Meiying Shao

Dental erosion and severe tooth decay related to soft drinks: a case report and literature review.

Soft drinks have many potential health problems. The inherent acids and sugars have both acidogenic and cariogenic potential, resulting in dental caries and potential enamel erosion. In this report we present a 25-year-old man complaining with the severe worn-out of the front teeth during the past 3 years. He had a history of drinking cola for more than 7 years and had a poor oral hygiene. Severe decays were present in the incisors and the canines, while less severe lesions were noted on the premolars and the molars. The review is to show the relationship between dental erosion and caries and soft drinks. Some efforts have been taken to reduce the harmful effect of soft drinks.

Interleukin-6 polymorphisms modify the risk of periodontitis: a systematic review and meta-analysis

ObjectiveTo clarify the association of IL-6 polymorphisms and periodontitis, a meta-analysis of case-control studies and a systemic review were conducted.Material and methodsWe performed a literature search using PubMed and Medline database to May 2009, with no restrictions. We also reviewed references from all retrieved articles. Six case-control studies involving 1 093 periodontitis cases and 574 controls were selected for meta-analysis to assess the purported associations between IL-6 polymorphisms and the risk of periodontitis. IL-6 −174 G/C and −572 C/G polymorphisms were included in the present meta-analysis, and the association between IL-6 −6331 T/C polymorphism and the risk of periodontitis was adequately reviewed as well.Results and conclusionThe present meta-analysis indicates that the IL-6 −174 G allele could not modify the risk of chronic periodontitis, but increased the risk of aggressive periodontitis. And −572 C/G polymorphism is associated with the pathogenesis of periodontitis, including chronic periodontitis or aggressive periodontitis.

Lipopolysaccharide-induced dental pulp cell apoptosis and the expression of Bax and Bcl-2 in vitro.

Lipopolysaccharide exerts many effects on many cell lines, including cytokine secretion, and cell apoptosis and necrosis. We investigated the in vitro effects of lipopolysaccharide on apoptosis of cultured human dental pulp cells and the expression of Bcl-2 and Bax. Dental pulp cells showed morphologies typical of apoptosis after exposure to lipopolysaccharide. Flow cytometry showed that the rate of apoptosis of human dental pulp cells increased with increasing lipopolysaccharide concentration. Compared with controls, lipopolysaccharide promoted pulp cell apoptosis (P < 0.05) from 0.1 to 100 μg/mL but not at 0.01 μg/mL. Cell apoptosis was statistically higher after exposure to lipopolysaccharide for 3 days compared with 1 day, but no difference was observed between 3 and 5 days. Immunohistochemistry showed that expression of Bax and Bcl-2 was enhanced by lipopolysaccharide at high concentrations, but no evident expression was observed at low concentrations (0.01 and 0.1 μg/mL) or in the control groups. In conclusion, lipopolysaccharide induced dental pulp cell apoptosis in a dose-dependent manner, but apoptosis did not increase with treatment duration. The expression of the apoptosis regulatory proteins Bax and Bcl-2 was also up-regulated in pulp cells after exposure to a high concentration of lipopolysaccharide.

Roles of lysophosphatidic acid and the Rho-associated kinase pathway in the migration of dental pulp cells.

During the dental pulp repair process, dental pulp cells (DPCs) migrate to the site of injury and differentiate into odontoblasts or odontoblast-like cells. Although migration of DPCs is an important reparative process, the underlying mechanism remains unknown. The objective of this study was to determine the roles of lysophosphatidic acid (LPA) and the Rho-associated kinase (ROCK) pathway in the migration and morphology of dental pulp cells and alpha smooth muscle actin expression in vitro. We demonstrated that both LPA and ROCK inhibition enhanced cell motility and that their combined effects significantly increased migration rate. LPA induced fine cytoskeleton assembly and increased the level of alpha smooth muscle actin (alpha-SMA). ROCK inhibition by Y-27632 and ROCK-(1+2) small interfering RNA (siRNA) resulted in less actin cytoskeleton formation, a lower alpha-SMA level, a star-like cellular morphology and membrane ruffling. LPA and ROCK inhibition induced activation of another Rho GTPase, Rac, which may explain how LPA and ROCK inhibition increases cellmigration and lamellipodium formation.

