Differential expression of transforming growth factors-β1, -β2, -β3 and the type I, II, III receptors in the lining epithelia of inflamed gingiva

Role of MAPKs in TGF-β1-induced maturation and mineralization in human osteoblast-like cells

OBJECTIVES

Our study aimed to clarify the role of mitogen-activated protein kinases (MAPKs) in transforming growth factor (TGF)-β1-stimulated mineralization in the human osteoblast-like MG63 cells.

METHODS

The viability of MG63 cells under TGF-β1 stimulation was assessed by MTS assay. Western blotting determined TGF-β1-mediated activation of extracellular signal-related protein kinase (ERK), p38, and c-Jun amino-terminal kinase (JNK). Mineralization-related gene expression was examined by quantitative real-time PCR, and mineral deposition levels were evaluated by alizarin red S staining.

RESULTS

TGF-β1 had no effect on MG63 cell proliferation. Activation of p38 was observed at 3 h post TGF-β1 stimulation. Moreover, JNK phosphorylation was upregulated by TGF-β1 from 1 to 6 h post stimulation, but had no activation on ERK phosphorylation throughout the experimental period. Treatment with JNK inhibitor diminished the alizarin red S-stained area in a dose-dependent manner. Mineral deposition was unaffected by MEK inhibitor, whereas p38 inhibitor increased the red-stained area. Gene expression levels of ALP and BSP were significantly decreased under treatment with JNK inhibitor and p38 inhibitor. The MEK inhibitor had no effect on the TGF-β1-mediated upregulation of ALP and BSP. Although all three inhibitors suppressed expression of COL I, none were found to stimulate expression of OCN.

CONCLUSIONS

Human osteoblast-like MG63 cells maturation and mineralization are induced through JNK activation of MAPK signaling in response to TGF-β1.

miR-9-1 gene methylation and DNMT3B (rs2424913) polymorphism may contribute to periodontitis

BACKGROUND

Genetic and epigenetic changes have been associated with periodontitis in various genes; however, little is known about genes involved in epigenetic mechanisms and in oxidative stress.

OBJECTIVE

This study aims to investigate the association of polymorphisms C677T in MTHFR (rs1801133) and -149C→T in DNMT3B (rs2424913), as well as the methylation profiles of MTHFR, miR-9-1, miR-9-3, SOD1, and CAT with periodontitis. The association between polymorphisms and DNA methylation profiles was also analyzed.

METHODOLOGY

The population studied was composed of 100 nonsmokers of both sexes, divided into healthy and periodontitis groups. Genomic DNA was extracted from the epithelial buccal cells, which were collected through a mouthwash. Polymorphism analysis was performed through polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), while methylation-specific PCR (MSP) or combined bisulfite restriction analysis techniques were applied for methylation analysis.

RESULTS

For DNMT3B, the T allele and the TT genotype were detected more frequently in the periodontitis group, as well as the methylated profile on the miR-9-1 promoter region. There was also a tendency towards promoter region methylation on the CAT sequence of individuals with periodontal disease.

CONCLUSION

The polymorphism -149C→T in DNMT3B (rs2424913) and the methylated profile of the miR-9-1 promoter region are associated with periodontitis.

Cell culture models of oral mucosal barriers: A review with a focus on applications, culture conditions and barrier properties

Understanding the function of oral mucosal epithelial barriers is essential for a plethora of research fields such as tumor biology, inflammation and infection diseases, microbiomics, pharmacology, drug delivery, dental and biomarker research. The barrier properties are comprised by a physical, a transport and a metabolic barrier, and all these barrier components play pivotal roles in the communication between saliva and blood. The sum of all epithelia of the oral cavity and salivary glands is defined as the blood-saliva barrier. The functionality of the barrier is regulated by its microenvironment and often altered during diseases. A huge array of cell culture models have been developed to mimic specific parts of the blood-saliva barrier, but no ultimate standard in vitro models have been established. This review provides a comprehensive overview about developed in vitro models of oral mucosal barriers, their applications, various cultivation protocols and corresponding barrier properties.

