Immunomodulatory Properties of Dental-Derived Mesenchymal Stem Cells

Mesenchymal stem cells are considered as an attractive tool for tissue regeneration. Almost all dental tissues contain a population of MSC-like cells, which were extensively studied within the last few years. Besides their ability to differentiate into different cell types, dental MSCs also possess strong immunomodulatory properties. Dental MSCs modulate both innate and adaptive immune response and influence the activity of almost all components of the immune system. The interaction between dental MSCs and the immune system is reciprocal because immunomodulatory activity of MSCs is strongly regulated by cytokines produced by immune cells. MSCs isolated from inflamed tissues might exhibit impaired immunomodulatory capacity, suggesting a potential role of these cells in inflammatory diseases and particularly periodontitis. Recent studies suggest that immunomodulatory properties of MSCs can also play an important role in their tissue regenerative capacity. The therapeutic effects of MSCs, including their immunomodulatory capacity, are largely explained by their tropic activity, including production of immunomodulatory proteins and growth factors. Summarizing, dental MSCs play an important role in tissue homeostasis under healthy and diseased conditions

Oxidative Stress and Antioxidant System in Periodontitis

Periodontitis is a common inflammatory disease, which is initiated by bacterial infection and subsequently progressed by aberrant host response. It can result in the destruction of teeth supporting tissues and have an influence on systemic health. When periodontitis occurs, reactive oxygen species, which are overproduced mostly by hyperactive neutrophils, could not be balanced by antioxidant defense system and cause tissues damage. This is characterized by increased metabolites of lipid peroxidation, DNA damage and protein damage. Local and systemic activities of antioxidants can also be influenced by periodontitis. Total antioxidant capacity, total oxidant status and oxidative stress index have been used to evaluate the oxidative stress associated with periodontitis. Studies have confirmed that inflammatory response in periodontitis is associated with an increased local and systemic oxidative stress and compromised antioxidant capacity. Our review focuses on increased oxidative stress in periodontal disease, specifically, on the relationship between the local and systemic biomarkers of oxidative stress and periodontitis and their association with the pathogenesis of periodontitis. Also, the relationship between periodontitis and systemic inflammation, and the effects of periodontal therapy on oxidative stress parameters will be discussed

Potential Suppressive Effect of Nicotine on the Inflammatory Response in Oral Epithelial Cells: An In Vitro Study

Smoking is a well-recognized risk factor for oral mucosal and periodontal diseases. Nicotine is an important component of cigarette smoke. This study aims to investigate the impact of nicotine on the viability and inflammatory mediator production of an oral epithelial cell line in the presence of various inflammatory stimuli. Oral epithelial HSC-2 cells were challenged with nicotine (10−8–10−2 M) for 24 h in the presence or absence of Porphyromonas gingivalis lipopolysaccharide (LPS, 1 µg/mL) or tumor necrosis factor (TNF)-α (10−7 M) for 24 h. The cell proliferation/viability was determined by MTT assay. Gene expression of interleukin (IL)-8, intercellular adhesion molecule (ICAM)-1, and β-defensin was assayed by qPCR. The production of IL-8 protein and cell surface expression of ICAM-1 was assessed by ELISA and flow cytometry, respectively. Proliferation/viability of HSC-2 cells was unaffected by nicotine at concentrations up to 10−3 M and inhibited at 10−2 M. Nicotine had no significant effect on the basal expression of IL-8, ICAM-1, and β-defensin. At the same time, it significantly diminished P. gingivalis LPS or the TNF-α-induced expression levels of these factors. Within the limitations of this study, the first evidence was provided in vitro that nicotine probably exerts a suppressive effect on the production of inflammatory mediators and antimicrobial peptides in human oral epithelial cells

Vitamin D3 and Dental Mesenchymal Stromal Cells

Vitamin D3 is a hormone involved in the regulation of bone metabolism, mineral homeostasis, and immune response. Almost all dental tissues contain resident mesenchymal stromal cells (MSCs), which are largely similar to bone marrow-derived MSCs. In this narrative review, we summarized the current findings concerning the physiological effects of vitamin D3 on dental MSCs. The existing literature suggests that dental MSCs possess the ability to convert vitamin D3 into 25(OH)D3 and subsequently to the biologically active 1,25(OH)2D3. The vitamin D3 metabolites 25(OH)D3 and 1,25(OH)2D3 stimulate osteogenic differentiation and diminish the inflammatory response of dental MSCs. In addition, 1,25(OH)2D3 influences the immunomodulatory properties of MSCs in different dental tissues. Thus, dental MSCs are both producers and targets of 1,25(OH)2D3 and might regulate the local vitamin D3-dependent processes in an autocrine/paracrine manner. The local vitamin D3 metabolism is assumed to play an essential role in the local physiological processes, but the mechanisms of its regulation in dental MSCs are mostly unknown. The alteration of the local vitamin D3 metabolism may unravel novel therapeutic modalities for the treatment of periodontitis as well as new strategies for dental tissue regeneration