The effect of lysophosphatidic acid and Rho-associated kinase patterning on adhesion of dental pulp cells

AIM To investigate the effects of lysophosphatidic acid (LPA) and the Rho/Rho-associated kinase (ROCK) pathway on adhesion of dental pulp cells (DPCs). METHODOLOGY Human DPCs were cultured ex vivo. After treatment of LPA and Y-27632, a specific ROCK inhibitor, changes in focal contacts (FCs) were examined by immunofluorescent staining. Activation of FCs proteins was examined by measuring tyrosine 397 phosphorylation of focal adhesion kinase (FAK) and paxillin using immunoblotting. The data were analysed by Students t-test. RESULTS The immunofluorescent staining indicated LPA stimulation induced larger focal adhesion in the cell periphery, compared with the control. Inhibition of ROCK by Y-27632 decreased the formation of FCs markedly, even in the LPA-stimulated cells. LPA also increased the level of tyrosine phosphorylation of paxillin at 30min (P<0.05) and FAK at 5 and 30min (P<0.05). Furthermore, p-paxillin levels declined immediately after Y-27632 treatment and remained low at 5, 30, 60min. Y-27632 also suppressed the effects of LPA on p-paxillin and p-FAK at 5 and 30min (P<0.05). CONCLUSION LPA activated Rho and then subsequently activated ROCK, suggesting that LPA influences the FCs of DPCs by modulating tyrosine phosphorylation of FAK and paxillin via the Rho/ROCK pathway.

Interaction between mDia1 and ROCK in Rho‐induced migration and adhesion of human dental pulp cells

AIM To investigate the effects of mammalian homologue of Drosophila diaphanous-1(mDia1) and Rho-associated coiled-coil-containing protein kinase (ROCK) on the migration and adhesion of dental pulp cells (DPCs). METHODOLOGY Lysophosphatidic acid (LPA) was used to activate Rho signalling. mDia1 and ROCK were inhibited by short interfering RNA and the specific inhibitor, Y-27632, respectively. The migration of DPCs was assessed using the transwell migration assay and scratch test. Formation of cytoskeleton and focal adhesions(FAs) was observed by confocal laser scanning microscopy. Cell adhesion and spreading assays were performed. Phosphorylation of focal adhesion kinase (FAK) and paxillin was detected by Western blotting, and the bands were analysed using Adobe Photoshop CS5 software. All experiments were performed at least three times, and data were analysed with one-way anova and a post hoc test. RESULTS LPA-triggered activation of Rho and inhibition of ROCK significantly increased the cell migration rate. Cell migration was inhibited by silencing mDia1. mDia1 silencing and ROCK inhibition suppressed the LPA-induced formation of the cytoskeleton, FA and phosphorylation of FAK and paxillin. Inhibition of ROCK or mDia1 facilitated early cell adhesion and spreading; by contrast, the combined inhibition of ROCK and mDia1 neutralized these effects. CONCLUSIONS mDia1 promoted RhoA-induced migration of DPCs, but ROCK had an opposite effect. Both mDia1 and ROCK participated in cytoskeleton formation and adhesion of DPCs. The interactions between mDia1 and ROCK might influence dental pulp repair by determining the migration and adhesion of DPCs.

Sphingosine‐1‐phosphate mediates AKT/ERK maintenance of dental pulp homoeostasis

AIM To investigate the cell status of dental pulp cells (DPCs) in a sphingosine-1-phosphate (S1P)-induced microinflammation environment and the possible mechanisms of cell homoeostasis maintenance by S1P. METHODOLOGY Sphingosine-1-phosphate receptor (S1PR) expression was examined in DPCs within a local S1P-induced microinflammation model established using 1 μmol L(-1) S1P. U0126 [extracellular signal-regulated kinase (ERK) inhibitor], LY294002 (AKT inhibitor) and Y27632 (ROCK inhibitor) were used to inhibit corresponding signalling pathways of DPCs. CCK8 and cell cycle analysis tested cell proliferation. Immunofluorescence staining JC-1 detected changes of mitochondrial membrane potential (ΔΨm). Tests for apoptosis and the apoptosis-related proteins Bax and Bcl-2 were assessed by flow cytometry and western blot analysis, respectively. Expressions of ERK and AKT were evaluated by western blot analysis. The results were analysed using the Students t-test and the significance level set at P < 0.05. RESULTS Expressions of S1PR1, S1PR2 and S1PR3 in DPCs differed amongst individuals. DPCs maintained self-homoeostasis in response to S1P-induced microinflammation via S1PRs. During this repair process, ERK, AKT and ROCK had a short-term complementary interaction at 60 min, but then AKT and ERK gradually played decisive roles after 24 h in proliferation enhancement and apoptosis inhibition, respectively (P > 0.05). CONCLUSIONS The AKT-ERK balance may determine whether DPC homoeostasis in S1P-induced microinflammation is maintained by synergistic regulation of cell growth and apoptosis.

