Effects of parathyroid hormone and cytokines on prostaglandin E synthesis and bone resorption by human periodontal ligament fibroblasts

Osteoporosis and Alveolar Bone Health in Periodontitis Niche: A Predisposing Factors-Centered Review

Periodontitis is a periodontal inflammatory condition that results from disrupted periodontal host-microbe homeostasis, manifested by the destruction of tooth-supporting structures, especially inflammatory alveolar bone loss. Osteoporosis is characterized by systemic deterioration of bone mass and microarchitecture. The roles of many systemic factors have been identified in the pathogenesis of osteoporosis, including endocrine change, metabolic disorders, health-impaired behaviors and mental stress. The prevalence rate of osteoporotic fracture is in sustained elevation in the past decades. Recent studies suggest that individuals with concomitant osteoporosis are more vulnerable to periodontal impairment. Current reviews of worse periodontal status in the context of osteoporosis are limited, mainly centering on the impacts of menopausal and diabetic osteoporosis on periodontitis. Herein, this review article makes an effort to provide a comprehensive view of the relationship between osteoporosis and periodontitis, with a focus on clarifying how those risk factors in osteoporotic populations modify the alveolar bone homeostasis in the periodontitis niche.

Long non-coding RNA SNHG5 mediates periodontal inflammation through the NF-κB signaling pathway

AIM

We investigated the role of the long non-coding RNA (lncRNA), small nucleolar RNA host gene 5 (SNHG5), in the pathogenesis of periodontitis.

MATERIALS AND METHODS

A ligature-induced periodontitis mouse model was established, and gingival tissues from patients with periodontitis and healthy controls were collected. Inflammatory cytokines were detected using qRT-PCR and western blotting analyses. Direct interactions between SNHG5 and p65 were detected by RNA pull-down and RNA immunoprecipitation assays. Micro-computed tomography, hematoxylin and eosin staining, and immunohistochemical staining were used to measure periodontal bone loss.

RESULTS

SNHG5 expression was downregulated in human and mouse periodontal tissues compared to that in the healthy controls. In vitro experiments demonstrated that SNHG5 significantly ameliorated tumor necrosis factor-α (TNFα)-induced inflammation. Mechanistically, SNHG5 directly binds to the nuclear factor-kappa B (NF-κB) p65 subunit and inhibits its translocation, thereby suppressing the NF-κB signaling pathway activation and reducing the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 inflammasome expression. Locally injecting si-SNHG5 aggravated the periodontal destruction.

CONCLUSION

This study revealed that SNHG5 mediates periodontal inflammation through the NF-κB signaling pathway, providing a potential therapeutic target for periodontitis treatment. This article is protected by copyright. All rights reserved.

An Evaluation of Microbial Flora, Alkaline Phosphatase and IL-8 Levels in GCF of Orthodontic Patients with Self-Ligating and Conventional Brackets

PURPOSE

To compare the microbial flora, alkaline phosphatase (ALP) and interleukin-8 (IL-8) levels during orthodontic treatment with self-ligating brackets versus conventional brackets.

PATIENTS AND METHODS

Forty patients were included in this study and distributed equally between two groups. One group received conventional edgewise brackets while the other group received DAMON self-ligating brackets. Periodontal parameters were recorded and biochemical and microbial analyses were conducted before bonding (baseline), and 14, 30, and 45 days after bonding. Paired t-test was performed to estimate the intergroup differences from the baseline at the various time points; unpaired t-test was used for intragroup comparisons.

RESULTS

A significantly higher prevalence of gram-negative as well as gram-positive microorganisms was found in the group with conventional brackets than that with self-ligating brackets. Alkaline phosphatase (ALP) activity and interleukin-8 (IL-8) levels were significantly higher in the gingival crevicular fluid of the group with conventional brackets than that with self-ligating brackets.

CONCLUSION

The conventional bracket-ligature technique exhibited an increase in IL-8 levels, ALP activity, and microbial colonization compared with that of the self-ligature technique. Accordingly, self-ligating brackets are recommended in orthodontic patients to improve periodontal health and minimize damage outcomes of periodontal tissue interventions.

Infection and inflammatory mechanisms

This introductory article examines the potential mechanisms that may play a role in the associations between periodontitis and the systemic conditions being considered in the EFP/AAP Workshop in Segovia, Spain. Three basic mechanisms have been postulated to play a role in these interactions; metastatic infections,inflammation and inflammatory injury, and adaptive immunity. The potential role of each alone and together is considered in in vitro and animal studies and in human studies when available. This is not a systematic or critical review, but rather an overview of the field to set the stage for the critical reviews in each of the working groups.

