Single-Cell Transcriptomic Analysis of Dental Pulp and Periodontal Ligament Stem Cells

The regeneration of periodontal, periapical, and pulpal tissues is a complex process requiring the direct involvement of cells derived from pluripotent stem cells in the periodontal ligament and dental pulp. Dental pulp stem cells (DPSCs) and periodontal ligament stem cells (PDLSCs) are spatially distinct with the potential to differentiate into similar functional and phenotypic cells. We aimed to identify the cell heterogeneity of DPSCs and PDLSCs and explore the differentiation potentials of their specialized organ-specific functions using single-cell transcriptomic analysis. Our results revealed 7 distinct clusters, with cluster 3 showing the highest potential for differentiation. Clusters 0 to 2 displayed features similar to fibroblasts. The trajectory route of the cell state transition from cluster 3 to clusters 0, 1, and 2 indicated the distinct nature of cell differentiation. PDLSCs had a higher proportion of cells (78.6%) at the G1 phase, while DPSCs had a higher proportion of cells at the S and G2/M phases (36.1%), mirroring the lower cell proliferation capacity of PDLSCs than DPSCs. Our study suggested the heterogeneity of stemness across PDLSCs and DPSCs, the similarities of these 2 stem cell compartments to be potentially integrated for regenerative strategies, and the distinct features between them potentially particularized for organ-specific functions of the dental pulp and periodontal ligament for a targeted regenerative dental tissue repair and other regeneration therapies.

RvE1 Promotes Axin2+ Cell Regeneration and Reduces Bacterial Invasion

Vital pulp therapy and root canal therapy (RCT) are the dominant treatment for irreversible pulpitis. While the success rate of these procedures is favorable, they have some limitations. For instance, RCT leads to removing significant dentin in the coronal third of the tooth that increases root-fracture risk, which forces tooth removal. The ideal therapeutic goal is dental pulp regeneration, which is not achievable with RCT. Specialized proresolving mediators (SPMs) are well known for inflammatory resolution. The resolution of inflammation and tissue restoration or regeneration is a dynamic and continuous process. SPMs not only have potent immune-modulating functions but also effectively promote tissue homeostasis and regeneration. Resolvins have been shown to promote dental pulp regeneration. The purpose of this study was to explore further the cellular target of Resolvin E1 (RvE1) therapy in dental pulp regeneration and the impact of RvE1 in infected pulps. We investigated the actions of RvE1 on experimentally exposed pulps with or without microbial infection in an Axin2Cre-Dox;Ai14 genetically defined mouse model. Our results showed RvE1 promoted Axin2-tdTomato+ cell expansion and odontoblastic differentiation after direct pulp capping in the mouse, which we used to mimic reversible pulpitis cases in the clinic. In cultured mouse dental pulp stem cells (mDPSCs), RvE1 facilitated Axin2-tdTomato+ cell proliferation and odontoblastic differentiation and also rescued impaired functions after lipopolysaccharide stimulation. In infected pulps exposed to the oral environment for 24 h, RvE1 suppressed inflammatory infiltration, reduced bacterial invasion in root canals, and prevented the development of apical periodontitis, while its proregenerative impact was limited. Collectively, topical treatment with RvE1 facilitated dental pulp regenerative properties by promoting Axin2-expressing cell proliferation and differentiation. It also modulated the resolution of inflammation, reduced infection severity, and prevented apical periodontitis, presenting RvE1 as a novel therapeutic for treating endodontic diseases.

Impact of low-level laser therapy as an adjunct to non-surgical periodontal treatment on the levels of tissue plasminogen activator and plasminogen activator inhibitor 1 in Stage 3-4, Grade C periodontitis patients: a split-mouth, randomized control study

AIM

To investigate the effects of low-level laser therapy (LLLT) as an adjunct to non-surgical periodontal treatment (NSPT) on the plasminogen-activating system.

MATERIALS AND METHODS

Stage 3-4 Grade C periodontitis and age-gender-matched healthy individuals participated in the split-mouth study (ClinicalTrials.gov identifier, NCT05233501). The study groups were Periodontitis/NSPT (Sham); Periodontitis/NSPT + LLLT (LLLT); Healthy (Control). Following NSPT, LLLT was applied on Days 0, 2 and 7. Clinical parameters were recorded at baseline and on Day 30. Gingival crevicular fluid (GCF) was collected at baseline, on days 7, 14, and 30; tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) levels were measured with ELISA.

RESULTS

Clinical parameters, total GCF tPA (tPAt) and PAI-1 (PAI-1t) levels significantly reduced in LLLT and Sham groups (< 0.001). GCF tPAt levels in LLLT were significantly lower (< 0.05) than Sham on Day 7. GCF tPAt levels in periodontitis groups were significantly higher than the Control at baseline, on Days 7 and 14 (< 0.01). By Day 30, both groups decreased to control levels (> 0.05). GCF PAI-1t levels were significantly lower in LLLT than the Sham on day 30 (< 0.01), comparable to healthy controls (> 0.05).

CONCLUSION

Adjunctive LLLT modulates the plasminogen activating system in severe periodontitis by altering GCF tPA and PAI-1 levels.

CLINICAL RELEVANCE

LLLT as an adjunct to non-surgical periodontal treatment in patients with Stage 3-4 Grade C leads to reduced plasminogen activation.

