Immunohistochemical localization of epidermal growth factor receptors in human gingival epithelia

Submandibular Gland Pathogenesis Following SARS-CoV-2 Infection and Implications for Xerostomia

Although SARS-CoV-2 induces mucin hypersecretion in the respiratory tract, hyposalivation/xerostomia has been reported by COVID-19 patients. We evaluate the submandibular gland (SMGs) pathogenesis in SARS-CoV-2-infected K18-hACE2 mice, focusing on the impact of infection on the mucin production and structural integrity of acini, ductal system, myoepithelial cells (MECs) and telocytes. The spike protein, the nucleocapsid protein, hACE2, actin, EGF, TNF-α and IL-1β were detected by immunofluorescence, and the Egfr and Muc5b expression was evaluated. In the infected animals, significant acinar hypertrophy was observed in contrast to ductal atrophy. Nucleocapsid proteins and/or viral particles were detected in the SMG cells, mainly in the nuclear membrane-derived vesicles, confirming the nuclear role in the viral formation. The acinar cells showed intense TNF-α and IL-1β immunoexpression, and the EGF-EGFR signaling increased, together with Muc5b upregulation. This finding explains mucin hypersecretion and acinar hypertrophy, which compress the ducts. Dying MECs and actin reduction were also observed, indicating failure of contraction and acinar support, favoring acinar hypertrophy. Viral assembly was found in the dying telocytes, pointing to these intercommunicating cells as viral transmitters in SMGs. Therefore, EGF-EGFR-induced mucin hypersecretion was triggered by SARS-CoV-2 in acinar cells, likely mediated by cytokines. The damage to telocytes and MECs may have favored the acinar hypertrophy, leading to ductal obstruction, explaining xerostomia in COVID-19 patients. Thus, acinar cells, telocytes and MECs may be viral targets, which favor replication and cell-to-cell viral transmission in the SMG, corroborating the high viral load in saliva of infected individuals.

Epidermal growth factor receptor signaling suppresses αvβ6 integrin and promotes periodontal inflammation and bone loss

In periodontal disease (PD), bacterial biofilms cause gingival inflammation, leading to bone loss. In healthy individuals, αvβ6 integrin in junctional epithelium maintains anti-inflammatory transforming growth factor-β1 (TGF-β1) signaling, whereas its expression is lost in individuals with PD. Bacterial biofilms suppress β6 integrin expression in cultured gingival epithelial cells (GECs) by attenuating TGF-β1 signaling, leading to an enhanced pro-inflammatory response. In the present study, we show that GEC exposure to biofilms induced activation of mitogen-activated protein kinases and epidermal growth factor receptor (EGFR). Inhibition of EGFR and ERK stunted both the biofilm-induced ITGB6 suppression and IL1B stimulation. Furthermore, biofilm induced the expression of endogenous EGFR ligands that suppressed ITGB6 and stimulated IL1B expression, indicating that the effects of the biofilm were mediated by autocrine EGFR signaling. Biofilm and EGFR ligands induced inhibitory phosphorylation of the TGF-β1 signaling mediator Smad3 at S208. Overexpression of a phosphorylation-defective mutant of Smad3 (S208A) reduced the β6 integrin suppression. Furthermore, inhibition of EGFR signaling significantly reduced bone loss and inflammation in an experimental PD model. Thus, EGFR inhibition may provide a target for clinical therapies to prevent inflammation and bone loss in PD.

Betacellulin in Chronic Periodontitis Patients With and Without Type 2 Diabetes Mellitus: An Immunohistochemical Study

BACKGROUND

The host immune response to bacterial dental plaque determines periodontal disease susceptibility by increasing the secretion of inflammatory cytokines. The Epidermal Growth Factor family cytokines stimulate proliferation and keratinization of cells in dermis and oral epithelium. Epidermal Growth Factor family consists of Amphiregulin, Betacellulin, Epiregulin, Epigen, Heparin binding Epidermal Growth Factor like growth factor and transforming Growth Factor-alpha.

AIM

The current study aimed to investigate expression of Betacellulin in chronic periodontitis patients with and without type 2 diabetes mellitus and thereby assessing role of betacellulin in periodontal health and disease.

MATERIALS AND METHODS

Present study comprised of 90 participants, age ranges from 18 to 60-year-old, for the period of March 2010 to May 2011. Participants were categorized into three groups based Gingival index (GI), probing depth (PD) and clinical attachment loss (CA Loss). Group 1 consisted 30 individuals with clinically healthy periodontium, Group-2 consisted 30 individuals with GI>1, PD≥5 mm, and CA Loss>3 mm. Group-3 (Chronic Periodontitis with type 2 diabetes mellitus) consisted 30 with GI >1, PD≥5 mm, and CA Loss>3 mm. Immunohistochemical localization and quantification of Betacellulin was done in gingival tissue samples from all groups.

RESULTS

Data showed expression of Betacellulin were higher in chronic periodontitis as compared to healthy. A positive correlation found in Betacellulin expression and Probing Depth in chronic periodontitis.

CONCLUSION

This footmark study impacts the role of Betacellulin in pathogenesis and progression of periodontal disease which will help in exploration of novel immunotherapeutic strategies and immunological research activity in this field.

