Platelet factor 4 upregulates matrix metalloproteinase-1 production in gingival fibroblasts

BACKGROUND AND OBJECTIVE

Periodontitis is a highly prevalent chronic inflammatory disease that causes tooth loss, morbidity and confers an increased risk for systemic disease. Tissue destruction during periodontitis is due in large part to collagen-degrading matrix metalloproteinases (MMPs) released by resident cells of the periodontium in response to proinflammatory cytokines. Platelets are immune-competent blood cells with a newly recognized role in chronic inflammation; however, their role in the pathogenesis of periodontitis is undefined. Consequently, the objective of this study was to assess the effect of platelet factor 4 (PF4), a major platelet-derived cytokine, on MMP-1 (collagenase) expression in human gingival fibroblasts (HGFs).

MATERIAL AND METHODS

HGFs were cultured in the presence or absence of recombinant PF4. Pro-MMP-1 secretion was quantified by enzyme-linked immunosorbent assay analysis of the cell culture supernatants. MMP-1 transcription was quantified by real-time polymerase chain reaction. Regulation of MMP-1 production by the p44/42 MAP kinase (MAPK) signaling pathway was examined in the presence or absence of PF4.

RESULTS

Exposure to PF4 caused a ~ 2-3-fold increase in MMP-1 transcription and secretion from cultured HGFs. PF4 treatment also enhanced phosphorylation of p44/42 MAPK, which has been previously shown to induce MMP-1 expression in fibroblasts. Blockade of p44/42 MAPK signaling with the cell-permeant inhibitors PD98059 and PD184352 abrogated PF4-induced pro-MMP-1 transcription upregulation and release from cultured HGFs.

CONCLUSION

We conclude that PF4 upregulates MMP-1 expression in HGFs in a p44/42 MAPK-dependent manner. These findings point to a previously unidentified role for platelets in the pathogenesis of periodontal diseases.

Epithelial Microvesicles Promote an Inflammatory Phenotype in Fibroblasts

Microvesicles (MVs) are extracellular vesicles secreted by various cell types that are involved in intercellular communication. We hypothesized that in human periodontal disease, the pocket epithelium releases MVs, which then modulate gene expression in the underlying fibroblasts to control periodontal inflammation. MVs were isolated from culture medium of gingival epithelial cells (GECs) treated with oral bacterial biofilm extract or left untreated. Biofilm treatment significantly increased MV release from the GECs. Mass spectrometry of GEC-MVs identified a total of 2,173 proteins, of which about 80% were detected in MVs from both control and biofilm-treated GECs. Among 80 signature genes of human gingival fibroblasts, 20 were significantly regulated ( P < 0.05) by MVs from control and biofilm-treated GECs in a similar manner. Matrix metalloproteinase 1 and 3 and interleukin 6 and 8 showed the strongest regulation at the mRNA and protein levels. Several cellular signaling pathways were activated by GEC-MVs in human gingival fibroblasts, including Smad and mitogen-activated protein kinase–associated pathways ERK1/2, JNK, and p38. However, ERK1/2 signaling dominated in the MV-induced gene expression changes. The results demonstrate that GEC-MVs have a strong regulatory effect on the expression of fibroblast genes associated with inflammation and matrix degradation and that bacterial biofilm stimulates the generation of GEC-MVs. This suggests that bacterial biofilms can contribute to the initiation and progression of periodontal disease by promoting a tissue-destructive phenotype in gingival fibroblasts via the enhanced secretion of epithelial MVs.

Characterisation of human gingival neural crest-derived stem cells in monolayer and neurosphere cultures

Neural crest (NC)-derived stem cells (NCSC) have an exceptionally wide differentiation potential, but their use in regenerative therapy has been hampered by their scarcity in adult tissues and complex isolation protocols. Human oral mucosal gingiva may provide an attractive source of these cells as it contains NC-derived cells, the tissue is easily accessible and wound healing is fast and scarless with very little morbidity. To this end, we first investigated whether NC-derived cells are retained in adult gingiva by examining 8-months-old NC-reporter Wnt1-Cre/R26RYFP mice. We then hypothesised that gingival cell NC-like phenotype can be further enhanced by floating neurosphere cultures generated from standard human gingival fibroblast (GF) and pooled CFU-F (GSC) cultures. Findings showed that NC-derived cells are retained in the gingival connective tissue of aged mice. Human GFs and GSCs expressed NC-related genes nestin, Snai1, Twist1, Pax3, Sox9 and FoxD3, and generated neurospheres. This was mediated via calcium- and connexin 43-dependent cell communication, which is similar to neurospheres formed by neural progenitors. Cells in the spheres showed significantly increased expression of NC-related genes, and down regulation of fibroblast-related type I collagen. Structurally, the neurospheres were polarised with nestin positive cells located on the outer layers underlined with an extracellular matrix rich in molecules typical to embryonic NC. Sphere-derived cells expressed significantly elevated levels of neural markers, and differentiated into Tau, neurofilament-M and GFAP-positive cells suggesting neural differentiation potential. Thus, human GF and GSC cultures may provide an efficient source of NC-derived cells via enrichment by floating sphere cultures.

Antimicrobial Resistance Profiles of Campylobacter spp. Isolated from Broiler Chicken Meat of Estonian, Latvian and Lithuanian Origin at Estonian Retail Level and from Patients with Severe Enteric Infections in Estonia

The resistance patterns of Campylobacter spp. isolated from retail broiler chicken meat originating either from Estonia, Lithuania or Latvia collected in Estonia were determined. Additionally, in collaboration with the laboratories of several Estonian hospitals, antimicrobial susceptibility patterns were determined for Campylobacter isolates from patients with severe Campylobacter enteric infections. The isolates were identified at the species level by the PCR method. Respectively, 88.8% of the isolates were C. jejuni, and 11.2% were C. coli. In total, 126 Campylobacter isolates of broiler chicken meat and human origin were tested for minimal inhibitory concentrations (MICs) with the broth microdilution VetMIC(TH) method (National Veterinary Institute; Uppsala, Sweden) for a total of six antimicrobials. Resistance to one or more antimicrobials was detected in 62 (63.3%) of Campylobacter broiler chicken meat isolates and in 20 (71.4%) of human-origin isolates. Large proportions of the broiler chicken meat isolates were resistant to ciprofloxacin (60.2%). Multidrug resistance (i.e. to three or more unrelated antimicrobials) was detected in five (5.1%) C. jejuni isolates. Among the human isolates, 20 (71.4%) were resistant to fluoroquinolones, and two (7.1%) C. jejuni isolates exhibited multidrug resistance. The chicken meat isolates of Estonian origin were the most susceptible. However, a high proportion of fluoroquinolone-resistant C. jejuni isolates were found in Latvian and Lithuanian products. The results of this study indicate that the problems caused by the inappropriate use of antimicrobials extend beyond the country in which a food originates; therefore, both domestic and international interventions and agreements are required to implement common policies on antimicrobial usage and to minimize the emergence of Campylobacter drug resistance.

