The dento-epithelial junction: cell adhesion by type I hemidesmosomes in the absence of a true basal lamina

Laminin 332 functionalized surface improve implant roughness and oral keratinocyte bioactivity

Objective

The biological seal (BS) at the implant-tissue interface is essential for the success of dental implants (DIs), and the absence of a proper BS can lead to peri-implantitis. The basement membrane (BM) and junctional epithelium are critical for sealing the peri-implant mucosa, and laminin 332 is an important protein in binding the epithelium to the implant surface. The aim of this study was to evaluate the response of oral keratinocytes to titanium dental implant surfaces biofunctionalized with laminin 332.

Design

The dental implant surface was treated with a piranha solution to create hydroxyl (OH) groups, facilitating biofunctionalization with laminin 332. The modified surface underwent scanning electron microscopy, surface roughness evaluation, and chemical composition analysis. Human keratinocytes from the Cal-27 line were then cultured on the modified implants for 24 and 48 h to assess viability, morphology, cytokine secretion, and mRNA expression of tissue repair-associated genes.

Results

The results showed that laminin 332 biofunctionalization of the implant surface resulted in lower values of Ra, Rq and positive surface roughness parameters Rsk, Rku and Rv. The elemental composition showed an increase in nitrogen and carbon content corresponding to protein binding. The biofunctionalized surfaces did not affect cell viability and promoted cytokine secretion (IL-1a and IL-8) and a significant increase (p < 0.05) in MCP-1, EGF, FGF, TGF and VEGF gene expression compared to the control.

Conclusion

In conclusion, laminin 332 coating Ti implants was shown to be effective in promoting keratinocyte adhesion, spreading, and viability. This approach could be an alternative way to improve biocompatibility.

Cell Junctions in Periodontal Health and Disease: An Insight

Cells are the building blocks of all living organisms. The presence of cell junctions such as tight junctions, gap junctions, and anchoring junctions between cells play a role in cell-to-cell communication in periodontal health and disease. A literature search was done in Scopus, PubMed, and Web of Science to gather information about the effect of cell junctions on periodontal health and disease. The presence of tight junction in the oral cavity helps in cell-to-cell adhesiveness and assists in the barrier function. The gap junctions help in controlling growth and development and in the cell signaling process. The presence of desmosomes and hemidesmosomes as anchoring junctions aid in mechanical strength and tissue integrity. Periodontitis is a biofilm-induced disease leading to the destruction of the supporting structures of the tooth. The structures of the periodontium possess multiple cell junctions that play a significant role in periodontal health and disease as well as periodontal tissue healing. This review article provides an insight into the role of cell junctions in periodontal disease and health, and offers concepts for development of therapeutic strategies through manipulation of cell junctions.

Periostin regulates integrin expression in gingival epithelial cells

OBJECTIVE

Human gingival epithelial cells (HGECs) function as a mechanical barrier against invasion by pathogenic organisms through epithelial cell-cell junction complexes, which are complex components of integrin. Integrins play an important role in the protective functions of HGECs. Human periodontal ligament (HPL) cells regulate periodontal homeostasis. However, periodontitis results in the loss of HPL cells. Therefore, as replenishment, HPL cells or mesenchymal stem cells (MSCs) can be transplanted. Herein, HPL cells and MSCs were used to elucidate the regulatory mechanisms of HGECs, assuming periodontal tissue homeostasis.

METHODS

Human gingival fibroblasts (HGFs), HGECs, HPL cells, and MSCs were cultured, and the conditioned medium was collected. With or without silencing periostin mRNA, HGECs were cultured under normal conditions or in a conditioned medium. Integrin and periostin mRNA expression was determined using real-time polymerase chain reaction. Integrin protein expression was analyzed using flow cytometry, and periostin protein expression was determined via western blotting.

RESULTS

The conditioned medium affected integrin expression in HGECs. Higher expression of periostin was observed in MSCs and HPL cells than in HGFs. The conditioned medium that contained periostin protein regulated integrin expression in HGECs. After silencing periostin in MSCs and HPL cells, periostin protein was not detected in the conditioned medium, and integrin expression in HGECs remained unaffected.

CONCLUSIONS

Integrins in HGECs are regulated by periostin secreted from HPL cells and MSCs. This result suggests that periostin maintains gingival cell adhesion and regulates bacterial invasion/infection. Therefore, the functional regulation of periostin-secreting cells is important in preventing periodontitis.

Fluorapatite-Coated Percutaneous Devices Promote Wound Healing and Limit Epithelial Downgrowth at the Skin-Device Interface

A percutaneous osseointegrated device becomes deeply ingrown by endosteal bone and traverses the overlying soft tissues of the residual limb, providing a direct link to the bone-anchored artificial limb. Continuous wound healing around these devices can result in the formation of sinus tracts as “down-growing” epithelial cells are unable to recognize and adhere to the “nonbiological” implant surface. Such sinus tracts provide paths for bacterial colonization and deep infection. In order to limit adverse outcomes and provide a robust seal, it was hypothesized that by coating the titanium surface of the percutaneous post with the mineral component of dental enamel, down-growing epidermal cells might recognize the coating as “biological” and adhere to this nonliving surface. To test this hypothesis, sintered partially and fully fluoridated hydroxyapatite (HA) was chosen as coatings. Using an established surgical protocol, fluorapatite (FA), hydroxyfluorapatite (FHA), HA-coated percutaneous posts, and titanium controls were surgically placed under the dorsal skin in 20 CD hairless rats. The animals were sacrificed at four weeks, and implants and surrounding tissues were harvested and subjected to further analyses. Downgrowth and granulation tissue area data showed statistically significant reductions around the FA-coated devices. Moreover, compared to the control group, the FA- and HA-coated groups showed downregulation of mRNA for EGFr, EGF, and FGF-10. Interestingly, the FA-coated group had upregulation of TGF-α. These data suggest that FA could become an ideal coating material for preventing downgrowth, assuming the long-term stability of these coated surfaces can be verified in a clinically relevant animal model.

Junctional epithelium and hemidesmosomes: Tape and rivets for solving the "percutaneous device dilemma" in dental and other permanent implants

The percutaneous device dilemma describes etiological factors, centered around the disrupted epithelial tissue surrounding non-remodelable devices, that contribute to rampant percutaneous device infection. Natural percutaneous organs, in particular their extracellular matrix mediating the "device"/epithelium interface, serve as exquisite examples to inspire longer lasting long-term percutaneous device design. For example, the tooth's imperviousness to infection is mediated by the epithelium directly surrounding it, the junctional epithelium (JE). The hallmark feature of JE is formation of hemidesmosomes, cell/matrix adhesive structures that attach surrounding oral gingiva to the tooth's enamel through a basement membrane. Here, the authors survey the multifaceted functions of the JE, emphasizing the role of the matrix, with a particular focus on hemidesmosomes and their five main components. The authors highlight the known (and unknown) effects dental implant - as a model percutaneous device - placement has on JE regeneration and synthesize this information for application to other percutaneous devices. The authors conclude with a summary of bioengineering strategies aimed at solving the percutaneous device dilemma and invigorating greater collaboration between clinicians, bioengineers, and matrix biologists.

Investigating wound healing characteristics of gingival and skin keratinocytes in organotypic cultures

OBJECTIVES

The gingiva heals at an accelerated rate with reduced scarring when compared to skin. Potential well-studied factors include immune cell number, angiogenesis disparities and fibroblast gene expression. Differential keratinocyte gene expression, however, remains relatively understudied. This study explored the contrasting healing efficiencies of gingival and skin keratinocytes, alongside their differential gene expression patterns.

METHODS

3D organotypic culture models of human gingiva and skin were developed using temporarily immortalised primary keratinocytes. Models were wounded for visualisation of re-epithelialisation and analysis of keratinocyte migration to close the wound gap. Concurrently, differentially expressed genes between primary gingival and skin keratinocytes were identified, validated, and functionally assessed.

RESULTS

Characterisation of the 3D cultures of gingiva and skin showed differentiation markers that recapitulated organisation of the corresponding in vivo tissue. Upon wounding, gingival models displayed a significantly higher efficiency in re-epithelialisation and stratification versus skin, repopulating the wound gap within 24 hours. This difference was likely due to distinct patterns of migration, with gingival cells demonstrating a form of sheet migration, in contrast to skin, where the leading edge was typically 1-2 cells thick. A candidate approach was used to identify several genes that were differentially expressed between gingival and skin keratinocytes. Knockdown of PITX1 resulted in reduced migration capacity of gingival cells.