Inactivation of epidermal growth factor by Porphyromonas gingivalis as a potential mechanism for periodontal tissue damage

Porphyromonas gingivalis is a Gram-negative bacterium associated with the development of periodontitis. The evolutionary success of this pathogen results directly from the presence of numerous virulence factors, including peptidylarginine deiminase (PPAD), an enzyme that converts arginine to citrulline in proteins and peptides. Such posttranslational modification is thought to affect the function of many different signaling molecules. Taking into account the importance of tissue remodeling and repair mechanisms for periodontal homeostasis, which are orchestrated by ligands of the epidermal growth factor receptor (EGFR), we investigated the ability of PPAD to distort cross talk between the epithelium and the epidermal growth factor (EGF) signaling pathway. We found that EGF preincubation with purified recombinant PPAD, or a wild-type strain of P. gingivalis, but not with a PPAD-deficient isogenic mutant, efficiently hindered the ability of the growth factor to stimulate epidermal cell proliferation and migration. In addition, PPAD abrogated EGFR-EGF interaction-dependent stimulation of expression of suppressor of cytokine signaling 3 and interferon regulatory factor 1. Biochemical analysis clearly showed that the PPAD-exerted effects on EGF activities were solely due to deimination of the C-terminal arginine. Interestingly, citrullination of two internal Arg residues with human endogenous peptidylarginine deiminases did not alter EFG function, arguing that the C-terminal arginine is essential for EGF biological activity. Cumulatively, these data suggest that the PPAD-activity-abrogating EGF function in gingival pockets may at least partially contribute to tissue damage and delayed healing within P. gingivalis-infected periodontia.

Reactions of periodontal ligament epithelial cell clusters and OX6-immunopositive cells to experimental tooth movement and periodontitis

BACKGROUND AND OBJECTIVE

The aim of this study was to investigate reactions of periodontal ligament epithelial cell clusters and major histocompatibility complex class II (OX6)-immunopositive cells to simultaneously induced tooth movement and periodontitis employing Waldo's method.

MATERIAL AND METHODS

Elastic gums were inserted between the right upper first and second molars of rats. Animals were killed by intracardiac perfusion on days 1, 3, 7 and 14 after the experimental procedures, and maxillary molars were decalcified and processed for OCT compound. Cytokeratin and OX6 antibodies to detect epithelial and immunocompetent cells were used for double-fluorescence immunohistochemistry. Immunostained sections of rat upper molar regions were examined with a fluorescence microscope.

RESULTS

Large periodontal ligament epithelial cell clusters appeared and became contiguous with each other, and OX6-immunopositive cells surrounded the clusters over time in the periodontal ligament near the gum insertion site. In the periodontal ligament distant from the gum insertion site, epithelial cell clusters and OX6-immunopositive cells were scattered. After 14 d, thickened epithelium and elongated rete pegs were found close to large epithelial cell clusters in the periodontal ligament near the gum insertion site.

CONCLUSION

These findings suggest proliferation and/or aggregation of periodontal ligament epithelial cells, and interaction between OX6-immunopositive cells and the periodontal ligament epithelial cells, in response to tooth movement and periodontal inflammation. This method may be a useful experimental model to elucidate the relationship between rete pegs and periodontal ligament epithelial cell clusters in inflammatory conditions.

Effects of epidermal growth factor and/or nerve growth factor on Malassez's epithelial rest cells in vitro: expression of mRNA for osteopontin, bone morphogenetic protein 2 and vascular endothelial growth factor

BACKGROUND AND OBJECTIVE

Malassez's epithelial rest (MER) cells are involved in the maintenance and homeostasis of the periodontal ligament (PDL). The purpose of this study was to determine the effects of epidermal growth factor (EGF) and/or nerve growth factor (NGF) in vitro on these functions of MER cells.

MATERIAL AND METHODS

MER cells from porcine PDL were incubated for 3 or 9 h after the addition of EGF and/or NGF to final concentrations of 10 ng/mL. Cells cultured without those growth factors were used as controls. The expression of mRNA for osteopontin, bone morphogenetic protein 2 (BMP-2) and vascular endothelial growth factor (VEGF) was analyzed using quantitative RT-PCR.

RESULTS

There was a decrease in the expression of osteopontin mRNA by MER cells treated for 9 h with NGF and the level of mRNA expressed was lower than that of the control and EGF-treated groups. The expression of BMP-2 mRNA by MER cells treated with NGF for 9 h also decreased, and was lower than that of the control and EGF-treated groups. The expression of VEGF mRNA by MER cells treated with EGF for 3 or 9 h was higher than in the control and NGF-treated groups. The expression of VEGF mRNA was lower in MER cells treated with NGF for 3 and 9 h than in the control and EGF-treated groups, and decreased from 3 to 9 h of treatment. EGF stimulated MER cells to secrete VEGF, which suggests that EGF plays an important role in maintaining the homeostasis of the PDL. NGF acts on MER cells to inhibit calcification in the PDL. Furthermore, in the EGF+NGF-treated MER cells, expression of mRNA for BMP-2 and VEGF was similar to that of the NGF-treated group, but cell proliferation and expression of osteopontin mRNA were similar to that of the EGF-treated group.

CONCLUSION

EGF and NGF play important roles in maintaining the PDL.

The regeneration of gingiva: its potential value for the recession of healthy gingiva

The partial withdrawal of healthy gingiva not only affects the appearance but also can bring about some complaints when the healthy gingiva is stimulated for some reasons. The junctional epithelium of gingiva moves to the root with aging, and compared with the tooth crown, the tooth root which has lower mineral content is prone to decay. Thus, gingival recession could lead to the root surface decay and make the tooth sensitive. Gingival recession is not reversible. Once the healthy gingiva shrinked, the teeth could feel uncomfortable, food impaction appeared and the original restorations have to be dismantled with new restorations on account of the exposure of coronal edges. Then the regeneration of gingiva is important. In this article, a hypothesis is proposed that free gingiva could get back to the former non-recessive location through guiding the healthy junctional epithelium to propagate along the crowns. Then the gingiva not only restores the beautiful outlook but also returns the natural barrier function.

