Molecular imaging assessment of periodontitis lesions in an experimental mouse model.

OBJECTIVE: We aimed to evaluate molecular imaging as a novel diagnostic tool for mice periodontitis model induced by ligature and Porphyromonas gingivalis (Pg) inoculation. MATERIALS AND METHODS: Twelve female mice were assigned to the following groups: no treatment as control group (n = 4); periodontitis group induced by ligature and Pg as Pg group (n = 4); and Pg group treated with glycyrrhizinic acid (GA) as Pg + GA group (n = 4). All mice were administered a myeloperoxidase (MPO) activity-specific luminescent probe and observed using a charge-coupled device camera on day 14. Image analysis on all mice was conducted using software to determine the signal intensity of inflammation. Additionally, histological and radiographic evaluation for periodontal inflammation and bone resorption at the site of periodontitis, and quantitative enzyme-linked immunosorbent assay (ELISA) were conducted on three mice for each group. Each experiment was performed three times. RESULTS: Levels of serum IgG antibody against P. gingivalis were significantly higher in the Pg than in the Pg + GA group. Histological analyses indicated that the number of osteoclasts and neutrophils were significantly lower in the Pg + GA than in the Pg group. Micro-CT image analysis indicated no difference in bone resorption between the Pg and Pg + GA groups. The signal intensity of MPO activity was detected on the complete craniofacial image; moreover, strong signal intensity was localized specifically at the periodontitis site in the ex vivo palate, with group-wise differences. CONCLUSIONS: Molecular imaging analysis based on MPO activity showed high sensitivity of detection of periodontal inflammation in mice. CLINICAL RELEVANCE: Molecular imaging analysis based on MPO activity has potential as a diagnostic tool for periodontitis.

Aggregatibacter actinomycetemcomitans regulates the expression of integrins and reduces cell adhesion via integrin α5 in human gingival epithelial cells.

Gingival epithelial cells form a physiological barrier against bacterial invasion. Excessive bacterial invasion destroys the attachment between the tooth surface and the epithelium, resulting in periodontitis. Integrins play a significant role in cell attachment; therefore, we hypothesized that bacterial infection might decrease the expressions of these integrins in gingival epithelial cells, resulting in reduced cell adhesion. Immortalized human gingival epithelial cells were co-cultured with Aggregatibacter actinomycetemcomitans Y4 (Aa Y4), and the gene expression levels of IL-8, proliferating cell nuclear antigen (PCNA), and integrins (α2, α3, α5, ß4, and ß6) were measured using quantitative reverse transcription polymerase chain reaction. Expression of PCNA and integrins, except integrin α5, was significantly downregulated, while expression of IL-8 and integrin α5 was significantly upregulated in the cells co-cultured with Aa Y4. The number of adherent cells significantly decreased when co-cultured with Aa Y4, as determined using cell adhesion assays. In the cells co-cultured with Aa Y4 and an integrin α5 neutralizing antibody, there was no effect on the expression of IL-8 and PCNA, while the expressions of integrins α2, α3, ß4, and ß6, and the number of adherent cells did not decrease. The number of invading bacteria in the cells was reduced in the presence of the antibody and increased in the presence of TLR2/4 inhibitor. Therefore, integrin α5 might be involved in Aa Y4 invasion into gingival epithelial cells, and the resulting signal transduction cascade reduces cell adhesion by decreasing the expression of integrins, while the TLR2/4 signaling cascade regulates IL-8 expression.

Rho-kinase regulates extracellular matrix-mediated osteogenic differentiation of periodontal ligament cells.

The periodontal ligament (PDL) cells contain heterogeneous mesenchymal cell populations, which have the ability to differentiate into cells that produce adjacent mineralized tissues and abundant extracellular matrix (ECM). ECM is essential not only for the homeostasis of the periodontal tissue, but also for controlling the differentiation of the PDL cells. The process of differentiation involves mechanotransduction, which links the ECM to the cytoskeleton. The present study investigated the roles of Rho-associated coiled-coil containing protein kinase (ROCK) signaling, a crucial regulator of the cytoskeleton, during ECM-mediated osteogenic differentiation of PDL cells in vitro. The PDL cells were isolated from human periodontal ligaments of extracted teeth and cultured in osteogenic medium with or without Y-27632, a pharmacological inhibitor of ROCK. ECM-coated plates were used for ECM-mediated differentiation. The osteogenic phenotype was evaluated at different time points by real-time RT-PCR for the gene encoding alkaline phosphatase (ALP) and an ALP activity assay. The effects of ROCK on cytoskeletal changes and ECM synthesis were examined by immunofluorescence analysis. Y-27632 significantly inhibited ALP at the mRNA and protein activity levels in the late stage of differentiation; concomitantly, the actin filament content and the extracellular levels of collagen-I and fibronectin were markedly decreased by Y-27632. Exogenous collagen-I and fibronectin temporally increased ALP activity, with fibronectin showing a more pronounced effect. Importantly, ECM-mediated differentiation was almost completely inhibited by Y-27632. These findings indicated that ECM-mediated differentiation is dependent on ROCK signaling, and ROCK signaling contributes to the establishment of the ECM microenvironment for PDL cell differentiation.

Smad2 overexpression enhances adhesion of gingival epithelial cells.