CONCLUSION

Gingival keratinocytes retain in vivo superior wound healing capabilities in in vitro 2D and 3D environments. Intrinsic gene expression differences could result in gingival cells being 'primed' for healing and play a role in faster wound resolution.

CLINICAL SIGNIFICANCE STATEMENT

The successful development of organotypic models, that recapitulate re-epithelialisation, will underpin further studies to analyse the oral response to wound stimuli, and potential therapeutic interventions, in an in vitro environment.

An SCPPPQ1/LAM332 protein complex enhances the adhesion and migration of oral epithelial cells: Implications for dentogingival regeneration

Common periodontal disease treatment procedures often fail to restore the structural integrity of the junctional epithelium (JE), the epithelial attachment of the gum to the tooth, leaving the tooth-gum interface prone to bacterial colonization. To address this issue, we introduced a novel bio-inspired protein complex comprised of a proline-rich enamel protein, SCPPPQ1, and laminin 332 (LAM332) to enhance the JE attachment. Using quartz crystal microbalance with dissipation monitoring (QCM-D), we showed that SCPPPQ1 and LAM332 interacted and assembled into a protein complex with high-affinity adsorption of 5.9e^-8 [M] for hydroxyapatite (HA), the main component of the mineralized tooth surfaces. We then designed a unique shear device to study the adhesion strength of the oral epithelial cells to HA. The SCPPPQ1/LAM332 complex resulted in a twofold enhancement in adhesion strength of the cells to HA compared to LAM332 (from 31 dyn/cm² to 63 dyn/cm²). In addition, using a modified wound-healing assay, we showed that gingival epithelial cells demonstrated a significantly high migration rate of 2.7 ± 0.24 µm/min over SCPPPQ1/LAM332-coated surfaces. Our collective data show that this protein complex has the potential to be further developed in designing a bioadhesive to enhance the JE attachment and protect the underlying connective tissue from bacterial invasion. However, its efficacy for wound healing requires further testing in vivo. STATEMENT OF SIGNIFICANCE: This work is the first functional study towards understanding the combined role of the enamel protein SCPPPQ1 and laminin 332 (LAM332) in the epithelial attachment of the gum, the junctional epithelium (JE), to the tooth hydroxyapatite surfaces. Such studies are essential for developing therapeutic approaches to restore the integrity of the JE in the destructive form of gum infection. We have developed a model system that provided the first evidence of the strong interaction between SCPPPQ1 and LAM332 on hydroxyapatite surfaces that favored protein adsorption and subsequently oral epithelial cell attachment and migration. Our collective data strongly suggested using the SCPPPQ1/LAM332 complex to accelerate the reestablishment of the JE after surgical gum removal to facilitate gum regeneration.

Interleukin-1β regulates odontogenic ameloblast-associated protein gene transcription in human gingival epithelial cells

Junction epithelium (JE) is located apical to the bottom of the gingival sulcus and binds enamel to hemidesmosomes to protect the periodontal tissue from bacterial infection. Function of odontogenic ameloblast-associated protein (ODAM) is suggested by its expression sites (JE and maturation stage ameloblasts) to be involved in the adhesion between the JE and enamel, and odontogenesis. To analyze the changes in ODAM gene and protein expressions in inflamed gingiva, Ca9-22 gingival epithelial cells were stimulated with 1 ng/ml interleukin-1β (IL-1β) for 3-24 h, and ODAM mRNA and protein levels were analyzed by real-time PCR and Western blotting. Luciferase (LUC) constructs were made ligating various lengths of human ODAM gene promoters and performed LUC analyses in Ca9-22 cells. Gel shift and chromatin immunoprecipitation (ChIP) assays were performed. IL-1β induced ODAM mRNA and protein levels at 6-24 h. IL-1β increased LUC activities of the ODAM gene promoter constructs from - 85 to - 950. These activities were blocked by protein kinase A, tyrosine kinase, mitogen-activated protein (MAP) kinase kinase and phosphoinositide 3-kinase inhibitors. Gel shift and ChIP assays showed that IL-1β induced CCAAT/enhancer-binding protein (C/EBP) β and Yin Yang1 (YY1) binding to C/EBP1, 2, 3, and YY1 elements. These data indicate that IL-1β stimulates ODAM gene transcription mediated through C/EBP1, C/EBP2, C/EBP3, and YY1 elements in the human ODAM gene promoter.

3D engineered human gingiva fabricated with electrospun collagen scaffolds provides a platform for in vitro analysis of gingival seal to abutment materials

In order to advance models of human oral mucosa towards routine use, these models must faithfully mimic the native tissue structure while also being scalable and cost efficient. The goal of this study was to develop a low-cost, keratinized human gingival model with high fidelity to human attached gingiva and demonstrate its utility for studying the implant-tissue interface. Primary human gingival fibroblasts (HGF) and keratinocytes (HGK) were isolated from clinically healthy gingival biopsies. Four matrices, electrospun collagen (ES), decellularized dermis (DD), type I collagen gels (Gel) and released type I collagen gels (Gel-R)) were tested to engineer lamina propria and gingiva. HGF viability was similar in all matrices except for Gel-R, which was significantly decreased. Cell penetration was largely limited to the top layers of all matrices. Histomorphometrically, engineered human gingiva was found to have similar appearance to the native normal human gingiva except absence of rete pegs. Immunohistochemical staining for cell phenotype, differentiation and extracellular matrix composition and organization within 3D engineered gingiva made with electrospun collagen was mostly in agreement with normal gingival tissue staining. Additionally, five types of dental material posts (5-mm diameter x 3-mm height) with different surface characteristics were used [machined titanium, SLA (sandblasted-acid etched) titanium, TiN-coated (titanium nitride-coated) titanium, ceramic, and PEEK (Polyetheretherketone) to investigate peri-implant soft tissue attachment studied by histology and SEM. Engineered epithelial and stromal tissue migration to the implant-gingival tissue interface was observed in machined, SLA, ceramic, and PEEK groups, while TiN was lacking attachment. Taken together, the results suggest that electrospun collagen scaffolds provide a scalable, reproducible and cost-effective lamina propria and 3D engineered gingiva that can be used to explore biomaterial-soft tissue interface.

Transcriptional regulation of human odontogenic ameloblast-associated protein gene by tumor necrosis factor-α

OBJECTIVE

Odontogenic ameloblast-associated protein (ODAM) is produced by maturation stage ameloblasts and junctional epithelium (JE). The function of ODAM is thought to be involved in the attachment of teeth and JE. To elucidate transcriptional regulation of human ODAM gene in inflamed gingiva, we have analyzed the effects of TNF-α on the expression of ODAM gene in Ca9-22 and Sa3 gingival epithelial cells.

MATERIALS AND METHODS

Total RNAs were extracted from Ca9-22 and Sa3 cells after stimulation by TNF-α (10 ng/ml). ODAM mRNA and protein levels were analyzed by qPCR and Western blotting. Luciferase (LUC) analyses were performed using LUC constructs inserted in various lengths of ODAM gene promoter. Gel shift and chromatin immunoprecipitation (ChIP) assays were carried out.

RESULTS

TNF-α increased ODAM mRNA and protein levels at 3 to 24 h. TNF-α induced LUC activities of the ODAM gene promoter constructs, and the activities were inhibited by protein kinase A, tyrosine kinase, MEK1/2, PI3-kinase and NF-κB inhibitors. Gel shift and ChIP assays revealed that TNF-α increased CCAAT/enhancer-binding protein (C/EBP) β and Yin Yang1 (YY1) binding to three kinds of C/EBPs and YY1 elements.

CONCLUSION

These results demonstrate that TNF-α stimulates ODAM gene transcription via C/EBPs and YY1 elements in the human ODAM gene promoter.

Effect of Aging on Homeostasis in the Soft Tissue of the Periodontium: A Narrative Review

Aging is characterized by a progressive decline or loss of physiological functions, leading to increased susceptibility to disease or death. Several aging hallmarks, including genomic instability, cellular senescence, and mitochondrial dysfunction, have been suggested, which often lead to the numerous aging disorders. The periodontium, a complex structure surrounding and supporting the teeth, is composed of the gingiva, periodontal ligament, cementum, and alveolar bone. Supportive and protective roles of the periodontium are very critical to sustain life, but the periodontium undergoes morphological and physiological changes with age. In this review, we summarize the current knowledge of molecular and cellular physiological changes in the periodontium, by focusing on soft tissues including gingiva and periodontal ligament.

