Highly Ordered Nanotube-Like Microstructure on Titanium Dental Implant Surface Fabricated via Anodization Enhanced Cell Adhesion and Migration of Human Gingival Fibroblasts

Background

Titanium (Ti) surface with nanotubes array via anodization has been used in dental implants to enhance bone regeneration but little research was carried out to evaluate whether the presence of highly ordered or disorderly distributed nanotubes array on titanium surface would have an effect on cell behaviors of gingival fibroblasts.

Methods

The present study fabricated nanotubes arrays with varied topography under different constant voltage of electrochemical anodization in fluorine-containing electrolyte. Human gingival fibroblasts (HGFs) from extracted third molar were harvested and co-cultured with titanium disks with different nanotubes topography. Then cell behaviors of gingival fibroblasts including cell proliferation, adhesive morphology and cell migration were estimated to investigate the influence of titanium nanotubes on cell biology. Besides, gene and protein expression of adhesion molecule (integrin β1/β4/α6, fibronectin, intracellular adhesion molecule-1 and collagen type I) were detected to evaluate the influence of different surfaces on cell adhesion.

Results

Highly ordered arrays of nanotubes with pore diameter of 60 nm and 100 nm were fabricated under 30 and 40 V of anodization (TNT-30 and TNT-40) while disorderedly distributed nanotube arrays formed on the titanium surface under 50 V of anodization (TNT-50). Our results demonstrated that compared with raw titanium surface and disorderly nanotubes, surface with orderly nanotubes array increased cell area and aspect ratio, as well as cell migration ability in the early phase of cell adhesion (p<0.05). Besides, compared with raw titanium surface, gene and protein expression of adhesion molecules were upregulated in nanotubes groups to different extents, no matter whether in an orderly or disorderly array.

Conclusion

Within the limitations of our study, we conclude that compared with raw titanium surface, the presence of nanotubes array on titanium surface could enhance cells adhesion and cell migration in the early phase. And compared with disorderly distributed nanotubes, highly ordered nanotubes array might provide a much more favorable surface for gingival fibroblasts to achieve a tight adhesion on the materials.

Analysis of soft tissue integration-supportive cell functions in gingival fibroblasts cultured on 3D printed biomaterials for oral implant-supported prostheses

To date, it is unknown whether 3D printed fixed oral implant-supported prostheses can achieve comparable soft tissue integration (STI) to clinically established subtractively manufactured counterparts. STI is mediated among others by gingival fibroblasts (GFs) and is modulated by biomaterial surface characteristics. Therefore, the aim of the present work was to investigate the GF response of a 3D printed methacrylate photopolymer and a hybrid ceramic-filled methacrylate photopolymer for fixed implant-supported prostheses in the sense of supporting an STI. Subtractively manufactured samples made from methacrylate polymer and hybrid ceramic were evaluated for comparison and samples from yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP), comprising well documented biocompatibility, served as control. Surface topography was analyzed by scanning electron microscopy and interferometry, elemental composition by energy-dispersive x-ray spectroscopy, and wettability by contact angle measurement. The response of GFs obtained from five donors was examined in terms of membrane integrity, adhesion, morphogenesis, metabolic activity, and proliferation behavior by a lactate-dehydrogenase assay, fluorescent staining, a resazurin-based assay, and DNA quantification. The results revealed all surfaces were smooth and hydrophilic. GF adhesion, metabolic activity and proliferation were impaired by 3D printed biomaterials compared to subtractively manufactured comparison surfaces and the 3Y-TZP control, whereas membrane integrity was comparable. Within the limits of the present investigation, it was concluded that subtractively manufactured surfaces are superior compared to 3D printed surfaces to support STI. For the development of biologically optimized 3D printable biomaterials, consecutive studies will focus on the improvement of cytocompatibility and the synthesis of STI-relevant extracellular matrix constituents.

Proliferative effect of cannabidiol in human gingival fibroblasts via the mitogen-activated extracellular signal-regulated kinase (MEK) 1/2

BACKGROUND AND OBJECTIVES

Cannabidiol exerts its anti-inflammatory and anti-oxidant activities in various human cells. However, its proliferative effect has not been extrapolated to human gingival fibroblasts (HGFs). This study aimed to determine the proliferative and promigratory effects of cannabidiol in HGFs and to elucidate the signaling mechanism(s).

MATERIALS AND METHODS

HGFs, characterized by their CD73, CD90, and CD105 expressions by flow cytometry, were treated with cannabidiol at 0.01-30 μM. The cytotoxicity was determined by the MTT assay, while the proliferative effect was examined by the BrdU assay, immunoblot and immunofluorescence for cyclin D1 and Ki-67 expressions, respectively, and cell cycle analysis. The promigratory effect of cannabidiol was investigated by a wound healing assay. Phosphorylation of the p38 MAPK, JNK, and ERK upon treatment with cannabidiol was explored, and their involvement in cell proliferation and cyclin D1 and Ki-67 expressions was studied using pharmacological inhibitors.

RESULTS

No toxicity was found in HGFs treated with any doses of cannabidiol up to 30 μM. The mean percentage of cell proliferation was significantly enhanced by treatment with cannabidiol at 3 or 10 μM (p < .001), consistent with upregulated expressions of cyclin D1 and Ki-67 and increased percentages of HGFs in the S and G2/M phases. Moreover, treatment with cannabidiol significantly induced cell migration (p < .05). The p38 MAPK and ERK1/2 were significantly activated by cannabidiol (p < .05), but only pretreatment with UO126, a MEK1/2 inhibitor, significantly inhibited cell proliferation and cyclin D1 and Ki-67 expressions (p < .05).

CONCLUSION

Treatment with cannabidiol at non-toxic doses promotes HGFs' proliferation and migration.

Mouse gingival single-cell transcriptomic atlas identified a novel fibroblast subpopulation activated to guide oral barrier immunity in periodontitis

Periodontitis, one of the most common non-communicable diseases, is characterized by chronic oral inflammation and uncontrolled tooth supporting alveolar bone resorption. Its underlying mechanism to initiate aberrant oral barrier immunity has yet to be delineated. Here, we report a unique fibroblast subpopulation activated to guide oral inflammation (AG fibroblasts) identified in a single-cell RNA sequencing gingival cell atlas constructed from the mouse periodontitis models. AG fibroblasts localized beneath the gingival epithelium and in the cervical periodontal ligament responded to the ligature placement and to the discrete topical application of Toll-like receptor stimulants to mouse maxillary tissue. The upregulated chemokines and ligands of AG fibroblasts linked to the putative receptors of neutrophils in the early stages of periodontitis. In the established chronic inflammation, neutrophils, together with AG fibroblasts, appeared to induce type 3 innate lymphoid cells (ILC3s) that were the primary source of interleukin-17 cytokines. The comparative analysis of Rag2-/- and Rag2-/-Il2rg-/- mice suggested that ILC3 contributed to the cervical alveolar bone resorption interfacing the gingival inflammation. We propose the AG fibroblast-neutrophil-ILC3 axis as a previously unrecognized mechanism which could be involved in the complex interplay between oral barrier immune cells contributing to pathological inflammation in periodontitis.

Gingival Fibroblasts Are Sensitive to Oral Cell Lysates Indicated by Their IL11 Expression

Damaged cells that appear as a consequence of invasive dental procedures or in response to dental materials are supposed to release damage-associated signals. These damage-associated signals not only support tissue regeneration but might also contribute to unwanted fibrosis. The aim of this study was to identify a molecular target that reflects how fibroblasts respond to necrotic oral tissue cells. To simulate the cell damage, we prepared necrotic cell lysates by sonication of the osteocytic cell line IDG-SW3 and exposed them to gingival fibroblasts. RNAseq revealed a moderate increase in IL11 expression in the gingival fibroblasts, a pleiotropic cytokine involved in fibrosis and inflammation, and also in regeneration following trauma. Necrotic lysates of the human squamous carcinoma cell lines HSC2 and TR146, as well as of gingival fibroblasts, however, caused a robust increase in IL11 expression in the gingival fibroblasts. Consistently, immunoassay revealed significantly increased IL11 levels in the gingival fibroblasts when exposed to the respective lysates. Considering that IL11 is a TGF-β target gene, IL11 expression was partially blocked by SB431542, a TGF-β receptor type I kinase inhibitor. Moreover, lysates from the HSC2, TR146, and gingival fibroblasts caused a moderate smad2/3 nuclear translocation in the gingival fibroblasts. Taken together and based on IL11 expression, our findings show that fibroblasts are sensitive to damaged oral tissue cells.