OBJECTIVE: Gingival epithelial cells play an important role in preventing the initiation of periodontitis, by their hemidesmosomal adhesion to the tooth root surface. Adhesion requires integrin-extracellular matrix (ECM) interactions that are intricately regulated by transforming growth factor-ß (TGF-ß) signaling. However, the mechanisms underlying the interplay between adhesion molecules and TGF-ß, especially the respective roles of Smad2 and Smad3, remain elusive. In this study, we examined the effects of Smad overexpression on gingival epithelial cell adhesion and expression profiles of integrin and ECM-related genes. METHODS: Human gingival epithelial cells immortalized by the SV40 T-antigen were transfected with Smad2- and Smad3-overexpression vectors. A cell adhesion assay involving fluorescence detection of attached cells was performed using the ArrayScan imaging system. Real-time PCR was performed to examine the kinetics of integrin and ECM gene expression. In vitro and in vivo localization of adhesion molecules was examined by immunofluorescence analysis. RESULTS: By using SB431542, a specific inhibitor of the TGF-ß type I receptor, Smad2/3 signaling was confirmed to be dominant in TGF-ß1-induced cell adhesion. The Smad2-transfectant demonstrated higher potency for cell adhesion and integrin expression (α2, α5, ß4, and ß6) than the Smad3-transfectant, whereas little or no change in ECM expression was observed in either transfectant. Moreover, the gingival epithelium of transgenic mice that overexpressed Smad2 driven by the keratin 14 promoter showed increased integrin α2 expression. CONCLUSION: These findings indicate the crucial role of Smad2 in increased adhesion of gingival epithelial cells via upregulation of integrin α2.

Oral infection control to assist infliximab therapy in a Behçet's disease patient with severe eye inflammation in response to dental treatment: a case report.

KEY CLINICAL MESSAGE: We report a case of Behçet's disease which was aggravated by psychological stress and oral infection. The control of oral infection under medical and dental collaboration is important for providing Behçet's disease patients with the optimal medical care and for facilitating the relief of the primary disease.

Osteogenic differentiation regulated by Rho-kinase in periodontal ligament cells.

The periodontal ligament is a multifunctional soft connective tissue, which functions not only as a cushion supporting the teeth against occlusal force, but is also a source of osteogenic cells that can regenerate neighboring hard tissues. Periodontal ligament cells (PDL cells) contain heterogeneous cell populations, including osteogenic cell progenitors. However, the precise mechanism underlying the differentiation process remains elusive. Cell differentiation is regulated by the local biochemical and mechanical microenvironment that can modulate gene expression and cell morphology by altering actin cytoskeletal organization mediated by Rho-associated, coiled-coil containing protein kinase (ROCK). To determine its role in PDL cell differentiation, we examined the effects of ROCK on cytoskeletal changes and kinetics of gene expression during osteogenic differentiation. PDL cells were isolated from human periodontal ligament on extracted teeth and cultured in osteogenic medium for 14 days. Y-27632 was used for ROCK inhibition assay. Osteogenic phenotype was determined by monitoring alkaline phosphatase (ALP) activity and calcium deposition by Alizarin Red staining. ROCK-induced cytoskeletal changes were examined by immunofluorescence analysis of F-actin and myosin light chain 2 (MLC2) expression. Real-time PCR was performed to examine the kinetics of osteogenic gene expression. F-actin and phospho-MLC2 were markedly induced during osteogenic differentiation, which coincided with upregulation of ALP activity and mineralization. Subsequent inhibition assay indicated that Y-27632 significantly inhibited F-actin and phospho-MLC2 expression in a dose-dependent manner with concomitant partial reversal of the PDL cell osteogenic phenotype. PCR array analysis of osteogenic gene expression indicated that extracellular matrix genes, such as fibronectin 1, collagen type I and III, and biglycan, were significantly downregulated by Y27632. These findings indicated crucial effects of ROCK in cytoskeletal reorganization and differentiation of PDL cells toward osteogenic cells. ROCK contributes to induction of osteogenic differentiation by synergistic increases in extracellular matrix gene expression in PDL cells.

Chronic periodontitis with multiple risk factor syndrome: a case report.

OBJECTIVE: Multiple risk factor syndrome is a clustering of cardiovascular risk factors, such as diabetes, dyslipidemia, hypertension, and obesity associated epidemiologically with insulin resistance. This report describes the clinical course of a patient suffering from severe periodontitis with multiple risk factor syndrome, and discusses the association between periodontal infection and systemic health. METHODS: The patient had a history of type 2 diabetes, dyslipidemia, and hypertension for over 10 years. At baseline, her hemoglobin A1 c was 8.1%. However, she had no diabetic complications except periodontitis. The IgG antibody titers against Porphyromonas gingivalis FDC 381 and SU63 were elevated above the mean of healthy subjects +2 standard deviations. Intensive periodontal treatment, including periodontal surgery, was performed to reduce periodontal infection and bacteremia. Her systemic and periodontal conditions were evaluated longitudinally for 10 years. RESULTS: Following periodontal treatment, antibody titers against Porphyromonas gingivalis and hemoglobin A1c values were significantly improved. The other clinical data and medication for her systemic condition also remained stable during supportive periodontal therapy. However, she developed myocardial infarction, and showed continuous deterioration of hemoglobin A1 c level and periodontitis. CONCLUSION: The long-term clustering of risk factors, such as diabetes, dyslipidemia, hypertension, and periodontitis, are associated with the development of myocardial infarction. Treatment of systemic conditions in combination with comprehensive periodontal treatment is important in management of patients with multiple risk factor syndrome.