Inflammatory and immune pathways in the pathogenesis of periodontal disease

The pathogenesis of periodontitis involves a complex immune/inflammatory cascade that is initiated by the bacteria of the oral biofilm that forms naturally on the teeth. The susceptibility to periodontitis appears to be determined by the host response; specifically, the magnitude of the inflammatory response and the differential activation of immune pathways. The purpose of this review was to delineate our current knowledge of the host response in periodontitis. The role of innate immunity, the failure of acute inflammation to resolve (thus becoming chronic), the cytokine pathways that regulate the activation of acquired immunity and the cells and products of the immune system are considered. New information relating to regulation of both inflammation and the immune response will be reviewed in the context of susceptibility to, and perhaps control of, periodontitis.

Oral inflammatory diseases and systemic inflammation: role of the macrophage

Inflammation is a complex reaction to injurious agents and includes vascular responses, migration, and activation of leukocytes. Inflammation starts with an acute reaction, which evolves into a chronic phase if allowed to persist unresolved. Acute inflammation is a rapid process characterized by fluid exudation and emigration of leukocytes, primarily neutrophils, whereas chronic inflammation extends over a longer time and is associated with lymphocyte and macrophage infiltration, blood vessel proliferation, and fibrosis. Inflammation is terminated when the invader is eliminated, and the secreted mediators are removed; however, many factors modify the course and morphologic appearance as well as the termination pattern and duration of inflammation. Chronic inflammatory illnesses such as diabetes, arthritis, and heart disease are now seen as problems that might have an impact on the periodontium. Reciprocal effects of periodontal diseases are potential factors modifying severity in the progression of systemic inflammatory diseases. Macrophages are key cells for the inflammatory processes as regulators directing inflammation to chronic pathological changes or resolution with no damage or scar tissue formation. As such, macrophages are involved in a remarkably diverse array of homeostatic processes of vital importance to the host. In addition to their critical role in immunity, macrophages are also widely recognized as ubiquitous mediators of cellular turnover and maintenance of extracellular matrix homeostasis. In this review, our objective is to identify macrophage-mediated events central to the inflammatory basis of chronic diseases, with an emphasis on how control of macrophage function can be used to prevent or treat harmful outcomes linked to uncontrolled inflammation.

Paracrine-mediated differentiation and activation of human haematopoietic osteoclast precursor cells by skin and gingival fibroblasts

OBJECTIVE

Fibroblasts appear to modulate osteoclastogenesis, but their precise role in this process remains unclear. In this work, paracrine-mediated osteoclastogenic potential of different human fibroblasts was assessed.

MATERIALS AND METHODS

Fibroblast-conditioned media (CM) from foetal skin (CM1), adult skin (CM2) and adult gingiva (CM3) were used to promote osteoclastogenesis of osteoclast precursor cells. Cultures supplemented with macrophage-colony stimulating factor (M-CSF) and receptor activator of nuclear factor-κB ligand (RANKL) were used as controls.

RESULTS

All fibroblast cultures expressed FSP-1, M-CSF and RANKL and produced osteoprotegerin (OPG); gingival fibroblasts presented lowest expression of osteoclastogenic genes and higher production of OPG. All fibroblast CM were able to induce osteoclastogenesis. CM1 showed behaviour similar to positive controls, and slightly higher osteoclastogenic potential than CM, from adult ones. Gingival fibroblasts revealed lowest osteoclastogenic ability. Presence of anti-MCSF or anti-RANKL partially inhibited osteoclastogenesis promoted by CM, although the former antibody revealed higher inhibitory response. Differences among the osteoclastogenic effect of CM were noted, mainly in expression of genes involved in differentiation and activation of osteoclast precursor cells, c-myc and c-src, and less regarding functional related parameters.

CONCLUSIONS

Fibroblasts are able to induce osteoclastogenesis by paracrine mechanisms, and age and anatomical location affect this ability. Other factors produced by fibroblasts, in addition to M-CSF and RANKL, appear to contribute to observed osteoclastogenic potential.

The effect of the topical administration of bioactive glass on inflammatory markers of human experimental gingivitis

Recent studies demonstrated that bioactive glass attenuated inflammatory reactions and bacterial growth in vitro. The aim of the present clinical study was to evaluate the effects of local bioactive glass-administration in vivo in subjects with experimental gingivitis. In each individual, contralateral teeth served as test and control over a 21-day non-hygiene (preventive phase) and a 7-day therapeutic phase. A 45S5 bioactive glass (10% solution) was applied daily (2 x 1 h) on the test teeth during the preventive and therapeutic phase of the study. Inflammation assessment was based on the plaque index record (PI), on the bleeding frequency (BOP) and the gingival crevicular fluid volume (GCF). Interleukin-1beta levels (IL-1beta) in the GCF were measured by ELISA. Bacterial deposits on teeth increased during the 21-days non-brushing period, with no difference in plaque accumulation between test and control sides. BOP levels were significantly reduced during the therapeutic phase by the application of bioactive glass. GCF-values showed a significant reduction on the test compared to control side during the preventive and therapeutic phase. IL-1beta counts decreased during the last 7 days of the study on the test side, but no significance was given. The topical application of 45S5 bioactive glass in humans with experimental gingivitis attenuated the clinical signs of inflammation, although the bacterial accumulation was not inhibited in this clinical trial.

