Immortalized gingival fibroblasts as a cytotoxicity test model for dental materials

Recombinant Human Keratinocyte Growth Factor Ameliorates Cancer Treatment-Induced Oral Mucositis on a Chip

Oral mucositis (OM) is a severe complication of cancer therapies caused by off-target cytotoxicity. Palifermin, which is recombinant human keratinocyte growth factor (KGF), is currently the only mitigating treatment available to a subset of OM patients. This study used a previously established model of oral mucositis on a chip (OM-OC) comprised of a confluent human gingival keratinocytes (GIE) layer attached to a basement membrane-lined subepithelial layer consisting of human gingival fibroblasts (HGF) and human dermal microvascular endothelial cells (HMEC) on a stable collagen I gel. Cisplatin, radiation, and combined treatments are followed by a recovery period in the OM-OC to determine possible cellular and molecular mechanisms of OM under effects of KGF. Cancer treatments affected the keratinocyte layer, causing death and epithelial barrier loss. Both keratinocytes and subepithelial cells died rapidly, as evidenced by propidium iodide staining. In response to radiation exposure, cell death occurred in the apical epithelial layer, predominantly, within 24h. Cisplatin exposure predominantly promoted death of basal epithelial cells within 32-36h. Presence of KGF in OM-OC protected tissues from damage caused by cancer treatments in a dose-dependent manner, being more effective at 10 ng/mL. As verified by F-actin staining and the Alamar Blue assay, KGF contributed to epithelial survival and induced proliferation of GIE and HGF as well as HMEC within 120h. When the expression of eighty inflammatory cytokines is evaluated at OM induction (Day 12) and resolution (Day 18) stages in OM-OC, some cytokines are identified as potential novel therapeutic targets. In comparison with chemoradiation exposure, KGF treatment showed a trend to decrease IL-8 and TNF-a expression at Day 12 and 18, and TGF-β1 at Day 18 in OM-OC. Taken together, these findings support the utility of OM-OC as a platform to model epithelial damage and evaluate molecular mechanisms following OM treatment.

Cytotoxicity and genotoxicity of bioceramic root canal sealers compared to conventional resin-based sealer

The aim of this study was to evaluate cytotoxicity and genotoxicity of calcium-silicate based sealers and comparing them with a gold standard-an epoxy-based sealant. Two experimental cell lines were used, gingival fibroblasts (hGF) and monocyte/macrophage peripheral blood cell line (SC). The cytotoxicity (XTT assay) and genotoxicity (comet assay) were evaluated both after 24-h and 48-h incubation. Additionally, after 48-h incubation, the cell apoptosis and cell cycle progression was detected. BioRoot Flow induced a significant decrease in hGF cells viability compared to the negative control groups both after 24-h (p < 0.001) and 48-h incubation (p < 0.01). In group with SC cells, after 24-h incubation significant increase in cells viability was detected for AH Plus Bioceramic Sealer in comparison to negative control (p < 0.05). BioRoot Flow and BioRoot RCS can be considered potentially genotoxic for the hGF cells after 48-h incubation (> 20% DNA damage). BioRoot Flow and BioRoot RCS, may have potential genotoxic effects and induce apoptosis in hGF cells which may irritate periapical tissues, resulting in a delayed healing. The findings of the study would be useful in selection of an appropriate sealant for root canal filling without causing cytotoxicity and genotoxicity.

Are Endodontic Solvents Cytotoxic? An In Vitro Study on Human Periodontal Ligament Stem Cells

The aim of this study was to assess the influence of eucalyptol, chloroform, and Endosolv on the proliferative capability, cell viability, and migration rates of human periodontal ligament stem cells (hPDLSCs) in vitro. Solvent eluates were formulated following ISO 10993-5 guidelines, and 1%, 0.25%, and 0.1% dilutions were prepared. The HPDLSCs were isolated from the extracted third molars of healthy donors. The following parameters were assessed: cell viability via trypan blue and IC50 assays, cell migration via horizontal wound healing assay, cell morphology via cell cytoskeleton staining (phalloidin labeling), and cell oxidative stress via reactive oxygen species assay. The data were analyzed using one-way ANOVA and Tukey’s posthoc tests, and their significance was established at p < 0.05. Chloroform and eucalyptol exhibited significantly higher cytotoxicity on the hPDLSCs in vitro compared to the control group, as shown by the cell viability, migration, morphology, and reactive oxygen species release assays. Alternatively, Endosolv showed adequate cytotoxicity levels comparable to those of the control group. The cytotoxicity of the tested endodontic solvents increased in a dose-dependent manner. The results from the present study highlight the cytotoxicity of chloroform and eucalyptol. Thus, their limited and cautious use is recommended, avoiding solvent extrusion.

Oral mucositis on a chip: modeling induction by chemo- and radiation treatments and recovery

Oral mucositis (OM) is a debilitating complication affecting roughly 70% of head and neck cancer patients receiving chemotherapy and/or radiation treatment. No broadly effective preventative treatment for OM exists. Therefore, anin vitromodel of cancer treatment-induced OM would aid studies into possible origins of the pathology and future drug targets to ameliorate it. In this study, we present a microfluidic oral mucosa triculture tissue construct consisting of a keratinocyte layer attached to a subepithelial fibroblast and endothelial cell-embedded collagen gel. To address the typically low stability of mucosal constructs in microfluidics, ruthenium-catalyzed photocrosslinking was implemented to strengthen the collagen gel and prevent the invasion of keratinocytes, thus maintaining tissue construct geometry and oral mucosa barrier function for over 18 d of culture. Next, the OM chip was exposed to cisplatin (day 10) and damaging radiation (day 11, ± cisplatin at day 10), mimicking damage from cancer therapy. Damage to and then recovery of the tissue layers and function were observed over days 11-18. Therefore, several important features of OM induction and resolution were modeled in microfluidic culture. The OM model on a chip allows for more sophisticated studies into mechanisms of OM and potential treatments.

Anti-Inflammatory and Anti-Bacterial Potential of Mulberry Leaf Extract on Oral Microorganisms

Mulberry leaves extract (Morus alba extracts; MAE) is known to have therapeutic potentials for numerous human diseases, including diabetes, neurological disorders, cardiovascular diseases, and cancers. However, there has not been sufficient research proving therapeutic effects on oral disease and its related oral risk factors. Thus, we investigated whether MAE has any anti-inflammatory and anti-bacterial effects on risk factors causing oral infectious diseases. To examine the anti-inflammatory response and bacterial inhibition of MAE, we measured intracellular reactive oxygen species (ROS) generation, production of pro-inflammatory cytokines, and the bacterial growth rate. Our study showed that MAE has anti-inflammatory activities, which inhibit the ROS generation and suppressed the production of pro-inflammatory cytokines (TNF-α and IL-6) in human monocyte THP-1 cells by stimulating lipopolysaccharide (LPS) and/or F. nucleatum, which are the virulent factors in periodontal diseases. Furthermore, MAE inhibited the bacterial growth on oral microorganisms (F. nucleatum and S. mutans) infected THP-1 cells. These findings suggested that MAE could be a potential natural source for therapeutic drugs in oral infectious disease.