Proteoglycans in the periodontium: A review with emphasis on specific distributions, functions, and potential applications

Proteoglycans (PGs) are largely glycosylated proteins, consisting of a linkage sugar, core proteins, and glycosaminoglycans (GAGs). To date, more than 40 kinds of PGs have been identified, and they can be classified as intracellular, cell surface, pericellular, and extracellular PGs according to cellular locations. To illustrate, extracellular PGs are known for regulating the homeostasis of the extracellular matrix; cell-surface PGs play a role in mediating cell adhesion and binding various growth factors. In the field of periodontology, PGs are implicated in cellular proliferation, migration, adhesion, contractility, and anoikis, thereby exerting a profound influence on periodontal tissue development, wound repair, the immune response, biomechanics, and pathological process. Additionally, the expression patterns of some PGs are dynamic and cell-specific. Therefore, determining the roles and spatial-temporal expression patterns of PGs in the periodontium could shed light on treatments for wound healing, tissue regeneration, periodontitis, and gingival overgrowth. In this review, close attention is paid to the distributions, functions, and potential applications of periodontal PGs. Related genetically modified animal experiments and involved signal transduction cascades are summarized for improved understanding of periodontal PGs. To date, however, there is a large amount of speculation on this topic that requires rigorous experiments for validation.

Adenovirus-Mediated LAMA3 Transduction Enhances Hemidesmosome Formation and Periodontal Reattachment during Wound Healing

A robust dento-epithelial junction prevents external pathogenic factors from entering connective tissue and could be crucial for periodontal reattachment after periodontal surgery. The junctional epithelium (JE) is attached to the tooth surface through the hemidesmosome (HD) and internal basal lamina, where the primary component is laminin-332. Destruction of the JE leads to the loss of periodontal attachment. Traditional treatments are effective in eliminating local inflammation of the gingiva; however, few directly promote periodontal reattachment and HD formation. Here, we designed a gene-therapy strategy using the adenovirus-mediated human laminin-332 α3 chain (LAMA3) gene (Ad-LAMA3) transduced into a human-immortalized epidermal cell line (HaCaT) to study the formation of HD in vitro. Ad-LAMA3 promoted early adhesion and fast migration of HaCaT cells and increased expression of LAMA3 and type XVII collagen (BP180) significantly. Furthermore, HaCaT cells could facilitate formation of mature HDs after LAMA3 overexpression. In vivo experiments demonstrated that the JE transduced with Ad-LAMA3 could increase expression of LAMA3 and BP180 and “biological sealing” between the tooth and gingival epithelium. These results suggested that adenovirus-mediated LAMA3 transduction is a novel therapeutic strategy that promotes the stability and integration of the JE around the tooth during wound healing.

Follicular dendritic cell-secreted protein gene expression is upregulated and spread in nifedipine-induced gingival overgrowth

Follicular dendritic cell-secreted protein (FDC-SP) is secreted protein expressed in follicular dendritic cells, periodontal ligament and junctional epithelium (JE). Its expression could be controlled during inflammatory process of gingiva; however, responsible mechanism for gingival overgrowth and involvement of FDC-SP in clinical condition is still unclear. We hypothesized that JE-specific genes are associated with the initiation of drug-induced gingival enlargement (DIGE) called gingival overgrowth, and investigated the changes of JE-specific gene's expression and their localization in overgrown gingiva from the patients. Immunohistochemical analysis revealed that the FDC-SP localization was spread in overgrown gingival tissues. FDC-SP mRNA levels in GE1 and Ca9-22 cells were increased by time-dependent nifedipine treatments, similar to other JE-specific genes, such as Amelotin (Amtn) and Lamininβ3 subunit (Lamβ3), whereas type 4 collagen (Col4) mRNA levels were decreased. Immunocytochemical analysis showed that FDC-SP, AMTN, and Lamβ3 protein levels were increased in GE1 and Ca9-22 cells. Transient transfection analyses were performed using luciferase constructs including various lengths of human FDC-SP gene promoter, nifedipine increased luciferase activities of -345 and -948FDC-SP constructs. These results raise the possibility that the nifedipine-induced FDC-SP may be related to the mechanism responsible for gingival overgrowth does not occur at edentulous jaw ridges.

IL-1β enhances cell adhesion through laminin 5 and β4 integrin in gingival epithelial cells

The junctional epithelium and dental enamel adhere because of hemidesmosomes containing laminin 5 and α6β4 integrin, which are important adhesion molecules in the internal basal lamina. Interleukin (IL)-1 is important in the pathogenesis of periodontal disease. IL-1β induces bone resorption by activating osteoclasts; however, its effects on adhesion of epithelial cells remain to be clarified. Laminin β3, β4 integrin, and focal adhesion kinase mRNA levels were higher after 1 h and 3 h of stimulation with IL-1β (1 ng/mL), and IL-1β, type I α1, and type IV α1 collagen mRNA levels were higher after 1 h and lower after 3 h of stimulation with IL-1β. After IL-1β stimulation, colocalization of laminin 5 and β4 integrin was increased after 1 h, colocalization of β4 integrin and plectin was increased after 1 h and decreased after 3 h, and colocalization of β4 integrin and type IV collagen was decreased after 3 h. Wound healing assays showed that IL-1β treatment (3 h) delayed wound healing. These results suggest that IL-1β enhances cell adhesion by altering localization of epithelial adhesion molecules.

Selective bacterial degradation of the extracellular matrix attaching the gingiva to the tooth

The junctional epithelium (JE) is a specialized portion of the gingiva that seals off the tooth‐supporting tissues from the oral environment. This relationship is achieved via a unique adhesive extracellular matrix that is, in fact, a specialized basal lamina (sBL). Three unique proteins – amelotin (AMTN), odontogenic ameloblast‐associated (ODAM), and secretory calcium‐binding phosphoprotein proline‐glutamine rich 1 (SCPPPQ1) – together with laminin‐332 structure the supramolecular organization of this sBL and determine its adhesive capacity. Despite the constant challenge of the JE by the oral microbiome, little is known of the susceptibility of the sBL to bacterial degradation. Assays with trypsin‐like proteases, as well as incubation with Porphyromonas gingivalis, Prevotella intermedia, and Treponema denticola, revealed that all constituents, except SCPPPQ1, were rapidly degraded. Porphyromonas gingivalis was also shown to alter the supramolecular network of reconstituted and native sBLs. These results provide evidence that proteolytic enzymes and selected gram‐negative periodontopathogenic bacteria can attack this adhesive extracellular matrix, intimating that its degradation could contribute to progression of periodontal diseases.

Visualization of junctional epithelial cell replacement by oral gingival epithelial cells over a life time and after gingivectomy

Junctional epithelium (JE), which is derived from odontogenic epithelial cells immediately after eruption, is believed to be gradually replaced by oral gingival epithelium (OGE) over a lifetime. However, the detailed process of replacement remains unclear. The aim of the present study was to clarify the process of JE replacement by OGE cells using a green fluorescent protein (GFP)–positive tooth germ transplantation method. GFP-positive JE was partly replaced by OGE cells and completely replaced on day 200 after transplantation, whereas there was no difference in the expression of integrin β4 (Itgb4) and laminin 5 (Lama5) between JE before and after replacement by OGE cells. Next, GFP-positive JE was partially resected. On day 14 after resection, the regenerated JE consisted of GFP-negative cells and also expressed both Itgb4 and Lama5. In addition, the gene expression profile of JE derived from odontogenic epithelium before gingivectomy was partly different from that of JE derived from OGE after gingivectomy. These results suggest that JE derived from the odontogenic epithelium is gradually replaced by OGE cells over time and JE derived from the odontogenic epithelium might have specific characteristics different to those of JE derived from OGE.