Dementia and the Risk of Periodontitis: A Population-Based Cohort Study

Dementia and Alzheimer's disease (AD) are proposed to be comorbid with periodontitis (PD). It is unclear whether PD is associated with dementia and AD independent of confounding factors. We aimed at identifying the relationship between the longitudinal risk of developing PD in a cohort of patients with dementia and AD who did not show any signs of PD at baseline. In this retrospective cohort study, 8,640 patients with dementia without prior PD were recruited, and 8,640 individuals without dementia history were selected as propensity score-matched controls. A Cox proportional hazard model was developed to estimate the risk of developing PD over 10 y. Cumulative probability was derived to assess the time-dependent effect of dementia on PD. Of the 8,640 patients, a sensitivity test was conducted on 606 patients with AD-associated dementia and 606 non-AD propensity score-matched controls to identify the impact of AD-associated dementia on the risk for PD. Subgroup analyses on age stratification were included. Overall 2,670 patients with dementia developed PD. The relative risk of PD in these patients was significantly higher than in the nondementia group (1.825, 95% CI = 1.715 to 1.942). Cox proportional hazard models showed that patients with dementia were more likely to have PD than individuals without dementia (adjusted hazard ratio = 1.915, 95% CI = 1.766 to 2.077, P < 0.0001, log-rank test P < 0.0001). The risk of PD in patients with dementia was age dependent (P values for all ages <0.0001); younger patients with dementia were more likely to develop PD. The findings persisted for patients with AD: the relative risk (1.531, 95% CI = 1.209 to 1.939) and adjusted hazard ratio (1.667, 95% CI = 1.244 to 2.232; log-rank test P = 0.0004) of PD in patients with AD were significantly higher than the non-AD cohort. Our findings demonstrated that dementia and AD were associated with a higher risk of PD dependent of age and independent of systemic confounding factors.

Multiple Functions of Lysyl Oxidase Like-2 in Oral Fibroproliferative Processes

Gingival overgrowth is a side effect of certain medications, including calcium channel blockers, cyclosporin A, and phenytoin. Phenytoin-induced gingival overgrowth is fibrotic. Lysyl oxidases are extracellular enzymes that are required for biosynthetic cross-linking of collagens, and members of this enzyme family are upregulated in fibrosis. Previous studies in humans and in a mouse model of phenytoin-induced gingival overgrowth have shown that LOXL2 is elevated in the epithelium and connective tissue in gingival overgrowth tissues and not in normal tissues. Here, using a novel LOXL2 isoform-selective inhibitor and knockdown studies in loss- and gain-of-function studies, we investigated roles for LOXL2 in promoting cultures of human gingival fibroblasts to proliferate and to accumulate collagen. Data indicate that LOXL2 stimulates gingival fibroblast proliferation, likely by a platelet-derived growth factor B receptor-mediated mechanism. Moreover, collagen accumulation was stimulated by LOXL2 enzyme and inhibited by LOXL2 inhibitor or gene knockdown. These studies suggest that LOXL2 could serve as a potential therapeutic target to address oral fibrotic conditions.

Connective Tissue Metabolism and Gingival Overgrowth

Gingival overgrowth occurs mainly as a result of certain anti-seizure, immunosuppressive, or antihypertensive drug therapies. Excess gingival tissues impede oral function and are disfiguring. Effective oral hygiene is compromised in the presence of gingival overgrowth, and it is now recognized that this may have negative implications for the systemic health of affected patients. Recent studies indicate that cytokine balances are abnormal in drug-induced forms of gingival overgrowth. Data supporting molecular and cellular characteristics that distinguish different forms of gingival overgrowth are summarized, and aspects of gingival fibroblast extracellular matrix metabolism that are unique to gingival tissues and cells are reviewed. Abnormal cytokine balances derived principally from lymphocytes and macrophages, and unique aspects of gingival extracellular matrix metabolism, are elements of a working model presented to facilitate our gaining a better understanding of mechanisms and of the tissue specificity of gingival overgrowth.

Positive effect of platelet rich fibrin on osseointegration

Background

Leukocyte-platelet rich fibrin (L-PRF) is a second generation platelet concentrate clinically used to accelerate tissue healing and bone regeneration. Achieving reduced implant osseointegration time could provide immediate or early loading of implants. The aim of this study was to evaluate the L-PRF-induced osseointegration and bone-implant contact (BIC) in an experimental animal model.

Material and Methods

Twelve 4-month-old New Zealand white rabbits were used. Following general anesthesia, 3-5 mL of blood was obtained from the central artery in rabbit ear and L-PRF was prepared. Two implant cavities (5 mm long and 3 mm in diameter) were created in each tibia with a total of four cavities in each animal. Two of these cavities were selected and covered with PRF (test group). The remaining L-PRF was used to soak the implants placed into the L-PRF covered sockets. Other cavities were left as controls. In total, 48 implants were placed. Animals were sacrificed after two, three, or four weeks. Histological samples were obtained and peri-implant tissues were histomorphometrically evaluated for bone-to-implant contact and new bone formation.

Results

Histomorphometric analyses of the defects revealed that the L-PRF was detectable up to the second week. Application of L-PRF increased the rate and amount of new bone formation in the experimental group compared to the control group. Bone-to-implant contact was enhanced when the surface was pre-wetted with L-PRF (p<0.01).

Conclusions

The results of this study demonstrated that L-PRF application may increases amount and rate of new bone formation during the early healing period and provides a faster osseointegration around implants.

Key words:Dental implants, platelet rich fibrin, osseointegration, bone regeneration, matrix for growth factors.