The Cytocompatibility of Silver Diamine Fluoride on Mesenchymal Stromal Cells from Human Exfoliated Deciduous Teeth: An In Vitro Study

Silver diamine fluoride (SDF) has been used for many years for the treatment of caries, and minimally invasive dentistry concepts have made it popular again. The fact that its application does not require the administration of anesthesia makes its use in children more desirable. The aim of this study was to determine the cytotoxicity of two new commercial SDF products: Riva Star (SDI Dental Limited) and e-SDF (Kids-e-Dental) on mesenchymal stromal cells from human exfoliated deciduous teeth (SHEDs). SHEDs were exposed to SDF products at different concentrations (0.1%, 0.01% and 0.005%). Then different assays were performed to evaluate their cytocompatibility on SHEDs: IC50, MTT, cell migration (wound healing), cell cytoskeleton staining, cell apoptosis, generation of intracellular reactive oxygen species (ROS), and ion chromatography. Statistical analyses were performed using one-way ANOVA and Tukey’s post hoc test (p < 0.05). Riva Star Step 2 showed the same cell metabolic activity when compared to the control condition at any time and concentration. Meanwhile, e-SDF displayed high cytotoxicity at any time and any concentration (*** p < 0.001), whereas Riva Star Step 1 displayed high cytotoxicity at any time at 0.1% and 0.01% (*** p < 0.001). Only e-SDF showed a statistically significant decreased cell migration rate (*** p < 0.001) at all times and in all concentrations. At 0.1%, e-SDF and Riva Star Step 1 only showed 4.37% and 4.47% of viable cells, respectively. These results suggest that Riva Star has better in vitro cytocompatibility on SHEDs than does e-SDF. Riva Star Step 1 was found to be as cytotoxic as e-SDF, but it had better biological properties when mixed with Riva Star Step 2. Our findings suggest that Riva Star is more suitable when used in deciduous teeth due to its lower cytotoxicity compared to e-SDF.

Cytotoxic effects of different detergent containing children's toothpastes on human gingival epithelial cells

Background

This study aimed to evaluate possible cytotoxic effects to gingival epithelial cells exposed to children toothpastes containing different detergent.

Methods

Tissues required for the isolation of human gingival epithelial cells were obtained by biopsy during the extraction of the impacted third molar tooth. Toothpaste solutions of different concentrations were prepared from five different children’s toothpastes with different detergent contents. Isolated gingival epithelial cells were stimulated with experimental groups consisting of toothpaste solutions (Colgate, Sensodyne, Splat, Nenedent, Perlodent) at different concentrations and a control group consisting of complete Dulbecco’s modified eagle medium. After the experiments, cell viability was evaluated using flow cytometry. 2 Way ANOVA was used to see the interaction effect of the main effects of toothpaste solution and concentration factors. Pairwise comparisons were made by Tukey post hoc tests. In the study, the significance level was taken as 0.05.

Results

As a result of the analysis, it was seen that the toothpaste solution and concentration factors and the interactions of these 2 factors were effective on the viable, early apoptotic, late apoptotic and necrotic cell rates. The statistically highest live cell ratios were detected in Splat’s toothpaste solutions (90.14% at 0.4% concentration) after the control group (90.82%) and the group with the lowest viability values was determined in Colgate group (75.74% at 0.4% concentration) (p < 0.05).

Conclusions

According to the results of the study, it was observed that toothpastes containing SLS affected the viability of cells more negatively than toothpastes with other detergent contents.

In vitro biocompatibility testing of different base materials used for elevation of proximal subgingival margins using human gingival epithelial cells

PURPOSE

To analyze the biological effects of four base materials used for elevation of proximal subgingival margins on gingival epithelial cells.

METHODS

Twenty-eight specimens for each of the four base materials (total 112 specimens) were used: resin-modified glass ionomer (RMGI), glass hybrid (HV-GIC), flowable bulk fill resin composite (Bulk Flow) and bioactive ionic resin (Activa). Proximal enamel and root dentin were used as controls. Gingival epithelial cell viability was calculated after direct incubation on all four types of material for either 24 h or 72 h using both the methyl tetrazolium and trypan blue dye exclusion assays. Data were analyzed statistically using one-way analysis of variance, Tukey post hoc test and independent sample t-test (P < 0.05).

RESULTS

Cell viability values in both assays showed significant differences among the study groups. Bulk Flow showed the highest values, followed in order by Activa and the control groups. Both HV-GIC and RMGI had the lowest values. Cell viability in all of the study groups was higher after incubation for 72 h than after 24 h.

CONCLUSION

In terms of biocompatibility with epithelial tissues, bulk fill resin composite appears to be most suitable, followed by bioactive composite, for subgingival placement than glass ionomer-based materials, especially that containing 2-hydroxy-ethyl methacrylate.

Cytotoxic Effects on Gingival Mesenchymal Stromal Cells and Root Surface Modifications Induced by Some Local Antimicrobial Products Used in Periodontitis Treatment

(1) Background: this study aims to test the cytotoxicity of three antimicrobial products used in periodontitis treatment on gingival mesenchymal stem cells (gMSCs) and their influence on root surfaces and gMSC adhesion. We tested the null hypothesis that the effects of the antimicrobials did not differ. (2) Methods: the commercial products based on sulphonic/sulphuric acids, sodium hypochlorite and silver nanoparticles, in five different concentrations, were added to culture medium for growing gMSCs. Cell proliferation capacity was tested using the Cell Counting Kit-8 (CCK8) and their viability was determined by succinate dehydrogenase activity (MTT) assay. Scanning electron microscopy evaluated the adhesion of gMSCs on root samples treated mechanically and with commercial products. (3) Results: the products induced a dose-dependent cytotoxicity in terms of reduced proliferation and viability of gMSCs, as well as cell shape modifications. Significant differences in CCK8 values between the different commercial products were observed. Based on proliferation tests, the null hypothesis was rejected. When MTT values of the three products were compared with each other, no significant differences were observed for any of the five concentrations (p = 0.065, p = 0.067, p = 0.172, p = 0.256, p = 0.060). (4) Conclusions: the three antimicrobials had a certain degree of cytotoxicity on gMSCs. gMSCs repopulated treated root surfaces.

Assessment of the cytotoxic effects and chemical composition of the insoluble precipitate formed from sodium hypochlorite and chlorhexidine gluconate

AIM

To investigate (1) the cytotoxic potential of the brown precipitate (BP) formed with sodium hypochlorite (NaOCl) and chlorhexidine gluconate (CHX), using both a small animal model of Caenorhabditis elegans (C. elegans) and cultured human gingival fibroblasts; and (2) the chemical composition of BP using Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS).

METHODOLOGY

Brown precipitate was obtained by mixing equal volumes of 6% NaOCl and 2% CHX and separating the BP from clear supernatant by centrifugation. The brown precipitate was weighed and solubilized in dimethyl sulfoxide for cytotoxicity experiments. The cytotoxic effect of BP was assessed using C. elegans larvae and primary immortalized human gingival fibroblasts-hTERT (hTERT-hNOF) cells. Various dilutions of BP (25 ng/µL-150 ng/µL), supernatant (0.15% v/v), NaOCl (1:100-1:1000 dilutions of 6% NaOCl) or CHX (1:500-1:1000 dilutions of 2% CHX) along with vehicle control (0.5% v/v ethanol and 0.15% v/v DMSO) or untreated control (growth medium) were tested on C. elegans larvae and hTERT-hNOF cells. Viability was assessed in C. elegans larvae using stereomicroscopy and in hTERT-hNOF cells using dehydrogenase-based colorimetric assay. ToF-SIMS was used to assess the chemical composition of BP in comparison with CHX and para-chloroaniline (PCA). The C. elegans and cell line data were analysed using Log-Rank test and Student's t-test, respectively (p < .05).

RESULTS

BP-75 ng/µL and BP-150 ng/µL were significantly more toxic to C. elegans larvae than the untreated, vehicle, supernatant or CHX treatment groups (p < .0001). Similarly, in hTERT-hNOF cells, BP-50 ng/µL, BP-75 ng/µL and BP-150 ng/µL induced significant cytotoxicity within 2 h compared with untreated, vehicle, supernatant and CHX treatments (p < .05). ToF-SIMS analysis of BP revealed ion composition characteristic of both CHX and the carcinogen PCA.