Critical role for αvβ6 integrin in enamel biomineralization

Tooth enamel has the highest degree of biomineralization of all vertebrate hard tissues. During the secretory stage of enamel formation, ameloblasts deposit an extracellular matrix that is in direct contact with ameloblast plasma membrane. Although it is known that integrins mediate cell-matrix adhesion and regulate cell signaling in most cell types, the receptors that regulate ameloblast adhesion and matrix production are not well characterized. Thus, we hypothesized that αvβ6 integrin is expressed in ameloblasts where it regulates biomineralization of enamel. Human and mouse ameloblasts were found to express both β6 integrin mRNA and protein. The maxillary incisors of Itgb6−/− mice lacked yellow pigment and their mandibular incisors appeared chalky and rounded. Molars of Itgb6−/− mice showed signs of reduced mineralization and severe attrition. The mineral-to-protein ratio in the incisors was significantly reduced in Itgb6−/− enamel, mimicking hypomineralized amelogenesis imperfecta. Interestingly, amelogenin-rich extracellular matrix abnormally accumulated between the ameloblast layer of Itgb6−/− mouse incisors and the forming enamel surface, and also between ameloblasts. This accumulation was related to increased synthesis of amelogenin, rather than to reduced removal of the matrix proteins. This was confirmed in cultured ameloblast-like cells, which did not use αvβ6 integrin as an endocytosis receptor for amelogenins, although it participated in cell adhesion on this matrix indirectly via endogenously produced matrix proteins. In summary, integrin αvβ6 is expressed by ameloblasts and it plays a crucial role in regulating amelogenin deposition/turnover and subsequent enamel biomineralization.

Epithelial integrins with special reference to oral epithelia

Adhesion of epithelium to the extracellular matrix is crucial for the maintenance of systemic and oral health. In the oral cavity, teeth or artificial dental implants penetrate the soft tissue of the gingiva. In this interface, gingival soft tissue needs to be well attached via the epithelial seal to the tooth or implant surface to maintain health. After injury or wounding, epithelial tissue rapidly migrates to form the initial epithelial cover to restore the barrier against infection. These events are crucially dependent on deposition of extracellular matrix and proper activation and function of integrin receptors in the epithelial cells. Recent experimental evidence suggests that epithelial integrins also participate in the regulation of periodontal inflammation. In this review, we will discuss the structure and function of epithelial integrins and their extracellular ligands and elaborate on their potential role in disease and repair processes in the oral cavity.

Mortality in offspring of mothers with psychotic disorder

BACKGROUND

Previous studies suggest that offspring of mothers with psychotic disorders have an almost two-fold higher mortality risk from birth until early adulthood. We investigated predictors of mortality from late adolescence until middle age in offspring of mothers with psychotic disorders.

METHOD

The Helsinki High-Risk Study follows up offspring (n=337) of women treated for schizophrenia spectrum disorders in mental hospitals in Helsinki before 1975. Factors related to mortality up to 2005 among offspring of these mothers was investigated with a survival model. Hazard rate ratios (HRR) were calculated using sex, diagnosis of psychotic disorder, childhood socio-economic status, maternal diagnosis, and maternal suicide attempts and aggressive symptoms as explanatory variables. The effect of family was investigated by including a frailty term in the model. We also compared mortality between the high-risk group and the Finnish general population.

RESULTS

Within the high-risk group, females had lower all-cause mortality (HRR 0.43, p=0.05) and mortality from unnatural causes (HRR 0.24, p=0.03) than males. Having themselves been diagnosed with a psychotic disorder was associated with higher mortality from unnatural causes (HRR 4.76, p=0.01), while maternal suicide attempts were associated with higher suicide mortality (HRR 8.64, p=0.03). Mortality in the high-risk group was over two-fold higher (HRR 2.44, p<0.0001) than in the general population, and remained significantly higher when high-risk offspring who later developed psychotic disorders were excluded from the study sample (HRR 2.30, p<0.0001).

CONCLUSIONS

Offspring of mothers with psychotic disorder are at increased risk of several adverse outcomes, including premature death.

Growth pattern and risk of schizophrenia

BACKGROUND

Foetal nutrition and growth seem to affect the risk of developing schizophrenia. Exposure to famine during foetal development and low birthweight increase the risk. However, few studies have investigated the association between schizophrenia and adult height and weight or patterns of growth.

METHOD

The study population consisted of two subpopulations: families with at least one member with schizophrenia, and families of offspring of mothers with psychotic disorder, and controls. Using a seven-parameter model of height growth curves, we compared the parameters of persons who later developed schizophrenia and their unaffected siblings from the same families. We also studied how growth curve parameters differed in children with genetic risk for schizophrenia and controls, and whether weight, height and body mass index (BMI) at different ages predicted later development of schizophrenia.

RESULTS

The predicted growth curves based on a parametric model were nearly identical for persons with schizophrenia and their unaffected siblings. Adult height of daughters of mothers with psychoses was borderline significantly (p=0.0536) lower compared to controls, while no difference was detected among sons (p=0.3283).

CONCLUSIONS

No association between growth characteristics and schizophrenia in families with at least one member with schizophrenia was found. Family-related factors should be taken into account as possible confounders in future studies on growth and schizophrenia.

Expression of fibronectin-binding integrins in gingival epithelium in drug-induced gingival overgrowth

BACKGROUND AND OBJECTIVE

Gingival overgrowth is a side-effect of nifedipine and cyclosporin medications. Integrins are transmembrane glycoproteins that mediate cell adhesion, regulate cell proliferation and participate in the regulation of tissue fibrosis. The aim of this study was to investigate whether expression of epithelial cell integrins is linked to the development of drug-induced gingival overgrowth.

MATERIAL AND METHODS

Human gingival biopsies of patients taking nifedipine, cyclosporin, or a combination of both medications, were used. Expression of the alpha5beta1, alphavbeta1 and alphavbeta6 integrins, and of cellular extra domain A of fibronectin, was localized in frozen sections using immunohistochemistry.

RESULTS

The activated conformation of the beta1, alpha5beta1 and alphavbeta6 integrins were more frequently expressed in distinct locations in the oral epithelium in the combined drug group. Cellular extra domain A of fibronectin, a ligand for both alpha5beta1 and alphavbeta6 integrins, was expressed within the connective tissue of all groups. It was also expressed around the basal keratinocytes of the control, nifedipine and cyclosporin-induced gingival overgrowth groups, but not in the combined medication group. No relationship between the presence of inflammation and integrin expression was found.

CONCLUSION

The results indicate that expression of certain integrins is up-regulated in the epithelium of drug-induced gingival overgrowth where they could participate in controlling the formation of elongated rete ridges and tissue fibrosis.

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.

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.

Distinctive localization and function for lumican, fibromodulin and decorin to regulate collagen fibril organization in periodontal tissues

BACKGROUND

Small leucine-rich proteoglycans (SLRPs) decorin, biglycan, fibromodulin and lumican are secreted extracellular matrix molecules that associate with fibrillar collagens and regulate collagen fibrillogenesis. Collagens are the major extracellular matrix components of periodontal connective tissues where they provide mechanical attachment of the tooth to the bone and gingiva and mediate signals that regulate cell functions, including remodeling of the periodontal ligament and bone. Structural organization of collagen may also be important for the defense against periodontal disease, because in certain conditions abnormal collagen fibrils associate with increased susceptibility to periodontal disease.

OBJECTIVES

The purpose of this study was to find out the role of SLRPs to regulate collagen fibril and fibril bundle formation in periodontal tissues.

METHODS

The localization of SLRPs in human and mouse periodontal tissues was studied using immunohistochemical methods. To assess the function of SLRPs we studied periodontal tissues of mice harboring targeted deletions of decorin, fibromodulin or lumican genes and lumican and fibromodulin double knockout mice using histological and electronmicroscopical methods.