The effect of epidermal growth factor on matrix metalloproteinases and tissue inhibitors of metalloproteinase gene expression in cultured human gingival fibroblasts

OBJECTIVE

Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) play a role in the breakdown of the extracellular matrix during normal physiological processes, and in pathological processes, including periodontitis. The aim of this study was to evaluate the effect of epidermal growth factor (EGF) on the expression of MMPs and TIMPs in cultured human gingival fibroblasts.

METHODS

Fibroblasts were stimulated with 10(-3), 10(-6) or 10(-12)M EGF for 24h; untreated fibroblasts served as controls. Alterations in the expression of MMP-1, 2, 3, 7, 11, TIMP-1 and 2 were evaluated using real-time PCR and Western blotting. beta-Actin expression was used as a reference to normalize gene expression.

RESULTS

Increased MMP-1, 3, 7 and 11 expressions were observed at all EGF concentrations (p<0.05). At the lowest EGF concentration, MMP-1, 3 and 7 presented the lowest expression and MMP-11 presented the greatest expression; at higher EGF concentrations, MMP-1, 3 and 7 presented greater up-regulation, and MMP-11 lower up-regulation (p<0.05). Protein expression was similarly regulated by EGF: increased up-regulation of MMP-1, 3 and 7 was observed with increasing EGF concentrations, except for MMP-11 that exhibited greater up-regulation at the lower EGF concentration. The gene expression of MMP-2, TIMP-1 and 2 was not affected by EGF (p<0.05).

CONCLUSIONS

We conclude that EGF regulates expression for MMP-1, 3, 7 and 11 in a dose-dependent manner, suggesting that EGF may play a role in periodontal destruction and wound repair.

Role of growth factors on periodontal repair

Regeneration of periodontal structures lost during periodontal diseases constitutes a complex biological process regulated among others by interactions between cells and growth factors. Growth factors are biologically active polypeptides affecting the proliferation, chemotaxis and differentiation of cells from epithelium, bone and connective tissue. They express their action by binding to specific cell-surface receptors present on various target cells including osteoblasts, cementoblasts and periodontal ligament fibroblasts. The observation that growth factors participate in all cell functions led to exogenous application during periodontal tissue repair aiming to their use as an alternative therapeutic approach to periodontal therapy. Cell types and cultures conditions, dose, carrier materials, application requirements are of critical importance in the outcome of periodontal repair. The purpose of this article is to review the literature with respect to the biological actions of PDGF, TGF, FGF, IGF and EGF on periodontal cells and tissues, which are involved in periodontal regeneration.

Regulation of epithelial cell growth factor receptor protein and gene expression using a rat periodontitis model

BACKGROUND AND OBJECTIVE

Regulation of epithelial cell behavior associated with periodontitis is not well elucidated but many responses will ultimately be regulated by growth factor receptors. Using a rat experimental periodontitis model, protein and gene expression of select growth factor receptors in junctional and pocket epithelium were examined.

MATERIAL AND METHODS

Periodontal disease was induced by daily topical application of lipopolysaccharide using an established protocol. Animals were killed at time 0 (control), and at 2 and 8 wk. Frozen tissue samples were collected from the right palatal gingival soft tissue, and the left periodontal tissues were decalcified and embedded in paraffin. Laser microdissection and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to quantify keratinocyte growth factor receptor (KGFR), hepatocyte growth factor receptor (HGFR), epidermal growth factor receptor (EGFR) and fibroblast growth factor receptor 1 (FGFR1) gene expression, and in situ RT-PCR localized these increases to specific epithelial cells. Receptor protein expression was examined immunohistochemically. In cell culture, induction of HGFR and KGFR protein expression by serum, lipopolysaccharide and pro-inflammatory cytokines were examined using flow cytometry.

RESULTS

Eight-week tissue samples exhibited histological changes consistent with periodontitis. KGFR and HGFR gene and protein expression were significantly induced at the 8 wk time point. KGFR expression was significantly up-regulated in basal and parabasal pocket epithelial cells, but HGFR was up-regulated throughout the pocket epithelium. In cell culture serum, lipopolysaccharide and pro-inflammatory cytokines, interleukin-1beta and tumour necrosis factor-alpha significantly induced KGFR protein receptor expression, but HGFR expression was only induced by serum.

CONCLUSION

KGFR and HGFR are highly up-regulated in this model of periodontal disease and may play a significant role in regulating the proliferation and migration of pocket epithelium.

The epithelial cell rests of Malassez--a role in periodontal regeneration?

This article reviews general aspects about the epithelial cell rests of Malassez (ERM). The historical and general morphological features of the ERM are briefly described. The embryological derivation of the ERM is presented as an important consideration in understanding the events associated with their origin and possible functional roles within the periodontal ligament. The ultrastructural description of the ERM is also included to complement the morphological characteristics which distinguish these cells as the unique epithelial element of the periodontal ligament. The unique ability of these cells to synthesize and secrete a number of proteins usually associated with cells of mesenchymal origin, rather than ectodermal origin, is discussed in light of their role in cementum repair and regeneration. Such considerations lead to our hypothesis that one of the functional roles of the ERM may lie not only their role in maintaining and contributing to the normal periodontal cellular elements and function but also contributing, in a significant manner, to periodontal regeneration.

