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.

Periodontal Stem Cells Synthesize Maresin Conjugate in Tissue Regeneration 3.

Periodontal disease is a significant public health problem worldwide. Excess unresolved chronic inflammation destroys the periodontal tissues that surround and support the teeth, and efforts to control inflammation by removal of bacterial deposits on the teeth have limited long-term impact. Likewise, procedures aimed at regeneration of the periodontal tissues have shown limited success. Recent advances in stem cell research have shown promising novel prospects for the use of periodontal ligament stem cells (PDLSCs) in tissue regeneration; however, control of inflammation remains a barrier. Human PDLSCs have been shown to release specialized proresolving lipid mediators (SPMs) that modulate the immune response and promote resolution of inflammation, tissue repair, and regeneration. Studies on stem cell biology in periodontology have also been limited by the lack of a good large animal model. Herein, we describe PDLSC biology of the Yorkshire pig (pPDLSCs). pPDLSCs were isolated and characterized. Using lipid mediator profiling, we demonstrate for the first time that pPDLSCs biosynthesize cysteinyl-containing SPMs (cys-SPMs), specifically, maresin conjugates in tissue regeneration 3 (MCTR3) and its authentication using liquid chromatography/tandem mass spectrometry. The exogenous addition of the n-3 precursor docosahexaenoic acid enhances MCTR3 biosynthesis. Using immunocytochemistry, we show that pPDLSCs express 4 of the SPM biosynthetic pathway enzymes necessary for SPM biosynthesis, including 5-lipoxygenase, 12-lipoxygenase, and 15-lipoxygenase-1. In addition, we identified and quantified the cytokine/chemokine profile of pPDLSCs using a 13-plex immunology multiplex assay and found that the pretreatment of pPDLSCs with MCTR3 in an inflammatory environment reduced the production of acute and chronic proinflammatory cytokines/chemokines. Together, these results suggest that enhancing resolution of inflammation pathways and mediators may be a possible key early event in predictable periodontal regeneration.

Host Modulation and Treatment of Periodontal Disease.

Periodontitis is the sixth-most prevalent disease in the world and the first cause for tooth loss in adults. With focus shifted to the inflammatory/immune response in the pathogenesis of periodontitis, there is a critical need to evaluate host modulatory agents. Synthetic and biological disease-modifying antirheumatic drugs are a cornerstone for the treatment of inflammatory diseases. Recent prospective cohort studies showed that synthetic disease-modifying antirheumatic drugs improved periodontal clinical parameters following nonsurgical periodontal treatment in patients with rheumatoid arthritis. Treatment with recombinant humanized monoclonal antibodies against CD20 (rituximab) and IL-6 receptor (tocilizumab), the latter also in clinical trials for the treatment of COVID-19 pneumonia, resulted in decreased periodontal inflammation and improved periodontal status. Studies on the effect of TNF-α inhibitors in patients with periodontitis yielded inconsistent results. Recent data suggest that probiotics provide anti-inflammatory clinical benefit, as do nutritional supplements, such as n-3 fatty acids, when combined with periodontal therapy. Probiotics reduce the production of proinflammatory cytokines/chemokines by suppressing NF-κB pathways and promote the accumulation of T regulatory cells. Statins, like aspirin, have been shown to exhibit anti-inflammatory and bone-preserving actions by upregulating production of Specialized Proresolving Mediators (SPMs). Currently, there is insufficient scientific support for the topical delivery of statins or bisphosphonates as adjuncts to periodontal therapy. Here, we present a critical review of the most recent host modulatory agents applied in humans and the key immune pathways that they target. Emerging evidence from novel drug candidates, including SPMs and complement inhibitors as previously studied in animal models and currently in human clinical trials, suggests future availability of adjunctive therapeutic strategies for the management of periodontitis.

Serum Amyloid A Contributes to Chronic Apical Periodontitis via TLR2 and TLR4.