RESULTS

The SLRPs were coexpressed in human and mouse gingival and periodontal ligament connective tissues where they colocalized with collagen fibril bundles. Teeth in the knockout animals were fully erupted and showed normal gross morphology. Targeted deletion of decorin, fibromodulin, lumican or both lumican and fibromodulin resulted in abnormal collagen fibril and fibril bundle morphology that was most evident in the periodontal ligament. Each of the gene deletions resulted in a unique fibril and fibril bundle phenotype.

CONCLUSIONS

These findings indicate that decorin, fibromodulin and lumican coordinately regulate the fibrillar and suprafibrillar organization of collagen in the periodontal ligament.

Colocalization of the collagen-binding proteoglycans decorin, biglycan, fibromodulin and lumican with different cells in human gingiva

BACKGROUND AND OBJECTIVE

Decorin, biglycan, fibromodulin and lumican are structurally related molecules that belong to the family of small leucine-rich proteoglycans (SLRPs). These SLRPs are secreted extracellular matrix molecules that interact with type I collagen and regulate collagen fibrillogenesis. They may also modulate cell functions that are important in maintenance of connective tissue structure. The aim of this study was to localize decorin, biglycan, fibromodulin and lumican in human gingiva.

METHODS

Localization of decorin and its proform (prodecorin), biglycan, fibromodulin and lumican and mature and proform of type I collagen was studied by immunohistochemical staining of frozen tissue sections from healthy human attached gingiva. Double immunostaining with anti-SLRP or anti-type I procollagen antibodies and specific markers for different connective tissue cells was used to study association of these molecules with cells.

RESULTS

The mature and proforms of decorin and collagen and biglycan, fibromodulin and lumican showed distinct localization in the extracellular matrix, where they associated with type I collagen fiber bundles. Prodecorin also localized to the epithelial basement membrane zone. Fibroblasts, myofibroblasts, endothelial cells and pericytes showed immunoreactivity for procollagen, prodecorin, biglycan and fibromodulin, whereas lumican associated with fibroblasts and myofibroblasts only. Biglycan and fibromodulin were also associated with macrophages. Basal epithelial cells of the gingival epithelium showed immunoreactivity for biglycan, fibromodulin and lumican.

CONCLUSIONS

Decorin, biglycan, fibromodulin and lumican associate with type I collagen and may collaborate to regulate collagen fibrillogenesis in human gingiva. Each of the SLRPs showed a distinct association with different connective tissue cells, suggesting that the cells produce these molecules and/or that the cells interact with them. Localization of biglycan, fibromodulin and lumican at the epithelial cells suggests novel functions for these SLRPs in human gingival epithelium.

An improved method for culture of epidermal keratinocytes from newborn mouse skin

Reproducible isolation and long term culture of epidermal keratinocytes from transgenic mouse lines is critically needed but most techniques have been unsuccessful. In this report we describe in detail a simplified method to isolate putative keratinocyte stem cells from newborn mouse skin and to maintain them for long term in culture. The cell cultures were established by enzymatically separating keratinocytes from newborn mouse skin. For selecting the putative keratinocyte stem cells for culture, the cells are allowed to attach for 10 minutes on a composite matrix made of type I collagen and fibronectin. Unattached cells were discarded and the attached cells were cultured in a defined culture medium containing low Ca2+ concentration, 9% FBS, conditioned medium from newborn mouse skin fibroblasts, and EGF. For subculturing, the cells were seeded on tissue culture plastic. The isolated cells showed the typical basal keratinocyte morphology and expressed the epithelial cell specific integrin alpha v beta 6. The expression level of alpha v beta 6 integrin was comparable to human skin keratinocytes. The keratinocytes were also able to differentiate to form an epidermis in an organotypic culture model. By using the described protocol, the keratinocytes from frozen stocks have been subcultured up to 26 times without change in cell viability, proliferation rate or morphology.

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.

Characterization of organotypic keratinocyte cultures on de-epithelialized bovine tongue mucosa

Organotypic cultures have been used to study epithelial cell behavior for many years. The aim of this study was to develop an organotypic culture method that better mimics the three-dimensional morphology of interdigitating rete ridges and connective tissue papillae and that also conserves the basement membrane zone (BMZ). Bovine tongue mucosa connective tissue, separated from epithelium after 1 M NaCl incubation, was used as organotypic culture substratum for different human keratinocyte cell lines. Organotypic cultures were characterized by electron and immunofluorescence microscopy for expression of integrin subunits and extracellular matrix components. While spontaneously immortalized mucosal keratinocytes produced highly irregular stratified organotypic cultures, the normal human epidermal keratinocytes (NHEK) demonstrated culture morphology that resembled in vivo epidermis. However, in this model, the histomorphology, expression of differentiation markers involucrin, keratin 10 and 14, and integrins varied significantly between the cell lines. Some cultures appeared to have an extended survival since they were maintained up to 40 days without histological signs of degeneration. The ultrastructure of the BMZ including hemidesmosomes was similar to the normal dermo-epidermal junction. Extracellular matrix molecules, including tenascin, laminin-1 and -5, were expressed in the cultures demonstrating their secretion solely by keratinocytes. Distribution and expression of integrins in NHEK cultures was similar to that seen in vivo skin with the exception of additional expression of alpha5beta1 and alpha(v)beta6 integrins. Organotypic NHEK cultures show similarities to normal stratified epithelium and are potentially useful for multiple applications for studies on epithelial cell behavior in vitro.

Successful periodontal maintenance of a case with Papillon-Lefèvre syndrome: 12-year follow-up and review of the literature

BACKGROUND

Various approaches to treating the periodontal condition associated with Papillon-Lefèvre syndrome have been reported. These include oral hygiene instruction, use of mouthrinses, frequent debridement, multiple antibiotic regimens, periodontal surgery, extraction of hopeless teeth, and extraction of all deciduous teeth. Because Papillon-Lefèvre syndrome is rare, most publications are case reports, and very few document long-term successful treatment of the periodontal condition.

METHODS

In 1986, a 3.5-year-old Indo-Canadian male was diagnosed with Papillon-Lefèvre syndrome and began periodontal treatment. Initial therapy consisted of debridement every 3 weeks, a 0.12% chlorhexidine mouthrinse, 2 regimens of metronidazole, and oral hygiene instruction for his parents. After 10 months it became apparent that the treatment was having little beneficial effect, since the periodontal destruction continued and teeth 51 and 61 exfoliated. At age 4, all remaining deciduous teeth were extracted and complete dentures inserted for the following 2-year edentulous period; then a 3-month maintenance schedule was maintained.

RESULTS

The patient is now 17 years old and all his adult teeth are present with the exception of the third molars. His oral hygiene varies between moderate and good, with his most recent plaque score at 80% effectiveness. There are no probing depths greater than 4 mm, with the exception of the distal of the lower second molars where opercula are present.

CONCLUSIONS

Extraction of all the deciduous teeth followed by a period of edentulousness may partially explain the fact that there has been no recurrent attachment loss in the permanent teeth up to age 17. Other explanations are discussed as part of the literature review of Papillon-Lefèvre syndrome.