Inhibition of gingival fibroblast necroptosis mediated by RIPK3/MLKL attenuates periodontitis

AIM

Necroptosis participates in the pathogenesis of many inflammatory diseases, including periodontitis. Here, we aimed to investigate the role and mechanism of necroptosis inhibitors in attenuating periodontitis.

MATERIALS AND METHODS

The Gene Expression Omnibus (GEO) dataset GSE164241 was re-analysed to identify the role of necroptosis in periodontitis. Gingival specimens from healthy subjects or periodontitis patients were collected to evaluate the expression level of necroptosis-associated proteins. The therapeutic effect of necroptosis inhibitors on periodontitis was assessed in vivo and in vitro. Moreover, Transwell assays and Western blotting and siRNA transfection were used to identify the effects of necroptotic human gingival fibroblasts (hGFs) on THP-1 macrophages.

RESULTS

Re-analysis revealed that gingival fibroblasts (GFs) in periodontitis gingiva showed the highest area under the curve score of necroptosis. Elevated levels of necroptosis-associated proteins were identified in GFs in periodontitis gingiva collected from patients and mice. In ligature-induced periodontitis mice, local administration of receptor interacting protein kinase 3(RIPK3) inhibitor GSK'872 or sh-mixed-lineage kinase domain-like pseudokinase (Mlkl) markedly abrogated necroptosis and rescued periodontitis. Analogously, necroptosis inhibitors alleviated the inflammatory response and release of damage-associated molecular patterns in lipopolysaccharide- or LAZ (LPS + AZD'5582 + z-VAD-fmk, necroptosis inducer)-induced GFs and then reduced THP-1 cell migration and M1 polarization.

CONCLUSIONS

Necroptosis in GFs aggravated gingival inflammation and alveolar bone loss. Necroptosis inhibitors attenuate this process by modulating THP-1 macrophage migration and polarization. This study offers novel insights into the pathogenesis and potential therapeutic targets of periodontitis.

Behaviour of the Peri-Implant Soft Tissue with Different Rehabilitation Materials on Implants

(1) Background: Mucointegration seems to gain interest when talking about success in the maintenance of dental implants. As we well know, collagen fibres cannot be inserted due to the lack of root structure on the implant surface, so the structural integration of peri-implant tissues that provide a firm seal around implants seems to be of interest when it comes to ensuring the survival of dental implants. To achieve a good epithelial barrier, the physicochemical characteristics of the surfaces of the restorative materials are of vital importance; therefore, the objective of this study is to analyse the histological behaviour of the peri-implant soft tissues in three different restorative materials. (2) Methods: Histological analysis of biopsied peri-implant keratinised mucosa, inflammatory epithelium and connective tissue in contact with a reinforced composite (BRILLIANT Crios), a cross-linked polymethylmethacrylate (TELIO CAD), and a hybrid ceramic (Vita Enamic), restored on a customised Atlantis-type abutment (Dentsply Sirona) between 60 and 180 days after restoration. (3) Results: A greater number of cells per mm2 of keratinised epithelium is observed in the reinforced composite, which could indicate greater surface roughness with greater inflammatory response. In this way, the greater number of lymphocytes and the lateral cellular composition of the inflammatory cells confirm the greater inflammatory activity towards that material. The best material to rehabilitate was hybrid ceramic, as it shows a better cellular response. (4) Conclusions: Knowing the limitations of the proposed study, despite the fact that greater inflammation is observed in the reinforced composite relative to the other materials studied, no statistically significant differences were found.

Effect of ascorbic acid on cellular respiration with mitochondrial reductase in gingival fibroblast

Vitamin C or L-ascorbic acid has diverse functions in the body, especially healing promotion in tissue injury via participating in the hydroxylation reactions required for collagen formation. Systemic administration of vitamin C plays an important role on gingival fibroblast proliferation and functions. Whether local or rinsing administration of vitamin C alters gingival fibroblast wound healing behavior remains unclear. Therefore, it is of interest to investigate the effect of vitamin C on gingival fibroblast behavior utilizing cell culture. Primary human gingival fibroblasts isolated from gingival tissue were rinsed with medium containing various concentrations of vitamin C. Cell migration, cell viability was assessed using MTT assay. The viability assay showed >95% live cells, and no significant (P > 0.05) difference in these values was observed at different concentrations at 24 hrs. The levels of cell proliferation were not significantly different among the control and experimental groups in 24 hrs experimental time-points (p > 0.05). Vitamin C is nontoxic and can be used for further experiments to validate for clinical application. This was further confirmed with morphological examination after 24hrs incubation on control and experimental group drugs observed under the phase contrast microscope.

Regulation of osteogenesis in bone marrow-derived mesenchymal stem cells via histone deacetylase 1 and 2 co-cultured with human gingival fibroblasts and periodontal ligament cells

OBJECTIVE

This study aimed to determine the regulatory mechanism of bone marrow-derived mesenchymal stem cell (BM-MSC) differentiation mediated by humoral factors derived from human periodontal ligament (HPL) cells and human gingival fibroblasts (HGFs). We analyzed histone deacetylase (HDAC) expression and activity involved in BM-MSC differentiation and determined their regulatory effects in co-cultures of BM-MSCs with HPL cells or HGFs.

BACKGROUND

BM-MSCs can differentiate into various cell types and can, thus, be used in periodontal regenerative therapy. However, the mechanism underlying their differentiation remains unclear. Transplanted BM-MSCs are affected by periodontal cells via direct contact or secretion of humoral factors. Therefore, their activity is regulated by humoral factors derived from HPL cells or HGFs.

METHODS

BM-MSCs were indirectly co-cultured with HPL cells or HGFs under osteogenic or growth conditions and then analyzed for osteogenesis, HDAC1 and HDAC2 expression and activity, and histone H3 acetylation. BM-MSCs were treated with trichostatin A, or their HDAC1 or HDAC2 expression was silenced or overexpressed during osteogenesis. Subsequently, they were evaluated for osteogenesis or the effects of HDAC activity.

RESULTS

BM-MSCs co-cultured with HPL cells or HGFs showed suppressed osteogenesis, HDAC1 and HDAC2 expression, and HDAC phosphorylation; however, histone H3 acetylation was enhanced. Trichostatin A treatment remarkably suppressed osteogenesis, decreasing HDAC expression and enhancing histone H3 acetylation. HDAC1 and HDAC2 silencing negatively regulated osteogenesis in BM-MSCs to the same extent as that achieved by indirect co-culture with HPL cells or HGFs. Conversely, their overexpression positively regulated osteogenesis in BM-MSCs.

CONCLUSION

The suppressive effects of HPL cells and HGFs on BM-MSC osteogenesis were regulated by HDAC expression and histone H3 acetylation to a greater extent than that mediated by HDAC activity. Therefore, regulation of HDAC expression has prospects in clinical applications for effective periodontal regeneration, mainly, bone regeneration.

Mapping of DNA methylation-sensitive cellular processes in gingival and periodontal ligament fibroblasts in the context of periodontal tissue homeostasis

Interactions between gingival fibroblasts (GFs) and oral pathogens contribute to the chronicity of inflammation in periodontitis. Epigenetic changes in DNA methylation are involved in periodontitis pathogenesis, and recent studies indicate that DNA methyltransferase (DNMT) inhibitors may protect against epithelial barrier disruption and bone resorption. To assess the impact of DNMT inhibition on GFs, cells were cultured with decitabine (5-aza-2'-deoxycytidine, DAC) for 12 days to induce DNA hypomethylation. We observed several potentially detrimental effects of DAC on GF biological functions. First, extended treatment with DAC reduced GF proliferation and induced necrotic cell death. Second, DAC amplified Porphyromonas gingivalis- and cytokine-induced expression and secretion of the chemokine CCL20 and several matrix metalloproteinases (MMPs), including MMP1, MMP9, and MMP13. Similar pro-inflammatory effects of DAC were observed in periodontal ligament fibroblasts. Third, DAC upregulated intercellular adhesion molecule-1 (ICAM-1), which was associated with increased P. gingivalis adherence to GFs and may contribute to bacterial dissemination. Finally, analysis of DAC-induced genes identified by RNA sequencing revealed increased expression of CCL20, CCL5, CCL8, CCL13, TNF, IL1A, IL18, IL33, and CSF3, and showed that the most affected processes were related to immune and inflammatory responses. In contrast, the genes downregulated by DAC were associated with extracellular matrix and collagen fibril organization. Our observations demonstrate that studies of DNMT inhibitors provide important insights into the role of DNA methylation in cells involved in periodontitis pathogenesis. However, the therapeutic potential of hypomethylating agents in periodontal disease may be limited due to their cytotoxic effects on fibroblast populations and stimulation of pro-inflammatory pathways.