Epidermal growth factor synergistically enhances interleukin-8 production in human gingival fibroblasts stimulated with interleukin-1beta

The chemokine interleukin-8 (IL-8) has been implicated in inflammatory diseases including periodontitis. In this study the effect of epidermal growth factor (EGF) on the production and regulation of interleukin-8 (IL-8) in human gingival fibroblasts challenged with interleukin-1beta (IL-1beta) was investigated. EGF, in comparison to the effect of IL-1beta, weakly increased the mRNA and protein expression of IL-8 in gingival fibroblasts. When the cells were treated simultaneously with EGF and IL-1beta, however, EGF synergistically enhanced the mRNA expression and production of IL-8. The stimulatory effect of EGF on IL-1beta-induced IL-8 production was completely abolished by the broad range tyrosine kinase inhibitor Herbimycin A, and considerably reduced by the receptor tyrosine kinase specific inhibitor PD 153035. Herbimycin A abolished IL-8 production induced by IL-1beta, whereas PD 153035 had no effect on the cytokine-induced IL-8 production. Furthermore, the p38 mitogen-activated protein (MAP) kinase inhibitor SB 203580 reduced IL-8 production induced by IL-1beta as well as by the combination of EGF and IL-1beta but had no effect on EGF-induced IL-8 production. In conclusion, the study demonstrates that EGF synergistically stimulates IL-8 production in the presence of IL-1beta and that tyrosine kinase(s) seem to be involved in the signalling pathway of IL-1beta and EGF. The synergistic interactions between EGF and IL-1beta on IL-8 production may play an essential role in the pathogenesis of the inflammatory disease periodontitis.

Upregulation of the Expression of Epidermal Growth Factor and Its Receptor in Gingiva Upon Cyclosporin A Treatment

BACKGROUND

To understand the roles of epidermal growth factor (EGF) and EGF receptor (EGF-R) in cyclosporin A (CsA)-induced gingival overgrowth, expression of EGF and EGF-R upon CsA treatment was examined in an oral epidermoid carcinoma cell line of humans (OECM-1) and in edentulous gingiva of rats.

METHODS

In vitro study: after CsA treatment, OECM-1 cells were harvested to evaluate their mRNA and protein expression of EGF and EGF-R with reverse transcriptase-polymerase chain reaction (RT-PCR), Western blot, and immunocytochemistry (ICC). In vivo study: 3 weeks after extraction of all maxillary molars, 20 male Sprague-Dawley rats were assigned to a CsA group (30 mg/kg, fed daily) and a control group. Five rats per group were sacrificed at weeks 1 and 4. Edentulous ridge specimens were obtained for evaluating their mRNAs and protein expression with RT-PCR, real-time RT-PCR, and immunohistochemistry (IHC). In both in vitro and in vivo experiments, the proliferating potential of epithelial cells was examined by the presence of proliferating cell nuclear antigen (PCNA).

RESULTS

In vitro: dose-dependently increased mRNA expression of EGF and EGF-R in OECM-1 cells was noted after CsA treatment. Protein expressions of EGF and EGF-R were higher in OECM-1 with CsA treatment than without CsA. In vivo: higher mRNA and protein expressions of EGF and EGF-R were also observed in the gingival tissues of CsA-treated rats. In both in vitro and in vivo experiments, greater PCNA expression after CsA treatment was demonstrated.

CONCLUSIONS

Higher expression of EGF and EGF-R upon CsA therapy was observed in OECM-1 epithelial cells of humans and in edentulous gingiva of rats. We suggest that CsA could upregulate gene and protein expression of EGF and EGF-R, and the upregulation may play a role in gingival overgrowth.

Epidermal growth factor receptor distribution in pericoronal follicles: relationship with the origin of odontogenic cysts and tumors

OBJECTIVE

Investigate the distribution of epidermal growth factor receptor (EGFR) in pericoronal follicles as a predictor of progression to odontogenic cysts and tumors.

STUDY DESIGN

Immunohistochemical EGFR staining patterns (membrane-only, cytoplasm-only, or combined membrane and cytoplasmic staining) in the reduced enamel epithelium and nests of odontogenic epithelium associated with follicles of impacted molar teeth were evaluated. The staining pattern of 20 specimens of pericoronal follicle was compared with that of 16 normal oral mucosa samples and to squamous cell carcinoma samples.

RESULTS

Combined membrane and cytoplasmic staining was observed for normal oral mucosa mostly in proliferating layers (basal and suprabasal), decreasing in intensity toward the surface. Seven epithelial nests presented membrane-only staining, and the majority presented either a cytoplasm-only or a combined staining pattern. The staining patterns observed in reduced enamel epithelium were cytoplasm-only and combined.

CONCLUSION

EGFR membrane-only staining may be an indicator of increased potential for epithelial nests to become odontogenic cysts or tumors.

The junctional epithelium: from health to disease

The junctional epithelium is located at a strategically important interface between the gingival sulcus, populated with bacteria, and the periodontal soft and mineralized connective tissues that need protection from becoming exposed to bacteria and their products. Its unique structural and functional adaptation enables the junctional epithelium to control the constant microbiological challenge. The antimicrobial defense mechanisms of the junctional epithelium, however, do not preclude the development of gingival and periodontal lesions. The conversion of the junctional to pocket epithelium, which is regarded as a hallmark in disease initiation, has been the focus of intense research in recent years. Research has shown that the junctional epithelial cells may play a much more active role in the innate defense mechanisms than previously assumed. They synthesize a variety of molecules directly involved in the combat against bacteria and their products. In addition, they express molecules that mediate the migration of polymorphonuclear leukocytes toward the bottom of the gingival sulcus. Periodontopathogens-such as Actinobacillus actinomycetemcomitans or, in particular, Porphyromonas gingivalis-have developed sophisticated methods to perturb the structural and functional integrity of the junctional epithelium. Research has focused on the direct effects of gingipains, cysteine proteinases produced by Porphyromonas gingivalis, on junctional epithelial cells. These virulence factors may specifically degrade components of the cell-to-cell contacts. This review will focus on the unique structural organization of the junctional epithelium, on the nature and functions of the various molecules expressed by its cells, and on how gingipains may attenuate the junctional epithelium's structural and functional integrity.