A role for decorin in the structural organization of periodontal ligament

Decorin is a small leucine-rich proteoglycan that interacts with several matrix molecules, including various types of collagen and growth factors, and suppresses the growth of neoplastic cells by an epidermal growth factor (EGF) receptor-mediated pathway. Decorin is abundantly expressed in the periodontal connective tissues during development and tissue maintenance. In periodontal disease, which is one of the most common diseases in the human kind, the level of decorin is decreased in the periodontal connective tissue. Abnormal expression of decorin may also associate with certain inherited disorders that involve increased susceptibility to severe periodontal disease in the early childhood. Therefore, we investigated the periodontal tissues of mice with targeted disruption of the decorin gene. Gross and microscopic analyses showed that decorin-deficient mice appeared to have normal tooth development and eruption, and there were no signs of periodontal disease. However, electron microscopic analysis revealed abnormal morphology and organization of the collagen fibrils in the periodontal ligament. The number of periodontal ligament fibroblasts in the decorin-deficient mice was also increased about two-fold as compared with the wild-type mice. In cell culture, ectopic overexpression of decorin in NIH 3T3 fibroblasts or decorin added exogenously to periodontal fibroblasts suppressed cell growth. However, blocking the EGF receptor tyrosine kinase activity did not prevent the decorin-elicited growth suppression in periodontal fibroblasts. Additionally, decorin did not induce a marked increase in the relative expression of p21 mRNA in periodontal fibroblasts. Therefore, decorin appeared to regulate growth of normal periodontal fibroblasts by a mechanism distinct from that reported for neoplastic cells. The findings demonstrate that decorin plays a role in the organization of collagen fibrils and regulates cell proliferation in the periodontal ligament.

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.

Immunolocalization of tenascin-C, alpha9 integrin subunit, and alphavbeta6 integrin during wound healing in human oral mucosa

Tenascin-C (TN-C) and its isoforms are multidomain extracellular matrix (ECM) proteins that are believed to be involved in the regulation of stromal-epithelial interactions. Some of the interactions between TN-C and cells are mediated by integrins. In this study we analyzed the expression of TN-C and its large molecular weight splice isoform (TN-C(L)) and the putative TN-C-binding alpha9 and alphavbeta6 integrins during human wound repair. In 3-day-old oral mucosal wounds, immunoreactivity for alpha9 integrin localized abundantly at the migrating basal wound epithelial cells. TN-C and TN-C(L) were localized in the matrix between and underneath alpha9-expressing epithelial cells. In parallel with gradual downregulation of alpha9 integrin immunoreactivity in 7-day and older wounds, the expression of alphavbeta6 integrin was temporarily induced. Integrin alphavbeta6 co-localized in the same area as TN-C and TN-C(L) immunoreactivity at the cell-cell contacts of the basal and suprabasal cell layers of the wound epithelium. During granulation tissue formation and reorganization from 7 to 28 days after wounding, TN-C and TN-C(L) were abundantly localized in the granulation tissue. The findings show that TN-C(L) is expressed under the migrating epithelial front and in the granulation tissue during matrix deposition in wound repair. Preferential localization of alpha9 integrin in migrating epithelial cells and of alphavbeta6 integrin in epithelium after wound closure suggests different functions for these integrins in wound repair.

Different integrins mediate cell spreading, haptotaxis and lateral migration of HaCaT keratinocytes on fibronectin

Collaborative role of various fibronectin-binding integrins (alpha5beta1, alphavbeta1 and alphavbeta6) as mediators of cell adhesion and migration on fibronectin was studied using cultured HaCaT keratinocytes. This cell line spontaneously expressed all three fibronectin-binding integrins. In addition, the expression of alphavbeta6 integrin was strongly and specifically upregulated by transforming growth factor-beta1 (TGFbeta1) whereas the amount of other integrins remained practically unchanged on the cell surface. Adhesion, spreading and motility of HaCaT keratinocytes on fibronectin were promoted by TGFbeta1. Based on antibody blocking experiments, both untreated and TGFbeta1-treated HaCaT cells used alphavbeta6 integrin as their main fibronectin receptor for cell spreading. In contrast to TGFbeta1-treated cells, the untreated cells also needed alpha5beta1 integrin for maximal cell spreading on fibronectin. Combinations of antibodies blocking both of these receptors totally prevented spreading of both untreated and TGFbeta1-treated cells. Haptotactic motility of individual HaCaT cells through fibronectin-coated membranes was again mainly dependent on alphavbeta6 integrin, while alphavbeta1 and alpha5beta1 integrins played a lesser role both in untreated and TGFbeta1-treated HaCaT cells. However, unlike haptotaxis, lateral migration of HaCaT cell sheet was mainly mediated by beta1 integrins, and alphavbeta6 integrin showed a minor role. The migration process appeared to involve a number of beta1 integrins that could adaptively replace each other when blocking antibodies were present. Thus, keratinocytes appear to use different fibronectin receptors for different functions, such as cell spreading, haptotaxis and lateral migration. The cells can also adapt to a situation where one receptor is unfunctional by switching to another receptor of the same ligand.

Transforming growth factor-beta induces collagenase-3 expression by human gingival fibroblasts via p38 mitogen-activated protein kinase

Human collagenase-3 (matrix metalloproteinase 13 (MMP-13)) is characterized by exceptionally wide substrate specificity and restricted tissue specific expression. Human skin fibroblasts in culture express MMP-13 only when they are in three-dimensional collagen (Ravanti, L., Heino, J., López-Otín, C., and Kähäri. V.-M. (1999) J. Biol. Chem. 274, 2446-2455). Here we show that MMP-13 is expressed by fibroblasts during normal human gingival wound repair. Expression of MMP-13 by human gingival fibroblasts cultured in monolayer or in collagen gel was induced by transforming growth factor-beta1 (TGF-beta1). Treatment of gingival fibroblasts with TGF-beta1 activated two distinct mitogen-activated protein kinases (MAPKs): extracellular signal-regulated kinase 1/2 (ERK1/2) in 15 min and p38 MAPK in 1 and 2 h. Induction of MMP-13 expression by TGF-beta1 was blocked by SB203580, a specific inhibitor of p38 MAPK, but not by PD98059, a selective inhibitor of ERK1/2 activation. Adenovirus-mediated expression of dominant negative p38alpha and c-Jun potently inhibited induction of MMP-13 expression in gingival fibroblasts by TGF-beta1. Infection of gingival fibroblasts with adenovirus for constitutively active MEK1 resulted in activation of ERK1/2 and JNK1 and up-regulation of collagenase-1 (MMP-1) and stromelysin-1 (MMP-3) production but did not induce MMP-13 expression. In addition, activation of p38 MAPK by constitutively active MKK6b or MKK3b was not sufficient to induce MMP-13 expression. These results show that TGF-beta-elicited induction of MMP-13 expression by gingival fibroblasts is dependent on the activity of p38 MAPK and the presence of functional AP-1 dimers. These observations demonstrate a fundamental difference in the regulation of collagenolytic capacity between gingival and dermal fibroblasts and suggest a role for MMP-13 in rapid turnover of collagenous matrix during repair of gingival wounds, which heal with minimal scarring.

Expression of integrin alpha9 subunit and tenascin in oral leukoplakia, lichen planus, and squamous cell carcinoma

OBJECTIVES

Integrin alpha9 subunit is a member of beta1 integrin family and binds tenascin (TN). It is expressed by stratified squamous epithelium and may be associated with cell differentiation and growth. We studied if the expression of alpha9 integrin and TN is altered in leukoplakia, lichen planus, and squamous cell carcinoma (SCC).