C/EBPβ and YY1 bind and interact with Smad3 to modulate lipopolysaccharide-induced amelotin gene transcription in mouse gingival epithelial cells

Junctional epithelium (JE) develops from reduced enamel epithelium during tooth formation and is critical for the maintenance of healthy periodontal tissue through ensuring appropriate immune responses and the rapid turnover of gingival epithelial cells. We have previously shown a relationship between inflammatory cytokines and expression of JE‐specific genes, such as amelotin (AMTN), in gingival epithelial cells. Here, we elucidated the effects of Porphyromonas gingivalis‐derived lipopolysaccharide (PgLPS) on Amtn gene transcription and the interaction of transcription factors. To determine the molecular basis of transcriptional regulation of the Amtn gene by PgLPS, we performed real‐time PCR and carried out luciferase assays using a mouse Amtn gene promoter linked to a luciferase reporter gene in mouse gingival epithelial GE1 cells. Gel mobility shift and chromatin immunoprecipitation assays were performed to identify response elements bound to LPS‐induced transcription factors. Next, we analyzed protein levels of the LPS‐induced transcription factors and the interaction of transcription factors by western blotting and immunoprecipitation. LPS increased Amtn mRNA levels and elevated luciferase activities of constructs containing regions between −116 and −238 of the mouse Amtn gene promoter. CCAAT/enhancer‐binding protein (C/EBP) 1–, C/EBP2– and Ying Yang 1 (YY1)–nuclear protein complexes were increased by LPS treatment. Furthermore, we identified LPS‐modulated interactions with C/EBPβ, YY1 and Smad3. These results demonstrate that PgLPS regulates Amtn gene transcription via binding of C/EBPβ–Smad3 and YY1–Smad3 complexes to C/EBP1, C/EBP2 and YY1 response elements in the mouse Amtn gene promoter.

Transcriptional regulation of human amelotin gene by interleukin-1β

One of the major causes of tooth loss is chronic inflammation of the periodontium, the tissues surrounding the tooth. Amelotin (AMTN) is a tooth enamel protein which is expressed in maturation‐stage ameloblasts and also in the internal basal lamina of junctional epithelium, a unique epithelial structure attached to the tooth surface which protects against the constant microbiological challenge to the periodontium. Localization of AMTN suggests that its function could be involved in the dentogingival attachment. The purpose of this study was to investigate the effect of interleukin‐1β (IL‐1β) on AMTN gene transcription in human gingival epithelial Ca9‐22 cells. IL‐1β increased AMTN mRNA and protein levels at 3 h, and the levels reached maximum at 6 and 12 h. IL‐1β induced luciferase activities of human AMTN gene promoter constructs (−211, −353, −501, −769, and −950AMTN), but these activities were partially inhibited in −353AMTN constructs that included 3‐bp mutations in CCAAT/enhancer binding protein 1 (C/EBP1), C/EBP2, and Ying Yang 1 (YY1) elements. Transcriptional activities induced by IL‐1β were abrogated by protein kinase A (PKA), tyrosine kinase, mitogen‐activated protein kinase kinase (MEK1/2), and phosphatidylinositol 3‐kinase (PI3K) inhibitors. Gel shift and ChIP assays showed that IL‐1β increased C/EBPβ binding to C/EBP1 and C/EBP2, and YY1 binding to YY1 elements after 3 h, and that these DNA–protein interactions were inhibited by PKA, tyrosine kinase, MEK1/2, and PI3K inhibitors. These results demonstrated that IL‐1β increases AMTN gene transcription in human gingival epithelial cells mediated through C/EBP1, C/EBP2, and YY1 elements in the human AMTN gene promoter.

Histological and immunological characteristics of the junctional epithelium

The continuity of epithelial tissue is collapsed by tooth eruption. The junctional epithelium (JE) is attached to the tooth surface by hemidesmosomes, which constitutes the front-line defense against periodontal bacterial infection. JE constitutively expresses intercellular adhesion molecule-1 (ICAM-1), and neutrophils and lymphocytes penetrate into JE via interaction between ICAM-1 and LFA-1 expressed on the surface of these migrating cells. JE also expresses cytokines and chemokines. These functions of JE are maintained even in germ-free condition. Therefore, the constitutive expression of adhesion molecules, cytokines, and chemokines might be used not only for anti-pathogenic defense but also for maintaining the physiological homeostasis of JE. In this review, we have mainly focused on the structural and functional features of JE, and discussed the function of intraepithelial lymphocytes in JE as a front-line anti-microbial defense barrier and regulator of JE hemostasis.

Tumor necrosis factor-α stimulates human amelotin gene transcription in gingival epithelial cells

OBJECTIVE

Amelotin (AMTN) is an enamel protein that is localized in the basal lamina of ameloblasts in their maturation stage and the internal basal lamina of junctional epithelium (JE) and it is suggested that AMTN could be involved in the dentogingival attachment. To elucidate the transcriptional regulation of human AMTN gene in inflamed gingiva, we have analyzed the effect of tumor necrosis factor-α (TNF-α) on the expression of AMTN gene in Ca9-22 and Sa3 human gingival epithelial cells.

MATERIALS AND METHODS

Total RNAs were extracted from Ca9-22 and Sa3 cells after stimulation by TNF-α (10 ng/ml). AMTN mRNA and protein levels were measured by real-time PCR and Western blotting. Transient transfection analyses were completed using the various lengths of human AMTN gene promoter constructs with or without TNF-α. Gel mobility shift and chromatin immunoprecipitation assays were performed to investigate the transcription factors bindings to the human AMTN gene promoter by TNF-α.

RESULTS

TNF-α (10 ng/ml) increased AMTN mRNA and protein levels after 12 h. TNF-α induced luciferase activities of human AMTN gene promoter constructs (- 211AMTN, - 353AMTN, and - 501AMTN). TNF-α-induced luciferase activities were partially inhibited in the mutation - 353AMTN constructs that included 3-bp mutations in CCAAT enhancer-binding protein 1 (C/EBP1), C/EBP2 and Ying Yang 1 (YY1) elements. Transcriptional activities induced by TNF-α were inhibited by protein kinase A, Src-tyrosine kinase, MEK1/2, p38 kinase, NF-κB, and PI3-kinase inhibitors. Gel shift assays showed that TNF-α increased nuclear proteins binding to two types of C/EBP elements (C/EBP1 and C/EBP2) and YY1 element. The results of the chromatin immunoprecipitation assays showed that C/EBPβ binding to C/EBP1 and C/EBP2, and YY1 binding to YY1 were increased by TNF-α.

CONCLUSIONS

These findings demonstrated that TNF-α stimulates AMTN gene transcription in human gingival epithelial cells via C/EBP1, C/EBP2, and YY1 elements in the human AMTN gene promoter.

Strategies for Optimizing the Soft Tissue Seal around Osseointegrated Implants

Percutaneous and permucosal devices such as catheters, infusion pumps, orthopedic, and dental implants are commonly used in medical treatments. However, these useful devices breach the soft tissue barrier that protects the body from the outer environment, and thus increase bacterial infections resulting in morbidity and mortality. Such associated infections can be prevented if these devices are effectively integrated with the surrounding soft tissue, and thus creating a strong seal from the surrounding environment. However, so far, there are no percutaneous/permucosal medical devices able to prevent infection by achieving strong integration at the soft tissue-device interface. This review gives an insight into the current status of research into soft tissue-implant interface and the challenges associated with these interfaces. Biological soft/hard tissue interfaces may provide insights toward engineering better soft tissue interfaces around percutaneous devices. In this review, focus is put on the history and current findings as well as recent progress of the strategies aiming to develop a strong soft tissue seal around osseointegrated implants, such as orthopedic and dental implants.

Localization and expression pattern of amelotin, odontogenic ameloblast-associated protein and follicular dendritic cell-secreted protein in the junctional epithelium of inflamed gingiva

The purpose of this study is to elucidate the localization of amelotin (AMTN), odontogenic ameloblast-associated protein (ODAM) and follicular dendritic cell-secreted protein (FDC-SP) at the junctional epithelium (JE) in Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans infected mice and inflamed and non-inflamed human gingiva. We performed immunostaining to determine the localization and expression pattern of AMTN, ODAM and FDC-SP. AMTN, ODAM and FDC-SP in A. actinomycetemcomitans infected mice did not change dramatically compared with non-infected mice. AMTN and FDC-SP expressions were observed stronger in P. gingivalis infected mice at early stage. However, at the following stage, the coronal part of the AMTN expression disappeared from the JE, and FDC-SP expression decreased due to severe inflammation by P. gingivalis. ODAM expressed internal and external basal lamina, and the expression increased not only at early stage but also at the following stage in the inflammatory JE induced by P. gingivalis. In the human gingival tissues, AMTN was detected at the surface of the sulcular epithelium and JE in the non-inflamed and inflamed gingiva, and the localization did not change the process of inflammation. ODAM and FDC-SP were more widely detected at the sulcular epithelium and JE in the non-inflamed gingiva. In the inflamed gingiva, localization of ODAM and FDC-SP was spread into the gingival epithelium, compared to AMTN. These studies demonstrated that the expression pattern of AMTN, ODAM and FDC-SP at the JE were changed during inflammation process and these three proteins might play an important role in the resistance to inflammation.