TGF-Beta Negatively Regulates the BMP2-Dependent Early Commitment of Periodontal Ligament Cells into Hard Tissue Forming Cells

Transforming growth factor beta (TGF-β) is a multi-functional growth factor expressed in many tissues and organs. Genetic animal models have revealed the critical functions of TGF-β in craniofacial development, including the teeth and periodontal tissue. However, the physiological function of TGF-β in the periodontal ligament (PDL) has not been fully elucidated. In this study, we examined the roles of TGF-β in the cytodifferentiation of PDL cells using a TGF-β receptor kinase inhibitor, SB431542. Mouse PDL cell clones (MPDL22) were cultured in calcification-inducing medium with or without SB431542 in the presence or absence of various growth factors, such as bone morphogenetic protein (BMP)-2, TGF-β and fibroblast growth factor (FGF)-2. SB431542 dramatically enhanced the BMP-2-dependent calcification of MPDL22 cells and accelerated the expression of ossification genes alkaline phosphatase (ALPase) and Runt-related transcription factor (Runx) 2 during early osteoblastic differentiation. SB431542 did not promote MPDL22 calcification without BMP-2 stimulation. The cell growth rate and collagen synthesis during the late stage of MPDL22 culture were retarded by SB431542. Quantitative reverse transcription polymerase chain reaction analysis revealed that the expressions of Smurf1 and Smad6, which are negative feedback components in the TGF-β/BMP signaling pathway, were downregulated in MPDL22 cells with SB431542 treatment. These results suggest that an endogenous signal from TGF-β negatively regulates the early commitment and cytodifferentiation of PDL cells into hard tissue-forming cells. A synthetic drug that regulates endogenous TGF-β signals may be efficacious for developing periodontal regenerative therapies.

Prospective potency of TGF-β1 on maintenance and regeneration of periodontal tissue

Periodontal ligament (PDL) tissue, central in the periodontium, plays crucial roles in sustaining tooth in the bone socket. Irreparable damages of this tissue provoke tooth loss, causing a decreased quality of life. The question arises as to how PDL tissue is maintained or how the lost PDL tissue can be regenerated. Stem cells included in PDL tissue (PDLSCs) are widely accepted to have the potential to maintain or regenerate the periodontium, but PDLSCs are very few in number. In recent studies, undifferentiated clonal human PDL cell lines were developed to elucidate the applicable potentials of PDLSCs for the periodontal regenerative medicine based on cell-based tissue engineering. In addition, it has been suggested that transforming growth factor-beta 1 is an eligible factor for the maintenance and regeneration of PDL tissue.

Smad2 is involved in the apoptosis of murine gingival junctional epithelium associated with inhibition of Bcl-2

OBJECTIVE

Gingival junctional epithelium (JE) actively contributes to the homeostasis of the periodontium. Altered activation of TGF-β signalling is implicated in the epithelium from chronic periodontitis. However, little is known about the effects of TGF-β signalling on the JE. In this study, we investigated the relationship between Smad2, which plays an important role in mediating TGF-β signal, and induction of apoptosis in the JE.

METHODS

K14-Smad2 transgenic mice were used to observe the effect of over-expression of Smad2 driven by CK14 promoter in the JE. We performed TUNEL technique to evaluate the epithelial apoptosis. Expression of apoptosis related genes was examined using real-time PCR and immunofluorescence.

RESULTS

K14-Smad2 mice showed an increased number of phospho-Smad2 positive JE cells associated with an increase in TGF-β1 expression. K14-Smad2 mice have a significantly higher percentage of TUNEL positive cells in the JE. Immunofluorescence double labelling revealed that TUNEL positive cells showed immunoreactivity to phospho-Smad2. Real-time PCR analysis of apoptosis related gene expression provided evidence of lower expression of Bcl-2 in the gingival tissue from K14-Smad2 mice. There was a strong positive reaction for Bcl-2 protein in the junctional epithelium of wild type mice, while the gingival tissue of K14-Smad2 transgenic mice had only a faint signal for Bcl-2.