METHODS

Frozen sections of tissue samples obtained from normal human keratinized (16 subjects) and non-keratinized (three subjects) oral mucosa, oral leukopakias with dysplasia (19 subjects), reticular type lichen planus (nine subjects), or oral mucosal SCC (23 subjects) were stained immunohistochemically with antibodies against alpha9 integrin and TN.

RESULTS

In contrast to its most prominent localization at the cell membranes of the basal epithelial cells in the normal mucosa, alpha9 integrin was localized in a more diffuse pattern with focal loss of expression at the epithelial cell membranes in leukoplakic dysplasia, lichen planus, and SCC. In some areas of SCC, alpha9 integrin localized throughout all cell layers of the tumor epithelium. In most areas, alpha9 integrin colocalized with TN but in heavily inflamed areas there was focal loss of TN and alpha9 integrin at the basement membrane zone.

CONCLUSIONS

The findings show that alpha9 integrin expression is altered in leukoplakic dysplasia, lichen planus, and SCC.

Enhancement of fibroblast collagenase (matrix metalloproteinase-1) gene expression by ceramide is mediated by extracellular signal-regulated and stress-activated protein kinase pathways

Inflammatory cytokines tumor necrosis factor-alpha and interleukin-1 trigger the ceramide signaling pathway, initiated by neutral sphingomyelinase-elicited hydrolysis of cell membrane phospholipid sphingomyelin to ceramide, a new lipid second messenger. Here, we show that triggering the ceramide pathway by sphingomyelinase or C2- and C6-ceramide enhances collagenase-1 (matrix metalloproteinase-1; MMP-1) gene expression by fibroblasts. C2-ceramide activates three distinct mitogen-activated protein kinases (MAPKs) in dermal fibroblasts, i.e. extracellular signal-regulated kinase 1/2 (ERK1/2), stress-activated protein kinase/Jun N-terminal-kinase (SAPK/JNK), and p38. Stimulation of MMP-1 promoter activity by C2-ceramide is dependent on the presence of a functional AP-1 cis-element and is entirely inhibited by overexpression of MAPK inhibitor, dual specificity phosphatase CL100 (MAPK phosphatase-1). Activation of MMP-1 promoter by C2-ceramide is also effectively inhibited by kinase-deficient forms of ERK1/2 kinase (MEK1/2) activator Raf-1, ERK1 and ERK2, SAPK/JNK activator SEK1, or SAPKbeta. In addition, ceramide-dependent induction of MMP-1 expression is potently prevented by PD 98059, a selective inhibitor of MEK1 activation, and by specific p38 inhibitor SB 203580. These results show that triggering the ceramide signaling pathway activates MMP-1 gene expression via three distinct MAPK pathways, i.e. ERK1/2, SAPK/JNK, and p38, and suggest that targeted modulation of the ceramide signaling pathway may offer a novel therapeutic approach for inhibiting collagenolytic activity, e.g. in inflammatory disorders.

Suprabasal expression of epidermal alpha 2 beta 1 and alpha 3 beta 1 integrins in skin treated with topical retinoic acid

In normal adult human skin, expression of epidermal integrins is confined to keratinocytes in the basal layer. However, suprabasal expression of alpha 2, alpha 3 and beta 1 integrin subunits is noted in hyperproliferative epidermis in wound repair and psoriasis. In this study, we examined the effect of topical all-trans-retinoic acid (RA), known to induce epidermal hyperplasia, on expression of integrins in human epidermis. Immunostaining of vehicle-treated skin revealed expression of alpha 2, alpha 3 and beta 1, as well as alpha 6 and beta 4 integrin subunits entirely on basal keratinocytes. Topical application of RA (0.1%) for 2 weeks resulted in marked suprabasal expression of alpha 2, alpha 3 and beta 1 integrin subunits, whereas alpha 6 and beta 4 staining remained on basal keratinocytes. Staining for putative ligands of alpha 2 beta 1 and alpha 3 beta 1 integrins, i.e. type IV collagen, laminin-5 and fibronectin, was not detected in the epidermal layer in RA- or vehicle-treated skin. Treatment of HaCaT keratinocytes in culture with RA (1 mumol/L) enhanced alpha 2 and beta 1 mRNA abundance. Furthermore, RA slightly up-regulated the expression of alpha 2, alpha 3 and beta 1 integrin subunits on primary epidermal keratinocytes and HaCaT cells in culture with no effect on cell proliferation. These results provide evidence that RA-elicited epidermal hyperplasia is associated with aberrant suprabasal expression of alpha 2 beta 1 and alpha 3 beta 1 integrins, and that this also involves direct stimulation of keratinocyte integrin expression by RA.

Lactoferrin impedes epithelial cell adhesion in vitro

In the process of host defence against microbial challenge, neutrophils release granule contents with the potential side effect of damaging structural tissues. In the junctional epithelium such damage may contribute to the degeneration and renewal of the epithelial cells attached directly to the tooth (DAT cells), and subsequently to periodontal pocket formation. This study reports on lactoferrin, one of the substances released by neutrophils, and its effects on epithelial cell adhesion, growth, DNA synthesis and spreading of cell colonies at concentrations recorded in the crevicular fluid. We show that, in opposition to what has been reported on bacterial cells, lactoferrin has no effect on the DNA synthesis of attached epithelial cells in model systems attempting to simulate the DAT cells in vivo. However, both iron-saturated and unsaturated lactoferrin hampered cell adhesion, growth and spreading of cell colonies in a dose-dependent manner. These findings suggest that lactoferrin does not affect epithelial cell proliferation but it may have a role in delaying the repair of the DAT cell population during inflammation by interfering with cell adhesion.

Regulation of CD44v6-containing isoforms during proliferation of normal and malignant epithelial cells

CD44 is a family of molecules involved in cell-cell and cell-matrix interactions. Various isoforms of CD44 arise by insertion of one or more of the variant exons into the common backbone shared by all forms of CD44. In this work, we studied the expression of CD44 and exon v6-containing CD44 isoforms (CD44v6) in several nonmalignant and malignant conditions and the possibilities for regulating the expression of CD44v6. In primary squamocellular carcinomas of the head and neck, CD44 and CD44v6 were down-regulated in poorly differentiated tumors, whereas these molecules were uniformly expressed in the normal squamocellular epithelium, in proliferating skin diseases, and in nonmalignant tumors. When CD44v6 expression of original tumors and that of squamocellular carcinoma cell lines derived from them were compared, no CD44v6 up-regulation could be observed on in vitro growing cells. Moreover, several regulators were unable to up-regulate CD44v6 expression on cultured cell lines in vitro. When the same cell lines formed tumors after s.c. injection into severe combined immunodeficient mice, some of them up-regulated their CD44v6 expression. These data suggest that cell lines at certain differentiation stages can be induced to express CD44v6. Our results further indicate that CD44v6 positivity cannot be used as a universal indicator of tumor metastasis. Instead, the down-regulation of CD44v6 in squamocellular tumors is a sign of malignant transformation of the epithelium.