Proinflammatory cytokines induce amelotin transcription in human gingival fibroblasts

Amelotin (AMTN) is a secreted protein transcribed predominantly during the maturation stage of enamel formation and localized in the junctional epithelium. We investigated differences in the levels of AMTN gene expression between non-inflamed gingiva and inflamed gingiva from patients with chronic periodontitis. Total RNAs were isolated from these tissues and their gene expression profiles were monitored by DNA microarray. The observed induction of AMTN mRNA in inflamed gingiva and cultured human gingival fibroblasts (HGF) was confirmed by real-time PCR. Transient transfection assays were performed using chimeric constructs of mouse AMTN gene promoter fragments linked to a luciferase reporter gene. Immunohistochemical localization of AMTN in inflamed and non-inflamed gingiva was assessed by immunohistochemistry. Among many differentially expressed genes, the level of AMTN mRNA was significantly increased in inflamed gingiva. Treatment of HGF with interleukin-1β (IL-1β), IL-6 and tumor necrosis factor-α (TNF-α) induced the expression of AMTN mRNA, and increased the luciferase activities of the AMTN promoter constructs. AMTN protein was detected in inflamed gingival connective tissue and junctional epithelium. These findings demonstrate that proinflammatory cytokines induce AMTN gene expression in human gingival fibroblasts and suggest a role for AMTN in gingival inflammation.

Fabrication, characterization, and biological assessment of multilayer laminin γ2 DNA coatings on titanium surfaces

The purpose of this work was to fabricate a multilayer laminin γ2 DNA coating on a titanium surface and evaluate its biological properties. A multilayer laminin γ2 DNA coating was fabricated on titanium using a layer-by-layer assembly technique. The rate of coating degradation was evaluated by detecting the amount of cDNA remaining. Surface analysis using X-ray photoelectron spectroscopy, atomic force microscopy, and surface contact angle measurements revealed the multilayer structure to consist of cationic lipid and confirmed that a laminin γ2 DNA layer could be fabricated on titanium via the layer-by-layer assembly process. The transfection efficiency was highest for five layers in the multilayer structure. HEK293 cells cultured on the multilayer films displayed significantly higher adhesion activity than the control group. The expression of laminin γ2 and the co-localization of integrin β4 and plectin were more obvious in HN4 cells cultured on the multilayer laminin γ2 DNA coating, while weak immunoreactivities were observed in the control group. We concluded that the DNA-loaded multilayer provided a surface with good biocompatibility and that the multilayer laminin γ2 DNA coating might be effective in improving cell adhesion and the formation of hemidesmosomes on titanium surfaces.

Ultrastructural immunolocalization of laminin 332 (laminin 5) at dento-gingival interface in Macaca fuscata monkey

Although laminin 332 (laminin 5), an extracellular matrix molecule involved in cell adhesion and migration, has been localized at the interface between the tooth enamel and junctional epithelium, its ultrastructural localization remains to be fully clarified. The purpose of the present study was to investigate the ultrastructural distribution of laminin 332 at the dento-gingival interface in Japanese monkey (Macaca fuscata) using pre- and post-embedding immunoelectron microscopy. Pre-embedding immunoelectron microscopy revealed a broad band of internal basal lamina together with supplementary lamina densa, and both showed immunolabeling for laminin 332. Immunoreaction products for laminin 332 were observed in the rough-surfaced endoplasmic reticulum of the junctional epithelial cells close to the tooth enamel. Post-embedding immunoelectron microscopy revealed an increase in the number of immunogold particles toward the coronal portion, resulting in a large accumulation of particles on the basal lamina, preferentially on the lamina densa. Concomitantly the dental cuticle at the dento-gingival interface was sporadically, but specifically, immunogold-labeled with anti-laminin 332 antibody. These data suggest that junctional epithelium actively produces laminin 332, and that the products accumulate at the dento-gingival interface during cell migration coronally towards the gingival sulcus.

Anti-inflammatory effects of bamboo salt and sodium fluoride in human gingival fibroblasts--An in vitro study

Dental caries preventive agents, such as sodium fluoride (NaF) and bamboo salt (BS), are known to cause cellular growth that is characterized by morphological and gene expression changes. This study was designed to investigate the dual effect of NaF and BS on interleukin (IL)-1β-induced gingival inflammation. Under in vitro experimental conditions, exposure to a subcytotoxic dose of IL-1β enhanced human gingival fibroblast inflammation, as characterized by increased levels of inflammation-associated proteins. A combination of NaF and BS significantly protected fibroblasts from IL-1β-induced cellular deterioration. Exposure to NaF and BS induced the cell growth and no changes in viability were found with the Lactate Dehydrogenase Assay (LDH) assay at the NaF and BS concentration analyzed. Molecular analysis demonstrated that NaF and BS increased resistance to inflammation by reduction of IL-1β, IL-8, and tumor necrosis factor (TNF)-α production. In addition, NaF and BS decreased the expression of IL-1β, IL-8, and TNF-α mRNA in IL-1β-induced human gingival fibroblast cells. The study identifies a new role for NaF and BS in the IL-1β-induced inflammation of gingival fibroblasts and provides a potential target for gingival protection.

Odontogenic Ameloblast-associated Protein (ODAM) Mediates Junctional Epithelium Attachment to Teeth via Integrin-ODAM-Rho Guanine Nucleotide Exchange Factor 5 (ARHGEF5)-RhoA Signaling

Adhesion of the junctional epithelium (JE) to the tooth surface is crucial for maintaining periodontal health. Although odontogenic ameloblast-associated protein (ODAM) is expressed in the JE, its molecular functions remain unknown. We investigated ODAM function during JE development and regeneration and its functional significance in the initiation and progression of periodontitis and peri-implantitis. ODAM was expressed in the normal JE of healthy teeth but absent in the pathologic pocket epithelium of diseased periodontium. In periodontitis and peri-implantitis, ODAM was extruded from the JE following onset with JE attachment loss and detected in gingival crevicular fluid. ODAM induced RhoA activity and the expression of downstream factors, including ROCK (Rho-associated kinase), by interacting with Rho guanine nucleotide exchange factor 5 (ARHGEF5). ODAM-mediated RhoA signaling resulted in actin filament rearrangement. Reduced ODAM and RhoA expression in integrin β₃- and β₆-knockout mice revealed that cytoskeleton reorganization in the JE occurred via integrin-ODAM-ARHGEF5-RhoA signaling. Fibronectin and laminin activated RhoA signaling via the integrin-ODAM pathway. Finally, ODAM was re-expressed with RhoA in regenerating JE after gingivectomy in vivo. These results suggest that ODAM expression in the JE reflects a healthy periodontium and that JE adhesion to the tooth surface is regulated via fibronectin/laminin-integrin-ODAM-ARHGEF5-RhoA signaling. We also propose that ODAM could be used as a biomarker of periodontitis and peri-implantitis.

Prevalence of human papilloma virus in marginal periodontium and its association with periodontitis: A cross sectional study

Context:

Bacterial pathogens in dental plaque are necessary for the development of periodontitis but this etiology alone does not explain all its clinicopathologic features. Researchers have proven the role of certain viruses like herpes virus in periodontal disease which implies that other viral agents like human papilloma virus may also be involved.

Aims:

This cross-sectional study was conducted to determine the proportion of patients with human papilloma virus (HPV-16) in marginal periodontium by analyzing DNA from the gingival tissue sample and to understand its association with periodontitis.

Settings and Design:

102 systemically healthy patients between the age group of 15 and 70 years reporting to the Department of Periodontology who required surgical intervention (flap surgery for patients with periodontitis and crown lengthening for healthy patients) with internal bevel gingivectomy were selected.

Materials and Methods:

After scaling and root planning, gingival tissue was collected during the respective surgical procedure. DNA was isolated and amplified using specific primers for HPV-16 by polymerase chain reaction (PCR). The amplified products were checked by agarose gel electrophoresis.

Results:

No HPV DNA was detected in the 102 samples analyzed.

Conclusion:

Marginal periodontium does not contain HPV in this study population and hence there was no association between HPV and periodontitis.