Salivary proteins and cytokines in drug-induced gingival overgrowth

Little is known about the involvement of saliva in gingival overgrowth (GO). It was hypothesized that, in this situation, the composition of saliva is altered. Thus, proteins, albumin, cytokines, and growth factors in whole and glandular saliva were investigated. Differences between glandular and gingival contributions to the composition of saliva were explored in patients medicated with cyclosporin who exhibited GO (responders), those without GO (non-responders), and non-medicated subjects (controls). In whole saliva, interleukin-1alpha (IL-1alpha), IL-6, IL-8, epidermal growth factor (EGF), nerve growth factor (NGF), and albumin were detected, but in glandular saliva only EGF and NGF were identified. Albumin and IL-6 differed significantly between responders and controls, although the overall profile of salivary proteins remained unchanged. Thus, inflammatory cytokines and albumin are confined to whole saliva and are associated with GO, whereas its content of EGF and NGF appears unaffected by cyclosporin.

Estrogen Suppression Induces Papillary Gingival Overgrowth in Pregnant Baboons

BACKGROUND

Alterations in sex steroids during pregnancy are associated with the development and exacerbation of reactive lesions involving the gingiva. Currently, few experimental animal models similar to humans are available to examine regulatory pathways involving sex steroids and the periodontium.

METHODS

In the present study, we used the baboon as a novel experimental model for the study of the regulatory actions of estrogen on the periodontium during pregnancy. Pregnant baboons (N = 5) were administered the potent, highly specific aromatase inhibitor CGS 20267 (2 mg/day subcutaneously) daily on days 60 through 165 of gestation (term = 184). Untreated females (N = 10) and females (5) concomitantly administered aromatase inhibitor and estradiol benzoate (2.0 mg/day each subcutaneously) served as controls. Gingival biopsies were taken between days 145 and 165 of gestation.

RESULTS

Administration of CGS 20267 in all females suppressed maternal serum concentrations of estradiol by 95% and induced the development of an exuberant papillomatous enlargement of the gingiva by gestational day 110, with the most prominent development involving the labial aspects of the anterior sextants. None of the untreated pregnant controls or females concomitantly administered aromatase inhibitor and estradiol benzoate developed gingival overgrowth. Thus, estradiol alone prevented the onset of gingival overgrowth induced by estrogen suppression. In all baboons, discontinuation of the aromatase inhibitor at time of cesarean section resulted in spontaneous regression and resolution of the papillomatous hyperplasia within 4 to 6 weeks. Clinically, the gingival papillary overgrowth was erythematous and edematous, with a propensity toward spontaneous subgingival hemorrhage. Histologically, the biopsy specimens demonstrated hyperplasia of the epithelium typified by mild hyperkeratosis, acanthosis, and elongation and isolated anastamoses of rete ridges. Subjacent to the intact epithelium was a loose connective tissue stroma with isolated areas of inflammatory cell infiltrate. Special stains verified the presence of isolated bacterial biofilms; however, no evidence of fungal filaments was present. Histological features suggestive of viral infection were notably absent in the epithelium. No evidence of viral particles or capsids was identified using transmission electron microscopy. Reverse transcription polymerase chain reaction analysis, using a panel of degenerate primers, was negative for papilloma family viruses.

CONCLUSIONS

These results are consistent with a significant role for estrogen during primate pregnancy in the regulation of cellular proliferation and differentiation within the gingiva. The baboon represents an important experimental model for studying the regulatory actions of estrogen on the periodontium during pregnancy.

Histomorphometric characteristics and expression of epidermal growth factor and its receptor by epithelial cells of normal gingiva and hereditary gingival fibromatosis

OBJECTIVE

The objective of this study was to examine the histomorphometric features and evaluate the expression of epidermal growth factor (EGF) and transmembranic receptor (EGFr) and the proliferative potential of epithelial cells from normal and hereditary gingival fibromatosis (HGF) gingival tissues.

BACKGROUND

EGF is a multifunctional cytokine with a variety of biological effects including stimulation of cell proliferation by binding to its specific EGFr.

METHODS

Immunohistochemistry was performed to measure EGF and EGFr expression and the epithelial cell proliferation was determined by measuring proliferating cell nuclear antigen (PCNA).

RESULTS

Histomorphometric evaluation indicated that in HGF the mean height of the epithelial papillae was higher compared to the normal gingiva (NG), whereas mean epithelial area and number of epithelial papillae were quite similar in both groups. The EGF and EGFr positive cells were observed in the basal, spinous and granular cell layers of both normal and HGF tissues, with a gradual reduction from the basal layer. Although the expressions of EGF and EGFr in the control group were significantly higher than those from HGF, in HGF the epithelial papilla tips showed increased number of proliferating cells and elevated expression of EGF and EGFr. There was a correlation between the proliferative potential of epithelial cells and the expression of EGF or EGFr only in the epithelial papilla tips of HGF gingiva.

CONCLUSION

Our data suggest that EGF and EGFr in the oral epithelium of HGF gingiva may stimulate epithelial cell proliferation, with the resultant apical migration of the oral epithelium and formation of the slender deep epithelial papillae; however, without hyperplastic alterations.

Analysis of in situ proliferative activity in oral gingival epithelium in patients with xerostomia

BACKGROUND

Sjögren's syndrome is an autoimmune disease characterized by xerostomia and keratoconjunctivitis sicca. The relationship between xero-stomia and proliferative activity in human gingival epithelium is not known. Proliferating cell nuclear antigen (PCNA) is a nuclear protein associated with the cell cycle. Nuclear PCNA immunoreactivity is found in the proliferative compartment of normal tissues. The aims of this study were to evaluate PCNA expression in oral gingival epithelium of healthy and inflamed gingiva obtained from patients with Sjögren's syndrome, and to compare the results to age- and gender-matched subjects with normal salivary function.