Expression of heparan sulphate and small dermatan/chondroitin sulphate proteoglycans in chronically inflamed human periodontium

Proteoglycans (PGs) function in regulating aspects of cell behavior, such as proliferation, adhesion, and migration. In this report, we investigated the localization of three heparan sulphate PGs (basement membrane [BM] heparan sulphate PG, CD44, and syndecan-1) and two small dermatan/chondroitin sulphate PGs (decorin and biglycan) in chronically inflamed human periodontium. Frozen sections were analyzed by immunofluorescence microscopy. In inflamed tissue, BM heparan sulphate PG showed reduced immunostaining in subepithelial and subendothelial basement membrane. Loss of CD44 and syndecan-1 was common in epithelial cells of inflamed periodontal tissue. Suprabasal keratinocytes of epithelium expressed involucrin, a cornified envelope protein and marker for epithelial differentiation, while the expression of syndecan-1 was weak or absent. In contrast, expression of the mesenchymal variant of CD44 and syndecan-1 was strong in infiltrating lymphocytes. Small dermatan/chondroitin sulphate PGs, decorin and biglycan, were also present in markedly reduced amounts in the periodontal connective tissue in chronic inflammation. In addition, decorin localized in the connective tissue along short rod-like structures. The results suggest that proteoglycan-dependent intercellular adhesion of keratinocytes is decreased and that adhesion of lymphocytes to matrix molecules via cell surface PGs increased in chronic inflammation. Disappearance of adhesion-modulating small dermatan/chondroitin sulphate PGs may further regulate cell migration in inflamed periodontium.

Effects of xylitol, xylitol-sorbitol, and placebo chewing gums on the plaque of habitual xylitol consumers

Xylitol reduces plaque but the reduction mechanism is largely unknown. The main aim of the present study was to determine whether the xylitol-induced reduction in the amount of plaque and the number of mutans streptococci could be demonstrated in subjects with (presumably) high levels of xylitol-resistant (XR; not inhibited by xylitol) mutans streptococci acquired following previous xylitol consumptions. 37 healthy dental students participated in the double-blind study. All subjects had been uncontrolled, habitual consumers of xylitol-containing products for at least 1 yr before the study. A 1-month washout period was followed by a 2-week test period during which either xylitol, xylitol-sorbitol or unsweetened chewing gum base was chewed 3-5 x a day. Plaque and saliva samples were collected at baseline and at the 2-week point for determination of the amount of plaque, microbiological variables, and hydrolytic enzymes. Mixtures of xylitol and sorbitol seemed to perform equally well with respect to reduction in the amount of plaque but not the number of mutans streptococci. Thus, polyols were the active ingredients of chewing gums able to modulate the amount of plaque and its microbial composition. Xylitol reduced plaque with a mechanism which appeared not to be associated with the study-induced changes in the proportion (%) of mutans streptococci in plaque, the number of salivary mutans streptococci, the proportion of XR strains in plaque or saliva, or the hydrolytic enzyme activities of plaque.

Collagenase 3 (matrix metalloproteinase 13) gene expression by HaCaT keratinocytes is enhanced by tumor necrosis factor alpha and transforming growth factor beta

Collagenase-3 (matrix metalloproteinase 13; MMP-13) is a novel matrix metalloproteinase, the expression of which to date has only been detected in human breast carcinoma tissue and osteoarthritic cartilage. Here, we show that MMP-13 transcripts are expressed by human HaCaT keratinocytes but not by primary human epidermal keratinocytes. The levels of MMP-13 mRNAs in HaCaT cells were enhanced up to 130- and 45-fold by tumor necrosis factor alpha (TNF-alpha) and transforming growth factor beta (TGF-beta), respectively. The maximal induction of MMP-13 mRNAs by TNF-alpha was noted after a 6-h incubation, whereas with TGF-beta, the maximal stimulation was observed after 24 h. The up-regulation of MMP-13 mRNA abundance by TNF-alpha and TGF-beta was dependent on protein synthesis and was prevented partially by dexamethasone and retinoic acid. Nuclear run-on assays demonstrated activation of MMP-13 gene transcription by TNF-alpha maximally at the 2-h time point and by TGF-beta after 12 h of treatment. Incubation of HaCaT keratinocytes with TNF-alpha and TGF-beta also increased production of proMMP-13 into the culture media, as detected by Western blotting. Our data indicate that the MMP-13 gene is expressed by transformed epidermal keratinocytes, suggesting a role for MMP-13 in the invasive capacity of human epidermal malignancies.

Human granulation-tissue fibroblasts show enhanced proteoglycan gene expression and altered response to TGF-beta 1

Granulation-tissue fibroblasts are phenotypically unique cells that play an important role in wound repair and the development of chronic inflammatory lesions in connective tissue. In the present study, we compared proteoglycan, type I, and type III procollagen gene expression by granulation-tissue fibroblasts from wound and chronically inflamed tissues with normal gingival fibroblasts. We also analyzed the effect of TGF-beta 1 on proteoglycan mRNA levels and macromolecule production by these cells. One granulation-tissue fibroblast strain that was composed exclusively of alpha-smooth-muscle actin-positive cells (myofibroblasts) expressed strongly elevated basal levels of biglycan, fibromodulin, and versican (the large chondroitin sulphate proteoglycan), as well as type I and III procollagen mRNA. TGF-beta 1 enhanced more potently the expression of types I and III procollagen, biglycan, and versican mRNA by these cells as compared with normal fibroblasts. Other granulation-tissue fibroblast strains, in which about half of the cells expressed alpha-smooth-muscle actin, also showed enhanced proteoglycan and types I and III procollagen expression as compared with normal fibroblasts. These results suggest that alterations in matrix composition during inflammation and wound healing are regulated partly by altered phenotypes of the cells that produce the matrix, and partly by altered responses of these cells to TGF-beta 1.

TNF-R55-specific form of human tumor necrosis factor-alpha induces collagenase gene expression by human skin fibroblasts

Tumor necrosis factor-alpha (TNF-alpha) is a potent inhibitor of connective tissue formation. The cellular effects of TNF-alpha are mediated by two distinct cell-surface receptors, TNF-R55 and TNF-R75, both present on various types of cells, including fibroblasts. In this study we wanted to elucidate the role of TNF-R55 as a mediator of the connective tissue effects of TNF-alpha by using a mutant, TNF-R55-specific form of human TNF-alpha. This mutant TNF-alpha markedly induced collagenase and stromelysin-1 gene expression in dermal fibroblasts, the maximal activation (up to 42-fold) being 65%-89% of that noted with wild-type human TNF-alpha. In addition, TNF-R55-specific TNF-alpha suppressed type I collagen mRNA levels as potently as wild-type TNF-alpha (by 60%). The enhancement of collagenase gene expression by TNF-R55-specific TNF-alpha was augmented by simultaneous treatment of normal and scleroderma skin fibroblasts with interferon-gamma, indicating specific enhancement of TNF-R55 signaling pathway by interferon-gamma. These results show that stimulation of the TNF-R55 signaling pathway is sufficient for the inhibitory effects of TNF-alpha on extracellular matrix formation by dermal fibroblasts. It is conceivable that due to reduced systemic toxicity, TNF-R55-specific forms of human TNF-alpha may prove to be feasible in the therapy of fibrotic disorders.