Characterisation of secretory calcium-binding phosphoprotein-proline-glutamine-rich 1: a novel basal lamina component expressed at cell-tooth interfaces

Functional genomic screening of the rat enamel organ (EO) has led to the identification of a number of secreted proteins expressed during the maturation stage of amelogenesis, including amelotin (AMTN) and odontogenic ameloblast-associated (ODAM). In this study, we characterise the gene, protein and pattern of expression of a related protein called secretory calcium-binding phosphoprotein-proline-glutamine-rich 1 (SCPPPQ1). The Scpppq1 gene resides within the secretory calcium-binding phosphoprotein (Scpp) cluster. SCPPPQ1 is a highly conserved, 75-residue, secreted protein rich in proline, leucine, glutamine and phenylalanine. In silico data mining has revealed no correlation to any known sequences. Northern blotting of various rat tissues suggests that the expression of Scpppq1 is restricted to tooth and associated tissues. Immunohistochemical analyses show that the protein is expressed during the late maturation stage of amelogenesis and in the junctional epithelium where it localises to an atypical basal lamina at the cell-tooth interface. This discrete localisation suggests that SCPPPQ1, together with AMTN and ODAM, participates in structuring the basal lamina and in mediating attachment of epithelia cells to mineralised tooth surfaces.

Transcriptional regulation of amelotin gene by proinflammatory cytokines in gingival fibroblasts

Amelotin (AMTN) is a secreted protein expressed during the late stages of enamel formation and in the junctional epithelium. Among many differentially expressed genes, we found significantly increased AMTN mRNA level in inflamed gingiva by DNA microarray. The inductions of AMTN mRNA expressions in inflamed gingiva and human gingival fibroblasts (HGF) were confirmed by real-time polymerase chain reaction. To determine the molecular basis of the expression of AMTN and its regulation by proinflammatory cytokines, we have isolated and characterized the promoter region of mouse AMTN gene. Transient transfection assays were performed using luciferase constructs including mouse AMTN gene promoter. Interleukin-1β, Interleukin-6 and tumor necrosis factor-α induced AMTN mRNA levels in HGF. These cytokines increased the luciferase activities of the AMTN promoter constructs in HGF. The results suggest that proinflammatory cytokines induce AMTN gene transcription and a role for AMTN in gingival inflammation.

Expression and localization of laminin 5, laminin 10, type IV collagen, and amelotin in adult murine gingiva

The biochemical composition of the internal and external basal laminae in the junctional epithelium differs significantly, and the precise cellular origin of their respective molecules remains to be determined. In the present study, the expression and localization of three basement membrane-specific molecules-laminin 5 (γ2 chain), type IV collagen (α1 chain), and laminin 10 (α5 chain)-and one tooth-specific molecule, amelotin, was analyzed in adult murine gingiva by using in situ hybridization and immunohistochemistry. The results showed that the outermost cells in junctional epithelium facing the tooth enamel strongly expressed laminin 5 mRNA, supporting the immunohistochemical staining data. This suggests that laminin 5 is actively synthesized in junctional epithelial cells and that the products are incorporated into the internal basal lamina to maintain firm epithelial adhesion to the tooth enamel throughout life. Conversely, no amelotin mRNA signals were detected in the junctional epithelial cells, suggesting that the molecules localized on the internal basal lamina are mainly derived from maturation-stage ameloblasts. Weak and sporadic expression of type IV collagen in addition to laminin 10 in the gingiva indicates that these molecules undergo turnover less frequently in adult animals.

Morphological and functional characteristics of human gingival junctional epithelium

BACKGROUND

This study aims to observe the morphological characteristics and identify the function characteristics of junctional epithelium (JE) tissues and cultured JE cells.

METHODS

Paraffin sections of human molar or premolar on the gingival buccolingual side were prepared from 6 subjects. HE staining and image analysis were performed to measure and compare the morphological difference among JE, oral gingival epithelium (OGE) and sulcular epithelium (SE). Immunohistochemistry was applied to detect the expression pattern of cytokeratin 5/6, 7, 8/18, 10/13, 16, 17, 19, and 20 in JE, OGE and SE. On the other hand, primary human JE and OGE cells were cultured in vitro. Cell identify was confirmed by histology and immunohistochemistry. In a co-culture model, TEM was used to observe the attachment formation between JE cells and tooth surface.

RESULTS

Human JE was a unique tissue which was different from SE and OGE in morphology. Similarly, morphology of JE cells was also particular compared with OGE cells cultured in vitro. In addition, JE cells had a longer incubation period than OGE cells. Different expression of several CKs illustrated JE was in a characteristic of low differentiation and high regeneration. After being co-cultured for 14 d, multiple cell layers, basement membrane-like and hemidesmosome-like structures were appeared at the junction of JE cell membrane and tooth surface.

CONCLUSIONS

JE is a specially stratified epithelium with low differentiation and high regeneration ability in gingival tissue both in vivo and in vitro. In co-culture model, human JE cells can form basement membrane-like and hemidesmosome-like structures in about 2 weeks.

Alumina-zirconia composites functionalized with laminin-1 and laminin-5 for dentistry: effect of protein adsorption on cellular response

The present paper describes a study on laminin interaction with the surface of two alumina-zirconia composites with different percentages of ZrO2, both with submicrometric grain size. As major molecules within the basement membrane (BM), laminins are important protein fragments for epithelial cell adhesion and migration. On the other hand, alumina-zirconia composites are very attractive materials for dental applications due to their esthetic and mechanical properties. X-Ray photoelectron spectroscopy and atomic force microscopy were used to study the adsorption of two types of laminin, laminin-1 (Ln-1) and laminin-5 (Ln-5), onto the ceramics surfaces. The in vitro cell response was determined by intracellular phosphorylation of major kinases. Ceramics samples functionalized with laminins showed better cellular activation than untreated specimens; furthermore, cellular activation was found to be greater for the composite with higher percentage in zirconia when functionalized with Ln-5, whereas the adsorption of Ln-1 resulted in a greater activation for the alumina-rich oxide.

Initial attachment, subsequent cell proliferation/viability and gene expression of epithelial cells related to attachment and wound healing in response to different titanium surfaces

OBJECTIVES

A tight seal between the epithelium and the dental implant surface is required to prevent bacterial inflammation and soft tissue recession and therefore to demonstrate a long-term success. Surface hydrophilicity was recently shown to promote osseointegration. The aim of this study was to investigate the influence of surface hydrophilicity in combination with surface topography of Ti implant surfaces on the behavior and activation/differentiation of epithelial cells using a set of in vitro experiments mimicking the implant-soft tissue contact.

METHODS

Hydrophobic acid-etched (A) and coarse-grit-blasted, acid-etched (SLA) surfaces and hydrophilic acid-etched (modA) and modSLA surfaces were produced. The behavior of an oral squamous cell carcinoma cell line (HSC-2) grown on all surfaces was compared through determination of cell attachment and proliferation/viability (CCK-8 and MTT assay), time-lapse microscopy of fluorescence labeled cells and determination of gene expression by real time polymerase chain reaction.

RESULTS

Within the surfaces with similar wettability cell spreading and cell movements observed by time-lapse microscopy after one day of incubation were most pronounced on smoother (A and modA) surfaces compared to rougher (SLA and modSLA) surfaces. Within the surfaces with similar roughness the hydrophilic surfaces (modA and modSLA) showed more cell spreading and cell activity compared to the hydrophobic surfaces (A and SLA). The relative gene expressions of cytokeratin14, integrin α6, integrin β4, vinculin, transforming growth factor (TGF)-β, TGF-β1, and TGF-β3 were decreased in HSC-2 on all four types of Ti surfaces compared to control surfaces (tissue culture polystyrene; p<0.01) and there was no significant difference of gene expression on the four different implant-surfaces.

SIGNIFICANCE

We have demonstrated that for proliferation and spreading of HSC-2 cells the smoother and hydrophilic surface is optimal (modA). These results suggest that surface hydrophilicity might positively influence the epithelial seal around dental implants. All tested titanium surfaces downregulate cell attachment, cell proliferation, expression of adhesion promoters, and cytokines involved in wound healing in HSC-2 cells compared to control surfaces.

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.

Comprehensive analysis of gene expression in the junctional epithelium by laser microdissection and microarray analysis

BACKGROUND AND OBJECTIVE

The junctional epithelium attaches to the tooth enamel at the dentogingival junction. The attachment mechanisms of the junctional epithelium have been studied histologically, but the molecular functions of the junctional epithelium have not been elucidated. The aim of this study was to perform a comprehensive analysis of gene expression in the junctional epithelium and to search for specific genetic markers of the junctional epithelium.