METHODS

Eighteen Sjögren's syndrome patients and 28 controls (14 with chronic periodontitis and 14 with no clinical evidence of periodontal disease) were included in the study. Biopsies were obtained from both inflamed and healthy gingiva. The expression of PCNA was evaluated in formalin-fixed, paraffin-embedded gingival samples using an immunoperoxidase technique and PC10 monoclonal antibody to PCNA.

RESULTS

PCNA expression was observed both in the basal and suprabasal layers, and was found to be more prominent in the suprabasal layers. Proliferative index (PI) in inflamed gingiva was significantly lower in the Sjögren's syndrome group. However, no significant difference was observed between the study and control groups with respect to PI in healthy gingiva. In both groups, PI was found to be increased due to inflammation.

CONCLUSIONS

Our data indicate that proliferative activity is observed in the suprabasal layers and, less frequently, in the basal layer. Inflammation caused increased proliferative activity. However, this positive effect of inflammation on epithelial cell proliferation decreased significantly with a lack of saliva. Therefore, it appears that saliva-derived biological mediators may also contribute to increased proliferative activity observed during inflammation.

Evidence for a role of mitogen-activated protein kinases in proliferating and differentiating odontogenic epithelia of inflammatory and developmental cysts

OBJECTIVE

The activation of intracellular signaling cascades involving serine/threonine kinases ERK1/2 has been variably reported either to stimulate or inhibit epithelial cell differentiation in response to extracellular signals. The purpose of our study was to determine the distribution of the signaling molecule ERK1 and its activated form pERK1/2 in the epithelial components of developmental and inflammatory odontogenic cysts in relation to parameters of differentiation and proliferation.

STUDY DESIGN

Thirty samples of dental follicles, dentigerous cysts, and radicular cysts were immunostained with antibodies to ERK1, pERK1/2, and proliferating cell nuclear antigen (a marker for proliferation). The tissues were subclassified according to the pattern of histomorphological differentiation (ie, squamous differentiation) and the proliferation rate of their epithelial components. The significance of differences in the proportion of ERK1- and pERK1/2-expressing cells among the tissue groups was determined by chi-square analysis or Fisher's exact test.

RESULTS

ERK1 and pERK1/2 were found to be expressed in a significantly higher proportion of cells with differentiated and highly proliferating epithelial components, as compared with those of nondifferentiated, quiescent epithelial rests. The epithelium of radicular cysts exhibited the highest proportion of pERK1/2-positive cells. In both dentigerous and radicular cyst samples, pERK1/2 expression was significantly higher in the inflamed tissues.

CONCLUSIONS

These data demonstrate that ERK1 and its active form pERK1/2 are associated with differentiating and actively proliferating epithelia of odontogenic cysts, and are consistent with pERK1/2 involvement in the activation of odontogenic epithelia in response to inflammation.

Immunohistochemical analysis of epidermal growth factor receptor in cyclosporin A-induced gingival overgrowth

Cyclosporin A (CsA)induced gingival overgrowth represents a tissue of fibrosis and epidermal growth factor (EGF) has been shown to induce extracellular matrix synthesis by fibroblasts. The purpose of this study was to evaluate the expression of EGF-receptor (EGF-r) in frozen sections of CsA-induced overgrown gingival tissue using immunohistochemical and semiquantitative techniques. Gingival biopsies were obtained from 12 renal transplant patients receiving CsA as well as 9 systemically and periodontally healthy individuals. Immunohistochemical staining procedures were carried out in frozen sections of gingival tissue and the expression of EGF-r was compared between the two study groups. The expression of EGF-r was more pronounced in the oral gingival epithelium of CsA-induced overgrown gingiva as compared to those of the clinically healthy gingival specimens. The reactivity in the inflammatory infiltrate and connective tissue cells of both of the study groups was similar. In conclusion, the results of the present study may suggest that CsA affects EGF-r metabolism in gingival keratinocytes resulting in an increased number of cell surface receptors, which may eventually play a role in the pathogenesis of gingival tissue alterations.

Isolation, cloning, and expression of an acid phosphatase containing phosphotyrosyl phosphatase activity from Prevotella intermedia

A novel acid phosphatase containing phosphotyrosyl phosphatase (PTPase) activity, designated PiACP, from Prevotella intermedia ATCC 25611, an anaerobe implicated in progressive periodontal disease, has been purified and characterized. PiACP, a monomer with an apparent molecular mass of 30 kDa, did not require divalent metal cations for activity and was sensitive to orthovanadate but highly resistant to okadaic acid. The enzyme exhibited substantial activity against tyrosine phosphate-containing peptides derived from the epidermal growth factor receptor. On the basis of N-terminal and internal amino acid sequences of purified PiACP, the gene coding for PiACP was isolated and sequenced. The PiACP gene consisted of 792 bp and coded for a basic protein with an M(r) of 29,164. The deduced amino acid sequence exhibited striking similarity (25 to 64%) to those of members of class A bacterial acid phosphatases, including PhoC of Morganella morganii, and involved a conserved phosphatase sequence motif that is shared among several lipid phosphatases and the mammalian glucose-6-phosphatases. The highly conservative motif HCXAGXXR in the active domain of PTPase was not found in PiACP. Mutagenesis of recombinant PiACP showed that His-170 and His-209 were essential for activity. Thus, the class A bacterial acid phosphatases including PiACP may function as atypical PTPases, the biological functions of which remain to be determined.