CONCLUSIONS

The present study provided evidence that Smad2 plays a crucial role in the induction of apoptosis in gingival JE through inhibition of Bcl-2.

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 E-cadherin and TGF-β3 expression by CD24 in cultured oral epithelial cells

We previously reported evidence that patients with periodontitis have serum antibodies to oral Gram positive bacteria that are cross-reactive with epithelial antigens, including CD24. High level expression of CD24 was confined to the reactive periodontal epithelium and inflamed gingival attachment. As a model for the reactive epithelium of chronic periodontitis, H413 epithelial cells derived from a human oral squamous cell carcinoma were cloned and lines expressing high levels of CD24 were selected. RNA interference protocols were designed to determine if CD24 could modulate intercellular interactions and regulate the biology of these epithelial cells. Knock-down of CD24 protein was demonstrated by Western blot and flow cytometry. The level of mRNA for CD24 was reduced 90% by RNAi treatment as assayed by real-time, reverse transcriptase (RT)-PCR. Gene products known to be important in epithelial biology, including E-cadherin and TGF-beta3 that were demonstrated to undergo altered expression patterns in the periodontal lesion, were investigated. Down-regulation of CD24 mRNA was associated with reduced e-cadherin expression and up-regulated expression of snail, twist, and tgf-beta3. The cells were treated with monoclonal antibodies to CD24 to mimic the action of auto-reactive antibodies to CD24 detected in affected patients. Relative to isotype control antibody, stimulation by anti-CD24 antibodies induced up-regulated expression of e-cadherin and down-regulation of tgf-beta3 as assessed by real-time RT-PCR. No consistent changes for expression of beta-catenin, connexins, integrins, icam-1, tgf-beta1 or tgf-beta2 were observed. CD24 could play an important role in modulating expression of genes that regulate epithelial differentiation in periodontal disease.

Effect of Interleukin-1β on Transforming Growth Factor-Beta and Bone Morphogenetic Protein-2 Expression in Human Periodontal Ligament and Alveolar Bone Cells in Culture: Modulation by Avocado and Soybean Unsaponifiables

BACKGROUND

In periodontal disease, interleukin-1beta (IL-1beta) is responsible for the matrix breakdown through excessive production of degrading enzymes by periodontal ligament fibroblasts and osteoblasts. Transforming growth factor-beta (TGF-beta) plays an important role in tissue regeneration as one of the factors capable of counteracting IL-1beta effects. In this study, we investigated the in vitro effect of avocado and soya unsaponifiables (ASU) on the expression of TGF-beta1, TGF-beta2, and bone morphogenetic protein-2 (BMP-2) by human periodontal ligament (HPL) and human alveolar bone (HAB) cells in the presence of IL-1beta.

METHODS

HPL and HAB cells were incubated for 48 hours with ASU (10 microg/ml) in the presence or absence of IL-1beta (10 ng/ml). The steady-state levels of TGF-beta1, TGF-beta2, and BMP-2 mRNAs were determined by Northern blot or reverse transcription-polymerase chain reaction (RT-PCR). The amounts of TGF-beta1 and TGF-beta2 proteins were measured by enzyme-linked immunosorbent assay (ELISA).

RESULTS

The data indicated that IL-1beta strongly decreases the expression of TGF-beta1 and TGF-beta2 by HPL cells. ASU were capable of opposing the cytokine effect. In HAB cells, TGF-beta1 and BMP-2 mRNA levels were downregulated by the cytokine. ASU were found to reverse the IL-1beta-inhibiting effect. In contrast, the cytokine stimulated the production of TGF-beta2 in alveolar bone cells, with no significant effect of ASU.

CONCLUSIONS

The results indicate that the IL-1beta-driven erosive effect in periodontitis could be enhanced by a decreased expression of members of the TGF-beta family. The ASU stimulation of TGF-beta1, TGF-beta2, and BMP-2 expression may explain their promoting effects in the treatment of periodontal disorders, at least partly. These findings support the hypothesis that ASU could exert a preventive action on the deleterious effects exerted by IL-1beta in periodontal diseases.