CONCLUSIONS

Brown precipitate was toxic in both C. elegans larvae and hTERT-hNOF cells. The ToF-SIMS analysis of BP revealed ions characteristic of CHX and PCA that could account for the toxicities observed in C. elegans larvae and human gingival fibroblasts. Because of the insoluble and toxic nature of BP, consecutive use of CHX and NaOCl irrigants should be avoided in root canal treatment.

hTERT-immortalized gingival fibroblasts respond to cytokines but fail to mimic primary cell responses to Porphyromonas gingivalis

In periodontitis, gingival fibroblasts (GFs) interact with and respond to oral pathogens, significantly contributing to perpetuation of chronic inflammation and tissue destruction. The aim of this study was to determine the usefulness of the recently released hTERT-immortalized GF (TIGF) cell line for studies of host–pathogen interactions. We show that TIGFs are unable to upregulate expression and production of interleukin (IL)-6, IL-8 and prostaglandin E2 upon infection with Porphyromonas gingivalis despite being susceptible to adhesion and invasion by this oral pathogen. In contrast, induction of inflammatory mediators in TNFα- or IL-1β-stimulated TIGFs is comparable to that observed in primary GFs. The inability of TIGFs to respond directly to P. gingivalis is caused by a specific defect in Toll-like receptor-2 (TLR2) expression, which is likely driven by TLR2 promoter hypermethylation. Consistently, TIGFs fail to upregulate inflammatory genes in response to the TLR2 agonists Pam2CSK4 and Pam3CSK4. These results identify important limitations of using TIGFs to study GF interaction with oral pathogens, though these cells may be useful for studies of TLR2-independent processes. Our observations also emphasize the importance of direct comparisons between immortalized and primary cells prior to using cell lines as models in studies of any biological processes.

Assessing Biocompatibility of Face Mask Materials during COVID-19 Pandemic by a Rapid Multi-Assays Strategy

During the coronavirus disease 2019 (COVID-19) pandemic, scientific authorities strongly suggested the use of face masks (FMs). FM materials (FMMs) have to satisfy the medical device biocompatibility requirements as indicated in the technical standard EN ISO 10993-1:2018. The biologic evaluation must be confirmed by in vivo tests to verify cytotoxicity, sensitisation, and skin irritation. Some of these tests require an extensive period of time for their execution, which is incompatible with an emergency situation. In this study, we propose to verify the safety of FMMs combining the assessment of 3-[4,5-dimethylthiazolyl-2]-2,5-diphenyltetrazolium bromide (MTT) with quantification of nitric oxide (NO) and interleukin-6 (IL-6), as predictive markers of skin sensitisation or irritation based on human primary fibroblasts. Two hundred and forty-two FMMs were collected and classified according to spectrometer IR in polypropylene, paper, cotton, polyester, polyethylene terephthalate, 3-dimensional printing, and viscose. Of all FMMs tested, 50.8% passed all the assays, 48% failed at least one, and only 1.2% failed all. By a low cost, rapid and highly sensitive multi assays strategy tested on human skin fibroblasts against a large variety of FMMs, we propose a strategy to promptly evaluate biocompatibility in wearable materials.

Effects of different detergent-containing children's toothpastes on the viability, osteogenic and chondrogenic differentiation of human dental periodontal ligament stem cells and gingival stem cells in vitro

BACKGROUND

Detergents are the most commonly used compounds in toothpastes due to their foaming and cleaning peoperties. This study aimed to investigate the effects of children's toothpastes with different detergent content on the viability, the osteogenic and chondrogenic differentiation potentials of human mesenchymal stem cells.

METHODS

The necessary tissues for human periodontal ligament mesenchymal stem cells (hPDLMSCs) and human gingival mesenchymal stem cells (hGMSCs) isolation were obtained during extraction of 10 impacted third molar teeth. The viability of the cells stimulated with different concentratiaons of Colgate, Sensodyne, Splat, Nenedent, Perlodent toothpaste solutions and complete Dulbocco's modified eagle medium (control group) were evaluated by using the flow cytometer. In addition, the osteogenic and chondrogenic differentiation potential of human gingival and periodontal ligament mesenchymal stem cells exposed to toothpaste solutions were examined morphologically. Datas were analyzed with IBM SPSS V23. One way ANOVA test was used to determine the differences between the groups for multiple comparisons, while the Tukey post-hoc test was used for pair wise comparisons in determining which groups differed.

RESULTS

A higher percentage of cell viability was detected in Control group at 20 %, 50 % and 80 % (p = 0.000) on hGMSCs. After the Control group, the highest cell viability ratios were observed in the detergent-free Splat group (p = 0.000) followed by the Sensodyne experimental group containing CABP (p = 0.000). While the cell viability rates in Nenedent group was found significantly higher than the Perlodent group at other concentrations except for 20 % concentration (p = 0.000). Colgate group had the lowest percentage of cell viability among the experimental groups at all concentrations on hPDMSCs (p = 0.000). The highest live cell ratios was detected in Control group (p = 0.000), followed by Splat and Sensodyne groups (p = 0.000). The cell viability ratios at 50 % concentration were higher in Perlodent group than Nenedent group (p = 0.000). The highest osteogenic and chondrogenic differentiation potential of mesenchymal stem cells stimulated with different toothpaste was determined in Control and Splat group.

CONCLUSIONS

As a result of the findings, it was observed that toothpaste containing SLS had a more negative effect on the viability of the cells and the differentiation potentials than the other groups.

Evaluation of cytotoxicity of areca nut and its commercial products on normal human gingival fibroblast and oral squamous cell carcinoma cell lines

Consumption of areca nut products is the most common cause of oral cancers, particularly in South Asian countries. This study evaluates the cytotoxic and necrotizing effects of areca nut and its formulations on normal human gingival fibroblasts (HGF-1) and oral squamous cell carcinoma (OSCC, CAL-27) cell lines. Identification of various carcinogens and adulterants using LC-HR-ESI-MS/MS analysis was performed in the extracts of areca nut and its products. Apart from alkaloids and flavonoids, a major adulterant, saccharin was found in all the samples of chalia (one of the most common chewing products of areca nut) in the ranges between 1.697-7.170 mg/g of the sample. Cytotoxic studies showed that most of the areca nut products were found cytotoxic to HGF-1 cells while being relatively non-cytotoxic against CAL-27 cells, rather they promote the growth of cancer cells. Our findings revealed that the components of areca nut and its products were injurious to HGF-1 cells and caused necrosis, which may attenuate HGF-1 protection toward oral epithelial cells. Moreover, the non-cytotoxic effect of these products on cancer cell lines suggests further predisposal of the habitual chewers for developing oral carcinomas. This study will give a better understanding of the hazardous effects of areca nut products.

An Oral-mucosa-on-a-chip sensitively evaluates cell responses to dental monomers

Knowledge of human gingival cell responses to dental monomers is critical for the development of new dental materials. Testing standards have been developed to provide guidelines to evaluate biological functionality of dental materials and devices. However, one shortcoming of the traditional testing platforms is that they do not recapitulate the multi-layered configuration of gingiva, and thus cannot evaluate the layer-specific cellular responses. An oral mucosa-chip with two cell layers was previously developed as an alternative platform to assess the oral mucosa responses to dental biomaterials. The mucosa-chip consists of an apical keratinocyte layer attached to a fibroblast-embedded collagen hydrogel through interconnecting pores in a three-microchannel network. Here, cell responses in the mucosa-chip were evaluated against 2-hydroxyethyl methacrylate (HEMA), a common monomer used in restorative and aesthetic dentistry. The response of mucosal cell viability was evaluated by exposing the chip to HEMA of concentrations ranging from 1.56 to 25 mM and compared to cells in conventional well-plate monoculture. The co-cultured cells were then stained and imaged with epifluorescence and confocal microscopy to determine the layer-specific responses to the treatment. Mucosa-chips were demonstrated to be more sensitive to assess HEMA-altered cell viability than well-plate cultures, especially at lower doses (1.56 and 6.25 mM). The findings suggest that the mucosa-chip is a promising alternative to traditional platforms or assays to test a variety of biomaterials by offering a multi-layered tissue geometry, accessible layer-specific information, and higher sensitivity in detecting cellular responses.