The Potential Application of Human Gingival Fibroblast-Conditioned Media in Pulp Regeneration: An In Vitro Study

Regenerative endodontic treatment based on tissue engineering has recently gained interest in contemporary restorative dentistry. However, low survival rates and poor potential differentiation of stem cells could undermine the success rate of pulp regenerative therapy. Human gingival fibroblast-conditioned medium (hGF-CM) has been considered a potential therapy for tissue regeneration due to its stability in maintaining multiple factors essential for tissue regeneration compared to live cell transplantation. This study aimed to investigate the potency of hGF-CM on stem cells from human dental pulp (DPSC) in pulp regeneration. A series of experiments confirmed that hGF-CM contributes to a significant increase in proliferation, migration capability, and cell viability of DPSC after H2O2 exposure. Moreover, it has been proved to facilitate the odontogenic differentiation of DPSC via qRT-PCR, ALP (alkaline phosphatase), and ARS (Alizarin Red S) staining. It has been discovered that such highly upregulated odontogenesis is related to certain types of ECM proteins (collagen and laminin) from hGF-CM via proteomics. In addition, it is found that the ERK pathway is a key mechanism via inhibition assay based on RNA-seq result. These findings demonstrate that hGF-CM could be beneficial biomolecules for pulp regeneration.

Aging envisage imbalance of the periodontium: A keystone in oral disease and systemic health

Aging is a gradual and progressive deterioration of integrity across multiple organ systems that negatively affects gingival wound healing. The cellular responses associated with wound healing, such as collagen synthesis, cell migration, proliferation, and collagen contraction, have been shown to be lower in gingival fibroblasts (the most abundant cells from the connective gingival tissue) in aged donors than young donors. Cellular senescence is one of the hallmarks of aging, which is characterized by the acquisition of a senescence-associated secretory phenotype that is characterized by the release of pro-inflammatory cytokines, chemokines, growth factors, and proteases which have been implicated in the recruitment of immune cells such as neutrophils, T cells and monocytes. Moreover, during aging, macrophages show altered acquisition of functional phenotypes in response to the tissue microenvironment. Thus, inflammatory and resolution macrophage-mediated processes are impaired, impacting the progression of periodontal disease. Interestingly, salivary antimicrobial peptides, such as histatins, which are involved in various functions, such as antifungal, bactericidal, enamel-protecting, angiogenesis, and re-epithelization, have been shown to fluctuate with aging. Several studies have associated the presence of Porphyromonas gingivalis, a key pathogen related to periodontitis and apical periodontitis, with the progression of Alzheimer's disease, as well as gut, esophageal, and gastric cancers. Moreover, herpes simplex virus types 1 and 2 have been associated with the severity of periodontal disease, cardiovascular complications, and nervous system-related pathologies. This review encompasses the effects of aging on periodontal tissues, how P. gingivalis and HSV infections could favor periodontitis and their relationship with other pathologies.

Comparison of Pulsed and Continuous Wave Diode Laser at 940 nm on the Viability and Migration of Gingival Fibroblasts

Gingival fibroblasts have critical roles in oral wound healing. Photobiomodulation (PBM) has been shown to promote mucosal healing and is now recommended for managing oncotherapy-associated oral mucositis. This study examined the effects of the emission mode of a 940 nm diode laser on the viability and migration of human gingival fibroblasts. Cells were cultured in a routine growth media and treated with PBM (average power 0.1 W/cm² , average fluence 3 J/cm² , every 12h for 6 sessions) in one continuous wave (CW) and two pulsing settings with 20 % and 50 % duty cycles. Cell viability was assessed using MTT, and digital imaging quantified cell migration. After 48 and 72 hours, all treatment groups had significantly higher viability (n = 6, p < 0.05) compared to the control. The highest viability was seen in the pulsed (20% duty cycle) group at the 72-hour time point. PBM improved fibroblast migration in all PBM-treated groups, but differences were not statistically significant (n = 2, p > 0.05). PBM treatments can promote cell viability in both continuous and pulsed modes. Further studies are needed to elucidate the optimal setting for PBM-evoked responses for its rationalized use in promoting specific phases of oral wound healing.

Novel Titanium Nanospike Structure Using Low-Energy Helium Ion Bombardment for the Transgingival Part of a Dental Implant

AIM(S)

The aim of the study was to fabricate a nanospike surface on a titanium alloy surface using a newly established method of low-energy helium ion bombardment. Various methods to achieve nanospike formation on titanium have been introduced recently, and their antibacterial properties have been mainly investigated with respect to Escherichia coli and Staphylococcus aureus. Oral pathogens such as Porphyromonas gingivalis play an important role in the development of peri-implantitis. For that reason, the antibacterial properties of the novel, nanostructured titanium surface against P. gingivalis were assessed, and a possible effect on the viability of gingival fibroblasts was evaluated.

MATERIALS AND METHODS

Helium sputtering was employed for developing titanium surfaces with nanospikes of 500 nm (ND) in height; commercially available smooth-machined (MD) and sandblasted and acid-etched titanium disks (SLA) were used as controls. Surface structure characterization was performed through scanning electron microscopy (SEM) and atomic force microscopy (AFM). Following incubation with P. gingivalis, antibacterial properties were determined via conventional culturing and SEM. Additionally, the viability of human gingival fibroblasts (HGFs) was tested through MTT assay, and cell morphology was assessed through SEM.

RESULTS

SEM images confirmed the successful establishment of a nanospike surface with required heights, albeit with heterogeneity. AFM images of the 500 nm nanospike surface revealed that the roughness is dominated by large-scale hills and valleys. For frame sizes of 5 × 5 μm and smaller, the average roughness is dominated by the height of the titanium spikes. ND successfully induces dysmorphisms within P. gingivalis cultures following the incubation period, while conventional culturing reveals a 17% and 20% reduction for ND compared to MD and SLA, respectively. Moreover, the nanospike surfaces did not affect the viability of human growth fibroblasts despite their sharp surface.

CONCLUSION(S)

This study successfully developed a novel titanium-nanospike-based structuration technique for titanium surfaces. In addition, the nanospikes did not hinder gingival fibroblast viability. Enhanced antimicrobial effects for such a novel nanospike-based resurfacing technique can be achieved through further optimizations for nanospike spacing and height parameters.

Pathogenesis of Enamel-Renal Syndrome Associated Gingival Fibromatosis: A Proteomic Approach

The enamel renal syndrome (ERS) is a rare disorder featured by amelogenesis imperfecta, gingival fibromatosis and nephrocalcinosis. ERS is caused by bi-allelic mutations in the secretory pathway pseudokinase FAM20A. How mutations in FAM20A may modify the gingival connective tissue homeostasis and cause fibromatosis is currently unknown. We here analyzed conditioned media of gingival fibroblasts (GFs) obtained from four unrelated ERS patients carrying distinct mutations and control subjects. Secretomic analysis identified 109 dysregulated proteins whose abundance had increased (69 proteins) or decreased (40 proteins) at least 1.5-fold compared to control GFs. Proteins over-represented were mainly involved in extracellular matrix organization, collagen fibril assembly, and biomineralization whereas those under-represented were extracellular matrix-associated proteins. More specifically, transforming growth factor-beta 2, a member of the TGFβ family involved in both mineralization and fibrosis was strongly increased in samples from GFs of ERS patients and so were various known targets of the TGFβ signaling pathway including Collagens, Matrix metallopeptidase 2 and Fibronectin. For the over-expressed proteins quantitative RT-PCR analysis showed increased transcript levels, suggesting increased synthesis and this was further confirmed at the tissue level. Additional immunohistochemical and western blot analyses showed activation and nuclear localization of the classical TGFβ effector phospho-Smad3 in both ERS gingival tissue and ERS GFs. Exposure of the mutant cells to TGFB1 further upregulated the expression of TGFβ targets suggesting that this pathway could be a central player in the pathogenesis of the ERS gingival fibromatosis. In conclusion our data strongly suggest that TGFβ -induced modifications of the extracellular matrix contribute to the pathogenesis of ERS. To our knowledge this is the first proteomic-based analysis of FAM20A-associated modifications.

