylation sites, a characteristic repetitive threonine rich domain, and a possible glycosylphosphatidylinositol (GPI) anchoring site near the C terminus. We examined various conditions in which expression of AgK114 was enhanced in vivo. Interestingly, AgK114 molecule was expressed accompanying tissue damages of the skin. It was transiently induced in basal epidermal keratinocytes after UV exposure. In addition, AgK114 was also induced in elongating edge epidermal keratinocytes during tissue regeneration after an excised wounding. These results suggest that AgK114 is involved in the recovering process from injury.

Contributions of the MMP-2 collagen binding domain to gelatin cleavage. Substrate binding via the collagen binding domain is required for hydrolysis of gelatin but not short peptides

Two matrix metalloproteinases, MMP-2 and MMP-9, contain each three fibronectin type II-like modules, which form their collagen binding domains (CBDs). The contributions of CBD substrate interactions to the catalytic activities of these gelatinases have attracted special interest. Recombinant (r) CBDs retain collagen binding properties and deletions of CBDs in these MMPs reduce activities on collagen and elastin. We have characterized further the requirement of the CBD for MMP-2 cleavage of gelatin. The analyses used intact rMMP-2 and rCBD to eliminate any confounding effects that might result from structural perturbations in rMMP-2 induced by deletion of the approximately 20 kDa internal CBD. In protein-protein binding assays, 2% DMSO disrupted gelatin interactions of both rCBD and rMMP-2. At this concentration, DMSO also reduced the gelatinolytic activity by approximately 70%, pointing to a central role of CBD-substrate interactions during MMP-2 cleavage of gelatin. Subsequently, soluble rCBD was determined to competitively inhibit gelatin binding of unmodified rMMP-2 to gelatin by 73% and to reduce the MMP-2 degradation of gelatin by 70-80%. The residual gelatin cleavage that was not inhibited even by molar excess rCBD could be accounted for by degradation of short substrate molecules. Indeed, rCBD inhibited rMMP-2 cleavage of an 11 amino acid collagen-like peptide substrate (NFF-1) by less than 10%. These observations were confirmed with enzyme extracts from experimental tumors in mice. In the presence of rCBD, approximately 65% of the MMP-derived gelatinolytic activity was eliminated. Together, these results demonstrate that the CBD is absolutely required for MMP-2 cleavage of full-length collagen alpha-chains, but not for short protein fragments such as those generated by hydrolysis of gelatin.

Matrix Metalloproteinase-2 Contributes to Cancer Cell Migration on Collagen

Matrix metalloproteinases (MMP) are central to tissue penetration by cancer cells, as tumors expand and form metastases, but the mechanism by which MMP-2 contributes to cancer cell migration is not well understood. In the present experiments, both a broad-spectrum MMP inhibitor and the isolated collagen binding domain (CBD) from MMP-2 inhibited cell migration on native type I collagen. These results verified the involvement of MMPs in general and showed that MMP-2, specifically, contributes to cell migration by a mechanism involving MMP-2 interaction with collagen. To exclude potential overlapping effects of MMP-9, additional experiments showed that MMP-2 also contributed to migration of MMP-9−/− cells. To investigate whether the homologous CBD from human fibronectin also inhibited cell migration, we first showed that fragmentation of fibronectin is a feature of breast cancer tumors and that several fragments contained the CBD. However, the recombinant fibronectin domain did not alter cell migration on collagen. This lack of effect on cell migration was explored in competitive protein-protein binding assays, which showed that the affinity of MMP-2 for collagen exceeds that of fibronectin. Furthermore, whereas the isolated MMP-2 CBD inhibited the gelatinolytic activities of MMP-2 and tumor extracts, such an inhibition was not characteristic of the corresponding fibronectin domain. Together, our results provide evidence that MMP-2 is an important determinant of cancer cell behavior but is not inhibited by the collagen binding segment of fibronectin.