Differential regulation of decorin and biglycan gene expression by dexamethasone and retinoic acid in cultured human skin fibroblasts

Proteoglycans participate in the assembly of extracellular matrix, directly by interacting with other matrix components and indirectly by regulating cellular growth-factor responses. We have studied the regulation of gene expression of two small extracellular matrix chondroitin/dermatan sulfate proteoglycans, decorin and biglycan, by dexamethasone and retinoic acid in cultured human skin fibroblasts. Dexamethasone increased decorin production, maximally 4.8-fold, and decorin mRNA levels up to 2.3-fold, but had no effect on biglycan production or mRNA levels. Dexamethasone also prevented transforming growth factor-beta-elicited down-regulation of decorin mRNA levels and production by dermal fibroblasts. In addition, dexamethasone potently inhibited enhancement of biglycan production and mRNA levels by transforming growth factor-beta. Retinoic acid dose dependently reduced decorin mRNA levels (by 51%) and production (by 72%), but had no effect on biglycan gene expression. Retinoic acid did not alter the effect of transforming growth factor-beta on decorin or biglycan production or mRNA levels. These results provide evidence that the effects of glucocorticoids and retinoids on dermal connective tissue are partially mediated via altered expression of decorin and biglycan, which both in turn regulate the activity of transforming growth factor-beta, the most potent stimulator of connective tissue deposition.

Expression of proteoglycans and hyaluronan during wound healing

We investigated the expression of proteoglycans (PGs) and hyaluronan (HA) during healing of human mucosal wounds. Biopsy specimens of experimental wounds were taken 1, 3, and 7 days after wounding. Frozen sections were used for immunolocalization of CD44, syndecan-1, basement membrane-associated heparan sulfate proteoglycan (BM-HSPG), decorin, and biglycan. HA was localized in paraffin sections with a specific HA-binding probe. Epithelium showed first signs of migration on Day 1, more progressive migration on Day 3, and epithelial sheets confronted on Day 7. CD44 surrounded migrating keratinocytes at all stages of wound healing. In epithelium, CD44 and HA remarkably localized to the same region. Expression of syndecan-1 was switched from the suprabasal cell layer of unwounded epithelium to the basal cell layer of the migrating wound epithelium. BM-HSPG was absent under migrating keratinocytes. It started to reappear at the basement membrane zone on Day 7. The area under the wound epithelium containing newly synthesized collagen fibers first became positive for decorin on Day 7, whereas staining of biglycan was negative. Granulation tissue was also strongly positive for CD44 and hyaluronan. Our results indicate that migrating keratinocytes express both CD44 and syndecan-1 but not BM-HSPG. During differentiation of keratinocytes, expression of CD44 preceded that of syndecan-1. The results suggest that different HSPGs have multiple functions in keratinocyte migration and differentiation during reepithelialization.

Altered interaction of human granulation-tissue fibroblasts with fibronectin is regulated by alpha 5 beta 1 integrin

Granulation-tissue fibroblasts express an unique phenotype distinct from normal fibroblasts. Due to the importance of the cell-matrix interactions in the regulation of cell morphology and behavior, we have compared the cell adhesion apparatus, especially integrin-type receptors, in fibroblasts cultured from healthy human periodontal connective tissues and from chronic and wound granulation tissues. The spreading of granulation-tissue cells on fibronectin, but not on type I collagen or laminin, was slower when compared with the normal fibroblasts. Cell spreading on fibronectin could be inhibited by RGD-containing peptide, suggesting integrin-mediated interaction. Both cell types expressed beta 1 integrin subunit, which associated with several integrin alpha subunits, namely alpha 1, alpha 2, alpha 3, alpha 5 and alpha v. In addition to beta 1 subunit, alpha v chain formed heterodimers with beta 3 and beta 5 subunits. Thus, these cells have multiple putative fibronectin, laminin, collagen, and vitronectin receptors. Cell spreading of both cell types on fibronectin was inhibited with anti-beta 1 and anti-alpha 5 antibodies, but antibodies against other putative FN-binding integrins (alpha 3, alpha v, and alpha v beta 3) had no effects. Furthermore, granulation-tissue fibroblasts showed delayed spreading on substrates coated with anti-beta 1 or anti-alpha 5 integrin antibodies. On substrates coated with anti-alpha 3 antibody, both cell types spread equally well. By FACS analysis, the amount of beta 1 and alpha 5 integrin subunits expressed on the cell surfaces was slightly elevated in GTFs compared with HGFs. Thus, the findings in this study indicate that the weakened interaction of granulation-tissue fibroblasts with fibronectin is regulated by altered function of alpha 5 beta 1 integrin.

The size of the intracellular beta 1-integrin precursor pool regulates maturation of beta 1-integrin subunit and associated alpha-subunits

A large pool of precursor beta 1-integrin subunits is frequently found intracellularly. During malignant transformation this pool often disappears. Concomitantly, integrin-mediated cell-adhesion functions are disturbed, even though no change in the number of beta 1-integrin receptors on the cell surface can be observed. Here, we have studied the role of an intracellular pre-beta 1-integrin pool by transfecting human MG-63 osteosarcoma cells with plasmid construction producing an antisense RNA for the beta 1-integrin subunit. Stable cell clones expressing beta 1-integrin antisense RNA were shown to have a reduced intracellular pool of pre-beta 1-integrin subunits. In the antisense-transfected cells, the synthesis of the beta 1-integrin chain was reduced by 65% compared with non-transfected or vector-transfected MG-63 cells. The decreased synthesis of the beta 1-integrin chain was associated with accelerated maturation of the beta 1-integrin chain (half-maturation time about 5 h in antisense-transfected cells compared with about 10.5 h in control cells), whereas maturation of the alpha-integrin chain slowed down. The amount of beta 1-integrins on the cell surface, however, remained unaltered. Cell clones with the largest decrease in the relative amount of the pre-beta 1-integrin subunit also showed altered integrin function. They were found to synthesize fibronectin, but were unable to assemble it into a fibronectin matrix on the cell surface. Thus we conclude that the repression of biosynthesis of the beta 1-integrin chain leads to alterations in receptor maturation and may be connected with altered receptor function.

Immunohistochemical localization of proteoglycans in human periodontium

Proteoglycans (PGs) are extracellular and cell surface-associated macromolecules that regulate cell adhesion, cell growth, matrix formation, and bind growth factors. In this work we studied the distribution of core proteins of four PGs (decorin, biglycan, a large molecular weight PG, and CD44) in human gingiva and periodontal ligament by immunohistochemical staining of frozen tissue sections with specific antibodies. Decorin, a major PG of this tissue, was localized on collagen fiber bundles in the gingival and periodontal connective tissues. Staining for decorin was most intense at the subepithelial region. Biglycan was a minor PG component of the human periodontium, showing some accumulation in connective tissue under the oral epithelium. At the immunohistochemical level, biglycan appeared to form fine filament-like structures on extracellular matrix fibers. Localization of large molecular weight PG differed from that of decorin and biglycan. It was concentrated in deep connective tissue areas of the gingiva and in the periodontal ligament, and was only weakly present at the subepithelial region. CD44 was mainly concentrated in cell-cell contact areas of basal and spinous layers of oral epithelium. In the connective tissue of gingiva and periodontal ligament, CD44 was localized on fibroblast cell surfaces. Connective tissue area under the junctional epithelium contained relatively small amounts of PGs. The results indicate that different parts of human periodontium contain a typical variety of PGs, suggesting a specific function for each PG species in the location at which they accumulate.