Novel role of Zonula Occludens‐1: a tight junction protein closely associated with the odontoblast differentiation of human dental pulp cells

Zonula occludens‐1 (ZO‐1), a tight junction protein, contributes to the maintenance of the polarity of odontoblasts and junctional complex formation in odontoblast layer during tooth development. However, expression and possible role of ZO‐1 in human dental pulp cells (hDPCs) during repair process remains unknown. Here, we investigated the expression of ZO‐1 in hDPCs and the relationship with odontoblast differentiation. We found the processes of two adjacent cells were fused and formed junction‐like structure using scanning electron microscopy. Fluorescence immunoassay and Western blot confirmed ZO‐1 expression in hDPCs. Especially, ZO‐1 was high expressed at the cell–cell junction sites. More interestingly, ZO‐1 accumulated at the leading edge of lamellipodia in migrating cells when a scratch assay was performed. Furthermore, ZO‐1 gradual increased during odontoblast differentiation and ZO‐1 silencing greatly inhibited the differentiation. ZO‐1 binds directly to actin filaments and RhoA/ROCK signaling mainly regulates cell cytoskeleton, thus RhoA/ROCK might play a role in regulating ZO‐1. Lysophosphatidic acid (LPA) and Y‐27632 were used to activate and inhibit RhoA/ROCK signaling, respectively, with or without mineralizing medium. In normal cultured hDPCs, RhoA activation increased ZO‐1 expression and especially in intercellular contacts, whereas ROCK inhibition attenuated the effects induced by LPA. However, expression of ZO‐1 was upregulated by Y‐27632 but not significantly affected by LPA after odontoblast differentiation. Hence, ZO‐1 highly expresses in cell–cell junctions and is related to odontoblast differentiation, which may contribute to dental pulp repair or even the formation of an odontoblast layer. RhoA/ROCK signaling is involved in the regulation of ZO‐1.

Focal adhesion kinase maintains, but not increases the adhesion of dental pulp cells.

Focal adhesion kinase (FAK) functions as a key enzyme in the integrin-mediated adhesion-signalling pathway. Here, we aimed to investigate the effects of FAK on adhesion of human dental pulp (HDP) cells. We transfected lentiviral vectors to silence or overexpress FAK in HDP cells ex vivo. Early cell adhesion, cell survival and focal contacts (FCs)-related proteins (FAK and paxillin) were examined. By using immunofluorescence, the formation of FCs and cytoskeleton was detected, respectively. We found that both adhesion and survival of HDP cells were suppressed by FAK inhibition. However, FAK overexpression slightly inhibited cell adhesion and exhibited no change in cell survival compared with the control. A thick rim of cytoskeleton accumulated and smaller dot-shaped FCs appeared in FAK knockdown cells. Phosphorylation of paxillin (p-paxillin) was inhibited in FAK knockdown cells, verifying that the adhesion was inhibited. Less cytoskeleton and elongated FCs were observed in FAK-overexpressed cells. However, p-paxillin had no significant difference compared with the control. In conclusion, the data suggest that FAK maintains cell adhesion, survival and cytoskeleton formation, but excessive FAK has no positive effects on these aspects.

Effect of cyclic uniaxial compressive stress on human dental pulp cells in vitro

ABSTRACT Purpose: Teeth are exposed to various forces during functional and parafunctional movements. These processes inevitably affect the dental pulp, and the mechanism of these influences has been the subject of many previous studies using different apparatuses and obtaining different results. In this study, we aimed to investigate the effects of compressive stress on the proliferation and differentiation of human dental pulp cells (hDPCs). Materials and Methods: A four-point bending strain system was adopted to apply low-density cyclic uniaxial compressive stress (2000 microstrain, 0.5 Hz) to hDPCs for 1.5, 3, 6, 12, and 24 h. The cell cycle progression and mRNA expression of differentiation-related genes (BMP2, ALP, DMP1, DSPP, COL I) were then examined to investigate the proliferation and differentiation of hDPCs. Results: The results showed that cyclic compressive stress changed the morphology of hDPCs after 12 and 24 h of mechanical loading; cell cycle progression was promoted, especially in the 24-h group (p < 0.05). The expression of BMP2 was significantly upregulated after 3 and 6 h of mechanical loading but declined in the 12- and 24-h groups, whereas the expression levels of DMP1 and DSPP were significantly upregulated in the 12- and 24-h loading groups (p < 0.05). Conclusions: Dental pulp cells were sensitive to compressive stress, especially after 12 and 24 h of applied force. Proliferation and odontogenic differentiation were significantly promoted in this in vitro model.