Advances in the Modulation of Cutaneous Wound Healing and Scarring

Cutaneous wounds inevitably heal with scars, which can be disfiguring and compromise function. In general, the greater the insult, the worse the scarring, although genetic make up, regional variations and age can influence the final result. Excessive scarring manifests as hypertrophic and keloid scars. At the other end of the spectrum are poorly healing chronic wounds, such as foot ulcers in diabetic patients and pressure sores. Current therapies to minimize scarring and accelerate wound healing rely on the optimization of systemic conditions, early wound coverage and closure of lacerations, and surgical incisions with minimal trauma to the surrounding skin. The possible benefits of topical therapies have also been assessed. Further major improvements in wound healing and scarring require an understanding of the molecular basis of this process. Promising strategies for modulating healing include the local administration of platelet derived growth factor (PDGF)-BB to accelerate the healing of chronic ulcers, and increasing the relative ratio of transforming growth factor (TGF)beta-3 to TGFbeta-1 and TGFbeta-2 in order to minimize scarring.

Jararhagin, a snake venom metalloproteinase-disintegrin, stimulates epithelial cell migration in an in vitro restitution model

The snake venom metalloproteinase-disintegrin jararhagin (JG) has no chemotactic activity but stimulates the migration of neutrophils in vivo through a mechanism still unclear. In this study we investigated the effects of jararhagin on epithelial cell adhesion and migration in vitro. F-actin arrangement and the distribution of laminin, fibronectin, several integrins and phosphorylated Focal Adhesion Kinase (FAK) were studied using rhodamine-phalloidin and immunofluorescence. Maximum stimulation of migration (about 100%) was obtained with 5 microg/ml JG, with about 38% inhibition of cellular adhesion. In migratory cells the toxin stimulated the formation of filopodia, lamellipodia and stress fibers. The pericellular fibronectin matrix was lost in migrating cells, while laminin was less affected. The toxin stimulated FAK phosphorylation and the recruitment of alphav-containing integrins to focal contacts, whereas integrins containing the alpha2 subunit were reduced in these junctions. Inactivation of the toxin with 1,10 phenanthroline showed that the catalytic activity is important for the effect of jararhagin on cell migration, FAK phosphorylation and for the recruitment of alphav, but not as much for the anti-adhesive effect. In conclusion, jararhagin stimulates the migration of epithelial cells in vitro through a mechanism that involves its proteolytic activity, qualitative changes in cellular adhesion and the formation of actin-rich cellular processes.

Heparin II domain of fibronectin uses alpha4beta1 integrin to control focal adhesion and stress fiber formation, independent of syndecan-4

Co-signaling events between integrins and cell surface proteoglycans play a critical role in the organization of the cytoskeleton and adhesion forces of cells. These processes, which appear to be responsible for maintaining intraocular pressure in the human eye, involve a novel cooperative co-signaling pathway between alpha5beta1 and alpha4beta1 integrins and are independent of heparan sulfate proteoglycans. Human trabecular meshwork cells isolated from the eye were plated on type III 7-10 repeats of fibronectin (alpha5beta1 ligand) in the absence or presence of the heparin (Hep) II domain of fibronectin. In the absence of the Hep II domain, cells had a bipolar morphology with few focal adhesions and stress fibers. The addition of the Hep II domain increased cell spreading and the numbers of focal adhesions and stress fibers. Cell spreading and stress fiber formation were not mediated by heparan sulfate proteoglycans because treatment with chlorate, heparinase, or soluble heparin did not prevent Hep II domain-mediated cell spreading. Cell spreading and stress fiber formation were mediated by alpha4beta1 integrin because soluble anti-alpha4 integrin antibodies inhibited Hep II domain-mediated cell spreading and soluble vascular cell adhesion molecule-1 (alpha4beta1 ligand)-induced cell spreading. This is the first demonstration of the Hep II domain mediating cell spreading and stress fiber formation through alpha4beta1 integrin. This novel pathway demonstrates a cooperative, rather than antagonistic, role between alpha5beta1 and alpha4beta1 integrins and suggests that interactions between the Hep II domain and alpha4beta1 integrin could modulate the strength of cytoskeleton-mediated processes in the trabecular meshwork of the human eye.