In the current concept of bacterial infections, pathogen-associated molecular patterns (PAMPs) derived from pathogens and damage-associated molecular patterns (DAMPs) released from damaged/necrotic host cells are crucial factors in induction of innate immune responses. However, the implication of DAMPs in apical and marginal periodontitis is unknown. Serum amyloid A (SAA) is a DAMP that is involved in the development of various chronic inflammatory diseases, such as rheumatoid arthritis. In the present study, we tested whether SAA is involved in the pathogenesis of periapical lesions, using human periapical surgical specimens and mice deficient in SAA and Toll-like receptors (TLR). SAA1/2 was locally expressed in human periapical lesions at the mRNA and protein levels. The level of SAA protein appeared to be positively associated with the inflammatory status of the lesions. In the development of mouse periapical inflammation, SAA1.1/2.1 was elevated locally and systemically in wild-type (WT) mice. Although SAA1.1/2.1 double-knockout and SAA3 knockout mice had redundant attenuation of the extent of periapical lesions, these animals showed strikingly improved inflammatory cell infiltration versus WT. Recombinant human SAA1 (rhSAA1) directly induced chemotaxis of WT neutrophils in a dose-dependent manner in vitro. In addition, rhSAA1 stimulation significantly prolonged the survival of WT neutrophils as compared with nonstimulated neutrophils. Furthermore, rhSAA1 activated the NF-κB pathway and subsequent IL-1α production in macrophages in a dose-dependent manner. However, TLR2/TLR4 double deficiency substantially diminished these SAA-mediated proinflammatory responses. Taken together, the SAA-TLR axis plays an important role in the chronicity of periapical inflammation via induction of inflammatory cell infiltration and prolonged cell survival. The interactions of PAMPs and DAMPs require further investigation in dental/oral inflammation.

Resolving Macrophages Counter Osteolysis by Anabolic Actions on Bone Cells.

Progression of inflammatory osteolytic diseases, including rheumatoid arthritis and periodontitis, is characterized by increased production of proinflammatory mediators and matrix-degrading enzymes by macrophages and increased osteoclastic activity. Phenotypic changes in macrophages are central to the healing process in virtually all tissues. Using a murine model of periodontitis, we assessed the timing of macrophage phenotypic changes and the impact of proresolving activation during inflammatory osteolysis and healing. Proinflammatory macrophage activation and TNF-α overproduction within 3 wk after induction of periodontitis was associated with progressing bone loss. Proresolving activation within 1 wk of stimulus removal and markers of resolving macrophages (IL-10, TGF-ß, and CD206) correlated strongly with bone levels. In vivo macrophage depletion with clodronate liposomes prevented bone resorption but impaired regeneration. Induction of resolving macrophages with rosiglitazone, a PPAR-γ agonist, led to reduced bone resorption during inflammatory stimulation and increased bone formation during healing. In vitro assessment of primary bone marrow-derived macrophages activated with either IFN-γ and LPS (proinflammatory activation) or IL-4 (proresolving activation) showed that IL-4-activated cells have enhanced resolving functions (production of anti-inflammatory cytokines; migration and phagocytosis of aged neutrophils) and exert direct anabolic actions on bone cells. Cystatin C secreted by resolving but not inflammatory macrophages explained, in part, the macrophage actions on osteoblasts and osteoclasts. This study supports the concept that therapeutic induction of proresolving functions in macrophages can recouple bone resorption and formation in inflammatory osteolytic diseases.

Task Force on Design and Analysis in Oral Health Research: Host-Microbiome Interactions in Dysbiosis.

Knowledge Transfer Statement: This article discusses the proceedings of the conference organized by the Task Force on Design and Analysis in Oral Health Research on the new advances in host-microbiome interactions, analytical methods, and their implication in inflammatory periodontal disease management.

Current and Emerging Treatments for Postsurgical Cleft Lip Scarring: Effectiveness and Mechanisms.

Cleft lip with or without cleft palate is the most common congenital malformation of the head and the third-most common birth defect. Surgical repair of the lip is the only treatment and is usually performed during the first year of life. Hypertrophic scar (HTS) formation is a frequent postoperative complication that impairs soft tissue form, function, or movement. Multiple lip revision operations are often required throughout childhood, attempting to optimize aesthetics and function. The mechanisms guiding HTS formation are multifactorial and complex. HTS is the result of dysregulated wound healing, where excessive collagen and extracellular matrix proteins are deposited within the wound area, resulting in persistent inflammation and resultant fibrosis. Many studies support the contribution of dysregulated, exaggerated inflammation in scar formation. Fibrosis and scarring result from chronic inflammation that interrupts tissue remodeling in normal wound healing. Failure of active resolution of inflammation pathways has been implicated. The management of HTS has been challenging for clinicians, since current therapies are minimally effective. Emerging evidence that specialized proresolving mediators of inflammation accelerate wound healing by preventing chronic inflammation and allowing natural uninterrupted tissue remodeling suggests new therapeutic opportunities in the prevention and management of HTS.

Clinical and microbiological parameters of naturally occurring periodontitis in the non-human primate Macaca mulatta.