MATERIAL AND METHODS

A comprehensive analysis of genes expressed in the mouse junctional epithelium and oral gingival epithelium was performed using laser microdissection and microarray analysis. To extract high-quality RNA from these tissues, we made frozen sections using a modified film method. Confirmation of the differential expression of selected genes was performed by quantitative real-time PCR and immunohistochemistry.

RESULTS

The modified method produced RNA of sufficient quality for microarray analysis. The result of microarray analysis showed that 841 genes were up-regulated in the junctional epithelium compared with the oral gingival epithelium, and five were increased more than 50-fold in the junctional epithelium. These five genes were secretory leukocyte protease inhibitor (Slpi), keratin 17 (Krt17), annexin A1 (Anxa1), myosin light peptide 6 (Myl6) and endoplasmic reticulum protein 29 (Erp29). In particular, Slpi expression in the junctional epithelium was approximately 100-fold higher than in the oral gingival epithelium by real-time PCR. Additionally, immunohistochemistry indicated that the Slpi protein is highly expressed in the junctional epithelium.

CONCLUSION

We developed a method for generating fresh-frozen tissue sections suitable for extraction of good-quality RNA. We determined that Slpi is characteristically expressed in the junctional epithelium. Our results provide a substantial advance in the analysis of gene expression in the junctional epithelium.

Expression and function of laminin and integrins on adhesion/migration of primary culture cells derived from rat oral epithelium

BACKGROUND AND OBJECTIVE

It remains controversial whether or not the junctional epithelium cells that are directly attached to teeth migrate on the enamel surface, as those cells are able to adhere firmly to the enamel. The aim of this study was to investigate the expression patterns of laminin gamma(2), integrin beta(4) and integrin alpha(3), and to examine their potential function in cell migration.

MATERIAL AND METHODS

Oral epithelium cells obtained from Sprague-Dawley rats were established in primary culture. We employed a wound-healing assay to characterize the direction of cell extension at the start of cell migration, and observed different localizations of laminin and integrins using immunofluorescence. For functional analyses of integrins, we employed a phosphatidylinositol-3-kinase (PI3K) activator to promote integrin beta(4) function and used P1B5 to inhibit integrin alpha(3) function, and we analyzed the percentage of re-epithelialization as the migration function.

RESULTS

Marked accumulation of laminin gamma(2) was detected in the peripheral cytoplasm of cells adjacent to the wound area, as shown by the results of the migration assay. Integrin beta(4) was detected in the distal cell processes of actively migrating cells, while integrin alpha(3) was found in cell membranes of cells adjacent to the wound area. In the functional analyses, the percentage of re-epithelialization was significantly lower in the PI3K-activator group and in the P1B5-treated group (2.5% and 7.2%, respectively) than in the control group (39.0%) (p < 0.01).

CONCLUSION

The results suggest that laminin gamma(2) is secreted as a foothold for cell migration, that integrin beta(4) participates in cell adhesion and that integrin alpha(3) is involved in cell migration in the primary culture cells.

Effect of the dental adhesive, 4-META/MMA-TBB resin, on adhesion and keratinization of regenerating oral epithelium

BACKGROUND AND OBJECTIVE

The 4-META/MMA-TBB [4-(2-methacryloxyethyl)trimellitic anhydride/methyl methacrylate-tributylborane] resin is widely used as a dental adhesive. It has also been applied in the dressing of gingival wound surfaces following periodontal surgery. However, its effect on the regeneration and/or cell attachment of the oral epithelium remains to be clarified. To evaluate the effect of the resin applied as a wound dressing, we investigated expression of laminin 5, integrin beta(4) and cytokeratin 14 in regenerating oral epithelium treated with this resin following gingivectomy from the viewpoint of cell attachment and differentiation.

MATERIAL AND METHODS

The resin was applied to the entire wound surface in rats after gingival surgery, and regenerating epithelium was examined immediately and at 1, 3, 5, 7 and 14 days later. The resin was removed 2 weeks after application in some animals and tissue further examined at 1, 3, 5 and 7 days later.

RESULTS

Regenerating epithelium under the resin was not keratinized, but became keratinized immediately after removal of the resin. Laminin 5 and integrin beta(4) were immunolocalized in the basal lamina, the internal basal lamina, in marginal cells of the regenerating epithelium and at the resin-regenerating epithelium interface. Cytokeratin 14 localized in the regenerating epithelium underneath the resin, as well as in healthy and regenerated junctional epithelial cells.

CONCLUSION

These results suggest that this resin covers the wound surface and that the regenerating epithelium biologically adheres to the resin during the initial process of its regeneration.

Immunolocalization of laminin and integrin in regenerating junctional epithelium of mice after gingivectomy

BACKGROUND AND OBJECTIVE

The expression patterns of adhesive proteins and extracellular matrix proteins in regenerating gingival epithelium after gingivectomy are unknown. The aim of this study was to examine the expression of laminin 1, laminin gamma(2) (a specific component of laminin 5), integrin beta(4) and integrin alpha(3) in the regenerating gingival epithelium in order to understand the mechanism of wound healing during reconstitution of the sulcular environment.

MATERIAL AND METHODS

The palatal gingivae of the maxillary molars of Institute of Cancer Research mice were excised, and the regenerating tissues were examined 1, 3, 5, 7 and 14 days later. Fresh, non-fixed and non-decalcified frozen sections were prepared and stained using immunofluorescence.

RESULTS

At 1 day post-surgery, intense expression of laminin gamma(2), integrin beta(4) and integrin alpha(3) was distinct in the frontal margin of the regenerating oral epithelium. Laminin gamma(2) was diffusely detected on the root surface and in connective tissues beneath the regenerating oral epithelium at 3 and 5 days. At 7 days, laminin gamma(2) was intermittently recognizable in the internal basal lamina (IBL) close to tooth-facing cells, while laminin gamma(2), integrin beta(4) and integrin alpha(3) were observed in the IBL and in the external basal lamina (EBL) of the regenerating junctional epithelium at 14 days.

CONCLUSION

These results suggest that secretion of laminin 5 in the connective tissue may induce epithelial cell migration, and that binding of laminin 5 to integrin alpha(6)beta(4) and integrin alpha(3)beta(1) in the IBL may provoke cell adhesion and migration of cells facing the tooth on the enamel surface of the regenerating junctional epithelium.

Involvement of laminin and integrins in adhesion and migration of junctional epithelium cells

BACKGROUND AND OBJECTIVE

The junctional epithelium attaches to the enamel surface with hemidesmosomes (of which laminin-5 and integrin-alpha(6)beta(4) are the main components) in the internal basal lamina. Laminin-5 is also involved in cell motility with integrin-alpha(3)beta(1), although their functions have not yet been clarified.The purpose of this study was to determine the functions of those adhesive components between the tooth and the junctional epithelium during cell migration.Because an idea has been proposed that directly attached to tooth cells (DAT cells) may not contribute to cell migration, 5-bromo-2-deoxyuridine staining was performed to confirm cell migration.

MATERIAL AND METHODS

We investigated laminin-gamma(2) (contained only in laminin-5), integrin-beta(4) (involved in cell-extracellular matrix contact) and integrin-alpha(3) (inducing cell migration) in the junctional epithelium, oral gingival epithelium and gingival sulcus epithelium of 6-wk-old ICR mice using laser microdissection, quantitative real-time reverse transcription-polymerase chain reaction, immunofluorescence and 5-bromo-2-deoxyuridine staining.

RESULTS

Laminin and integrins were clearly immuno-localized in the basal lamina of all epithelium. Quantitative analysis of laminin and integrin mRNAs by laser microdissection showed that they were more highly expressed in DAT cells than in basal cells in the oral gingival epithelium. In particular, a 12-fold higher expression of laminin-5 was observed in the junctional epithelium compared with the oral gingival epithelium. 5-Bromo-2-deoxyuridine staining showed rapid coronal migration of DAT cells.

CONCLUSION

These results suggest that the abundant expression of laminin-5 and integrin-alpha(6)beta(4) is involved in the attachment of DAT cells to teeth by hemidesmosomes. Abundant expression of laminin-5 and integrin-alpha(3)beta(1) might assist in DAT cell migration, confirmed by 5-bromo-2-deoxyuridine staining during the turnover of junctional epithelium.