Matrix metalloproteinase inhibitor GM 6001 attenuates keratinocyte migration, contraction and myofibroblast formation in skin wounds

In this study, we examined the impact of matrix metalloproteinases (MMP) on epithelialization, granulation tissue development, wound contraction, and alpha-smooth muscle actin (ASMA) expression during cutaneous wound repair through systemic administration of the synthetic broad-spectrum MMP inhibitor GM 6001 (N-[(2R)-2-(hydroxamidocarbonylmethyl)-4-methylpentanoyl]-L-tryptophan methylamide). Four full-thickness excisional wounds (50 mm2) on the back of 22 young female Sprague-Dawley rats, 12 treated with GM 6001 100 mg/kg and 10 with vehicle, were allowed to heal by secondary intention. GM 6001-treated wounds were minimally resurfaced with neoepithelium, despite unaltered keratinocyte proliferation in wound edges, whereas control wounds were completely covered with 3-7 cell layers of parakeratinized epithelium on post-wounding day 7. Hydroxyproline concentration, a marker of collagen, and cell proliferation in granulation tissue did not differ significantly between GM 6001-treated and control groups. Impaired wound contraction (P < 0.01) was associated with a dramatic reduction of ASMA-positive myofibroblasts in granulation tissue of GM 6001 wounds. This was not due to GM6001 blocking transforming growth factor-beta1 (TGF-beta1)-induced myofibroblast differentiation since GM 6001 did not inhibit TGF-beta1-induced ASMA expression and force generation in cultured rat dermal fibroblasts. The profound impairment of skin repair by the nonselective MMP inhibitor GM 6001 suggests that keratinocyte resurfacing, wound contraction, and granulation tissue organization are highly MMP-dependent processes.

An evaluation of Hyalofill-F plus compression bandaging in the treatment of chronic venous ulcers

OBJECTIVE

Hyaluronan, a component of the extracellular matrix, plays a significant role in several aspects of tissue repair and the wound healing process.

METHOD

In this Italian study Hyalofill-F, a partial benzyl ester derivative of hyaluronan, used in combination with compression bandaging, was compared with the well-established therapy in Italy of non-adherent gauze plus compression therapy in the treatment of chronic venous leg ulcers.

RESULTS

Hyalofill-F plus compression bandaging performed significantly better than non-adherent gauze plus compression bandage in all of the clinically relevant efficacy parameters. Mean reduction in ulcer area in the hyaluronan-derivative group was 8.1 cm2 after eight weeks of treatment, compared with 0.4 cm2 in the comparator group. The resulting difference of 7.7 cm2 between the two groups was statistically significant (p = 0.0019). Furthermore, statistically significant results in favour of the hyaluronan-derivative group were obtained in the following: speed of epithelialisation; leveling of the margins; degree of maceration; pain intensity and frequency.

CONCLUSION

Hyalofill-F plus compression bandaging resulted in an earlier and greater decrease in ulcer area compared with non-adherent gauze plus compression bandaging, therapy supporting its use in the treatment of chronic venous ulcers.

MT1‐MMP: A tethered collagenase

Gene ablation in mice offers a powerful tool to assay in vivo the role of selected molecules. Numerous new mouse models of matrix metalloproteinases (MMP) deficiency have been developed in the past 5 years and have yielded a new understanding of the role of MMPs while also putting to rest assumptions based on data predating the days of mouse models. The phenotype of the MT1-MMP deficient mouse is one example which illustrates the sometimes rather surprising insights into extracellular matrix remodeling in development and growth that can be gained with mouse genetics. While MT1-MMP appears to play little or no role in embryonic development, loss of this enzyme results in progressive impairment of postnatal growth and development affecting both the skeleton and the soft connective tissues. The underlying pathologic mechanism is loss of an indispensable collagenolytic activity, which remains essentially uncompensated. Our findings demonstrate that growth and maintenance of the skeleton requires coordinated and simultaneous MT1-MMP-dependent remodeling of all soft tissue attachments (ligaments, tendons, joint capsules). We note that the phenotype of the MT1-MMP deficient mouse bears no resemblance to those of mice deficient in MMP-2 and tissue inhibitors of metallo-proteinase (TIMP)-2 all but dispelling the view that activation of MMP-2 by the MT1-MMP/TIMP-2/proMMP-2 axis plays a significant role in growth and development throughout life. It is of interest to note that loss of a single catabolic function such as selective collagen degradation mediated by MT1-MMP gives rise to profound impairment of a number of both anabolic and catabolic functions.