Immunologic environment influences macrophage response to Porphyromonas gingivalis

Macrophages adapt both phenotypically and functionally to the cytokine balance in host tissue microenvironments. Recent studies established that macrophages contribute an important yet poorly understood role in the development of infection-elicited oral bone loss. We hypothesized that macrophage adaptation to inflammatory signals encountered before pathogen interaction would significantly influence the subsequent immune response of these cells to the keystone oral pathobiont Porphyromonas gingivalis. Employing classically activated (M1) and alternatively activated (M2) murine bone-marrow-derived macrophage (BMDMø), we observed that immunologic activation of macrophages before P. gingivalis challenge dictated phenotype-specific changes in the expression of inflammation-associated molecules important to sensing and tuning host response to bacterial infection including Toll-like receptors 2 and 4, CD14, CD18 and CD11b (together comprising CR3), major histocompatibility complex class II, CD80, and CD86. M2 cells responded to P. gingivalis with higher expression of tumor necrosis factor-α, interleukin-6, monocyte chemoattractant protein-1, macrophage inflammatory protein-1α, regulated on activation normal T cell expressed and secreted, and KC than M1 cells. M1 BMDMø expressed higher levels of interleukin-10 to P. gingivalis than M2 BMDMø. Functionally, we observed that M2 BMDMø bound P. gingivalis more robustly than M1 BMDMø. These data describe an important contribution of macrophage skewing in the subsequent development of the cellular immune response to P. gingivalis.

SOCS-3 Regulates Alveolar Bone Loss in Experimental Periodontitis

The host immune response plays a key role in bacteria-induced alveolar bone resorption. Endogenous control of the magnitude and duration of inflammatory signaling is considered an important determinant of the extent of periodontal pathology. Suppressor of cytokine signaling (SOCS) proteins are inhibitors of cytokine signaling pathways and may play a role in restraining periodontal inflammation. We hypothesized that SOCS-3 regulates alveolar bone loss in experimental periodontitis. Periodontal bone loss was induced in 16-wk-old myeloid-specific SOCS-3-knockout and wild-type (WT) C57Bl6-B.129 mice by oral inoculation 9 times with 10(9) colony-forming units of Porphyromonas gingivalis A7436 through an oral gavage model for periodontitis. Sham controls for both types of mice received vehicle without bacteria. The mice were euthanized 6 wk after the last oral inoculation. Increased bone loss was demonstrated in P. gingivalis-infected SOCS-3-knockout mice as compared with P. gingivalis-infected WT mice by direct morphologic measurements, micro-computed tomography analyses, and quantitative histology. Loss of SOCS-3 function resulted in an increased number of alveolar bone osteoclasts and increased RANKL expression after P. gingivalis infection. SOCS-3 deficiency in myeloid cells also promotes a higher P. gingivalis lipopolysaccharide-induced inflammatory response with higher secretion of IL-1β, IL-6, and KC (IL-8) by peritoneal macrophages as compared with WT controls. Our data implicate SOCS-3 as a critical negative regulator of alveolar bone loss in periodontitis.

Molecular and clinical aspects of drug-induced gingival overgrowth

Drug-induced gingival overgrowth is a tissue-specific condition and is estimated to affect approximately one million North Americans. Lesions occur principally as side-effects from phenytoin, nifedipine, or ciclosporin therapy in approximately half of the people who take these agents. Due to new indications for these drugs, their use continues to grow. Here, we review the molecular and cellular characteristics of human gingival overgrowth lesions and highlight how they differ considerably as a function of the causative drug. Analyses of molecular signaling pathways in cultured human gingival fibroblasts have provided evidence for their unique aspects compared with fibroblasts from the lung and kidney. These findings provide insights into both the basis for tissue specificity and into possible therapeutic opportunities which are reviewed here. Although ciclosporin-induced gingival overgrowth lesions exhibit principally the presence of inflammation and little fibrosis, nifedipine- and especially phenytoin-induced lesions are highly fibrotic. The increased expression of markers of gingival fibrosis, particularly CCN2 [also known as connective tissue growth factor (CTGF)], markers of epithelial to mesenchymal transition, and more recently periostin and members of the lysyl oxidase family of enzymes have been documented in phenytoin or nifedipine lesions. Some oral fibrotic conditions such as leukoplakia and oral submucous fibrosis, after subsequent additional genetic damage, can develop into oral cancer. Since many pathways are shared, the study of gingival fibrosis and comparisons with characteristics and molecular drivers of oral cancer would likely enhance understandings and functional roles of molecular drivers of these oral pathologies.

Proresolving nanomedicines activate bone regeneration in periodontitis

Therapies to reverse tissue damage from osteolytic inflammatory diseases are limited by the inability of current tissue-engineering procedures to restore lost hard and soft tissues. There is a critical need for new therapeutics in regeneration. In addition to scaffolds, cells, and soluble mediators necessary for tissue engineering, control of endogenous inflammation is an absolute requirement for success. Although significant progress has been made in understanding natural resolution of inflammation pathways to limit uncontrolled inflammation in disease, harnessing the biomimetic properties of proresolving lipid mediators has not been demonstrated. Here, we report the use of nano-proresolving medicines (NPRM) containing a novel lipoxin analog (benzo-lipoxin A4, bLXA4) to promote regeneration of hard and soft tissues irreversibly lost to periodontitis in the Hanford miniature pig. In this proof-of-principle experiment, NPRM-bLXA4 dramatically reduced inflammatory cell infiltrate into chronic periodontal disease sites treated surgically and dramatically increased new bone formation and regeneration of the periodontal organ. These findings indicate that NPRM-bLXA4 is a mimetic of endogenous resolving mechanisms with potent bioactions that offers a new therapeutic tissue-engineering approach for the treatment of chronic osteolytic inflammatory diseases.

Vascular endothelial cadherin and vascular endothelial growth factor in periodontitis and smoking

OBJECTIVE

This study investigated the vascularization in periodontal disease process via revealing: (i) vascular endothelial cadherin (VE-cadherin) and vascular endothelial growth factor (VEGF) productions in periodontitis and (ii) the impact of smoking on this phenomenon.