Quantitative scoring of epithelial and mesenchymal qualities of cancer cells using machine learning and quantitative phase imaging

SIGNIFICANCE

We introduce an application of machine learning trained on optical phase features of epithelial and mesenchymal cells to grade cancer cells' morphologies, relevant to evaluation of cancer phenotype in screening assays and clinical biopsies.

AIM

Our objective was to determine quantitative epithelial and mesenchymal qualities of breast cancer cells through an unbiased, generalizable, and linear score covering the range of observed morphologies.

APPROACH

Digital holographic microscopy was used to generate phase height maps of noncancerous epithelial (Gie-No3B11) and fibroblast (human gingival) cell lines, as well as MDA-MB-231 and MCF-7 breast cancer cell lines. Several machine learning algorithms were evaluated as binary classifiers of the noncancerous cells that graded the cancer cells by transfer learning.

RESULTS

Epithelial and mesenchymal cells were classified with 96% to 100% accuracy. Breast cancer cells had scores in between the noncancer scores, indicating both epithelial and mesenchymal morphological qualities. The MCF-7 cells skewed toward epithelial scores, while MDA-MB-231 cells skewed toward mesenchymal scores. Linear support vector machines (SVMs) produced the most distinct score distributions for each cell line.

CONCLUSIONS

The proposed epithelial-mesenchymal score, derived from linear SVM learning, is a sensitive and quantitative approach for detecting epithelial and mesenchymal characteristics of unknown cells based on well-characterized cell lines. We establish a framework for rapid and accurate morphological evaluation of single cells and subtle phenotypic shifts in imaged cell populations.

Evaluation of the biocompatibility of resin composite-based dental materials with gingival mesenchymal stromal cells

Resin composite-based dental materials can leach certain components into the oral environment, causing potentially harmful gingival biological effect. Gingival tissue is a rich source of mesenchymal stem cells (MSCs) that is easily accessible, and can be used as a complementary approach for the investigation of dental material biocompatibility. Using gingival MSCs (gMSCs), the present study aimed to investigate the cytotoxicity of two classes of restorative dental materials (ormocers and resin composites) used to restore class II cavities close to the gingival margin, in addition to analyzing the leached compounds from these resin composite-based materials. Functionality assays (Colony-forming unit, migratory potential, and proliferation assays) and a viability assay (MTT) were employed. Cells' aspect was observed by scanning electron microscopy (SEM). Leached monomers were also quantitated using high-performance liquid chromatography (HPLC). The cytotoxicity of the biomaterials was highlighted by impaired functionality and diminished viability of gMSCs. Despite being variants of the same commercial material, the two ormocers behaved differently one material having a more negative impact on cell functionality than the other. Cells appeared to attach well to all materials. Main monomer molecules were mostly released by the tested materials. For all samples, an increased elution of monomers was recorded in artificial saliva as compared with culture medium. One composite material has released nearly eight times more urethane dimetacrylate in artificial saliva than in culture medium. Significantly lower gMSC viability scores were recorded for all the investigated samples in comparison with the control.

Cytoskeletal alteration modulates cancer cell invasion through RhoA-YAP signaling in stromal fibroblasts

Cancer-associated fibroblasts(CAFs) participate in carcinogenesis through interaction with cancer cells. This study aimed to investigate the mechanism of cytoskeletal alteration of CAFs and its role in invasion of oral squamous cell carcinoma(OSCC).Immortalized normal fibroblasts(hTERT-hNOFs) co-cultured with OSCC cells showed myofibroblastic and senescent phenotypes like CAFs. Thus, this study substituted hTERT-hNOFs for CAFs. Next, the cytoskeletal alteration and its molecular mechanism were investigated in hTERT-hNOFs co-cultured with OSCC. As results, we found that RhoA regulated cytoskeletal organization in fibroblasts surrounding OSCC cells. Furthermore, as a downstream transcriptional factor of RhoA, YAP was mainly localized in the nucleus of hTERT-hNOFs co-cultured with OSCC. Consequently, we examined whether nuclear YAP localization of fibroblasts could influence cancer progression. YAPS127A fibroblasts manifesting nuclear localization of YAP induced cytoskeletal alteration and increased gel contractility and matrix stiffness, and thereby enhances the invasiveness of OSCC cells. In conclusion, the modification of tumor microenvironment, such as cytoskeletal change and matrix remodeling via RhoA-YAP in CAFs, modulates OSCC invasion. These understandings will provide the development of novel approaches for CAFs-based cancer therapy.

Bcl-2 is a prognostic marker and its silencing inhibits recurrence in ameloblastomas

OBJECTIVES

Ameloblastomas are the most common odontogenic epithelial tumors with high recurrence rate. The aim of this study was to identify apoptosis-related genes with recurrence of ameloblastomas and to evaluate its feasibility as a prognostic marker and as a target molecule preventing from recurrence.

MATERIALS AND METHODS

Public microarray data were analyzed. To evaluate their expression in ameloblastoma patients, immunohistochemical staining was performed in 89 human ameloblastoma tissues. Quantitative PCR was performed by use of ameloblastoma cell line (AM-1). Fluorescence activated cell sorting analysis and western blotting were conducted following transfection with siRNA. Further, AM-1 cells were implanted in the renal subcapsular layer of immunodeficient mice.

RESULTS

Microarray data analysis revealed that osteoprotegerin (OPG) and B-cell lymphoma 2 (Bcl-2) were the two most upregulated genes in ameloblastoma. Only Bcl-2 expression was significantly (p = 0.020) associated with recurrence in conservative treatment group (n = 17) among 89 patients. Silencing of Bcl-2 increased apoptosis in AM-1 cells in vitro and inhibited tumor nodule formation of AM-1 cells in vivo.

CONCLUSION

These results suggest that Bcl-2 expression is a useful biomarker to predict recurrence of ameloblastomas, and as a therapeutic target molecule to prevent recurrence of ameloblastoma.

The Effects of Non-Thermal Atmospheric Pressure Plasma treated Titanium Surface on Behaviors of Oral Soft Tissue Cells

Here, we investigated the possible use of the technology known as non-thermal atmospheric pressure plasma on integration and control of cytokine release of soft tissue on titanium surface. After NTAPP was applied to titanium samples, changes of surface characteristics were measured as topographical features, contact angle, surface tension, and with X-ray photoelectron spectroscopy (XPS). Protein absorption was evaluated using a bovine serum albumin absorption assay. The attachment, viability, morphology, proliferation, and cytokine release of soft tissue on titanium were assessed. No change in topographical features was observed between control and NTAPP-treated groups. However, NTAPP treatment resulted in significant lowering of the contact angle for polar and non-polar liquids and increase of surface tension. Protein absorption was significantly enhanced on the NTAPP-treated samples. Normal soft tissue attachment was improved on the NTAPP-treated groups with good viability. Cellular morphology was improved in NTAPP-treated groups whereas cellular proliferation was not enhanced. There was a significant reduction in the amounts of cytokine release for inflamed IHOK and hTERT-hNOF on the NTAPP-treated groups; except for IL-8 for IHOKs. This study demonstrates that surface functional consequences by NTAPP exposure enhanced behavior of oral soft tissue cells without topographical change.