Background: Non-human primates appear to represent the most faithful model of human disease, but to date the oral microbiome in macaques has not been fully characterized using next-generation sequencing. Objective: In the present study, we characterized the clinical and microbiological features of naturally occurring periodontitis in non-human primates (Macaca mulatta). Design: Clinical parameters of periodontitis including probing pocket depth (PD) and bleeding on probing (BOP) were measured in 40 adult macaques (7-22 yrs), at six sites per tooth. Subgingival plaque was collected from diseased and healthy sites, and subjected to 16S rDNA sequencing and identification at the species or higher taxon level. Results: All macaques had mild periodontitis at minimum, with numerous sites of PD ≥ 4 mm and BOP. A subset (14/40) had moderate-severe disease, with >2 sites with PD ≥ 5mm, deeper mean PD, and more BOP. Animals with mild vs moderate-severe disease were identical in age, suggesting genetic heterogeneity. 16S rDNA sequencing revealed that all macaques had species that were identical to those in humans or closely related to human counterparts, including Porphyromonas gingivalis which was present in all animals. Diseased and healthy sites harboured distinct microbiomes; however there were no significant differences in the microbiomes in moderate-severe vs. mild periodontitis. Conclusions: Naturally occurring periodontitis in older macaques closely resembles human adult periodontitis, thus validating a useful model to evaluate novel anti-microbial therapies.

Porphyromonas gingivalis-induced production of reactive oxygen species, tumor necrosis factor-α, interleukin-6, CXCL8 and CCL2 by neutrophils from localized aggressive periodontitis and healthy donors: modulating actions of red blood cells and resolvin E1.

BACKGROUND AND OBJECTIVES: Porphyromonas gingivalis is regarded as a significant contributor in the pathogenesis of periodontitis and certain systemic diseases, including atherosclerosis. P. gingivalis occasionally translocates from periodontal pockets into the circulation, where it adheres to red blood cells (RBCs). This may protect the bacterium from contact with circulating phagocytes without affecting its viability. MATERIAL AND METHODS: In this in vitro study, we investigated whether human peripheral blood neutrophils from 10 subjects with localized aggressive periodontitis (LAgP) and 10 healthy controls release the proinflammatory cytokines interleukin (IL)-6, tumor necrosis factor α (TNF-α), the chemokine (C-X-C motif) ligand 8 (CXCL8; also known as IL-8) and chemokine (C-C motif) ligand 2 (CCL2; also known as monocyte chemotactic protein-1) and intracellular reactive oxygen species (ROS) in response to challenge with P. gingivalis. In addition, the impact of RBC interaction with P. gingivalis was investigated. The actions of resolvin E1 (RvE1), a known regulator of P. gingivalis induced neutrophil responses, on the cytokine and ROS responses elicited by P. gingivalis in cultures of neutrophils were investigated. RESULTS: Upon stimulation with P. gingivalis, neutrophils from subjects with LAgP and healthy controls released similar quantities of IL-6, TNF-α, CXCL8, CCL2 and intracellular ROS. The presence of RBCs amplified the release of IL-6, TNF-α and CCL2 statistically significant in both groups, but reduced the generation of ROS in the group of healthy controls, and showed a similar tendency in the group of subjects with LAgP. RvE1 had no impact on the production of intracellular ROS, TNF-α, IL-6, CXCL8 and CCL2 by neutrophils from either group, but tended to reduce the generation of ROS in subjects with LAgP in the absence of RBCs. CONCLUSIONS: Our data support that binding to RBCs protects P. gingivalis from ROS and concomitantly enhances neutrophil release of proinflammatory cytokines providing a selective advantage for P. gingivalis growth.

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-1ß, 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.

Diet-Induced Obesity and Its Differential Impact on Periodontal Bone Loss.

Obesity is associated with abnormal lipid metabolism and impaired bone homeostasis. The aim of our study was to investigate the impact of specific elevated fatty acid (FA) levels on alveolar bone loss in a Porphyromonas gingivalis-induced model of periodontal disease and to analyze underlying cellular mechanisms in bone-resorbing osteoclasts and bone-forming osteoblasts in mice. Four-week-old male C57BL/6 mice were randomly divided in groups and subjected to a palmitic acid (PA)- or oleic acid (OA)-enriched high-fat diet (HFD) (20% of calories from FA) or a normal caloric diet (C group) (10% of calories from FA) for 16 wk. Starting at week 10, mice were infected orally with P. gingivalis (W50) or placebo to induce alveolar bone loss. Animals were sacrificed, and percentage fat, serum inflammation (tumor necrosis factor [TNF]-α), and bone metabolism (osteocalcin [OC], carboxy-terminal collagen crosslinks [CTX], and N-terminal propeptides of type I procollagen [P1NP]) markers were measured. Osteoblasts and osteoclasts were cultured in the presence of elevated PA or OA levels and exposed to P. gingivalis. Animals on FA-enriched diets weighed significantly more compared with animals on a normal caloric diet (P < 0.05). Both obese groups had similar percentages of fat (P = nonsignificant); however, alveolar bone loss was significantly greater in animals that were on the PA-enriched HFD (P < 0.05). TNF-α levels were highest in the PA group (P < 0.001) and increased in all groups in response to P. gingivalis inoculation (P < 0.01), whereas bone remodeling markers OC, CTX, and P1NP were lowest in the PA group (P < 0.001) and highest in the C group. Bacterial challenge decreased bone metabolism markers in all groups (P < 0.01). Further, osteoclasts showed an augmented inflammatory response to P. gingivalis in the presence of hyperlipidemic PA levels as opposed to OA cultures, which responded similarly to controls. These findings indicate that the specific FA profile of diet rather than weight gain and obesity alone modulates bone metabolism and can therefore influence alveolar bone loss.