MATERIALS AND METHODS

Fifteen smokers and 15 non-smokers with/without periodontitis were allocated by split-mouth randomization regarding their smoking and periodontal statuses. The teeth with periodontitis in smokers (group 1), without periodontitis in smokers (group 2), with periodontitis in non-smokers (group 3), and without periodontitis in non-smokers (group 4) constituted the study groups. Gingival crevicular fluid (GCF) levels of VE-cadherin and VEGF were determined by ELISA to evaluate their profiles in the groups.

RESULTS

There were increased VE-cadherin levels in groups 1 and 3 compared with groups 2 and 4 (P < 0.05). Group 2 demonstrated higher VE-cadherin level than group 4 (P < 0.05). Increased VEGF was noted in groups 1 and 3 compared with groups 2 and 4 (P < 0.05) with similar levels between groups 1 and 3 and groups 2 and 4 (P > 0.05). There were no correlations between the VE-cadherin and VEGF levels in all groups (P > 0.05).

CONCLUSION

The results suggest that VE-cadherin and VEGF may increase in periodontitis, and smoking may uniquely cause VE-cadherin production in GCF.

Testosterone regulates bone response to inflammation

This study evaluated the alveolar bone response to testosterone and the impact of Resolvin D2 (RvD2) on testosterone-induced osteoblast function. For the in vivo characterization, 60 male adult rats were used. Treatments established sub-physiologic (L), normal (N), or supra-physiologic (H) concentrations of testosterone. Forty rats were subjected to orchiectomy; 20 rats received periodical testosterone injections while 20 rats received testicular sham-operation. Four weeks after the surgeries, 10 rats in each group received a subgingival ligature around the lower first molars to induce experimental periodontal inflammation and bone loss. In parallel, osteoblasts were differentiated from neonatal mice calvariae and treated with various doses of testosterone for 48 h. Cell lysates and conditioned media were used for the determination of alkaline phosphatase, osteocalcin, RANKL, and osteoprotegerin. Micro-computed tomography linear analysis demonstrated that bone loss was significantly increased for both L and H groups compared to animals with normal levels of testosterone. Gingival IL-1β expression was increased in the L group (p<0.05). Ten nM testosterone significantly decreased osteocalcin, RANKL, and OPG levels in osteoblasts; 100 nM significantly increased the RANKL:OPG ratio. RvD2 partially reversed the impact of 10 nM testosterone on osteocalcin, RANKL, and OPG. These findings suggest that both L and H testosterone levels increase inflammatory bone loss in male rats. While low testosterone predominantly increases the inflammatory response, high testosterone promotes a higher osteoblast-derived RANKL:OPG ratio. The proresolving mediator RvD2 ameliorates testosterone-derived downregulation of osteocalcin, RANKL, and OPG in primary murine osteoblasts suggesting a direct role of inflammation in osteoblast function.

Effect of the pro-resolution lipid mediator Resolvin E1 (RvE1) on pulp tissues exposed to the oral environment

AIM

To evaluate the effects of topical Resolvin E1 (RvE1) application on infected dental pulps.

METHODOLOGY

Forty-two male Wistar rats (n = 6 per three groups/and two time periods) were used. To induce inflammation, pulps in mandibular right first molars were accessed and then left exposed to the oral environment for 24 h. After this period, topical medication with a corticosteroid/antibiotic blend, or RvE1, or its vehicle (Ethanol 0.1%) was directly applied onto the pulp tissue and teeth were restored with silver amalgam. The effects of the protocols were evaluated histologically and compared with control pulps not exposed to the oral environment. The inflammatory changes after 24 and 72 h were assessed through a scoring method and analysed using the Kruskal-Wallis test followed by Dunn's. Differences were considered significant if P < 0.05 (CI = 95%).

RESULTS

Ethanol and corticosteroid/antibiotic treatment were not effective in arresting severe inflammatory alterations of exposed pulps at 24 and 72 h (P < 0.05, CI = 95%). At both time periods, RvE1 treatment led to a reduction of tissue cellularity and extent of inflammation, whose changes were not different from control pulps (P > 0.05, CI = 95%).

CONCLUSIONS

A protective role for RvE1 in pulp inflammation was observed even in the presence of contamination, suggesting that it may be a candidate for a novel therapeutic strategy for conservative dental pulp treatment.

Loss of basement membrane integrity in human gingival overgrowth

Gingival overgrowth tissues have thickened connective tissue stroma, sometimes accompanied by the increased presence of collagen fibers, thickened epithelia, and elongated rete pegs. We have previously shown that expression of CCN2, also known as connective tissue growth factor (CTGF), correlates positively with the degree of gingival fibrosis, and that markers of epithelial to mesenchymal transition (EMT) are characteristic of all drug-induced forms of gingival overgrowth. Here we experimentally evaluate whether increased degradation of the basement membrane and apparent invasion of the underlying stroma by epithelial cells could be observed in human gingival overgrowth tissues. Tissues from 20 different individuals with human gingival overgrowth and 15 non-overgrowth samples were evaluated by histological analyses and by immunohistochemistry assays of basement membrane proteins. The results demonstrate that there are significantly higher numbers of basement membrane discontinuities in overgrowth tissues, sometimes containing epithelial-like cells. Disrupted basal membrane structure in gingival overgrowth tissues is accompanied by a discontinuous collagen type IV expression pattern and decreased laminin 5. These findings provide new additional support for the hypothesis that epithelial plasticity and EMT promote gingival overgrowth, resulting in compromised basal membrane structure and increased interactions between epithelial and connective tissue layers that contribute to fibrotic pathology.

Toll-like receptors regulate B cell cytokine production in patients with diabetes

AIMS/HYPOTHESIS

Understanding cellular and molecular events in diabetes mellitus will identify new approaches for therapy. Immune system cells are important modulators of chronic inflammation in diabetes mellitus, but the role of B cells is not adequately studied. The aim of this work was to define the function of B cells in diabetes mellitus patients through focus on B cell responses to pattern recognition receptors.