Comparison of the effects of 1,25 dihydroxycholecalciferol and prostaglandin E2 on orthodontic tooth movement

This study compared the effects of local administrations of prostaglandin E2 (PGE2) and 1,25-dihydroxycholecalciferol (1,25-DHCC) on orthodontic tooth movement in rats. Thirty-seven 6-week-old male Sprague-Dawley rats, weighing 160 +/- 10 g were used. Five rats served as the baseline control group. A fixed appliance system exerting 20 g of distally directed force was applied on the maxillary incisors of 32 animals for 9 days. Eight rats served as the appliance control group; 8 received a 20-microL injection of dimethyl sulfoxide (solvent for 1,25-DHCC) on days 0, 3, and 6; 8 received 20 microL of 10(-10) mol/L 1,25-DHCC on days 0, 3, and 6; 8 received a single injection of 0.1 mL of 0.1 microg PGE2 only on day 0. There was no significant difference in tooth movement between the PGE2 and the 1,25-DHCC groups. Both PGE2 and 1,25-DHCC enhanced the amount of tooth movement significantly when compared with the control group. The numbers of Howship's lacunae and capillaries on the pressure side were significantly greater in the PGE2 group than in the 1,25-DHCC group. On the other hand, the number of osteoblasts on the external surface of the alveolar bone on the pressure side was significantly greater in the 1,25-DHCC group than in the PGE2 group. Thus, 1,25-DHCC was found to be more effective in modulating bone turnover during orthodontic tooth movement, because its effects on bone formation and bone resorption were well balanced.

Cytokine levels in crevicular fluid are less responsive to orthodontic force in adults than in juveniles

OBJECTIVES

Bone remodelling during orthodontic tooth movement is related to the expression of mediators in gingival crevicular fluid (GCF). No information is available concerning the effect of age on the levels of these mediators in GCF. The purpose of this study was to quantify three mediators (prostaglandin E2, interleukin-6 and granulocyte-Macrophage Colony-Stimulating Factor) in GCF during orthodontic tooth movement in juveniles and adults.

MATERIAL AND METHODS

A total of 43 juvenile patients (mean age 11 +/- 0.7 year), and 41 adult patients (mean age 24 +/- 1.6 year) took part in the study. One of the lateral incisors of each patient was tipped labially, the other served as control. GCF samples were taken before force activation (t0) and 24 h later (t24). Mediator levels were determined by radioimmunoassay (RIA).

RESULTS

PGE2 concentrations were significantly elevated at t24 in juveniles and adults, while concentrations of IL-6 and GM-CSF were significantly elevated only in juveniles. Total amounts of all three mediators in GCF significantly increased at t24 in both groups.

CONCLUSIONS

In early tooth movement, mediator levels in juveniles are more responsive than levels in adults, which agrees with the finding that the initial tooth movement in juveniles is faster than in adults and starts without delay.

Treatment of childhood hypophosphatasia with nonsteroidal antiinflammatory drugs

Hypophosphatasia (HP) is an inborn error of metabolism that is characterized by reduced bone mineralization. The aim of this investigation was to evaluate treatment of incapacitating lower limb pain in patients with childhood HP using nonsteroidal antiinflammatory drugs (NSAID). All patients (seven boys; age 32 months to 16 years) presented with delayed walking, the typical waddling gait, muscular weakness of the lower limbs, and a limited walking distance. Six patients had severe diffuse lower limb pain following physical activity and were therefore treated with NSAID. The benefit of this treatment was evaluated clinically and by measurement of renally (PGE2) and systemically (PGE-M) derived prostaglandins (PG) in urine before and during therapy. After treatment with NSAID all six patients showed marked clinical improvement with reduced pain, increased muscle strength, and a normalized walking distance. Levels of PGE-M, which had been elevated in four patients prior to therapy, returned to normal. The use of NSAID in childhood HP should be considered as a possible therapeutic approach because the quality of life in these patients is markedly impaired by pain of the limbs. Elevated PG might play a role in the bone metabolism of HP patients.