Extracellular matrix metabolites as potential biomarkers of disease activity in wound fluid: lessons learned from other inflammatory diseases?

The new era of pharmacogenetics has identified a potential for individuals to receive customized treatments for a variety of disease states. For such individualized treatments to fulfil their potential, it will be essential for clinicians to be able to monitor disease activity, ideally in a rapid, noninvasive fashion. The accessibility of the skin offers much potential to develop noninvasive tests of metabolic and disease activity for clinical use. Impaired human wound healing in the skin is a chronic inflammatory disorder in which the development of such tests has considerable potential, aiding clinical decision making and monitoring responses to treatment. This review article discusses how studies in other human diseases have highlighted potential biochemical markers (biomarkers) of disease activity in secreted biofluids, as aids to determining disease and metabolic activity within tissues. Using, as examples, lessons learned in the study of disease activity and prognosis of other chronic inflammatory conditions, such as osteoarthritis and periodontal disease, this review highlights the potential of dermal extracellular matrix (ECM) components (collagens, proteoglycans, hyaluronan and glycoproteins) for such uses. The limitations of currently utilized techniques and the concept that analysis of ECM components in wound fluid may represent useful biomarkers of disease activity are also discussed.

Fibroblasts facilitate re-epithelialization in wounded human skin equivalents

The re-epithelialization of the wound involves the migration of keratinocytes from the edges of the wound. During this process, keratinocyte migration and proliferation will depend on the interaction of keratinocytes with dermal fibroblasts and the extracellular matrix. The present study aimed to investigate (1) the role of fibroblasts in the re-epithelialization process and on the reconstitution of the dermal-epidermal junction (DEJ) and (2) differential protein expression during re-epithelialization. For both purposes, three-dimensional human skin equivalents (HSE) were used. A full-thickness wound in HSE was introduced by freezing with liquid nitrogen and a superficial wound by linear incision with a scalpel. The closure of the wound in the absence or presence of exogenous growth factors was followed by monitoring the rate of re-epithelialization and regeneration of the DEJ. The results obtained in this study demonstrate that fibroblasts facilitate wound closure, but they differentially affected the deposition of various basement membrane components. The deposition of laminin 5 at the DEJ was delayed in superficial wounds as compared to the full-thickness wounds. During freeze injury, some basement membrane (BM) components remain associated with the dermal compartment and probably facilitate the BM reconstitution. The re-epithelialization process in full-thickness but not in superficial wounds was accelerated by the presence of keratinocyte growth factor and especially by epidermal growth factor. In addition, we have examined the deposition of various basement membrane components and the differences in protein expression in a laterally expanding epidermis in uninjured HSE. Laminin 5, type IV and VII collagen deposition was decreased in the laterally expanding epidermis, indicating that the presence of these proteins is not required for keratinocyte migration to occur in vitro. Using two-dimensional polyacrylamide gel electrophoresis, we have identified DJ-1, a protein not earlier reported to be differently expressed during the epithelialization process of the skin.

