Amelotin gene expression is temporarily being upregulated at the initiation of apoptosis induced by TGFβ1 in mouse gingival epithelial cells

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.

The RAS-PI3K-AKT-NF-κB pathway transcriptionally regulates the expression of BCL2 family and IAP family genes and inhibits apoptosis in fibrous epulis

Background

Epulis has a tumor‐like appearance but is considered to be a massive reactive lesion rather than a true neoplasia. Limited information about the pathogenesis of epulis is available. The purpose of our study was to identify potential signaling pathways in fibrous epulis through transcriptome profiling.

Methods

Differentially expressed genes (DEGs) between fibrous epulis lesions and normal gingival tissues were detected using RNA sequencing (RNAseq). The expression levels of eighteen genes were validated using quantitative real‐time PCR (qRT‐PCR).

Results

RNAseq identified 533 upregulated genes and 732 downregulated genes. The top 10 upregulated genes were IL11, OSM, MMP3, KRT75, MMP1, IL6, IL1B, IL24, SP7, and ADGRG3. The top 10 downregulated genes were BCHE, TYR, DCT, KRT222, RP11‐507K12.1, COL6A5, PMP2, GFRA1, SCN7A, and CDH19. KEGG pathway analysis further indicated that the DEGs were enriched in “Pathways in cancer” and the “Ras signaling pathway”. quantitative real‐time PCR verified that the expression levels of SOS1, HRAS, PIK3CA, AKT3, IKBKA, IKBKB, NFKB1, BCL2, BCL2L1, XIAP, BIRC2, and BIRC3 were increased significantly.

Conclusions

The current transcriptomic profiling study reveals that in fibrous epulis, RAS‐PI3K‐AKT‐NF‐κB pathway transcriptionally regulates the expression of BCL2 family and IAP family genes, leading to increased proliferation and apoptosis inhibition.

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.

Negative feedback by SNAI2 regulates TGFβ1-induced amelotin gene transcription in epithelial-mesenchymal transition

Junctional epithelium (JE) demonstrates biological responses with the rapid turnover of gingival epithelial cells. The state occurs in inflammation of gingiva and wound healing after periodontal therapy. To understand the underlying mechanisms and to maintain homeostasis of JE, it is important to investigate roles of JE-specific genes. Amelotin (AMTN) is localized at JE and regulated by inflammatory cytokines and apoptotic factors that represent a critical role of AMTN in stabilizing the dentogingival attachment, which is an entrance of oral bacteria. In this study, we demonstrated that the AMTN gene expression was regulated by SNAI2 and transforming growth factor β1 (TGFβ1)-induced epithelial-mesenchymal transition (EMT) that occurs in wound healing and fibrosis during chronic inflammation. SNAI2 downregulated AMTN gene expression via SNAI2 bindings to E-boxes (E2 and E4) in the mouse AMTN gene promoter in EMT of gingival epithelial cells. Meanwhile, TGFβ1-induced AMTN gene expression was attenuated by SNAI2 and TGFβ1-induced SNAI2, without inhibition of the TGFβ1-Smad3 signaling pathway. Moreover, SNAI2 small interfering RNA (siRNA) rescued SNAI2-induced downregulation of AMTN gene expression, and TGFβ1-induced AMTN gene expression was potentiated by SNAI2 siRNA. Taken together, these data demonstrated that AMTN gene expression in the promotion of EMT was downregulated by SNAI2. The inhibitory effect of AMTN gene expression was an independent feedback on the TGFβ1-Smad3 signaling pathway, suggesting that the mechanism can be engaged in maintaining homeostasis of gingival epithelial cells at JE and the wound healing phase.

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.