Epithelium-fibroblast co-culture for assessing mucosal irritancy of metals used in dentistry

No valid animal or in vitro model exists to assess the potential mucosal irritancy of dental materials. However, recently, a commercially available model system based on a recombined co-culture of human fibroblasts and human epithelial cells has been introduced for evaluating the time-dependent irritancy of cosmetic products. Cell viability and prostaglandin E2 (PGE2) release from the cells were used as markers for the irritative potential of test materials. The objective of the present study was to evaluate the suitability of this model for monitoring the irritative potential of metals and cast alloys used in dentistry. The human fibroblast-keratinocyte co-cultures were exposed to test specimens fabricated from copper, zinc, palladium, nickel, tin, cobalt, indium, a high noble cast alloy, and from a dental ceramic. Cell survival rates decreased after exposure to copper (14-25%), cobalt (60%), zinc (63%), indium (85%), nickel (87%), and the non-oxidized and oxidized high noble cast alloy (87%/90%) compared to untreated control cultures. Dental ceramic, palladium and tin did not influence cell viability. In parallel, the PGE2 release was continuously monitored up to 24 h using a competitive displacement enzyme immunoassay. PGE2 release increased most highly in the cultures exposed to copper (6-25 fold), cobalt (7 fold), indium (4 fold), and zinc (2 fold) compared to untreated control cultures. The PGE2 determination proved to be a non-destructive method for continuous monitoring of cell reactions in the same culture. The model used seems promising for evaluating the time-dependent mucosal irritancy of dental cast alloys.

Intracellular calcium response to hydraulic pressure in human periodontal ligament fibroblasts

Human periodontal ligament fibroblasts in culture were exposed to the controlled change in hydraulic pressure and were monitored continuously with an electric pressure gauge, and the concentration of intracellular calcium was measured in real time by a calcium-binding fluorescent dye, fluo-3. The elevation of hydraulic pressure to a level ranging from 20 to 50 mm Hg induced transient elevation of the intracellular calcium concentration in about 10% of the fibroblasts observed, indicating that these cells could respond to the pressure change. The results supported further an idea that periodontal ligament fibroblasts, responding to the pressure exerted by orthodontic force, would initiate the chain of events in orthodontic tooth movement, including alveolar bone remodeling. The threshold level of pressure (27 to 68 g/cm2) obtained in this experiment, at which the fibroblasts started to respond, would provide a biochemical basis to determine the optimal magnitude of stress for clinical orthodontics.

[The effect of static magnetic fields on prostaglandin synthesis in L-929 and 3T3 mouse fibroblasts. An in-vitro study]

The aim of this study was to examine the influence of static, inhomogeneous magnetic fields on prostaglandin synthesis in L-929 and 3T3 mouse fibroblasts. Two pairs of magnets, one CoSm and the other NdFeB, were attached 10 mm apart under the culture chamber. One pair was in the attracting position and the other in the repelling position. The maximum magnetic induction measured was 85 respectively 120 mT and the incubation time was 72 hours. Control groups consisted of untreated cells and cells under the influence of demagnetized magnets. The following measurements were taken: prostaglandin synthesis (PGE2), protein content (GP), and the number (Z) of cells (only L-929 mouse fibroblasts). The data were analyzed statistically using the Tukey test and the significance niveau was set at alpha = 0.05. The results using this method demonstrated that the measurable effects of in vitro treatment of mouse fibroblasts with static magnetic fields of varying induction did not significantly differ from the control groups. The sensitivity of our method was verified beforehand with a recombinant, human TNF alpha stimulated reference group.

The effect of conditioned medium from connective tissue fibroblasts and epithelium on calcium release from mouse calvarial organ culture

Fibroblasts from periodontal ligament and gingival explants were cultured in vitro. The conditioned media from four different periodontal ligament and four gingival explant cultures were examined to determine their effect on calcium release in mouse calvarial organ culture. All the cultures stimulated calcium release, with a range of 20.6-43% over control. Conditioned media from two periodontal ligament cultures and a gingival culture significantly stimulated calcium release from the bone organ culture. The stimulatory activity in the oral fibroblasts cell cultures was compared to that in conditioned medium from two non-oral, established, fibroblasts cell lines and an epidermal keratinocyte cell line. Similar to the oral fibroblast cultures, conditioned medium from all three cell lines resulted in stimulation of calcium release in the bone culture assay. In order to characterize the bone-stimulating activity, a 0.4 micron membrane was used to separate the cell cultures from the bone organ culture. Both gingival and periodontal ligament fibroblast cultures gave values for calcium release significantly less than control when the separating membrane was used. Both non-oral cell lines and the epidermal keratinocyte cell line gave values for calcium release similar to those when no membrane was used. These results suggest that oral fibroblasts, but not non-oral fibroblasts and epidermal keratinocytes, release a unique bone-resorption stimulating activity.