Effect of oral bacteria on peripheral blood leukocyte interleukin-6 and soluble interleukin-6 receptor production

To determine the effect of pathogenic oral bacteria on interleukin 6 (IL-6) and soluble IL-6 receptor production, we measured their release by human peripheral blood mononuclear cells in vitro. Unseparated peripheral blood mononuclear cells, peripheral blood lymphocytes (monocyte depleted), pure T cells, or monocytes were cultured with Actinobacillus actinomycetemcomitans, Capnocytophaga gingivalis, Capnocytophaga ochracea, Fusobacterium nucleatum or Porphyromonas gingivalis for 24 h. Supernatants were tested for IL-6 and soluble IL-6 receptor by enzyme-linked immunosorbent assay. Only monocytes and peripheral blood mononuclear cells responded with significant IL-6 release in the presence of all bacteria tested. However, peripheral blood lymphocytes were capable of producing IL-6 when activated by phytohemagglutinin or IL-2 followed by bacteria, though substantially less than cultures containing monocytes. No bacteria tested increased soluble IL-6 receptor release over spontaneous soluble IL-6 receptor release. We conclude that monocytes release IL-6 after contact with oral pathogens; however, soluble IL-6 receptor from T cells and monocytes is constitutively produced and may modulate IL-6 actions.

Epidermal growth factor in gingival crevicular fluid and its binding capacity in inflamed and non-inflamed human gingiva

Epidermal growth factor (EGF) is a pro-inflammatory small peptide (6000 Da) with a variety of biological activities including stimulation of cell differentiation and mediation of proteolysis by binding to its specific receptor on the cell surface. The purpose of this study was to determine the levels of EGF in gingival crevicular fluid (GCF) and the EGF-binding capacity to its receptor in gingival tissue. The GCF samples were collected from six patients by inserting paper strips into shallow (< 5 mm) and deep pockets (> or = 5 mm) for 30 s. The strips were soaked in 0.2 M acetate for extraction and the EGF in the supernatants was analysed by radioimmunoassay. To determine the binding capacity of EGF to its receptor, inflamed gingival tissues (pocket depth > or = 5 mm, Gingival Index = 1, 2 or 3) were collected during periodontal flap surgery and non-inflamed gingival tissues (pocket depth < 5 mm, Gingival Index = 0) were collected during surgical "crown lengthening' for aesthetic purposes. The tissues were pooled by group, homogenized for membrane preparation and the supernatants obtained after centrifugation were used in a 125IEGF binding assay. To determine the effect of inflammation on gingival EGF receptor, inflamed and non-inflamed gingival tissues were collected from six patients and prepared similarly to the binding assay. Gingival preparations were then electrophoresed for Western blot analysis with EGF receptor antiserum. The EGF level in GCF was significantly lower (P < 0.05) in the samples collected from pockets > or = 5 mm (0.9 +/- 0.6 ng/ml) than in those from pockets < 5 mm (2.4 +/- 2.1 ng/ml). The average Gingival Index was higher (2.6 +/- 0.6) in pockets > or = 5 mm than in pockets < 5 mm (1.4 +/- 1.0). Specific binding of 125I-EGF to its receptor in inflamed gingiva was 2.7-fold higher than in non-inflamed gingiva (14.4 +/- 4.9 vs 5.4 +/- 1.8 fmol/g wet tissue). Western blot analysis showed two major immunoreactive bands (180 and 120 kDa), which represent EGF receptor and its degradation products, in inflamed gingiva. The findings show that inflammation activates EGF binding capacity in gingiva and that the up-regulation of EGF receptor in inflamed gingiva might be associated with a lowered concentration of EGF in GCF produced adjacent to inflamed gingiva. This up-regulation of EGF receptor during inflammation might be an important mechanism in the pathogenesis of periodontal disease.

Detection of epidermal growth factor receptor in inflammatory periapical lesions

Epithelial cell proliferation is often observed in periapical lesions of endodontic origin. The mechanisms which stimulate the epithelial cell rests of Malassez to proliferate are not understood fully. Fifteen inflammatory periapical lesions (10 granulomas and five cysts) obtained from periapical surgery and six additional periapical lesions (four granulomas and two cysts) collected from extracted teeth were examined using immunohistochemical staining and 125I-EGF (epidermal growth factor) binding assay to detect the presence of epidermal growth factor receptor. The results indicated that the periapical lesions without epithelial cell proliferation had a weak immunoperoxidase staining or low specific binding of 125I-EGF. In contrast, the periapical lesions with epithelial cell proliferation and cyst formation exhibited a strong immunoperoxidase staining in the epithelial cells or high specific binding of 125I-EGF.

Signal transduction mechanisms in mesenchymal cells

Mesenchymal cells are continually stimulated by a wide spectrum of biological mediators. These mediators bind to receptors on the cell surface and initiate a cascade of signaling events. The initial signal transduction pathways known to be stimulated in mesenchymal cells included phospholipase C, phospholipase D, phospholipase A2, adenylate cyclase, receptor tyrosine kinases, and receptor serine/threonine kinases. These pathways are reviewed and specific applications for therapeutic intervention in wound healing and regenerative therapy in the periodontium are discussed.

Presence of secretory IgA in human periapical lesions

The concentration of secretory IgA in fluids present in the canals of 33 teeth was determined by the rocket immunoelectrophoresis technique. Except for the presence or absence of communication between the oral cavity and the root canals of the affected teeth, no other clinical finding showed significant statistical correlation with the presence of secretory IgA. The canals which were open to the oral flora had significantly higher concentrations of secretory IgA. Leaving canals open to the oral cavity may result in formation of periapical cysts.