Oral mucosa-on-a-chip to assess layer-specific responses to bacteria and dental materials

The human oral mucosa hosts a diverse microbiome and is exposed to potentially toxic biomaterials from dental restoratives. Mucosal health is partly determined by cell and tissue responses to challenges such as dental materials and pathogenic bacteria. An in vitro model to rapidly determine potential layer-specific responses would lead to a better understanding of mucosal homeostasis and pathology. Therefore, this study aimed to develop a co-cultured microfluidic mucosal model on-a-chip to rapidly assess mucosal remodeling and the responses of epithelial and subepithelial layers to challenges typically found in the oral environment. A gingival fibroblast-laden collagen hydrogel was assembled in the central channel of a three-channel microfluidic chamber with interconnecting pores, followed by a keratinocyte layer attached to the collagen exposed in the pores. This configuration produced apical and subepithelial side channels capable of sustaining flow. Keratinocyte, fibroblast, and collagen densities were optimized to create a co-culture tissue-like construct stable over one week. Cells were stained and imaged with epifluorescence microscopy to confirm layer characteristics. As proof-of-concept, the mucosal construct was exposed separately to a dental monomer, 2-hydroxylethyl methacrylate (HEMA), and the oral bacteria Streptococcus mutans. Exposure to HEMA lowered mucosal cell viability, while exposure to the bacteria lowered trans-epithelial electrical resistance. These findings suggest that the oral mucosa-on-a-chip is useful for studying oral mucosal interactions with bacteria and biomaterials with a histology-like view of the tissue layers.

Applications of inflammation-derived gingival stem cells for testing the biocompatibility of dental restorative biomaterials

BACKGROUND

Normal or inflamed gingival tissues are regarded as a source of mesenchymal stem cells (MSCs) abundant and easily accessible through minimally invasive dental procedures. Due to the proximity of dental resin composites to gingival tissues and to the possible local cytotoxic effect of the eluted components, gingiva-derived MSCs could be used to investigate the biocompatibility of dental biomaterials.

PURPOSE

The present research aimed to isolate (MSCs) from inflamed and normal gingiva, to fully characterize them and to observe their behavior in relation with some commercial resin composite materials and one experimental material.

MATERIAL AND METHODS

Following their isolation, putative MSCs from both gingival sources were grown under the same culture conditions and characterized by immunophenotyping of cell surface antigens by flow-cytometry and transcription factors by immunocytochemical staining. Moreover, stemness gene expression was evaluated by RT-PCR analysis. Multipotent mesenchymal differentiation potential was investigated. Osteogenic and neurogenic differentiated cells were highlighted by immunocytochemical staining, chondrogenic cells by cytochemical staining, and adipocytes by cytochemical staining and spectrophotometry, respectively. Resin composite cytotoxicity was evaluated by cell membrane fluorescent labeling with PKH 26 and MTT assay. The results of PKH labeling were statistically analysed using two-way RM ANOVA with Bonferroni post-tests. For MTT assay, two-way RM ANOVA with Bonferroni post-tests and unpaired t test with Welch's correction were used.

RESULTS

A similar expression pattern of surface markers was observed. The cells were positive for CD105, CD73, CD90, CD49e, CD29, CD44 and CD166 and negative for CD45, CD34, CD14, CD79, HLA-DR and CD117 indicating a mesenchymal stem cell phenotype. The qRT-PCR analysis revealed a low gene expression for NOG, BMP4 and Oct3/4 and an increased expression for Nanog in both cells lines. Immunocytochemical analysis highlighted a more intense protein expression for Nanog, Oct3/4 and Sox-2 in MSCs derived from normal gingiva than from inflamed gingiva. Multipotent differentiation capacity of MSCs isolated from both sources was highlighted. The tested materials had no hazardous effect on MSCs as the two cell lines developed well onto resin composite substrates. Cell counting revealed some significant differences in the number of PKH-labeled MSCs at some experimental moments. Also, some differences in cell viability were recorded indicating better developmental conditions offered by some of the tested biomaterials.

CONCLUSIONS

The experimental resin composite behaved like the most biocompatible commercial material. Inflamed gingiva-derived MSCs retain their stem cell properties and could be used as a valuable cell line for testing dental biomaterials.

Development of a Full-Thickness Human Gingiva Equivalent Constructed from Immortalized Keratinocytes and Fibroblasts

Organotypic models make it possible to investigate the unique properties of oral mucosa in vitro. For gingiva, the use of human primary keratinocytes (KC) and fibroblasts (Fib) is limited due to the availability and size of donor biopsies. The use of physiologically relevant immortalized cell lines would solve these problems. The aim of this study was to develop fully differentiated human gingiva equivalents (GE) constructed entirely from cell lines, to compare them with the primary cell counterpart (Prim), and to test relevance in an in vitro wound healing assay. Reconstructed gingiva epithelium on a gingiva fibroblast-populated collagen hydrogel was constructed from cell lines (keratinocytes: TERT or HPV immortalized; fibroblasts: TERT immortalized) and compared to GE-Prim and native gingiva. GE were characterized by immunohistochemical staining for proliferation (Ki67), epithelial differentiation (K10, K13), and basement membrane (collagen type IV and laminin 5). To test functionality of GE-TERT, full-thickness wounds were introduced. Reepithelialization, fibroblast repopulation of hydrogel, metabolic activity (MTT assay), and (pro-)inflammatory cytokine release (enzyme-linked immunosorbent assay) were assessed during wound closure over 7 days. Significant differences in basal KC cytokine secretion (IL-1α, IL-18, and CXCL8) were only observed between KC-Prim and KC-HPV. When Fib-Prim and Fib-TERT were stimulated with TNF-α, no differences were observed regarding cytokine secretion (IL-6, CXCL8, and CCL2). GE-TERT histology, keratin, and basement membrane protein expression very closely represented native gingiva and GE-Prim. In contrast, the epithelium of GE made with HPV-immortalized KC was disorganized, showing suprabasal proliferating cells, limited keratinocyte differentiation, and the absence of basement membrane proteins. When a wound was introduced into the more physiologically relevant GE-TERT model, an immediate inflammatory response (IL-6, CCL2, and CXCL8) was observed followed by complete reepithelialization. Seven days after wounding, tissue integrity, metabolic activity, and cytokine levels had returned to the prewounded state. In conclusion, immortalized human gingiva KC and fibroblasts can be used to make physiologically relevant GE, which resemble either the healthy gingiva or a neoplastic disease model. These organotypic models will provide valuable tools to investigate oral mucosa biology and can also be used as an animal alternative for drug targeting, vaccination studies, microbial biofilm studies, and testing new therapeutics.

Evaluation of Light-Activated Provisional Resin Materials for Periodontal Soft Tissue Management

The purpose of this study was to determine mechanical properties using a compressive test with cylinder specimen (h = 6 mm and ϕ = 4 mm) as well as cytotoxicity using elutes from disk specimen (ϕ = 10 mm and h = 2 mm) against human gingival fibroblasts and oral keratinocytes with light-activated provisional resin materials (Revotek LC and Luxatemp Solar) compared to chemically activated counterpart (Snap, Trim II, and Jet). Significantly increased compressive strength (210~280 MPa) was detected in light-activated products compared to chemically activated ones (20~65 MPa, P < 0.05) and similar compressive modulus was detected in both types (0.8~1.5 and 0.5~1.3 GPa). Simultaneously, the light-activated products showed less adverse effects on the periodontal soft tissue cells in any polymerization stage compared to the chemically activated products. Particularly, chemically activated products had significantly greater adverse effects during the “polymerizing” phase compared to those that were “already set” (P < 0.05), as shown in confocal microscopic images of live and dead cells. In conclusion, light-activated provisional resin materials have better mechanical properties as well as biocompatibility against two tested types of oral cells compared to the chemically activated counterpart, which are considered as more beneficial choice for periodontal soft tissue management.