METHODS

We measured expression and function of Toll-like receptors (TLRs) on peripheral blood B cells from diabetes mellitus patients by flow cytometry and multiplexed cytokine analysis. We similarly analysed B cells from non-diabetic donors and periodontal disease patients as comparative cohorts.

RESULTS

B cells from diabetes mellitus patients secrete multiple pro-inflammatory cytokines, and IL-8 production is significantly elevated in B cells from diabetic patients compared with those from non-diabetic individuals. These data, plus modest elevation of TLR surface expression, suggest B cell IL-8 hyperproduction is a cytokine-specific outcome of altered TLR function in B cells from diabetes mellitus patients. Altered TLR function is further evidenced by demonstration of an unexpected, albeit modest 'anti-inflammatory' function for TLR4. Importantly, B cells from diabetes mellitus patients fail to secrete IL-10, an anti-inflammatory cytokine implicated in inflammatory disease resolution, under a variety of TLR-stimulating conditions. Comparative analyses of B cells from patients with a second chronic inflammatory disease, periodontal disease, indicated that some alterations in B cell TLR function associate specifically with diabetes mellitus.

CONCLUSIONS/INTERPRETATION

Altered TLR function in B cells from diabetes mellitus patients increases inflammation by two mechanisms: elevation of pro-inflammatory IL-8 and lack of anti-inflammatory/protective IL-10 production.

Moesin-induced signaling in response to lipopolysaccharide in macrophages

BACKGROUND AND OBJECTIVE

Many physiological and pathophysiological conditions are attributable in part to cytoskeletal regulation of cellular responses to signals. Moesin (membrane-organizing extension spike protein), an ERM (ezrin, radixin and moesin) family member, is involved in lipopolysaccharide (LPS)-mediated events in mononuclear phagocytes; however, its role in signaling is not fully understood. The aim of this study was to investigate the LPS-induced moesin signaling pathways in macrophages.

MATERIAL AND METHODS

Macrophages were stimulated with 500 ng/mL LPS in macrophage serum-free medium. For blocking experiments, cells were pre-incubated with anti-moesin antibody. Moesin total protein and phosphorylation were studied with western blotting. Moesin mRNA was assessed using quantitative real-time PCR. To explore binding of moesin to LPS, native polyacrylamide gel electrophoresis (PAGE) gel shift assay was performed. Moesin immunoprecipitation with CD14, MD-2 and Toll-like receptor 4 (TLR4) and co-immunoprecipitation of MyD88-interleukin-1 receptor-associated kinase (IRAK) and IRAK-tumor necrosis factor receptor-activated factor 6 (TRAF6) were analyzed. Phosphorylation of IRAK and activities of MAPK, nuclear factor kappaB (NF-kappaB) and IkappaBalpha were studied. Tumor necrosis factor alpha, interleukin-1beta and interferon beta were measured by ELISA.

RESULTS

Moesin was identified as part of a protein cluster that facilitates LPS recognition and results in the expression of proinflammatory cytokines. Lipopolysaccharide stimulates moesin expression and phosphorylation by binding directly to the moesin carboxyl-terminus. Moesin is temporally associated with TLR4 and MD-2 after LPS stimulation, while CD14 is continuously bound to moesin. Lipopolysaccharide-induced signaling is transferred downstream to p38, p44/42 MAPK and NF-kappaB activation. Blockage of moesin function interrupts the LPS response through an inhibition of MyD88, IRAK and TRAF6, negatively affecting subsequent activation of the MAP kinases (p38 and ERK), NF-kappaB activation and translocation to the nucleus.

CONCLUSION

These results suggest an important role for moesin in the innate immune response and TLR4-mediated pattern recognition in periodontal disease.

PDK1 regulates chemotaxis in human neutrophils

Phosphoinositide-dependent kinase (PDK1) plays a central role in signal transduction mediated by phosphatidylinositol 3-kinases (PI3K) and regulates cellular functions in neutrophils. Neutrophils from individuals diagnosed with localized aggressive periodontitis (LAP) present an in vivo phenotype with depressed chemotaxis. The aim of this study was to test the hypothesis that PDK1 regulates chemotaxis in neutrophils and is responsible for the abnormal neutrophil chemotaxis LAP. Neutrophil chemotaxis was significantly suppressed by the PDK1 inhibitor staurosporine. When cells were transfected with PDK1 siRNA, there was a significant reduction in chemotaxis, while superoxide generation was not significantly affected. In primary neutrophils from persons with LAP, PDK1 expression and activation levels were significantly reduced, and this reduction was associated with the reduced phosphorylation of Akt (Thr308) and chemotaxis. Analysis of these data demonstrates that PDK1 is essential for the chemotactic migration of neutrophils, and in the absence of PDK1, neutrophil chemotaxis is impaired.

Apoptosis in gingival overgrowth tissues

Variations in the balance between cell proliferation and apoptosis could contribute to the etiology of gingival overgrowth. The aim of this study was to test the hypothesis that, in fibrotic gingival lesions, fibroblast proliferation is stimulated and apoptosis is decreased. Apoptotic index, caspase 3 expression, the proliferative index, FOXO1 expression, and histological inflammation were measured in situ. Analysis of data showed that apoptosis decreased in all forms of gingival overgrowth examined (p < 0.05), and inflammation caused a small but significant increase compared with non-inflamed tissues (p < 0.05). The greatest decrease of apoptosis occurred in the most fibrotic tissues. Cell proliferation was elevated in all forms of gingival overgrowth tested, independent of inflammation (p < 0.05). To identify potential mechanisms of transcriptional regulation of apoptosis, we assessed FOXO1 and caspase 3 expression levels and found them to correlate well with diminished apoptosis. Analysis of data suggests that increased fibroblast proliferation and a simultaneous decrease in apoptosis contribute to gingival overgrowth.