The effects of hyperglycemia on the biological behavior of human gingival fibroblasts on a titanium surface

BACKGROUND

It is well known that diabetes mellitus is one of the high-risk factors for periodontitis and also for the failure of implant restorations. Usually, the success of an implant restoration depends on both the good osseointegration and the stable soft tissue interface on the implant neck. A good gingival interface of the implant neck is the barrier that enables implant to resist oral microorganisms and the site of initiation of peri-implantitis. This study sought to investigate the effects of hyperglycemia on the attachment and proliferation of human gingival fibroblasts (HGFs) on pure titanium surfaces.

METHODS

HGFs were cultured in cell culture mediums with different glucose concentrations (i.e., 5.5, 8. 8, 10, and 15 mmol/L) for 7 d and seeded on pure titanium surfaces. The cells that were seeded on the titanium surfaces had been cultured in cell culture mediums with different glucose concentrations for 3 and 7 d. The attached HGFs on the titanium surfaces were counted for all groups using a blood cell counting plate, and the results were statistically analyzed. The morphologies of the attached HGFs on the titanium surfaces were observed for all the groups using a scanning electronic microscope.

RESULTS

As the glucose concentrations increased, the number of attached HGFs on the titanium surfaces decreased. The numbers of attached cells in Groups A and B 7 d after being seeded on the titanium surfaces were more than those 3 d after being seeded (P<0.05). The numbers of attached cells in Groups C and D 3 d after being seeded on the titanium were more than those 7 d after being seeded (P<0.05). The scanning electronic microscope showed that the attached cells in Groups A and B proliferated well, and most cells grew one on top of another. Conversely, the attached cells in Groups C and D proliferated sparsely and the cell morphologies were not good.

CONCLUSIONS

The attachment and proliferation of HGFs on pure titanium surfaces were inhibited by increases in glucose concentrations, and the inhibition was further enhanced by the passage of time.

Comparative In Vitro Evaluation of Commercial Periodontal Gels on Antibacterial, Biocompatibility and Wound Healing Ability

In the last years, several studies testing commercial periodontal gels that contain chlorhexidine (CHX) or other antibacterial agents, have raised concerns regarding their cytotoxicity in periodontal tissues. We aimed at comparing the biocompatibility but also the efficacy as regards to the antibacterial and wound healing ability of different commercial periodontal gels. In vitro human gingival fibroblasts (GF) and a 3D model of human tissue equivalents of gingiva (GTE) were used under inflammatory conditions to evaluate wound closure, cytotoxicity and gene expression. Antibacterial effects were also investigated on Porphyromonas gingivalis growth, viability and gingipain activity. In GF and in the bacterial study, we found cytotoxic effects on GF and a high inhibition on bacterial growth rate in gels containing CHX, asiaticoside, enoxolone, cetylpyridinium chloride, propolis and eugenol. Of the two gels that were non-cytotoxic, Syntoss Biogel (containing chondrontin sulfate) and Emdogain (EMD, containing amelogenin and propylene glycol alginate), EMD showed the best wound closure, with no effect on P. gingivalis growth but decreased gingipain activity. On the other hand, Syntoss Biogel reduced viability and gingipain activity of P. gingivalis, but lack wound healing capacity. In the 3D GTE, Syntoss Biogel and EMD showed a good biocompatibility. Among all the tested gels, formulations containing CHX, asiaticoside, enoxolone, cetylpyridinium chloride, propolis and eugenol showed high antibacterial effect but also showed high cytotoxicity in eukaryotic cells. EMD was the one with the best biocompatibility and wound healing ability at the conditions tested.

Cytotoxic and Genotoxic Effects of Composite Resins on Cultured Human Gingival Fibroblasts

The aim of the study was to evaluate the cytotoxic and genotoxic potential of five commercially available dental composite resins (CRs), investigating the effect of their quantifiable bisphenol-A-glycidyl-methacrylate (Bis-GMA) and/or triethylene glycol dimethacrylate (TEGDMA) release. Experiments were performed using the method of soaking extracts, which were derived from the immersion of the following CRs in the culture medium: Clearfil-Majesty-ES-2, GrandioSO, and Enamel-plus-HRi (Bis-GMA-based); Enamel-BioFunction and VenusDiamond (Bis-GMA-free). Human Gingival Fibroblasts (hGDFs) were employed as the cellular model to mimic in vitro the oral cavity milieu, where CRs simultaneously release various components. Cell metabolic activity, oxidative stress, and genotoxicity were used as cellular outcomes. Results showed that only VenusDiamond and Enamel-plus-HRi significantly affected the hGDF cell metabolic activity. In accordance with this, although no CR-derived extract induced a significantly detectable oxidative stress, only VenusDiamond and Enamel-plus-HRi induced significant genotoxicity. Our findings showed, for the CRs employed, a cytotoxic and genotoxic potential that did not seem to depend only on the actual Bis-GMA or TEGDMA content. Enamel-BioFunction appeared optimal in terms of cytotoxicity, and similar findings were observed for Clearfil-Majesty-ES-2 despite their different Bis-GMA/TEGDMA release patterns. This suggested that simply excluding one specific monomer from the CR formulation might not steadily turn out as a successful approach for improving their biocompatibility.

Hyaluronic acid vs. physiological saline for enlarging deficient gingival papillae: a randomized controlled clinical trial and an in vitro study

Background

loss of the interdental papillae leads to the formation of a black triangle, which compromises smile esthetics and contributes to food impaction and plaque accumulation. The aim of this study was to evaluate the efficacy of the injection of hyaluronic acid (HA) and compare it to that of physiological saline solution in the restoration of deficient gingival papillae in vivo and in vitro.

Methods

Twenty-four patients with 68 deficient gingival papillae were recruited for this clinical trial with a split-mouth design. The deficient gingival papillae on one side of the anterior maxilla were injected with HA, and those on the other side were injected with physiological saline solution. The heights of the gingival papillae and the areas of the black triangles were measured from clinical photographs obtained before and 6 and 12 months after treatment. Additionally, the proliferation and migration of gingival fibroblasts were evaluated after HA and physiological saline treatment by an in vitro study.

Results

the results revealed that the injection of HA yielded 0.198 and 0.28 mm gingival papilla increasement at 6 and 12 months, respectively, relative to the baseline (P<0.05). However, deficient gingival papillae also grew by 0.278 mm at 12 months in the group that received physiological saline solution (P<0.05). The injection of HA significantly improved deficient gingival papillae 6 months earlier than the injection of physiological saline solution. HA also significantly accelerated the proliferation and migration of gingival fibroblasts in vitro.

Conclusions

The present study confirms that the injection of HA could increase the height of gingival papillae for improving gingival papilla defects. However, the effect is not superior to that of physiological saline solution. This trial was registered in the Chinese Clinical Trial Registry (ChiCTR-ONC-17011781) (28/06/2017). http://www.chictr.org.cn/showproj.aspx?proj=19931

Cytotoxicity of Different Composite Resins on Human Gingival Fibroblast Cell Lines

The aim of the present study was to evaluate and compare the cytotoxic effects of eight composite resins on immortalized human gingival fibroblasts. Composite resins were eluted in cell culture medium for 48 or 72 h at 37 °C. Immortalized human gingival fibroblast-1 (HGF-1) cell lines were seeded in 96-well (1 × 10⁴) plates and incubated for 24 h at 37 °C with the obtained extraction medium. The percentage of viable cells in each well (MTT test) was calculated relative to control cells, which were set to 100%. Data observed were not normally distributed, and nonparametric statistical methods were used for statistical analysis. The Wilcoxon test was used for intragroup comparison, and the Kruskal–Wallis test was used for intergroup multiple comparisons. Significance value was set as p < 0.05. All materials tested showed cytotoxic effects on gingival fibroblasts, recordable as noncytotoxic, mildly cytotoxic or severely cytotoxic, depending on the percentage of cell viability. The Wilcoxon test for intragroup comparison showed that the percentage of viable cells decreased significantly for extracts, for all composite resins tested. The composite resins contained monomers that displayed cytotoxic properties. BisGMA, TEGDMA and UDMA had inhibitory effects and induced apoptotic proteins in pulp fibroblast. Composite resins that contained lower percentages of unbound free monomers—and that released less ions—possessed superior biocompatibility in vitro.