Interleukin-1 alpha and epidermal growth factor synergistically enhance the release of collagenase by periosteal connective tissue in vitro

The effects of recombinant human interleukin-1 alpha (IL-1 alpha) and murine epidermal growth factor (EGF) on the release of collagenase were studied in an in vitro model system using periosteal explants from rabbit calvariae. Following an incubation period of 72 h it was shown that IL-1 alpha in combination with EGF (IL-1 alpha + EGF) induced a synergistic increase in the amount of collagenase released by periosteal explants. This increase appeared to be at least 10-fold. Most of the enzyme was present in a latent form since the increase in enzyme activity was only detectable after activation by APMA and the molecular weight as determined in immunoblots corresponded to the latent form of this enzyme. Incubations carried out with IL-1 alpha alone resulted in a 2- to 4-fold increase of total enzyme activity, whereas the amount of collagenase in media of EGF-treated periosteal did not surpass control values. A neutralizing anti-IL-1 alpha antibody completely blocked the enhanced release of collagenase as induced both by IL-1 alpha and by IL-1 alpha + EGF. Indomethacin partially prevented the IL-1 alpha + EGF-induced increase in enzyme release, suggesting the involvement of prostaglandins. The amount of tissue inhibitor of metalloproteinases (TIMP) as determined by ELISA was slightly elevated in culture media obtained from all cytokine-treated explants. Comparable results were obtained by Western blot analysis as well as by a functional bioassay. It is suggested that the concomitant presence of the cytokines IL-1 alpha and EGF may play an important role in collagenase-mediated degradation of collagen.

Increased rate of salivary epidermal growth factor secretion in patients with juvenile periodontitis

We compared salivary epidermal growth factor (EGF) concentrations in patients with juvenile periodontitis (JP) and periodontally healthy controls. In initial screening of 45 JP patients and a group of healthy controls, significantly higher salivary EGF concentrations were measured in the JP patients. Subsequently, 17 JP patients who had high EGF concentrations in some of their salivary samples were chosen, and a group of age- and sex-matched controls was selected. We then examined their EGF concentrations and EGF secretion rates under standardized conditions in stimulated and unstimulated saliva and studied the expression of EGF receptor (EGF-R) in their gingival tissues. The results showed that the mean EGF concentration (pmol/ml) was slightly higher in JP patients than in controls. However, the difference was statistically significant only in stimulated saliva and when calculated per milligram salivary protein. When EGF release was measured as the rate of EGF secretion (pg/min), significantly higher values were observed in JP patients than in controls both in unstimulated and stimulated saliva. Immunofluorescence microscopy (IF) of gingival samples from JP patients and their controls revealed no quantitative or qualitative differences in the expression of EGF-R. Our results demonstrate the complex nature of salivary EGF release. The elevated rate of salivary EGF secretion in JP patients may be associated with the pathogenetic mechanisms of juvenile periodontitis.

Role of matrix metalloproteinases in human periodontal diseases

Matrix metalloproteinases (MMP) are a family of proteolytic enzymes that mediate the degradation of extracellular matrix macromolecules, including interstitial and basement membrane collagens, fibronectin, laminin, and proteoglycan core protein. The enzymes are secreted or released in latent form and become activated in the pericellular environment by disruption of a Zn(++)-cysteine bond which blocks the reactivity of the active site. The major cell types in inflamed and healthy periodontal tissues (fibroblasts, keratinocytes, endothelial cells, and macrophages) are capable of responding to growth factors and cytokines, as well as to products released from the microbial flora by induction of transcription of 1 or more MMP genes. Cytokines that are likely to regulate expression of MMP genes in periodontal tissues include IL-1, TNF-alpha, and TGF-alpha. In addition, triggered PMN leukocytes which express only 2 MMP (PMN-CL and Mr 92K GL) release these enzymes from specific granule storage sites in response to a number of stimuli. The evidence that MMP are involved in tissue destruction in human periodontal diseases is still indirect and circumstantial. Cells isolated from normal and inflamed gingiva are capable of expressing a wide complement of MMP in culture and several MMP can be detected in cells of human gingiva in vivo. In addition, PMN-CL and Mr 92K GL are readily detected in gingival crevicular fluid from gingivitis and periodontitis patients. Osteoclastic bone resorption does not appear to directly involve MMP, but a body of evidence suggests that bone resorption is initiated by removal of the osteoid layer by osteoblasts by means of a collagenase-dependent process.

Expression and regulation of insulin-like growth factor-I in the rat incisor

Growth factors play an important role in the regulation of cell growth, division and differentiation. In this study the distribution and regulation of insulin-like growth factor-I (IGF-I) in the continuously erupting rat incisor was determined by immunohistochemistry. Results were evaluated both visually and with a computer-based image analysis system. The distribution and intensity of IGF-I immunoreactivity varied with developmental stage of the rat incisor. Strong IGF-I immunoreactivity was observed in differentiating odontoblasts and ameloblasts. The most intense immunoreactivity was observed in secretory ameloblasts, secretory odontoblasts and in maturation ameloblasts. Staining was weak or absent in post-secretory ameloblasts but persisted in post-secretory odontoblasts. Weak to moderate immunoreactivity was also seen in cells of the stratum intermedium and in the reduced enamel epithelium. Surrounding alveolar bone showed strong IGF-I immunoreactivity in osteoblasts and in the stratum basale and stratum spinosum of the adjacent labial gingival epithelium. In order to assess the role of GH in IGF-I expression, GH (65 micrograms/100 g bw) was administered for six days to dwarf GH deficient rats, producing a significant increase in body weight (P < 0.01). Measurements at different stages of odontogenesis showed that the staining intensity of secretory ameloblasts (P < 0.01) and maturation ameloblasts (P < 0.001) was significantly different between untreated and treated animals. These results indicate that IGF-I is present in cell populations of the enamel organ of the rat incisor found previously to exhibit growth hormone receptors, and that expression of IGF is GH dependent.(ABSTRACT TRUNCATED AT 250 WORDS)