Epithelial and connective tissue cell CTGF/CCN2 expression in gingival fibrosis

Gingival overgrowth is a side effect of certain medications and occurs in non-drug-induced forms either as inherited (human gingival fibromatosis) or idiopathic gingival overgrowth. The most fibrotic drug-induced lesions develop in response to therapy with phenytoin; the least fibrotic lesions are caused by cyclosporin A; and intermediate fibrosis occurs in nifedipine-induced gingival overgrowth. Connective tissue growth factor (CTGF/CCN2) expression is positively related to the degree of fibrosis in these tissues. The present study has investigated the hypothesis that CTGF/CCN2 is expressed in human gingival fibromatosis tissues and contributes to this form of non-drug-induced gingival overgrowth. Histopathology/immunohistochemistry studies showed that human gingival fibromatosis lesions are highly fibrotic, similar to phenytoin-induced lesions. Connective tissue CTGF/CCN2 levels were equivalent to the expression in phenytoin-induced gingival overgrowth. The additional novel observation was made that CTGF/CCN2 is highly expressed in the epithelium of fibrotic gingival tissues. This finding was confirmed by in situ hybridization. Real-time polymerase chain reaction (PCR) analyses of RNA extracted from drug-induced gingival overgrowth tissues for CTGF/CCN2 were fully consistent with these findings. Finally, normal primary gingival epithelial cell cultures were analysed for basal and transforming growth factor beta1 (TGF-beta1) or lysophosphatidic acid-stimulated CTGF/CCN2 expression at protein and RNA levels. These data indicate that fibrotic human gingival tissues express CTGF/CCN2 in both the epithelium and connective tissues; that cultured gingival epithelial cells express CTGF/CCN2; and that lysophosphatidic acid further stimulates CTGF/CCN2 expression. These findings suggest that interactions between epithelial and connective tissues could contribute to gingival fibrosis.

Topical H2 antagonist prevents periodontitis in a rabbit model

Cimetidine is a powerful H2 receptor antagonist that eliminates histamine's effects on chemotaxis, phagocytosis, and superoxide anion production by phagocytes. The purpose of this study was to analyze the clinical and histopathological changes associated with experimental periodontitis in rabbits in response to topically applied cimetidine. Experimental periodontitis was induced in 21 New Zealand White rabbits using Porphyromonas gingivalis (10(9) CFU) topically applied three times a week for a 6-week period to previously ligatured teeth. Topical application of cimetidine in a liposome carrier for the prevention of periodontitis was evaluated in four groups of four animals each: 1, 10, and 100 mg/ml and no treatment (positive control). In addition, there was a vehicle group (n = 3) that received liposome preparation (carrier) only, and two animals with ligature application alone served as negative controls. Periodontal disease was quantified by direct visualization and radiographical evaluation of bone loss on defleshed skulls and by histological analyses of sections stained with hematoxylin-eosin and tartrate-resistant acid phosphatase. In the no-treatment (positive control) and liposome (vehicle) groups, direct visualization and radiological measurements revealed statistically significant bone loss compared to the negative control. Application of cimetidine at all concentrations tested inhibited inflammation and bone loss by >90%. Histological findings revealed that ligated sites of the positive control and vehicle groups showed significant reduction in bone level (P < 0.05) compared to the three cimetidine groups, with a marked decrease in inflammation. The findings of this study provide morphological and histological evidence that topically active cimetidine is a potent inhibitor of P. gingivalis-elicited periodontal inflammation, arresting and/or preventing tissue destruction and influencing cell populations present in the inflammatory cell infiltrate.

RvE1 protects from local inflammation and osteoclast- mediated bone destruction in periodontitis

Periodontitis is a well-appreciated example of leukocyte-mediated bone loss and inflammation that has pathogenic features similar to those observed in other inflammatory diseases such as arthritis. Resolvins are a new family of bioactive products of omega-3 fatty acid transformation circuits initiated by aspirin treatment that counter proinflammatory signals. Because it is now increasingly apparent that local inflammation plays a critical role in many diseases, including cardiovascular disease, atherosclerosis, and asthma, experiments were undertaken to evaluate the actions of the newly described EPA-derived Resolvin E1 (RvE1) in regulation of neutrophil tissue destruction and resolution of inflammation. The actions of an aspirin-triggered lipoxin (LX) analog and RvE1 in a human disease, localized aggressive periodontitis (LAP), were determined. Results indicate that neutrophils from LAP are refractory to anti-inflammatory molecules of the LX series, whereas LAP neutrophils respond to RvE1. In addition, RvE1 specifically binds to human neutrophils at a site that is functionally distinct from the LX receptor. Consistent with these potent actions, topical application of RvE1 in rabbit periodontitis conferred dramatic protection against inflammation induced tissue and bone loss associated with periodontitis.