Effects of a Nonthermal Atmospheric Pressure Plasma Jet on Human Gingival Fibroblasts for Biomedical Application

Nonthermal atmospheric pressure plasma jets (APPJ) have been developed and applied in biomedical research as a cancer treatment or bacterial sterilization. However, the drawback of APPJ on normal oral cells during plasma treatment and underlying cell death mechanisms have not been studied and clearly explained, although there is known to be an influence from reactive oxygen species (ROS). Hence, this study investigates whether and how a nonthermal atmospheric pressure air plasma jet kills human normal gingival cells using immortalized human gingival fibroblasts (hTERT-hNOF cells). In this study, a set of physicochemical or biological methods were used to illuminate the killing mechanisms. It was found that ROS were induced intracellularly without a breakdown of the cell wall and apoptosis was involved in cell death when an air APPJ treatment was performed on the cells directly without media; the air treatment only supported a detachment of the cells without increase of ROS. It was also revealed that a correlation between intracellular ROS concentration and cells viability existed. These results indicated that the direct air APPJ treatment possibly raises safety issue to normal tissue and thereby APPJ application in biomedical field needs more in vitro and in vivo study to optimize it.

Cytotoxic effects of mineral trioxide aggregate, calcium enrichedmixture cement, Biodentine and octacalcium pohosphate onhuman gingival fibroblasts

Background. This in vitro study compared the effects of mineral trioxide aggregate (MTA), calcium enriched mixture(CEM) cement, Biodentine (BD) and octacalcium phosphate (OCP) on the viability of human gingival fibroblasts (HGFs). Methods. After completion of the setting time of the materials under study, fibroblasts were placed in 24-well insert platesand 1 mg of each material was added to the respective wells. The plates were then incubated at 37°C. The inserts were removedat 24, 48 and 168 hours and 2,5-diphenyltetrazolium bromide was added to assess cytotoxicity via the MTT colorimetricassay. Data were analyzed at different time intervals using repeated-measures ANOVA, followed by the Bonferronitest at three levels of significance of P < 0.05, P < 0.01 and P < 0.001. Results. Cytotoxicity of the materials under study was not significantly different at 24 and 48 hours compared to the controlgroup. However, at 168 hours, a significant difference was noted between MTA (P < 0.05) and Biodentine (P < 0.01)and the control group. Conclusion. Cytotoxicity of MTA, CEM, Biodentine and OCP against HGFs was similar to that of the control group at 24and 48 hours. Over time, MTA and Biodentine exhibited less cytotoxicity than other materials.

Biocompatibility Evaluation of Dental Luting Cements Using Cytokine Released from Human Oral Fibroblasts and Keratinocytes

Dental luting cements are commonly used in dentistry for cementation of prosthetic restoration. Many previous studies focused on the measurement of the cell viability as the method of cytotoxicity evaluation during biocompatibility study for the material. In this study, the biocompatibility of various dental luting cements were evaluated using the new method of cytokine release measurement in order to better simulate inflammatory reactions in animal or clinical model using two different oral cells; immortalized human gingival fibroblast and immortalized human oral keratinocytes. Cells were exposed to extractions of various commercially available dental luting cements for different durations. Cytokines of IL-1α and IL-8 were measured from the supernatants of the cells and the results were then compared to the conventional MTT viability test. The result from the conventional cell viability study showed a relatively simple and straight forward indication that only one of the dental luting cements tested in this study was cytotoxic with increasing duration of exposure for both cells. Meanwhile, the result from the cytokine measurement study was much more complex at the time point they were measured, type of cells used for the study and the type of cytokines measured, all of which influenced the interpretation of the results. Hence, the better understanding of the cytokine release would be required for the application in biocompatibility evaluation.

Human telomerase reverse transcriptase (hTERT) promotes cancer invasion by modulating cathepsin D via early growth response (EGR)-1

Human telomerase reverse transcriptase (hTERT) contributes to tumor progression as well as maintaining telomere length, however, the mechanism by which hTERT promotes invasiveness is not yet completely understood. This study aims to unravel the precise mechanism through which hTERT promotes cancer invasion. We established an hTERT-overexpressed immortalized cell line (IHOK/hTERT). In orthotopic xenograft models, IHOK/hTERT harbors higher tumorigenicity than IHOK/Control. IHOK/hTERT showed much higher migration and invasion activities compared to IHOK/Control. IHOK/hTERT co-cultured with fibroblasts displayed increased invasion compared to IHOK/hTERT without fibroblasts. We screened for genes that play an important role in intermodulation between cancer cells and fibroblasts using a microarray and identified fibroblast activation protein (FAP). hTERT knockdown showed decreased expression of FAP and early growth response (EGR)-1, one of the transcriptional regulators of FAP in IHOK/hTERT and oral cancer cell line YD10B. Furthermore, EGR-1 knockdown in IHOK/hTERT and YD10B showed reduced invasion and reduced cathepsin D expression compared to Control-siRNA cells. Taken together, this study provides evidence that hTERT overexpression is responsible for the upregulation of the cysteine protease cathepsin D by regulating EGR-1 to activate invasiveness in cancer progression.

Areca nut exposure increases secretion of tumor-promoting cytokines in gingival fibroblasts that trigger DNA damage in oral keratinocytes

Molecular crosstalk between cancer cells and fibroblasts has been an emerging hot issue in understanding carcinogenesis. As oral submucous fibrosis (OSF) is an inflammatory fibrotic disease that can potentially transform into squamous cell carcinoma, OSF has been considered to be an appropriate model for studying the role of fibroblasts during early stage carcinogenesis. In this sense, this study aims at investigating whether areca nut (AN)‐exposed fibroblasts cause DNA damage of epithelial cells. For this study, immortalized hNOF (hTERT‐hNOF) was used. We found that the levels of GRO‐α, IL‐6 and IL‐8 increased in AN‐exposed fibroblasts. Cytokine secretion was reduced by antioxidants in AN‐exposed fibroblasts. Increase in DNA double strand breaks (DSB) and 8‐oxoG FITC‐conjugate was observed in immortalized human oral keratinocytes (IHOK) after the treatment of cytokines or a conditioned medium derived from AN‐exposed fibroblasts. Cytokine expression and DNA damage were also detected in OSF tissues. The DNA damage was reduced by neutralizing cytokines or antioxidant treatment. Generation of reactive oxygen species (ROS) and DNA damage response, triggered by cytokines, were abolished when NADPH oxidase (NOX) 1 and 4 were silenced in IHOK, indicating that cytokine‐triggered DNA damage was caused by ROS generation through NOX1 and NOX4. Taken together, this study provided strong evidence that blocking ROS generation might be a rewarding approach for cancer prevention and intervention in OSF.

What's new?

Fibroblasts in the tumor microenvironment influence tumor initiation and growth and are of particular interest in oral submucous fibrosis (OSF), a progressive fibrotic disease of malignant potential. This study shows that the release of tumor‐promoting cytokines by fibroblasts exposed to areca nut, the primary cause of OSF, induce DNA damage in oral keratinocytes. The findings suggest that fibroblasts indirectly promote epithelial transformation in OSF by secreting cytokines, whereby DNA damage of epithelial cells is inflicted by reactive oxygen species generated via NADPH oxidases. These insights could inform the development of new therapeutic approaches for OSF.

Cytotoxicity of four denture adhesives on human gingival fibroblast cells

OBJECTIVE

The purpose of this study was to compare the cytotoxicity of four denture adhesives on human gingival fibroblast cells.

MATERIALS AND METHODS

Immortalized human gingival fibroblasts were cultured with one of four different denture adhesives, Polident, Protefix, Staydent or Denfix-A, which was placed in insert dishes (10% w/v concentration) for 48 h. The MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay and flow cytometric apoptosis assay were used to evaluate cell viability and apoptosis rates. The fibroblasts were also examined under a scanning electron microscope.