Characterization of fibroblast clones from periodontal granulation tissue in vitro

Connective tissues are known to be composed of heterogeneous fibroblast subpopulations. The significance of this heterogeneity in different physiological and pathological conditions is poorly understood. Granulation tissue is formed in connective tissue during wound healing, chronic inflammation, and certain pathological conditions. In this study, heterogeneity of fibroblasts from granulation tissue was investigated by cell-cloning techniques. Granulation-tissue fibroblasts (GTFs) from both chronically inflamed periodontal lesions and healing wound granulation tissue behaved similarly. GTFs showed a more pronounced decrease in proliferative capacity with increasing cumulative population doubling levels (CPDLs) and 30-40% lower cloning efficiency compared with normal gingival fibroblasts (HGFs). Morphologically, cells in GTF cultures were mainly large, whereas HGFs were mainly small in size. Both cell-line types showed heterogeneity in cell morphology. Clones composed of large stellate-like cells predominated in GTF cultures, whereas clones composed of small spindle-shaped or epithelioid cells predominated in HGF cultures. In both cell-line type the proportion of clones composed of large cells increased without increasing CPDL. These findings show that the properties of the fibroblasts changed during their in vitro life spans. The finding that normal connective tissue and granulation tissues contain morphologically distinct fibroblast clones in different proportions suggests that local factors could stimulate local fibroblasts to differentiate into GTFs. Alternatively, local factors could select some fibroblast subpopulations to overgrow the others to form granulation tissue.

Growth of the ribs at the costochondral junction in the rat

The in situ growth of the ribs at the costochondral junction was examined by 2 methods. In the first, 3 threads were tied around the 5th, 6th or 7th ribs of 20-d-old rats. The first thread was located around the bony part of the rib close to the costochondral junction, the second around the cartilaginous part the same distance away from the junction, and the third also around the cartilaginous part but further away. The distances between the threads were measured at 20 and 40 d and were found to have increased considerably. In the second part, an immunohistochemical method using bromodeoxyuridine was employed to detect proliferating cells at the costochondral junction. The most active cell proliferation was observed in the proliferative zone, but mitoses were also noticed in the germinative zone. The results provide further evidence that the growth potential of costochondral grafts used in reconstructive surgery is related to the length of their cartilaginous portion.

A biochemical analysis of human periodontal tissue proteoglycans

Proteoglycans synthesized by periodontal (gingival, periodontal ligament, dental follicle) fibroblasts were analysed by SDS/polyacrylamide and agarose gel electrophoresis after being labelled with radioactive sulphate. Medium, cell membrane and extracellular matrix fractions were analysed separately. Samples were treated with chondroitinase AC, chondroitinase ABC, heparitinase or a combination of chondroitinase ABC and heparitinase before electrophoretic separation of proteoglycans. Antibodies to versican and decorin were used to identify these molecules by Western immunoblots. For steady-state metabolic radiolabelling of fibroblasts, medium and cell membrane fractions contained about equal proportions of radiolabelled proteoglycans (about 43%), whereas less radioactivity (about 14%) was found in proteoglycans of the matrix fraction. Periodontal fibroblasts produce six major proteoglycans: versican, a high-molecular-mass chondroitin sulphate proteoglycan (CSPG); decorin, a dermatan sulphate proteoglycan (DSPG); a membrane-associated heparan sulphate proteoglycan (HSPG); two medium- or matrix-associated HSPGs; and a 91 kDa membrane-associated CSPG. Variation in decorin molecular size was observed in mass cultures of fibroblasts. Similar polydispersity in molecular size of decorin was seen in several clones established from one mass culture.

Histochemical localization of hyaluronate in human oral epithelium using a specific hyaluronate-binding probe

Biochemical data suggest that gingival epithelium contains hyaluronate, but there is little histochemical information about its localization. Hyaluronate was here visualized in gingival and buccal mucosa using a specific probe derived from the hyaluronate binding region of cartilage proteoglycan. Hyaluronate was found both in the gingival and buccal epithelium, but its localization was correlated with the type of keratinization. In the keratinized epithelium of gingiva, whether ortho- or parakeratotic, the intercellular spaces from basal to upper spinous layers displayed strong staining, most intense in the middle spinous cell layer. The uppermost vital cell layers as well as the cornified cell layer remained unstained. In the non-keratinized epithelium of buccal mucosa and the local non-keratinized areas of gingiva, only the basal cells and the lowermost spinous cell layers stained for hyaluronate, whereas the majority of the upper epithelium was negative. Electron microscopic examination of the basal and spinous cell layers displayed hyaluronate, both associated with the cell surface and free in the intercellular space. The subepithelial connective tissue showed positive but diffuse staining in all specimens.

Gingival crevicular fluid fibronectin degradation in periodontal health and disease

The molecular forms of fibronectin (FN) in gingival crevicular fluid of five subjects with at least two sites exhibiting clinical signs of inflammation and pockets of at least 4 mm (test group) and five subjects with clinically healthy periodontium (control group) were investigated. Samples were collected with standard filter paper strips. In the test group samples from both diseased and healthy sites were collected. After collection the test group received one episode of periodontal treatment (scaling and root planning). The sampling and clinical recording were repeated for the diseased sites after about 2 wk. The crevicular fluid FN was analyzed using sodium dodecyl sulphate gel electrophoresis followed by western blotting with polyclonal antibodies against FN. Both intact FN and FN fragments were found in all samples. A larger proportion of FN was in degraded form in the diseased sites than in the healthy or the treated sites. FN was also degraded into smaller peptide fragments in the diseased than in the treated sites. These results suggest that crevicular fluid FN is partially degraded both in periodontal health and disease and that the degree of degradation of FN increases with periodontal inflammation and decreases with periodontal treatment.

Attachment and spreading of human gingival fibroblasts on potentially bioactive glasses in vitro

The attachment and spreading of cultured fibroblasts on potentially bioactive glasses (bioglasses) of ten different compositions were studied. Human gingival fibroblasts were allowed to attach and spread on bio-glasses for 1-72 h. Unreactive silica glass and cell culture polystyrene served as controls. The attachment and spreading of cells were examined by 3H-thymidine labeling of cells, planimetric analysis, cytological staining, immunocytochemistry, and scanning electron microscopy. The cell attachment to bioglasses and silica glass and the cell spreading on bioglasses were slower and cell morphology more elongated compared to control plastic. In spite of great differences in bioglass compositions no great differences in cell behavior on these surfaces were detected. Thus the initial events in the tissue-implant interface might be independent on the bioglass composition, and furthermore the differences in the organization of the tissue-implant interface in vivo might depend on the nature of the surrounding tissues and subsequent changes of the implant surface and the extracellular environment.

Effect of citric acid treatment on the migration of epithelium on root surfaces in vitro

Explants of bovine gingival mucosa were cultured for four days on scaled and citric acid-conditioned root surfaces. Demineralization of the hard tissue with citric acid exposed the collagenous matrix of the root. Undemineralized islands were frequently seen among the collagen fibers of the treated roots. When cultured on scaled, control root surfaces, the epithelium migrated inwards between the connective tissue of the explant and the root surface. On citric acid-treated roots, epithelial migration in this direction was rare although it was possible. Citric acid treatment of the substratum directed the epithelium to migrate outwards from the explant. Only a few of the controls showed epithelial migration to the outward direction. The findings indicate that demineralization of the root surface has an influence on the direction in which the epithelium initially starts to migrate. An induced delay of epithelial migration between the gingival connective tissue and the hard tissue may be favorable for connective tissue attachment to the root surface.