Biofabrication of Gingival Fibroblast Cell-Laden Collagen/Strontium-Doped Calcium Silicate 3D-Printed Bi-Layered Scaffold for Osteoporotic Periodontal Regeneration

Periodontal disease is a chronic disease that can lead to lose teeth and even tooth loss if left untreated. Osteoporosis and periodontal disease share similar characteristics and associated factors. Current regenerative techniques for periodontal diseases are ineffective in restoring complete function and structural integrity of periodontium due to unwanted migration of cells. In this study, we applied the concept of guided tissue regeneration (GTR) and 3D fabricated gingival fibroblast cell-laden collagen/strontium-doped calcium silicate (SrCS) bi-layer scaffold for periodontal regeneration. The results revealed that the bioactive SrCS had a hydroxyapatite formation on its surface after 14 days of immersion and that SrCS could release Sr and Si ions even after 6 months of immersion. In addition, in vitro results showed that the bi-layer scaffold enhanced secretion of FGF-2, BMP-2, and VEGF from human gingival fibroblasts and increased secretion of osteogenic-related proteins ALP, BSP, and OC from WJMSCs. In vivo studies using animal osteoporotic models showed that the 3D-printed cell-laden collagen/SrCS bi-layer scaffold was able to enhance osteoporotic bone regeneration, as seen from the increased Tb.Th and BV/TV ratio and the histological stains. In conclusion, it can be seen that the bi-layer scaffolds enhanced osteogenesis and further showed that guided periodontal regeneration could be achieved using collagen/SrCS scaffolds, thus making it a potential candidate for future clinical applications.

Porphyromonas gingivalis Mfa1 Induces Chemokine and Cell Adhesion Molecules in Mouse Gingival Fibroblasts via Toll-Like Receptors

Porphyromonas gingivalis Mfa1 fimbriae are thought to act as adhesion factors and to direct periodontal tissue destruction but their immunomodulatory actions are poorly understood. Here, we investigated the effect of Mfa1 stimulation on the immune and metabolic mechanisms of gingival fibroblasts from periodontal connective tissue. We also determined the role of Toll-like receptor (TLR) 2 and TLR4 in Mfa1 recognition. Mfa1 increased the expression of genes encoding chemokine (C-X-C motif) ligand (CXCL) 1, CXCL3, intercellular adhesion molecule (ICAM) 1 and Selectin endothelium (E) in gingival fibroblasts, but did not have a significant effect on genes that regulate metabolism. Mfa1-stimulated up-regulation of genes was significantly suppressed in Tlr4 siRNA-transfected cells compared with that in control siRNA-transfected cells, which indicates that recognition by TLR4 is essential for immunomodulation by Mfa1. Additionally, suppression of Tlr2 expression partially attenuated the stimulatory effect of Mfa1. Overall, these results help explain the involvement of P. gingivalis Mfa1 fimbriae in the progression of periodontal disease.

Investigating the effect of antiseptic solution on the release of interleukin-6 and transforming growth factor beta 1 from human gingival fibroblasts using wound healing assays

This in vitro study evaluated the effect of different antiseptics and different concentrations thereof in a model of wound healing using human gingival fibroblasts. The fibroblasts were rinsed with four different antiseptic solutions: sodium hypochlorite (HYP), hydrogen peroxide (H₂O₂), chlorhexidine digluconate (CHX), and benzalkonium chloride (BC). The effect on the release of interleukin-6 (IL-6) and transforming growth factor beta 1 (TGF-β1) was investigated using enzyme-linked immunosorbent assays (ELISAs). In addition, the effects of the antiseptics on wound healing at 1, 12, 24, and 48 h were assessed through a wound healing assay. The viability of the fibroblasts rinsed with antiseptics was investigated with respect to the concentrations inhibiting cell growth by 50% (IC₅₀), 25% (IC₂₅), and ≤2% (IC₂). A statistically significant increased release of IL-6 was obtained with BC IC₂₅ and IC₂ after 12, 24, and 48 h (P < 0.01). For TGF-β1, no significant release was found for CHX IC₂ after 24 and 48 h or for IC₅₀ and IC₂₅ after 12 h. There was no significant effect on wound healing capacity for CHX or for BC IC₂₅ and IC₂. This study demonstrated that antiseptic rinses of human gingival fibroblasts alter the release of IL-6 and TGF-β1 and impact wound healing capacity, with both BC and CHX conferring neutral effects.

Phenytoin sodium-ameliorated gingival fibroblast aging is associated with autophagy

BACKGROUND AND OBJECTIVE

Human gingival fibrolasts aging is an important cause of periodontal disease. Phenytoin sodium (phenytoin) has a side effect of gingival hyperplasia and an effect on the autophagy progress. This study investigated whether the effect of phenytoin on aging gingival fibroblast is related to the autophagy pathway.

MATERIAL AND METHODS

The aging model of gingival fibroblast cell line HGF-1 was induced by hydrogen peroxide (H₂ O₂ ), and the treatment of phenytoin and 3-methyladenine (3-MA) was performed simultaneously. Cell viability, cell cycle, and intracellular calcium ion were measured by flow cytometry. Changes in expression of basic fibroblast growth factor (bFGF), P16^INK4A , P21^cip1 , and bFGF, P16^INK4A , P21^cip1 , LC3II, p62, and Beclin were tested by using reverse transcription polymerase chain reaction, western blot, and immunofluorescence staining.

RESULTS

The results showed that aging HGF-1 proliferation was inhibited by H₂ O₂ , gene, protein expression of bFGF, P16^INK4A , and P21^cip1 were decreased, autophagy-related proteins LC3II, p62, and Becline were decreased, and the proportion of G0/G1 phase and intracellular calcium ion of cell cycle was increased. Phenytoin treatment could recovery above changes, but the effect of phenytoin could be blocked by 3-MA.

CONCLUSION

We propose that phenytoin alleviates the aging of gingival fibroblasts induced by H₂ O₂ . This condition is related to the enhancement of autophagy pathway.

Cytotoxicity evaluation of a new ozonized olive oil

Objective:

The cytocompatibility of a new ozonized olive oil toward immortalized human gingival fibroblasts (HGFs) was evaluated and compared with two common antimicrobial agents based on chlorhexidine digluconate (CHX).

Materials and Methods:

The cytocompatibility of the samples was tested on immortalized HGF-1 cells by 3-(4, 5-dimethyl thiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) assay. The cells were incubated for 2 or 24 h with increasing dilution of ozonized olive oil or CHX agents. The percentage of viable cells was calculated relative to control cells set to 100%.

Results:

The ozonized olive oil is cytocompatible, and the viability values of the cells treated for 2 or 24 h with increasing concentrations of ozonized olive oil were significantly higher (P < 0.01) compared with the values obtained using CHX.

Conclusions:

The present data demonstrate that due to its cytocompatibility, the new ozonized olive oil could be considered an alternative antibacterial agent.

BET Bromodomain Inhibitors Suppress Inflammatory Activation of Gingival Fibroblasts and Epithelial Cells From Periodontitis Patients

BET bromodomain proteins are important epigenetic regulators of gene expression that bind acetylated histone tails and regulate the formation of acetylation-dependent chromatin complexes. BET inhibitors suppress inflammatory responses in multiple cell types and animal models, and protect against bone loss in experimental periodontitis in mice. Here, we analyzed the role of BET proteins in inflammatory activation of gingival fibroblasts (GFs) and gingival epithelial cells (GECs). We show that the BET inhibitors I-BET151 and JQ1 significantly reduced expression and/or production of distinct, but overlapping, profiles of cytokine-inducible mediators of inflammation and bone resorption in GFs from healthy donors (IL6, IL8, IL1B, CCL2, CCL5, COX2, and MMP3) and the GEC line TIGK (IL6, IL8, IL1B, CXCL10, MMP9) without affecting cell viability. Activation of mitogen-activated protein kinase and nuclear factor-κB pathways was unaffected by I-BET151, as was the histone acetylation status, and new protein synthesis was not required for the anti-inflammatory effects of BET inhibition. I-BET151 and JQ1 also suppressed expression of inflammatory cytokines, chemokines, and osteoclastogenic mediators in GFs and TIGKs infected with the key periodontal pathogen Porphyromonas gingivalis. Notably, P. gingivalis internalization and intracellular survival in GFs and TIGKs remained unaffected by BET inhibitors. Finally, inhibition of BET proteins significantly reduced P. gingivalis-induced inflammatory mediator expression in GECs and GFs from patients with periodontitis. Our results demonstrate that BET inhibitors may block the excessive inflammatory mediator production by resident cells of the gingival tissue and identify the BET family of epigenetic reader proteins as a potential therapeutic target in the treatment of periodontal disease.