Enhanced superoxide release and elevated protein kinase C activity in neutrophils from diabetic patients: association with periodontitis

Inflammation and oxidative stress are important factors in the pathogenesis of diabetes and contribute to the pathogenesis of diabetic complications. Periodontitis is an inflammatory disease that is characterized by increased oxidative stress, and the risk for periodontitis is increased significantly in diabetic subjects. In this study, we examined the superoxide (O(2)(-))-generating reduced nicotinamide adenine dinucleotide phosphate-oxidase complex and protein kinase C (PKC) activity in neutrophils. Fifty diabetic patients were grouped according to glycemic control and the severity of periodontitis. Neutrophils from diabetic patients with moderate [amount of glycated hemoglobin (HbA(1c)) between 7.0% and 8.0%] or poor (HbA(1c) >8.0%) glycemic control released significantly more O(2)(-) than neutrophils from diabetic patients with good glycemic control (HbA(1c) <7.0%) and neutrophils from nondiabetic, healthy individuals upon stimulation with 4beta-phorbol 12-myristate 13-acetate or N-formyl-Met-Leu-Phe. Depending on glycemic status, neutrophils from these patients also exhibited increased activity of the soluble- and membrane-bound forms of PKC, elevated amounts of diglyceride, and enhanced phosphorylation of p47-phox during cell stimulation. In addition, we report a significant correlation between glycemic control (HbA(1c) levels) and the severity of periodontitis in diabetic patients, suggesting that enhanced oxidative stress and increased inflammation exacerbate both diseases. Thus, hyperglycemia can lead to a novel form of neutrophil priming, where elevated PKC activity results in increased phosphorylation of p47-phox and O(2)(-) release.

Connective tissue growth factor in drug-induced gingival overgrowth

BACKGROUND

Drug-induced gingival overgrowth is a known side effect of certain chemotherapeutic agents used for the treatment of systemic disorders. The pathogenesis and mechanisms responsible for this condition are not fully understood. This study assesses for the presence and localization of connective tissue growth factor (CTGF) in drug-induced gingival overgrowth tissues. CTGF immunostaining was compared with sections stained with transforming growth factor (TGF)-beta1 and CD31 antibodies in order to investigate possible pathogenic mechanisms.

METHODS

Gingival overgrowth samples were obtained from patients undergoing therapy with phenytoin (n = 9), nifedipine (n = 4), cyclosporin A (n = 5), and control tissues from systemically healthy donors (n = 9). Tissue sections were subjected to peroxidase immunohistochemistry and were stained with CTGF and TGF-beta1 polyclonal primary antibodies. Possible relationships between CTGF staining and angiogenesis were also studied using an anti-CD31 antibody as a marker for endothelial cells. Staining was analyzed by computer-assisted quantitative and semiquantitative methodology at 5 defined sites in all samples based on the location of specific landmarks including epithelium and underlying connective tissues.

RESULTS

Cellular and extracellular CTGF content in phenytoin gingival overgrowth tissues was significantly (P<0.05) higher compared to the other gingival overgrowth tissues and the controls. Higher CTGF staining in phenytoin gingival overgrowth tissues was accompanied by an increased abundance of fibroblasts and connective tissue fibers. No strong association of CTGF staining with TGF-beta1 or CD31 staining was found.

CONCLUSIONS

The data from the present study show significantly higher CTGF staining in phenytoin-induced gingival overgrowth tissues compared to controls, cyclosporin A-, or nifedipine-induced gingival overgrowth. Moreover, semiquantitative analyses of histologic samples support the concept that the phenytoin overgrowth tissues are fibrotic. These associations suggest a possible role for CTGF in promoting development of fibrotic lesions in phenytoin-induced gingival overgrowth.

Clinical effects of periodontal therapy on the severity of cyclosporin A-induced gingival hyperplasia

BACKGROUND

Gingival hyperplasia (GH) is a major side effect associated with cyclosporin A (CsA) therapy. The condition is further augmented due to the gingival inflammation. In this study, the effects of initial periodontal therapy and gingival curettage are analyzed in a group of patients with clinically significant (>30%) CsA-induced gingival hyperplasia.

METHODS

The test group of 15 patients received oral hygiene instructions, supra- and subgingival scaling, polishing, and gingival curettage only oral hygiene instructions were given to 16 control subjects. Plaque index (PI), gingival index (GI), calculus index (CI), periodontal probing depth (PD), and gingival hyperplasia were recorded at baseline and repeated 8 weeks after treatment. Current doses of immunosuppressive agents, serum concentrations of CsA, and duration of CsA therapy were recorded as the pharmacological parameters.

RESULTS

Statistical evaluation revealed that all clinical variables showed statistical decreases compared to baseline in the treated patients, while none of the parameters changed significantly in the control group. Initial GH scores of 53.63% in controls and 53.40% in the treated patients were 52.83% and 32.13% following treatment, respectively. A difference of 21.27% in the severity of treated GH was accompanied by a 0.56 decrease in GI scores in the test group.

CONCLUSIONS

Compared to the initial observations, the results suggested that nearly 60% of the condition could be of fibrotic origin. Initial periodontal therapy and curettage resulted in the resolution of the inflammation in CsA-induced GH. Further investigation of the treated patients has shown that 7 out of 15 patients (47%) in the test group responded well and their GH scores decreased below 30% at the end of the study. The treatment in this study was effective in eliminating the necessity of more extensive surgical modes of treatment, such as gingivectomy, in 47% of cases.

Analysis of peripheral blood leukocytes in patients with cyclosporine A-induced gingival hyperplasia

BACKGROUND

Gingival overgrowth is one of the major adverse effects of the immunosuppressive drug cyclosporine A (CsA). Although several studies have attempted to determine the immunological mechanisms of gingival hyperplasia (GO) due to CsA therapy, the pathogenesis remains unclear. In this study, the distribution of the peripheral blood leukocytes in a group of renal transplant patients undergoing CsA therapy was analyzed and possible correlations of periodontal and pharmacological variables to lymphocyte subpopulations, natural killer cells, and monocytes investigated.