The proliferation and differentiation of osteoblasts in co-culture with human umbilical vein endothelial cells: An improved analysis using fluorescence-activated cell sorting

The interaction of osteoblasts and endothelial cells plays a pivotal role in osteogenesis. This interaction has been extensively studied using their direct co-culture in vitro. However, co-culture experiments require clear discrimination between the two different cell types in the mixture, but this was rarely achieved. This study is the first to use fluorescence-activated cell sorting (FACS) for the separation and quantitative analysis of the proliferation and differentiation of MG-63 cells grown in direct co-culture with human umbilical vein endothelial cells (HUVECs). The cells of the MG-63 cell line have properties consistent with the characteristics of normal osteoblasts. We labeled HUVECs with fluorescent antibody against CD31 and used FACS to measure the proportions of each cell type and to separate them based on their different fluorescence intensities. The rate of proliferation of the MG-63 cells was estimated based on a count of the total viable cells and the proportion of MG-63 cells in the mixture. The mRNA expression levels of the osteoblast differentiation markers alkaline phosphatase (ALP), collagen type 1 (Coll-1) and osteocalcin (OC) in the MG-63 cells were measured via real-time PCR after the separation via FACS. We found that HUVECs stimulated the proliferation of the MG-63 cells after 72 h of co-culture, and inhibited it after 120 h of co-culture. The mRNA expression levels of ALP and Coll-1 significantly increased, whereas that of OC significantly decreased in MG-63 after co-culture with HUVECs. Using FACS for the quantitative analysis of the proliferation and differentiation of osteoblasts directly interacting with endothelial cells could have merit for further co-culture research

Hot Topics in Clinical Oral Implants Research: Recent Trends in Literature Coverage

This systematic review looks at thematic trends in clinical research publications on dental implants. For this purpose, MEDLINE electronic searches as well as additional hand searches of six main journals in the field were conducted. A total of 2875 clinical studies published between 2001 and 2012 met the inclusion criteria and were subjected to statistical analysis. Hot topics in dental implant literature included immediate loading (14.3%), bone substitutes (11.6%), cross-arch full bridges (8.0%), and immediate implant placement (7.5%). A significant increase in scientific interest for immediate loading (+6.3%, p = 0.001), platform switching (+2.9%, p = 0.001), guided implant surgery (+1.9%, p = 0.011), growth factors (p = 0.014, +1.4%), piezoelectric surgery (+1.3%, p = 0.015), and restorative materials (+0.7%, p = 0.011) was found. A declining scientific interest in onlay grafting (−0.3%, p = 0.042) was recorded. The findings regarding current clinical oral implants research tie in with better-informed consumers and increased patient demands. Our results demonstrate an increasing interest in techniques that avoid complicated procedures such as bone grafting and that reduce treatment duration

Is Topical Application of Hyaluronic Acid in Oral Lichen Planus Effective? A Randomized Controlled Crossover Study

Hyaluronic acid (HA) has anti-inflammatory and anti-edematous effects and, thus, could be promising in the treatment of oral lichen planus (OLP). The aim of the study was to evaluate the effects of topical hyaluronic acid, compared to placebo, on salivary levels of calprotectin, interleukin-6 (IL-6), and bacteria, as well as clinical and subjective parameters. Fourteen patients with confirmed OLP were included. After random selection, patients started with either 0.2% hyaluronic acid or a placebo gel for 6 weeks. Following a wash-out period, the groups changed the application. Whole saliva, clinical parameters, and questionnaires were evaluated before and after the intervention, as well as after the crossover phase. Salivary calprotectin, IL-6, and inflammation-related bacteria were determined by ELISA and PCR, respectively. There were no significant differences in clinical or subjective outcome parameters, salivary levels of IL-6, calprotectin, or bacteria after the application of hyaluronic acid, compared to placebo. However, only nine patients completed the study, as five out of seven patients starting with placebo were lost to follow-up. Significant effects of HA on inflammatory mediators and clinical parameters in OLP patients could not be proven, although a trend in clinical severity improvement could be observed

Characteristics and frequency distribution of bone defect configurations in peri-implantitis lesions : A series of 193 cases

Background: Knowledge on peri‐implantitis bone defect characteristics and predictors is still limited. Purpose: To describe peri‐implantitis bone defect characteristics and identify possible predictors. Methods: Various parameters at patient‐ (age, gender, smoking, and supra‐structure), implant‐ (surface, type, connection, platform, and misfit), and site level (region, alveolar ridge position, defect characteristics, neighboring structure) were recorded retrospectively. Results: Among 193 implants, the most prevalent defects were class Ic (25.4%), and Id (23.8%); a previously non‐described category “class Id with only one bone wall” was frequently observed (11.9%). Mean intrabony defect depth and width ranged from 4.5 to 6.2 mm and from 2.7 to 2.9 mm, respectively; mean dehiscence extent ranged from 2.8 to 7.0 mm. A total of 37.8% of the defects presented horizontal bone loss and an intrabony component; in 52.7% of the implants, total defect extent was >6 mm. Jaw region, implant position within the alveolar ridge, and implant/abutment misfit showed significant associations either to defect configuration and/or defect extent. Conclusion: (a) Most common peri‐implantitis defects exhibited a combination of intrabony component and a buccal/oral dehiscence, while purely circumferential defects were relatively seldom; (b) implants with defects with bone dehiscence were placed more frequently closer to the lateral aspect of the ridge harboring the dehiscence; (c) implants placed in the lower anterior region had the highest risk for more severe peri‐implant bone loss; and (d) peri‐implant bone defects with only a single bone wall appropriate for regenerative procedure were relatively frequent