In vitro Comparative Study of Fibroblastic Behaviour on Polymethacrylate (PMMA) and Lithium Disilicate Polymer Surfaces

Polymethyl methacrylate (PMMA) and lithium disilicate are widely used materials in the dental field. PMMA is mainly used for the manufacture of removable prostheses; however, with the incorporation of CAD-CAM technology, new applications have been introduced for this material, including as a provisional implant attachment. Lithium disilicate is considered the gold standard for definitive attachment material. On the other hand, PMMA has begun to be used in clinics as a provisional attachment until the placement of a definitive one occurs. Although there are clinical studies regarding its use, there are few studies on cell reorganization around this type of material. This is why we carried out an in vitro comparative study using discs of both materials in which human gingival fibroblasts (HGFs) were cultured. After processing them, we analyzed various cellular parameters (cell count, cytoskeleton length, core size and coverage area). We analyzed the surface of the discs together with their composition. The results obtained were mostly not statistically significant, which shows that the qualities of PMMA make it a suitable material as an implant attachment.

Evaluation of inductive effects of different concentrations of cyclosporine A on MMP-1, MMP-2, MMP-3, TIMP-1, and TIMP-2 in fetal and adult human gingival fibroblasts

Background The etiology of gingival overgrowth due to cyclosporine A (CsA) is still unknown. The aim of this study was to determine the possible role of matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs (TIMPs) on extra-cellular matrix (ECM) homeostasis when treated with different levels of CsA and its difference between fetal and adult human gingival fibroblasts (HGFs). Methods Each group of cells (adult and fetal) was cultured in 40 wells that consisted of four different CsA treatment concentrations. Every 10 wells were treated with 0, 50, 100, and 150 ng/mL of CsA which makes a total of 80 wells. Supernatants of every well were used to determine the concentration of MMPs and TIMPs using the Elisa kits from Boster, CA, USA. Results MMP-1 level increased with the treatment of CsA when treated with 50 and 150 ng/mL of CsA (p = 0.02 and p = 0.04) as TIMP-1 decreased (p < 0.0001) in adult group; while in the fetal group, TIMP-1 level increased with treatment of 150 ng/mL (p < 0.0001). MMP-2 level increased in both adult and fetal groups (p < 0.0001). MMP-3 level decreased in adult group (p < 0.0001) but went up in fetal HGFs (p = 0.01) when treated with 150 ng/mL CsA. TIMP-2 level increased in all wells significantly when treated with CsA (p < 0.0001). The study showed that CsA affects secretion of MMPs and TIMPs. MMP-1 increment and TIMP-1 decrement were observed, which indicate more degradation of ECM. This may be due to single donor use in this study. TIMP-2 and MMP-2 were both more active when treated with CsA which may be due to the gelatinase activity of them and that in CsA gingival overgrowth. There was more inflammation rather than fibrosis.

Human airway trypsin-like protease (HAT) is released into saliva

We first discovered human airway trypsin-like protease (HAT) in human mucoid sputum. Precursor HAT (47 kDa), a cell surface type Ⅱ transmembrane serine protease, is proteolyzed to mature HAT (27 kDa). Hitherto, HAT has not been detected in other biological fluids except for human sputum. We aimed to clarify whether human saliva contains mature HAT. Trypsin-like protease was isolated from saliva of healthy volunteers by a method adopted for isolation of HAT from sputum using Boc-Phe-Ser-Arg-MCA as the substrate. Biochemical properties of purified protease were similar to those of recombinant HAT (rHAT). HAT concentration in saliva was measured by ELISA, and immunoreactive HAT:total protein ratio (ng/mg) in saliva samples from healthy subjects was similar to that in mucoid sputum. RT-PCR showed that HAT mRNA was expressed in human gingival epithelial cells but not in gingival fibroblasts. Both indirect immunofluorescence and western blotting using monoclonal antibody for α-smooth muscle actin (α-SMA;a myofibroblast marker) showed that HAT enhanced α-SMA fiber expression in gingival fibroblasts. These results indicate that both mucoid sputum and saliva from healthy subjects have similar concentrations of mature HAT, and HAT is related to certain physiological functions and pathological states of myofibroblasts in the oral cavity. J. Med. Invest. 65:258-267, August, 2018.

Comparison of Cytomorphometry and Early Cell Response of Human Gingival Fibroblast (HGFs) between Zirconium and New Zirconia-Reinforced Lithium Silicate Ceramics (ZLS)

New zirconia-reinforced lithium silicate ceramics (ZLS) could be a viable alternative to zirconium (Y-TZP) in the manufacture of implantological abutments-especially in aesthetic cases-due to its good mechanical, optical, and biocompatibility properties. Although there are several studies on the ZLS mechanical properties, there are no studies regarding proliferation, spreading, or cytomorphometry. We designed the present study which compares the surface, cellular proliferation, and cellular morphology between Y-TZP (Vita YZ® T [Vita Zahnfabrik (Postfach, Germany)]) and ZLS (Celtra® Duo [Degudent (Hanau-Wolfgang, Germany)]). The surface characterization was performed with energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), and optical profilometry. Human gingival fibroblasts (HGFs) were subsequently cultured on both materials and early cellular response and cell morphology were compared through nuclear and cytoskeletal measurement parameters using confocal microscopy. The results showed greater proliferation and spreading on the surface of Y-TZP. This could indicate that Y-TZP continues to be a gold standard in terms of transgingival implant material: Nevertheless, more in vitro and in vivo research is necessary to confirm the results obtained in this study.

Effects of titanium oxide surface properties on bone-forming and soft tissue-forming cells

BACKGROUND

Previous studies have concluded that certain titanium oxide (TiO₂ ) surface properties promote bone-forming cell attachment. However, no comprehensive studies have investigated the effects of TiO₂ surface and film morphology on hard and soft tissues.

PURPOSE

The aim of this study is to understand the effects of TiO₂ morphology on the proliferation and differentiation of murine preosteoblasts (MC3T3-E1) and proliferation of human gingival fibroblasts (HGF-1) using in vitro experiments.

MATERIALS AND METHODS

Samples were fabricated with several TiO₂ thickness and crystalline structure to mimic various dental implant surfaces. in vitro analysis was performed for 1, 3, and 7 days on these samples to assess the viability of MC3T3-E1 and HGF-1 cells in contact with the modified oxide surfaces.

RESULTS

Results showed that HGF-1 cells exhibited no significant difference in viability on modified oxide surfaces versus a titanium control across experiments. MC3T3-E1 cells exhibited a significantly higher viability for the modified oxide surface in 1 day experiments, but not in 3 or 7 day experiments. Alkaline phosphatase expression in MC3T3-E1 was not significantly different on modified oxide surfaces versus the control across all experiments. A slight positive trend in viability was observed for cells in contact with rougher modified oxide surfaces versus a titanium control in both cell types.

CONCLUSIONS

These observations suggest that crystallinity and thickness do not affect the long-term viability of hard or soft tissue cells when compared to a cpTi surface. Therefore, treatments like anodization on implant components may not directly affect the attachment of hard or soft tissue cells in vivo.