Osteopontin inhibits interleukin-1beta-stimulated increases in matrix metalloproteinase activity in adult rat cardiac fibroblasts: role of protein kinase C-zeta

We have shown that osteopontin (OPN), an extracellular matrix protein, plays an important role in post myocardial infarction (MI) remodeling by promoting collagen synthesis and accumulation. Interleukin-1beta (IL-1beta), increased in the heart following MI, increases matrix metalloproteinase (MMP) activity in cardiac fibroblasts in vitro. Here, we show that OPN alone has no effect on MMP activity or expression. However, it reduces IL-1beta-stimulated increases in MMP activity and expression in adult rat cardiac fibroblasts. Pretreatment with bovine serum albumin had no effect on MMP activity or protein content, whereas GRGDS (glycine-arginine-glycine-aspartic acid-serine)-pentapeptide (which interrupts binding of RGD-containing proteins to cell surface integrins) and monoclonal antibody m7E3 (a rat beta3 integrins antagonist) inhibited the effects of OPN. Inhibition of PKC using chelerythrine inhibited the activities of both MMP-2 and MMP-9. Stimulation of cells using IL-1beta increased phosphorylation and translocation of PKC to membrane fractions, which was inhibited by OPN. OPN inhibited IL-1beta-stimulated increases in translocation of PKC-zeta from cytosolic to membrane fractions. Furthermore, the levels of phospho-PKC-zeta were lower in the cytosolic fractions of OPN knock-out mice hearts as compared with wild type 6 days post-MI. Inhibition of PKC-zeta using PKC-zeta pseudosubstrate inhibited IL-1beta-stimulated increases in MMP-2 and MMP-9 activities. These observations suggest that OPN, acting via beta3 integrins, inhibits IL-1beta-stimulated increases in MMP-2 and MMP-9 activity, at least in part, via the involvement of PKC-zeta. Thus, OPN may play a key role in collagen deposition during myocardial remodeling following MI by modulating cytokine-stimulated MMP activity.

Colonic anastomotic strength and matrix metalloproteinase activity in an experimental model of bacterial peritonitis

BACKGROUND

Clinical studies report conflicting results on the safety of primary intestinal anastomoses in the presence of peritonitis, and comprehensive experimental data are lacking. The present study investigated whether the strength of experimental colonic anastomoses is affected if surgery is performed in the presence of pre-existing bacterial peritonitis.

METHODS

Colonic anastomoses were constructed in Wistar rats 24 h after caecal ligation and puncture or a sham procedure. Anastomotic strength was assessed by measuring breaking strength and bursting pressure during the first 5 days after operation. Anastomotic hydroxyproline levels were measured and matrix metalloproteinase (MMP) activity was analysed by quantitative gelatin zymography.

RESULTS

Anastomotic strength was lowered in the presence of bacterial peritonitis but in a minor and transient way. The breaking strength was lower only immediately after construction of the anastomosis (- 15 per cent, P = 0.011) and the bursting pressure only on the third postoperative day (- 33 per cent, P = 0.038); no anastomotic dehiscence was observed. At 3 days after operation increased levels of MMP activity were observed but anastomotic hydroxyproline content was not affected by bacterial peritonitis.

CONCLUSION

The influence of bacterial peritonitis on the development of anastomotic strength is limited. This experimental finding lends support to recent clinical studies that have demonstrated the feasibility of constructing a primary anastomosis under these conditions.

Matrix metalloproteinase activity correlates with blastema formation in the regenerating MRL mouse ear hole model

The MRL mouse was proposed as a model of mammalian regeneration because it can close ear holes completely with the restoration of normal tissue. This regeneration process involves the formation of a blastema during healing, the re-appearance of cartilage and hair follicles, and healing without scarring. Such a process requires extensive tissue remodeling. To characterize differences in ear wounding responses between regenerating and nonregenerating mice, we examined and compared the extracellular matrix remodeling and the matrix metalloproteinase (MMP) and tissue inhibitor of metalloproteinase (TIMP) response in the MRL and C57BL/6 mouse strains after injury. We found a correlation between the MRL's ability to break down the basement membrane, form a blastema, and close ear hole wounds and an inflammatory response with neutrophils and macrophages seen in the ear after injury. These cells were positive for MMP-2 and MMP-9 as well as TIMP-2 and TIMP-3. Clear differences between the MRL and B6 response to injury were seen that could explain the differences in healing and blastema formation in the MRL and lack of it in the B6 mice. This finding was further supported by enzyme activity as determined by gelatin zymography.