METHODS

Thirty-six patients were classified into 2 groups of 18 each according to the degree of gingival overgrowth. The periodontal evaluation included plaque index (PI), gingival index (GI), gingival overgrowth (GO), calculus index (CI), and probing depth (PD). The pharmacological variables of current doses of the therapeutic serum levels of CsA were investigated. The peripheral blood leukocytes were studied by 2-color flow cytometric analysis using anti-human CD2, CD3, CD4, CD8, CD11b, CD11c, CD16, CD19, HLA-DR, and CD3+HLA-DR+ monoclonal antibodies.

RESULTS

Statistical evaluation revealed that none of the pharmacological variables varied between the 2 groups. Responders (GO >30%) had significantly higher GI, PD, and GO scores compared to nonresponders (GO < or =30%). Of the immunological parameters studied, only CD2 was higher in the responder group. None of the clinical parameters correlated to the immunological values.

CONCLUSIONS

The results of this study may be useful in explaining the underlying mechanisms of drug-induced gingival overgrowth. Several previously unsuspected cells and accessory activation mechanisms for T lymphocytes could play a role in the pathogenesis.

The effect of verapamil on the prevalence and severity of cyclosporine-induced gingival overgrowth in renal allograft recipients

Cyclosporine A (CsA) and verapamil are two agents used in renal transplantation, both of which are suspected of inducing gingival overgrowth. This study was conducted to investigate the effect of verapamil on the severity and prevalence of CsA-induced gingival overgrowth. Fifty-one (51) renal transplant recipients (total group) of whom 22 were using only CsA (Group A) and 29 of whom were prescribed CsA + verapamil (Group B) were evaluated for various periodontal and pharmacological parameters. No statistically significant differences were found in age, sex, plaque index, gingival index, calculus index, probing depth, CsA oral dose, CsA whole blood level, duration of CsA therapy, azathioprine dose, and prednisolone dose. Although the prevalence of the gingival overgrowth was more pronounced in CsA + verapamil group compared to CsA group (51.72% vs. 40.91%), the difference was not statistically significant. Similarly, the severity of gingival overgrowth, although more manifest in CsA + verapamil group than CsA patients (34.24% vs. 28.91%), was not significantly different. Gingival overgrowth scores in the main group, CsA, and CsA + verapamil groups were found to be positively correlated to periodontal probing depths (r = 0.60, r = 0.70, r = 0.52, respectively) and the gingival index (r = 0.60, r = 0.70, r = 0.54, respectively). CsA oral dose, whole blood level, and duration of CsA therapy were not found to be correlated with the gingival overgrowth in either group. Likewise, the dose of verapamil and the duration of verapamil therapy were not correlated with the gingival overgrowth in Group B. This study indicates that verapamil, when prescribed as the calcium channel blocker in renal transplant patients, has no augmenting effect on the severity and the prevalence of CsA-induced gingival overgrowth.

Periodontal management of Glanzmann's thrombasthenia: report of 3 cases

Glanzmann's thrombasthenia was reported and described as a bleeding diathesis seen in children and characterized by diminished clot retraction. It is an autosomal recessive bleeding disorder. The disease is marked by frequent mucocutaneous hemorrhages either due to defective function of the platelets or lack of fibrinogen binding membrane receptor glycoproteins IIb/IIIa which are located on the surface of the platelets. Case reports on 3 siblings, a girl of 11, and 2 boys of 12 and 16 years old with Glanzmann's thrombasthenia are reviewed. The major complaint of the patients was gingival bleeding. Periodontal treatment was performed under platelet transfusion and proper oral hygiene instruction was given. The patients were followed for 6 months and no periodontal complications developed during this time. Proper periodontal care for such patients is essential both for local and systemic health.

Evaluation of the frequency of HLA determinants in patients with gingival overgrowth induced by cyclosporine-A

This study has been designed to investigate the immunogenetic susceptibility of Cyclosporine-A (CsA) immunosuppressed renal transplant patients to development of gingival overgrowth, and the amplifying effect of calcium channel blockers on the severity of this clinical entity. 52 renal transplant recipients were selected and initially grouped as follows: group (Gp)1: CsA (n = 7); Gp 2: CsA + verapamil (n = 26); Gp 3: CsA + diltiazem (n = 6); Gp 4: CsA + nifedipine (n = 13). These groups were not found to be significantly different in age, sex, plaque index (PlI), gingival index (GI), calculus index, periodontal probing depth, serum CsA level, or duration of CsA therapy (p > 0.05). No significant (p > 0.05) additive effect of the calcium channel blockers on the gingival overgrowth (GO) was assessed. The main group (n = 52) was evaluated for the correlations between the clinical and the pharmacological variables and the GO. GI (rs = 0.60) and the periodontal probing depth (rs = 0.71) were found to be moderately correlated with the GO. The patients were regrouped based on the severity of overgrowth and recognized as responders (n = 26) and nonresponders (n = 26). Age, sex, calculus index, serum CsA level, duration of the CsA therapy, were not statistically different among these groups (p > 0.05). PlI, GI, periodontal probing depth, and GO were significantly higher in the responder group (p > 0.05). Analysis of HLA distribution of the responders and the nonresponders and comparison with the controls (n = 3731) revealed that a statistically significant (p < 0.001)% of the nonresponders were positive for HLA-DR1. These data would indicate that an immunogenetic predisposition should be suspected in the pathogenesis of the entity, and that HLA-DR1 would have a protective rôle against gingival overgrowth induced by CsA.

Association between HLA antigens and early onset periodontitis

HLA-A, B, C and DR antigen frequencies were determined in a group of patients with juvenile periodontitis and rapidly progressive periodontitis. In juvenile periodontitis patients, HLA-A24 and DR4 were found at a significantly higher level than in the control group, and in rapidly progressive periodontitis patients, A9 and DR4 were found at a significantly higher level than the control group. The presence of these antigens gives evidence as to the susceptibility of various forms of early onset periodontitis.