Survival, Retention, and Selective Proliferation of Lymphocytes Is Mediated by Gingival Fibroblasts

Periodontitis, a chronic inflammatory disease of the periodontium, is characterized by osteoclast-mediated alveolar bone destruction. Gingival fibroblasts (GFs) present in the bone-lining mucosa have the capacity to activate the formation of osteoclasts, but little is known about which local immune cells (co-)mediate this process. The aim of this study was to investigate the cellular interactions of GFs with immune cells, including the contribution of GFs to osteoclast formation and their possible role in the proliferation of these immune cells. In addition, we investigated the expression of adhesion molecules and the inflammatory cytokines that are evoked by this interaction. GFs were cocultured with peripheral blood mononuclear cells (PBMCs), CD14+ monocytes or peripheral blood lymphocytes (PBLs) for 7, 14, and 21 days. After 21 days, comparable numbers of multinucleated cells (osteoclasts) were found in gingival fibroblast (GF)-PBMC and GF-monocyte cocultures. No osteoclasts were formed in GF-PBL cocultures, indicating that the PBLs present in GF-PBMC cocultures do not contribute to osteoclastogenesis. Persisting mononuclear cells were interacting with osteoclasts in GF-PBMC cocultures. Remarkably, a predominance of CD3+ T cells was immunohistochemically detected in GF cocultures with PBLs and PBMCs for 21 days that frequently interacted with osteoclasts. Significantly more T, B (CD19+), and NK (CD56+CD3-) cells were identified with multicolor flow cytometry in both GF-PBMC and GF-PBL cocultures compared to monocultures without GFs at all time points. GFs retained PBLs independently of the presence of monocytes or osteoclasts over time, showing a stable population of T, B, and NK cells between 7 and 21 days. T helper and cytotoxic T cell subsets remained stable over time in GF cocultures, while the number of Th17 cells fluctuated. Lymphocyte retention is likely mediated by lymphocyte-function-associated antigen-1 (LFA-1) expression, which was significantly higher in GF-PBL cultures compared to GF-monocyte cultures. When assessing inflammatory cytokine expression, high tumor necrosis alpha expression was only observed in the GF-PBMC cultures, indicating that this tripartite presence of GFs, monocytes, and lymphocytes is required for such an induction. Carboxyfluorescein succinimidyl ester-labeling showed that only the CD3+ cells proliferated in presence of GFs. This study demonstrates a novel role for GFs in the survival, retention, and selective proliferation of lymphocytes.

Biotherapeutic Effect of Gingival Stem Cells Conditioned Medium in Bone Tissue Restoration

Bone tissue engineering is one of the main branches of regenerative medicine. In this field, the use of a scaffold, which supported bone development, in combination with mesenchymal stem cells (MSCs), has promised better outcomes for bone regeneration. In particular, human gingival mesenchymal stem cells (hGMSCs) may present advantages compared to other MSCs, including the easier isolation. However, MSCs’ secretome has attracted much attention for its potential use in tissue regeneration, such as conditioned medium (CM) that contains different soluble factors proved to be useful for the regenerative purposes. In this study, we evaluated the osteogenic capacity of a poly-(lactide) (3D-PLA) scaffold enriched with hGMSCs and hGMSCs derived CM and its ability to regenerate bone defects in rat calvarias. 3D-PLA alone, 3D-PLA + CM or 3D-PLA + hGMSCs with/without CM were implanted in Wistar male rats subjected to calvarial defects. We observed that 3D-PLA scaffold enriched with hGMSCs and CM showed a better osteogenic capacity, being able to repair the calvarial defect as revealed in vivo by morphological evaluation. Moreover, transcriptomic analysis in vitro revealed the upregulation of genes involved in ossification and regulation of ossification in the 3D-PLA + CM + hGMSCs group. All of these results indicate the great osteogenic ability of 3D-PLA + CM + hGMSCs supporting its use in bone regenerative medicine, in particular in the repair of cranial bone defects. Especially, hGMSCs derived CM played a key role in the induction of the osteogenic process and in bone regeneration.

Effect of Clinically Relevant CAD/CAM Zirconia Polishing on Gingival Fibroblast Proliferation and Focal Adhesions

Mucosal seal formation around dental abutments is critical to the successful integration of dental implants into the human oral cavity. No information exists for how clinically relevant polishing procedures for computer-aided design and computer-aided manufactured (CAD/CAM) zirconia abutments affects cellular responses important to mucosal seal formation. CAD/CAM zirconia was divided into four groups for clinically relevant polishing utilizing commercial polishing heads: control, coarse, coarse plus medium, and coarse plus medium plus fine. Surfaces were analyzed with scanning electron microscopy (SEM), atomic force microscopy (AFM), and optical profilometry (OP). Subsequently, human gingival fibroblasts (HGFs) were seeded onto the zirconia surfaces. Proliferation was measured via a quantitative SEM technique and focal adhesion kinase (FAK) phosphorylation status was measured by an enzyme-linked immunosorbent assay (ELISA). Results showed an increase in proliferation on all polished surfaces as compared to the control. Phosphorylation of FAK at tyrosine 397 (Y397) was up-modulated on the control surfaces. The associated cell adaptation is discussed. In all cases, FAK phosphorylation was greater at 24 h than 48 h. These results suggest that clinicians should be mindful of the effects of abutment polishing methodology, as this may have an impact on early mucosal seal formation.

Proinflammatory effects and mechanisms of calprotectin on human gingival fibroblasts

BACKGROUND AND OBJECTIVE

Calprotectin (S100A8/A9) is a heterodimer of S100A8 and S100A9 and is associated with multiple inflammatory diseases, including Crohn's disease, rheumatoid arthritis and periodontitis. Levels of calprotectin are elevated in the gingival crevicular fluid of patients with periodontitis; however, the effects of calprotectin on human gingival fibroblasts (HGFs) remain unknown. This study investigated the proinflammatory activity of calprotectin on HGFs and the functional receptors and signaling pathways engaged by calprotectin.

MATERIAL AND METHODS

HGFs were stimulated by equimolar concentrations of S100A8 and/or S100A9, and the expression levels of interleukin (IL)-6 and IL-8 were detected using real-time quantitative polymerase chain reaction and enzyme-linked immunosorbent assays. The calprotectin receptors were identified by pre-incubating HGFs with the toll-like receptor (TLR) 4 inhibitor or the antibody targeting the advanced glycation end product receptor (RAGE). The involvement of reactive oxygen species (ROS) and signaling pathways were also investigated by treating HGFs with ROS inhibitor or specific pathway inhibitors, respectively.

RESULTS

S100A9 and S100A8/A9 significantly upregulated IL-6 and IL-8 expression, which was inhibited upon treatment with the TLR4 inhibitor TAK242. Pretreatment with RAGE-blocking antibodies did not affect cytokine expression. Additionally, S100A9 promoted the production of IL-6 and IL-8 from HGFs via different signaling pathways. IL-6 expression was upregulated via the NF-κB, c-Jun amino-terminal kinase (JNK) 1/2 and p38 mitogen-activated protein kinase (MAPK) pathways, and IL-8 expression was upregulated via NF-κB, p38, JNK1/2 and extracellular-regulated kinase 1/2 MAPK pathways. The release of both cytokines was dependent upon the production of ROS.

CONCLUSION

Our findings suggest that calprotectin exerts proinflammatory effects on HGFs via the S100A9 subunit and TLR4-mediated NF-κB and MAPK signaling pathways.

Phenytoin-induced gingival overgrowth caused by death receptor pathway malfunction

OBJECTIVE

In this study, we investigated the role of phenytoin (PHT) in death receptor-induced apoptosis of gingival fibroblasts to clarify the mechanism of PHT-induced gingival overgrowth.

METHODS

Human gingival fibroblasts were cultured to semiconfluence and treated with PHT (0.025, 0.1, 0.25, and 1.0 μM) for 48 h, and then, the apoptotic cell numbers were relatively determined by absorptiometry. After 24 h of 0.25 μM PHT treatment, caspase activity was measured by absorptiometry, apoptotic and cell cycle phase distribution was analyzed by flow cytometry, expression levels of apoptotic genes were quantified by real-time qPCR, and expression of apoptotic proteins was detected by Western blot analysis. After 48 h of 0.25 μM PHT treatment, appearance of apoptotic cells was detected by TUNEL assay.

RESULTS

PHT treatment decreased the proportion of apoptotic cells in gingival fibroblasts compared to a serum-free control culture in response to the protein changes as follows: PHT upregulated c-FLIP and, in turn, downregulated FADD, caspase-8, and caspase-3; PHT upregulated c-IAP2 and downregulated TRAF2; PHT downregulated caspase-9 and caspase-3 via decreased RIPK1 activity and increased Bcl-2 activity.

CONCLUSION

PHT-induced gingival overgrowth may result from the above-mentioned mechanisms involving apoptosis inhibition in gingival fibroblasts.