Human laminin-332 degradation by Candida proteinases

BACKGROUND

Human laminin-332 (Lm-332) degradation by 12 Candida strains and effects of synthetic proteinase inhibitors [Ilomastat (ILM), EDTA, chemically modified tetracycline-3(CMT-3), CMT-308, synthetic peptide CTT-2, and Pefabloc] were studied.

MATERIALS AND METHODS

Laminin-332 was incubated with sonicated cell fractions and 10 times concentrated cell-free fractions of reference and clinical strains of C. albicans, C. dubliniensis, C. guilliermondii, C. glabrata, C. krusei, and C. tropicalis. Proteolysis, pH effects, and inhibitors were analyzed by fluorography and zymography.

RESULTS

Cell fractions of all species except C. guilliermondii and cell-free fractions of C. albicans, and C. dubliniensis showed 20-70 kDa gelatinases at pH 5.0 and 6.0. At pH 7.6, C. glabrata, C. krusei, and C. tropicalis cell fractions and C. tropicalis cell-free fractions showed 55-70 kDa gelatinases. CMT-3, CMT-308, and CTT-2 inhibited Candida gelatinases slightly better than Pefabloc, ILM, and EDTA. No Candida fractions degraded Lm-332 at pH 7.6, but at pH 5.0, 100 kDa bands were generated by cell fractions of C. dubliniensis and C. tropicalis; C. albicans and C. glabrata clinical strains; and C. guilliermondii reference strain. C. krusei reference strain yielded three 100-130 kDa bands. C. albicans, C. dubliniensis, and C. tropicalis reference and clinical strain's cell-free fractions generated 100 kDa band.

CONCLUSIONS

Laminin-332 degradation is pH-dependent and differences exist between studied Candida strains. Lm-332 degradation can exert functional disturbances on basement membrane integrity, possibly aiding Candida cell invasion into tissues. Certain synthetic matrix metalloproteinase inhibitors (CMTs, CTT) can inhibit Candida proteinases and may be therapeutically useful in future.

Sealing the skin barrier around transcutaneous implants

Conventional amputation prostheses rely on the attachment of the socket to the stump, which may lead to soft-tissue complications. Intraosseous transcutaneous amputation prostheses (ITAPs) allow direct loading of the skeleton, but their success is limited by infection resulting from breaching of the skin at the interface with the implant. Keratinocytes provide the skin’s primary barrier function, while hemidesmosomes mediate their attachment to natural ITAP analogues. Keratinocytes must attach directly to the surface of the implant. We have assessed the proliferation, morphology and attachment of keratinocytes to four titaniumalloy surfaces in order to determine the optimal topography in vitro. We used immunolocalisation of adhesion complex components, scanning electron microscopy and transmission electron microscopy to assess cell parameters.

We have shown that the proliferation, morphology and attachment of keratinocytes are affected by the surface topography of the biomaterials used to support their growth. Smoother surfaces improved adhesion. We postulate that a smooth topography at the point of epithelium-ITAP contact could increase attachment in vivo, producing an effective barrier of infection.

Lutheran blood group antigen as a receptor for alpha5 laminins in gingival epithelia

BACKGROUND

Lutheran blood group glycoprotein (Lu) is a transmembrane receptor of the immunoglobulin superfamily. Lu serves as a receptor for alpha5 laminins (Lm). The Lm alpha5 chain is a constituent of Lms-511 and -521. Lm-511 is found in most human basement membranes (BMs) and also is detected in BM of gingival epithelia. Recent studies indicated that Lu mediates cell adhesion to Lms-511/521 independently or in concert with integrins. This study focused on the expression of Lu in gingival epithelia and on cultured immortalized gingival keratinocytes. The role of Lu and alpha(3) and beta(1) integrin subunits in the adhesion of oral epithelial cells to Lms-511/521 was also studied.

METHODS

Immunofluorescence microscopy was used to study the expression of Lu in gingival tissues and in cultured gingival keratinocytes. Immunoprecipitation of radioactively metabolically labeled cells was used to detect Lu. Cell adhesion to Lm-511/521 preparation and to pure Lm-511 was studied in quantitative cell adhesion experiments. Morphological adhesion assays were carried out for visualization of the morphology and adhesion structure formation of the adhering cells.

RESULTS

Immunofluorescence studies on gingiva showed complete coalignment of Lu on basal epithelial cells with the BM Lm alpha5 chain. A surface-confined, punctate immunoreaction for Lu was detected throughout cell surfaces on cultured gingival cells. Immunoprecipitation showed a broad polypeptide with molecular weight 85,000. In quantitative cell adhesion assays, the adhesion of cells to both Lm alpha5 preparations was diminished with monoclonal antibodies (MAbs) against integrin alpha(3) and even more effectively with MAbs against the beta(1) subunit. When the adhesion sites were blocked with soluble recombinant Lu (sol-Lu), the adhesion of gingival epithelial cells to Lms-511/521 was reduced significantly, and sol-Lu increased the inhibition with integrin alpha(3) antibody. Lm-511 did not induce lamellipodia or focal contacts in cultured gingival keratinocytes.

CONCLUSIONS

Lu was in coalignment with Lm alpha5 chain in gingival epithelia. Lu also seemed to have a role in gingival epithelial cell adhesion together with integrin alpha(3)beta(1).

Expression pattern of adhesion molecules in junctional epithelium differs from that in other gingival epithelia

BACKGROUND AND OBJECTIVE

The gingival epithelium is the physiologically important interface between the bacterially colonized gingival sulcus and periodontal soft and mineralized connective tissues, requiring protection from exposure to bacteria and their products. However, of the three epithelia comprising the gingival epithelium, the junctional epithelium has much wider intercellular spaces than the sulcular epithelium and oral gingival epithelium. Hence, the aim of the present study was to characterize the cell adhesion structure in the junctional epithelium compared with the other two epithelia.

MATERIAL AND METHODS

Gingival epithelia excised at therapeutic flap surgery from patients with periodontitis were examined for expression of adhesion molecules by immunofluorescence.

RESULTS

In the oral gingival epithelium and sulcular epithelium, but not in the junctional epithelium, desmoglein 1 and 2 in cell-cell contact sites were more abundant in the upper than the suprabasal layers. E-cadherin, the main transmembranous molecule of adherens junctions, was present in spinous layers of the oral gingival epithelium and sulcular epithelium, but was scarce in the junctional epithelium. In contrast, desmoglein 3 and P-cadherin were present in all layers of the junctional epithelium as well as the oral gingival epithelium and sulcular epithelium. Connexin 43 was clearly localized to spinous layers of the oral gingival epithelium, sulcular epithelium and parts of the junctional epithelium. Claudin-1 and occludin were expressed in the cell membranes of a few superficial layers of the oral gingival epithelium.

CONCLUSION

These findings indicated that the junctional epithelium contains only a few desmosomes, composed of only desmoglein 3; adherens junctions are probably absent because of defective E-cadherin. Thus, the anchoring junctions connecting junctional epithelium cells are lax, causing widened intercellular spaces. In contrast, the oral gingival epithelium, which has a few tight junctions, functions as a barrier.

Junctional epithelium in rats is characterized by slow cell proliferation

BACKGROUND

The integrity of junctional epithelium (JE) and a firm epithelial adhesion to the tooth surface are maintained by the balance between cell proliferation and cell death. Maintaining the JE structure is essential for the protection of periodontal connective tissues against oral microbes. In this study, the proliferative activity and the expression of caspase 3, a cysteine protease associated with cell death, were studied in rat JE and other epithelial structures during molar tooth development.

METHODS

Fourteen rats aged 10 to 70 days were injected with bromodeoxyuridine (BrdU). Samples of first and second molars were selected for immunohistochemical staining. BrdU incorporation was studied in oral epithelium (OE) covering the erupting tooth, reduced enamel epithelium (REE), and gingival epithelium (GE), sulcular epithelium (SE), and JE. Samples were also subjected to immunohistochemical analysis for proliferating cell nuclear antigen (PCNA) and caspase 3.

RESULTS

The basal cells of the GE were actively proliferating, but in the JE, only a few cells were positive for BrdU or PCNA immunostaining. Some outer REE cells were proliferating during tooth eruption. Caspase 3 expression was in specific areas of REE after completion of amelogenesis.

CONCLUSIONS

Results showed slow proliferative activity in the rat JE. However, specific studies on cellular turnover and cell migration are needed to understand tissue homeostasis in this area.