IL-1β and TNF-α regulate mouse amelotin gene transcription in gingival epithelial cells

Amelotin (AMTN) is an enamel protein expressed in maturation-stage ameloblasts and junctional epithelium. To clarify the transcriptional regulation of the AMTN gene by interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), we conducted real-time PCR, Western blotting, transient transfection analyses with luciferase constructs including various lengths of the mouse AMTN gene promoter, and gel shift and chromatin immunoprecipitation assays using mouse gingival epithelial GE1 cells. The levels of AMTN mRNA and protein in GE1 cells were increased after 6 h of stimulation with IL-1β (1 ng/mL) and TNF-α (10 ng/mL). IL-1β and TNF-α induced luciferase activities of the constructs between -116AMTN and -705AMTN including the mouse AMTN gene promoter. Transcriptional activation by IL-1β and TNF-α was partially inhibited in -460AMTN including 3-bp mutations in the CCAAT-enhancer-binding protein 1 (C/EBP1), C/EBP2 and Yin Yang 1 (YY1) elements. Transcriptional activities induced by IL-1β and TNF-α were inhibited by tyrosine kinase, MEK1/2 and PI3-kinase inhibitors. Results of ChIP assays showed that IL-1β and TNF-α increased C/EBPβ and YY1 binding to the C/EBP1, C/EBP2 and YY1 elements. These results demonstrate that IL-1β and TNF-α increase AMTN gene transcription via the C/EBP1, C/EBP2 and YY1 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.

TGFβ1-induced Amelotin gene expression is downregulated by Bax expression in mouse gingival epithelial cells

Amelotin (AMTN) is induced upon initiation of apoptosis by transforming growth factor beta1 (TGFβ1) and is mediated by Smad3 in gingival epithelial cells (GE1 cells). This upregulation of AMTN gene expression is temporary, and the mechanism responsible is still unclear. The present study investigated the transcriptional downregulation of TGFβ1-induced AMTN gene expression in GE1 cells during the progression of apoptosis. To examine time-dependent changes in the levels of AMTN, Smad3 and Bax mRNA induced by TGFβ1, real-time PCR analyses were performed. Immunocytochemistry was carried out to detect the expression of Smad3 and Bax. Transient transfection analyses were performed using mouse AMTN gene promoter constructs of various lengths including Smad response elements (SBEs), in the presence or absence of TGFβ1. Changes in Smad3 binding to SBEs resulting from overexpression of Bax were examined using ChIP assays. Overexpression of Bax dramatically downregulated the levels of TGFβ1-induced AMTN mRNA and transcription of the AMTN gene. Smad3 binding to SBEs in the mouse AMTN gene promoter was induced by overexpression of Smad3 or TGFβ1, and this was inhibited by Bax overexpression. These results show that the levels of AMTN mRNA induced by TGFβ1 and Smad3 are decreased by robust expression of Bax in gingival epithelial cells.

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.

Spontaneous generation of a novel foetal human retinal pigment epithelium (RPE) cell line available for investigation on phagocytosis and morphogenesis

Objectives

Primary retinal pigment epithelium (RPE) cells have a limited capacity to re‐establish epithelial morphology and to maintain native RPE function in vitro, and all commercially available RPE cell lines have drawbacks of morphology or function; therefore, the establishment of new RPE cell lines with typical characteristics of RPE would be helpful in further understanding of their physiological and pathological mechanisms. Here, we firstly report a new spontaneously generated RPE line, fhRPE‐13A, from a 13‐week aborted foetus. We aimed to investigate its availability as a RPE model.

Materials and methods

RNA‐seq data were mapped to the human genome assembly hg19. Global transcriptional data were analysed by Weighted Gene Co‐expression Network Analysis (WGCNA) and differentially expressed genes (DEGs). The morphology and molecular characteristics were examined by immunofluorescence, transmission electron micrographs, PCR and western blot. Photoreceptor outer segments (POS) phagocytosis assay and transepithelial resistance measurement (TER) were performed to assess phagocytic activity and barrier function, respectively.

Results

The fhRPE‐13A cells showed typical polygonal morphology and normal biological processes of RPE. Meanwhile they were capable of POS phagocytosis in vitro, and the expression level of TYR and TYRP1 were significantly higher than that in ARPE‐19 cells.

Conclusions

The foetal human RPE line fhRPE‐13A is a valuable system for researching phagocytosis and morphogenesis of RPE in vitro.