Caveolin-1 serves as a negative effector in senescent human gingival fibroblasts during Fusobacterium nucleatum infection

It is well established that aging is associated with increased susceptibility to infectious diseases. Fusobacterium nucleatum is a well-known bacterial species that plays a central bridging role between early and late colonizers in the human oral cavity. Further, the ability of F. nucleatum to invade gingival fibroblasts (GFs) is critical to the development of periodontal diseases. However, the mechanisms underlying the age-related infection of GFs by F. nucleatum remain unknown. We used young (fourth passage) and senescent (22nd passage) GFs to investigate the mechanisms of F. nucleatum infection in aged GFs and first observed increased invasion of F. nucleatum in senescent GFs. We also found that the co-localization of caveolin-1 (Cav-1), a protein marker of aging, with F. nucleatum and the knockdown of Cav-1 in GFs reduced F. nucleatum invasion. Additionally, F. nucleatum infection triggered the production of reactive oxygen species (ROS) through activation of NADPH oxidase in GFs, but senescent GFs exhibited significantly lower levels of NADPH oxidase activity and ROS production compared with young GFs in both the uninfected and infected conditions. Also, senescent GFs exhibited a decline in proinflammatory cytokine production and extracellular signal regulated kinase (ERK) phosphorylation following F. nucleatum infection. Interestingly, the knockdown of Cav-1 in senescent GFs increased NADPH oxidase activity and caused the upregulation of interleukin-6 and interleukin-8 and the phosphorylation of ERK. Collectively, the increased expression of Cav-1 might play a critical role in F. nucleatum invasion and could hinder the host response in senescent GFs.

Autophagy Has a Beneficial Role in Relieving Cigarette Smoke-Induced Apoptotic Death in Human Gingival Fibroblasts

The deleterious role of cigarette smoke has long been documented in various human diseases including periodontal complications. In this report, we examined this adverse effect of cigarette smoke on human gingival fibroblasts (HGFs) which are critical not only in maintaining gingival tissue architecture but also in mediating immune responses. As well documented in other cell types, we also observed that cigarette smoke promoted cellular reactive oxygen species in HGFs. And we found that this cigarette smoke-induced oxidative stress reduced HGF viability through inducing apoptosis. Our results indicated that an increased Bax/Bcl-xL ratio and resulting caspase activation underlie the apoptotic death in HGFs exposed to cigarette smoke. Furthermore, we detected that cigarette smoke also triggered autophagy, an integrated cellular stress response. Interesting, a pharmacological suppression of the cigarette smoke-induced autophagy led to a further reduction in HGF viability while a pharmacological promotion of autophagy increased the viability of HGFs with cigarette smoke exposures. These findings suggest a protective role for autophagy in HGFs stressed with cigarette smoke, highlighting that modulation of autophagy can be a novel therapeutic target in periodontal complications with cigarette smoke.

Cytotoxic and genotoxic effects on gingival fibroblasts from static magnetic fields produced by dental magnetic attachments

OBJECTIVE

To investigate cytotoxic and genotoxic effects of static magnetic field (SMF) produced by dental magnetic attachments on human gingival fibroblasts in vitro.

BACKGROUND

Magnetic attachments have numerous roles in dental prosthesis fixation, but few reports evaluate possible biological effects of static magnetic field (SMF) on human gingival tissues, particular genotoxic effects.

MATERIALS AND METHODS

The Dyna (500-gr breakaway force) and Steco (173-gr breakaway force) dental magnetic attachments were embedded into autopolymerising acrylic resin in four different configurations each, including single and double magnets. Gingival biopsy was performed on 28 individuals during third molar extraction, and each sample was divided into two pieces for culture under SMF exposure or as a control. In total, seven test and seven control gingival fibroblast cultures were performed for each group resulting in 56 gingival fibroblast cultures. The test culture flasks were placed atop the magnet-embedded resin blocks. After cultures were terminated, mitotic index (MI) and micronucleus (MN) rates were analysed at a p = 0.05 significance level by Wilcoxon's test; intergroup differences were analysed with a Kruskal-Wallis test.

RESULTS

There was no significant difference in intragroup or intergroup MI rates. The double Dyna (p = 0.023) and double Steco (p = 0.016) groups had statistically significant intragroup differences in the MN rates. There were no statistically significant differences in MN rates in intergroup analyses.

CONCLUSION

In particular, higher magnetic fields from dental magnetic attachments might be toxic genetically to human gingival fibroblasts. However, there is need for further investigations from different aspects to detect any genotoxicity.

Transcriptional regulation of amelotin gene by proinflammatory cytokines in gingival fibroblasts

Amelotin (AMTN) is a secreted protein expressed during the late stages of enamel formation and in the junctional epithelium. Among many differentially expressed genes, we found significantly increased AMTN mRNA level in inflamed gingiva by DNA microarray. The inductions of AMTN mRNA expressions in inflamed gingiva and human gingival fibroblasts (HGF) were confirmed by real-time polymerase chain reaction. To determine the molecular basis of the expression of AMTN and its regulation by proinflammatory cytokines, we have isolated and characterized the promoter region of mouse AMTN gene. Transient transfection assays were performed using luciferase constructs including mouse AMTN gene promoter. Interleukin-1β, Interleukin-6 and tumor necrosis factor-α induced AMTN mRNA levels in HGF. These cytokines increased the luciferase activities of the AMTN promoter constructs in HGF. The results suggest that proinflammatory cytokines induce AMTN gene transcription and a role for AMTN in gingival inflammation.

Inhibition of G₁ cell cycle arrest in human gingival fibroblasts exposed to phenytoin

Gingival overgrowth is caused in response to the antiepileptic drug phenytoin (PHT). PHT-induced gingival overgrowth is characterized by the proliferation of fibroblasts and increased collagen formation in gingiva. Fibroblast proliferation is regulated through the cell cycle. Thus, in the present study, we examined the effects of PHT on the cell cycle, the expression of cell cycle control proteins and the proliferation in human gingival fibroblasts (hGFs). Cells were stimulated in serum-free DMEM with or without 0.25 μm PHT. Subsequently, the cell cycle phase distribution and the protein expression after 24 h and the cell proliferation after 24, 48 and 72 h were evaluated. PHT significantly inhibited synchronization at the G₀/G₁ phase of the cell cycle in hGFs through serum starvation. Stimulation with PHT for 48 and 72 h significantly induced a proliferative response in hGFs. PHT decreased the expression of the Cdk-inhibitory proteins p21 and p27 and increased the levels of the S phase-promoting proteins phospho-Thr160-Cdk2 and phospho-Ser807/811-Rb in serum-free DMEM. The inhibition of G₁ cell cycle arrest in hGFs may result from an increase in phosphorylated Cdk2 and Rb proteins and decreased levels of p21 and p27 proteins by PHT. The gingival overgrowth may be caused by the failure of the G1 cell cycle arrest in GFs exposed to PHT.

Pharmacological evidences for the stimulation of calcium-sensing receptors by nifedipine in gingival fibroblasts

OBJECTIVE

To investigate pharmacologically whether CaSRs are involved in the Ca(2+) antagonist-induced [Ca(2+)]i elevation in gingival fibroblasts.

MATERIALS AND METHODS

Gin-1 cells, normal human gingival fibroblasts, were used as the material. The [Ca(2+)] i was measured with fura-2/AM, a Ca(2+)-sensitive fluorescent dye.

RESULTS

At first, we confirmed the existence of CaSRs in these cells by showing that [Ca(2+)] i was elevated by high concentrations of extracellular Ca(2+) and by prototypic agonists of the CaSR such as gentamicin. The action of gentamicin was antagonized by inhibitors of phospholipase C (PLC), inositol trisphosphate (IP(3)) receptors, NSCCs, and, importantly, by the CaSR antagonist, NPS2390. Furthermore, the action of gentamicin was potentiated by activators of PLC and protein kinase C (PKC). This confirmed the pathway components mediating Ca(2+) responses to a known agonist of the CaSR. We then investigated whether nifedipine (an L-type Ca(2+) channel blocker) stimulates CaSRs to elevate [Ca(2+)] i via a similar mechanism. Nifedipine Ca(2+) responses were dose-dependently blocked by NPS2390 and by the same inhibitors of PLC, IP(3) receptors, and NSCCs that disrupted the action of gentamicin. Calphostin C (a PKC inhibitor) and TMB-8 (an inhibitor of Ca(2+) release from stores) also inhibited the nifedipine-induced [Ca(2+)] i elevation.

CONCLUSION

These findings suggest that CaSRs are involved in the nifedipine-induced [Ca(2+)] i elevation in gingival fibroblasts.