RESULTS

The MTT assay showed that all denture adhesives resulted in a significantly lower cell viability compared to the control cells propagated in normal culture medium (p < 0.05), with Staydent demonstrating the lowest cell viability. According to the flow cytometric apoptosis assay, Staydent and Protefix showed significantly higher apoptosis rates than the control group (p < 0.05), whereas Polident and Denfix-A did not demonstrate any significant differences (p > 0.05). Staydent showed the highest apoptosis rate. Scanning electron microscopy showed that the cells of the Staydent group underwent cytoplasmic membrane shrinkage, with cell free areas containing residual fragments of the membrane of dead cells.

CONCLUSIONS

The four denture adhesives evaluated in this study imparted cytotoxic effects on human gingival fibroblast cells. Staydent showed the highest toxicity.

Establishment and characterization of immortalized gingival epithelial and fibroblastic cell lines for the development of organotypic cultures

In vitro studies using 3D co-cultures of gingival cells can resemble their in vivo counterparts much better than 2D models that typically only utilize monolayer cultures with short-living primary cells. However, the use of 3D gingival models is still limited through lack of appropriate cell lines. We aimed to establish immortalized cell line models of primary human gingival epithelium keratinocytes (HGEK) and gingival fibroblasts (GFB). Immortalized cell lines (HGEK-16 and GFB-16) were induced by E6 and E7 oncoproteins of human papillomavirus. In addition, 3D multilayered organotypic cultures were formed by embedding GFB-16 cells within a collagen (Col) matrix and seeding of HGEK-16 cells on the upper surfaces. Cell growth was analyzed in both immortalized cell lines and their parental primary cells. The expression levels of cell type-specific markers, i.e. cytokeratin (CK) 10, CK13, CK16, CK18, CK19 for HGEK-16 and Col I and Col II for GFB-16, were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR). Expansion of the primary cultures was impeded at early passages, while the transformed immortalized cell lines could be expanded for more than 30 passages. In 3D cultures, immortalized HGEK formed a multilayer of epithelial cells. qRT-PCR showed that cell-specific marker expression in the 3D cultures was qualitatively and quantitatively closer to that in human gingival tissue than to monolayer cultures. These results indicate that immortalized gingival fibroblastic and epithelial cell lines can successfully form organotypic multilayered cultures and, therefore, may be useful tools for studying gingival tissue in vitro.

Confocal time lapse imaging as an efficient method for the cytocompatibility evaluation of dental composites

It is generally accepted that in vitro cell material interaction is a useful criterion in the evaluation of dental material biocompatibility. The objective of this study was to use 3D CLSM time lapse confocal imaging to assess the in vitro biocompatibility of dental composites. This method provides an accurate and sensitive indication of viable cell rate in contact with dental composite extracts. The ELS extra low shrinkage, a dental composite used for direct restoration, has been taken as example. In vitro assessment was performed on cultured primary human gingival fibroblast cells using Live/Dead staining. Images were obtained with the FV10i confocal biological inverted system and analyzed with the FV10-ASW 3.1 Software. Image analysis showed a very slight cytotoxicity in the presence of the tested composite after 5 hours of time lapse. A slight decrease of cell viability was shown in contact with the tested composite extracts compared to control cells. The findings highlighted the use of 3D CLSM time lapse imaging as a sensitive method to qualitatively and quantitatively evaluate the biocompatibility behavior of dental composites.

BMP-2 promotes oral squamous carcinoma cell invasion by inducing CCL5 release

Bone morphogenetic protein-2 (BMP-2)-containing bone grafts are useful regenerative materials for oral and maxillofacial surgery; however, several in vitro and in vivo studies previously reported cancer progression-related adverse effects caused by BMP-2. In this study, by quantifying the rhBMP-2 content released from bone grafts, the rhBMP-2 concentration that did not show cytotoxicity in each cell line was determined and applied to the in vitro monoculture or coculture model in the invasion assay. Our results showed that 1 ng/ml rhBMP-2, while not affecting cancer cell viability, significantly increased the invasion ability of the cancer cells cocultured with fibroblasts. Cocultured medium with rhBMP-2 also contained increased levels of matrix metalloproteinases. rhBMP-2-treated cocultured fibroblasts did not show a prominent difference in mRNA expression profile. Some cytokines, however, were detected in the conditioned medium by a human cytokine antibody array. Among them, the cancer invasion-related factor CCL5 was quantified by ELISA. Interestingly, CCL5 neutralizing antibodies significantly reduced the invasion of oral cancer cells. In conclusion, our results suggest that 1 ng/ml rhBMP-2 may induce invasion of oral squamous cell carcinoma (OSCC) cells by CCL5 release in coculture models. Therefore, we propose that a careful clinical examination before the use of rhBMP-2-containing biomaterials is indispensable for using rhBMP-2 treatment to prevent cancer progression.

An in vitro evaluation of the cytotoxicity of varying concentrations of sodium hypochlorite on human mesenchymal stem cells

AIM

To evaluate and compare the cytotoxicity of various concentrations of sodium hypochlorite on immortalized human bone marrow mesenchymal stem cells (MSCs).

MATERIALS AND METHODS

The 5.25 percent sodium hypochlo-rite (NaOCl) at concentrations of 0.5, 0.1, 0.025, 0.0125, and 0.005 mg/ml were used to assess the cytotoxic effect on MSCs. Immortalized human bone marrow mesenchymal stem cells (hTERT-MSCs) were exposed to NaOCl at 5 different concentrations. Cell viability was assessed by 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and alamarBlue assays. The cell morphology changes were assessed with scanning electron microscopy (SEM) after exposure to 2, 4, and 24 hour incubation. The ethidium bromide/acridine orange (EB/ AO) fuorescent stain was applied to the cells in the 8-chamber slides after they were incubated with the testing agents for 2 and 4 hours to detect live and dead cells. The observations were quantitatively and qualitatively analyzed.

RESULTS

The cell viability study using MTT assay and AB assay showed significant reduction with varying concentration at 2 and 4 hours incubation period. The cell viability decreased with the higher percentage of NaOCl. The exposure time also revealed an inverse relation to the cell viability. The SEM analysis showed reduction in the number of cells and morphological alterations with 0.5 mg/ml at 2 and 4 hours compared to 0.025 mg/ml NaOCl. Destruction of the cells with structural alterations and lysis was evident under fuorescence microscope when the cells were exposed to 0.5 mg/ml NaOCl.

CONCLUSION

Within the limitations of this in vitro study it can be concluded that NaOCl is toxic to the human bone marrow MSCs. The cell lysis was evident with higher concentration of sodium hypochlorite. From the observations, it can be concluded that a lower concentration of NaOCl may be used as endodontic irrigant due to its cytotoxic properties. Further studies are mandatory to evolve a consensus on the optimal concentration of sodium hypochlorite to be used as endodontic irrigant.

Modulation of human dermal microvascular endothelial cell and human gingival fibroblast behavior by micropatterned silica coating surfaces for zirconia dental implant applications

Dental ceramic implants have shown superior esthetic behavior and the absence of induced allergic disorders when compared to titanium implants. Zirconia may become a potential candidate to be used as an alternative to titanium dental implants if surface modifications are introduced. In this work, bioactive micropatterned silica coatings were produced on zirconia substrates, using a combined methodology of sol-gel processing and soft lithography. The aim of the work was to compare the in vitro behavior of human gingival fibroblasts (HGFs) and human dermal microvascular endothelial cells (HDMECs) on three types of silica-coated zirconia surfaces: flat and micropatterned (with pillars and with parallel grooves). Our results showed that cells had a higher metabolic activity (HGF, HDMEC) and increased gene expression levels of fibroblast-specific protein-1 (FSP-1) and collagen type I (COL I) on surfaces with pillars. Nevertheless, parallel grooved surfaces were able to guide cell growth. Even capillary tube-like networks of HDMEC were oriented according to the surface geometry. Zirconia and silica with different topographies have shown to be blood compatible and silica coating reduced bacteria adhesion. All together, the results indicated that microstructured bioactive coating seems to be an efficient strategy to improve soft tissue integration on zirconia implants, protecting implants from peri-implant inflammation and improving long-term implant stabilization. This new approach of micropatterned silica coating on zirconia substrates can generate promising novel dental implants, with surfaces that provide physical cues to guide cells and enhance their behavior.