Endocannabinoids and inflammatory response in periodontal ligament cells.

Endocannabinoids are associated with multiple regulatory functions in several tissues. The main endocannabinoids, anandamide (AEA) and 2-arachidonylglycerol (2-AG), have been detected in the gingival crevicular fluid of periodontitis patients, but the association between periodontal disease or human periodontal ligament cells (hPdLCs) and endocannabinoids still remain unclear. The aim of the present study was to examine the effects of AEA and 2-AG on the proliferation/viability and cytokine/chemokine production of hPdLCs in the presence/absence of Porphyromonas gingivalis lipopolysaccharide (P. gingivalis LPS). The proliferation/viability of hPdLCs was measured using 3,4,5-dimethylthiazol-2-yl-2,5-diphenyl tetrazolium bromide (MTT)-assay. Interleukin-6 (IL-6), interleukin-8 (IL-8), and monocyte chemotactic protein-1 (MCP-1) levels were examined at gene expression and protein level by real-time PCR and ELISA, respectively. AEA and 2-AG did not reveal any significant effects on proliferation/viability of hPdLCs in the absence of P. gingivalis LPS. However, hPdLCs viability was significantly increased by 10-20 µM AEA in the presence of P. gingivalis LPS (1 µg/ml). In the absence of P. gingivalis LPS, AEA and 2-AG did not exhibit any significant effect on the expression of IL-8 and MCP-1 expression in hPdLCs, whereas IL-6 expression was slightly enhanced by 10 µM 2-AG and not affected by AEA. In P.gingivalis LPS stimulated hPdLCs, 10 µM AEA down-regulated gene-expression and protein production of IL-6, IL-8, and MCP-1. In contrast, 10 µM 2-AG had an opposite effect and induced a significant up-regulation of gene and protein expression of IL-6 and IL-8 (P<0.05) as well as gene-expression of MCP-1 in P. gingivalis LPS stimulated hPdLCs. Our data suggest that AEA appears to have an anti-inflammatory and immune suppressive effect on hPdLCs' host response to P.gingivalis LPS, whereas 2-AG appears to promote detrimental inflammatory processes. In conclusion, AEA and 2-AG might play an important role in the modulation of periodontal inflammation

Both 25-hydroxyvitamin-D3 and 1,25-dihydroxyvitamin-D3 reduces inflammatory response in human periodontal ligament cells.

Periodontitis is an inflammatory disease leading to the destruction of periodontal tissue. Vitamin D3 is an important hormone involved in the preservation of serum calcium and phosphate levels, regulation of bone metabolism and inflammatory response. Recent studies suggest that vitamin D3 metabolism might play a role in the progression of periodontitis. The aim of the present study was to examine the effects of 25(OH)D3, which is stable form of vitamin D3 in blood, and biologically active form 1,25(OH)2D3 on the production of interleukin-6 (IL-6), interleukin-8 (IL-8), and monocyte chemotactic protein-1 (MCP-1) by cells of periodontal ligament. Commercially available human periodontal ligament fibroblasts (hPdLF) and primary human periodontal ligament cells (hPdLC) were used. Cells were stimulated with either Porphyromonas gingivalis lipopolysaccharide (LPS) or heat-killed P. ginigvalis in the presence or in the absence of 25(OH)D3 or 1,25(OH)2D3 at concentrations of 10-100 nM. Stimulation of cells with either P. gingivalis LPS or heat-killed P. gingivalis resulted in a significant increase of the expression levels of IL-6, IL-8, and MCP-1 in gene as well as in protein levels, measured by qPCR and ELISA, respectively. The production of these pro-inflammatory mediators in hPdLF was significantly inhibited by both 25(OH)D3 and 1,25(OH)2D3 in a dose-dependent manner. In primary hPdLCs, both 25(OH)D3 and 1,25(OH)2D3 inhibited the production of IL-8 and MCP-1 but have no significant effect on the IL-6 production. The effect of both 25(OH)D3 and 1,25(OH)2D3 was abolished by specific knockdown of vitamin D3 receptor by siRNA. Our data suggest that vitamin D3 might play an important role in the modulation of periodontal inflammation via regulation of cytokine production by cells of periodontal ligament. Further studies are required for better understanding of the extents of this anti-inflammatory effect and its involvement in the progression of periodontal disease