Cytotoxicity of QMix™ endodontic irrigating solution on human bone marrow mesenchymal stem cells

Background

Debridement and disinfection of the root canal system is a crucial step in endodontic procedures. The effectiveness of irrigation relies on both the mechanical flushing action and the ability of irrigants to dissolve tissue and kill bacteria. The objective of the present study is to evaluate and compare the cytotoxicity of QMix™ root canal irrigating solution on immortalized human bone marrow mesenchymal stem cells (hTERT-MSC-C1) and to compare it with that of sodium hypochlorite (NaOCl).

Methods

Immortalized human bone marrow mesenchymal stem cells (hTERT-MSCs) were exposed to QMix™ and NaOCl. Cell viability was assessed by 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and alamarBlue assays. The cell morphology was studied after two hours of exposure to QMix™ and NaOCl. Scanning electron microscopy (SEM) analyses were performed after 2- and 4-hour incubation periods. Finally, ethidium bromide/acridine orange (EB/AO) fluorescent stain was applied to the cells in the 8-chamber slides after they were incubated with the testing agents for 2 hours to detect live and dead cells. The observations were tabulated and analyzed statistically.

Results

QMix™ exposure resulted in a significantly higher percentage of cell viability than NaOCl in the MTT and alamarBlue assays at three time points compared to the control. The SEM analysis demonstrated minimal morphological changes associated with cells that were exposed to the QMix™ solution, with little shrinkage and fragmentation of the cell wall. The live/dead analysis showed that the number of live cells after exposure to QMix™ was similar to that of the untreated control. No cell structure could be observed with the NaOCl group, indicating cell lysis.

Conclusion

Both the QMix™ and NaOCl solutions were toxic to human bone marrow MSCs. Each solution might have induced cell death in a different way as evidenced in the cell viability, SEM and fluorescent studies. The slower cell death induced by QMix™ might therefore be less aggressive and more acceptable to living tissues.

Cytotoxicity evaluation of zinc oxide-eugenol and non-eugenol cements using different fibroblast cell lines

OBJECTIVES

Despite being commonly used as temporary cements in dentistry, there is a lack of studies regarding the cytotoxicity of zinc oxide-eugenol (ZOE) and zinc oxide non-eugenol (ZONE) cements. In addition, cytotoxicity evaluation of the materials often involves animal-based cells. Therefore, in this study, a cytotoxicity evaluation of commercially available ZOE and ZONE cements was carried out using both animal and human-based cells.

MATERIALS AND METHODS

The extraction or dilution of the extraction from four commercially available cements (two zinc oxide-eugenol and two zinc oxide non-eugenol) was tested for cytotoxicity, using three different cells and a water-soluble treatzolium salt assay. The results were confirmed using a confocal laser microscope following calcein AM and ethidium homodimer-1 staining.

RESULTS

The results showed that there was a significant difference in cell viability depending on which cell was used, even when the same material was tested. Generally, L929 showed relatively low cell viability with a low EC50 (effective concentration of extracts that caused 50% of cell viability compared to the control) value compared to both HGF-1 and hTERT-hNOF. Such results were also confirmed by a confocal laser microscope.

CONCLUSIONS

Careful consideration on interpreting the results for cytotoxicity evaluation of ZOE and ZONE cements is needed when different cells are used.

Construction of a functional silk-based biomaterial complex with immortalized chondrocytes in vivo

To explore the feasibility of constructing a functional biomaterial complex with regenerated silk fibroin membrane and immortalized chondrocytes in vivo. Rat auricular chondrocytes (RACs) were transfected with the lentivirus vector pGC-FU-hTERT-3FLAG or pGC-FU-GFP-3FLAG, encoding the human telomerase reverse transcriptase (hTERT) or GFP gene. The effects of regenerated silk fibroin film on the adhesion, growth of immortalized chondrocytes and expression of collagen II in vitro were analyzed with immunofluorescent histochemistry. Immortalized RACs were transformed. Induction by nutrient medium promoted higher expression levels of collagen II in transformed chondrocytes. The regenerated silk fibroin film was not cytotoxic to immortalized chondrocytes and had no adverse influence on their adhesion. Collagen II expression was good in the immortalized chondrocytes in vivo. The construction of a silk-based biomaterial complex with immortalized chondrocytes may provide a feasible kind of functional biomaterial for the repair of cartilage defects in clinical applications.

Effects of two low-shrinkage composites on dental stem cells (viability, cell damaged or apoptosis and mesenchymal markers expression)

To investigate the effects of new two low-shrinkage composites SDR(®) and Venus(®)Bulk Fill on the cell viability, cellular damage and expression of mesenchymal markers on dental stem cells. Specimens from two low-shrinkage composites were eluted with culture medium for 24 h. After 24 h of incubation, cytotoxicity of elutes were evaluated by MTT assay; apoptosis was determined using the DNA-specific fluorochrome Hoechst 33342 and the mesenchymal stem cells markers expression was analyzed by immunofluorescence staining. After 24 h of cell exposure to each extract media, dental stem cells expressed MSCs markers. The interaction among the material and cell line was not significantly correlated [F(1,60) = 2.251, P = 0.39], whereas statistically significant differences among cells lines were observed [F(1,60) = 9.157, P = 0.004], being dental pulp stem cells more resistant that periodontal ligament stem cells. Also, we did not find any significant effect between the tested materials [F(1,60) = 0.090, P = 0.765]. Furthermore, a very low proportion of exposed cells showed condensed or fragmented nuclei, typical of apoptotic cells at 24 h. The results suggest that SDR(®) and Venus(®) Bulk fill and should be considered when selecting an appropriate resin-based dental restorative material.

Derivation and characterization of goat fetal fibroblast cells induced with human telomerase reverse transcriptase

Fetal fibroblast cells (FFCs) are often used as donor cells for somatic cell nuclear transfer (SCNT) because they are easy to culture and suitable for genetic manipulation. However, through genetic modification process, which required FFCs to be cultured in vitro for several passages, cells tended to age very rapidly and became inappropriate for SCNT. Human telomerase reverse transcriptase (hTERT) possessed the activity of human telomerase and maintains telomere in dividing cells; therefore, hTERT can be transfected into somatic cells to extend their lifespan. In this study, we transfected a Xinong Saanen Dairy Goat FFC line with hTERT. Then, we tested several characteristics of transfected cells, including growth curve, expression and activity of hTERT, tumorigenicity, and expression of oct4 and nanog. The result showed that hTERT could significantly extend the lifespan of transfected cells in vitro. hTERT mRNA was expressed in hTERT-transfected cells. Moreover, hTERT-transfected cells presented enhanced telomerase activity and longer telomere than untransfected cells at the same passage. On the other hand, hTERT-transfected cells can maintain normal karyotype even after several times of subculture in vitro. After inoculation of hTERT-transfected cells in nude mouse, none of them developed tumors on the vaccination site. Interestingly, transfection of hTERT can improve expression of nanog and oct4 in Xinong Saanen Dairy Goat FFCs, especially in low generation after transfection, but with increasing subculture, this effect gradually weakened.