The complement system and its role in the pathogenesis of periodontitis: current concepts.

Periodontitis is a highly prevalent inflammatory disease in tooth supporting tissues, induced by bacteria growing in a biofilm on tooth surfaces. Components of the complement system are present in the periodontal tissue and the system is activated in periodontitis. Continuous complement activation and modulation by bacteria within the biofilm in periodontal pockets, however, may enhance local tissue destruction, providing the biofilm with both essential nutrients and space to grow. A more profound understanding of the mechanisms involved in complement-derived tissue degradation may facilitate the development of new treatment concepts for periodontitis. Further studies on the role of complement in periodontitis pathogenesis may also contribute to the understanding of why some individuals fail to resolve periodontitis. Here, we review evidence that links complement to the pathogenesis of periodontitis with an emphasis on interaction of complement with bacteria from periodontitis-associated biofilm.

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.

Subgingival microbial profiles of Sudanese patients with aggressive periodontitis.

BACKGROUND AND OBJECTIVE: Aggressive periodontitis (AgP) is prevalent and shows a rapid course in African individuals. Although a strong focus has been placed on Aggregatibacter actinomycetemcomitans, new methods support the existence of a complex subgingival microflora in AgP. The purpose of the present study was to map the subgingival microbiota as well as explore the presence of A. actinomycetemcomitans and the JP2 clone in a group of Sudanese individuals with AgP, using different analytical methods. MATERIAL AND METHODS: A study population consisting of 19 patients with AgP was recruited from patients seeking treatment at University of Science and Technology (UST) in Khartoum. Fifteen healthy subjects were included as controls. Plaque samples were analyzed for 272 taxa using human oral microbe identification microarrays and for 26 periodontal taxa using DNA-DNA hybridization checkerboard. Conventional polymerase chain reaction (PCR) was applied for the detection of A. actinomycetemcomitans and the JP2 clone in plaque. Saliva from patients with AgP was analyzed using quantitative PCR (qPCR) for the detection of A. actinomycetemcomitans. RESULTS: Eubacterium yurii was detected more frequently in patients with AgP than in controls, and E. nodatum was found in patients with AgP only. A. actinomycetemcomitans was found in plaque samples of two (12%) patients by human oral microbe identification microarrays and in five (29%) patients with AgP by conventional PCR, as well as in six (32%) of the AgP saliva samples by qPCR. The JP2 clone was identified in only one patient. CONCLUSION: The classical periodontal pathogens were not present in high amounts in AgP in the population studied here. Species of Eubacterium, which are not typically associated with AgP, were often detected in individuals with disease. Using laboratory methods with different sensitivities and detection levels allowed identification of variances in microbial communities. The findings reported in this study provide a basis for the further understanding of AgP.

Docosahexaenoic Acid and Periodontitis in Adults: A Randomized Controlled Trial.

Periodontitis is a common chronic inflammatory disease initiated by bacteria, resulting in bone resorption, tooth loss, and systemic inflammation. Long-chain omega-3 fatty acids such as docosahexaenoic acid (DHA) reduce periodontitis in animals. We aimed to determine whether DHA supplementation with low-dose aspirin would reduce periodontitis in humans. We conducted a double-blind placebo-controlled parallel trial lasting 3 mo. Fifty-five adults with moderate periodontitis were randomized to 2,000 mg of DHA or identical soy/corn oil capsules. All participants received 81 mg of aspirin but received no other treatments. We analyzed the primary outcome of per-pocket change in pocket depth using mixed models among teeth with pocket depth ≥5 mm. Secondary outcomes assessed with generalized estimating equations included gingival index, plaque index, and bleeding on probing. Gingival crevicular fluid samples were analyzed for changes in high-sensitivity C-reactive protein (hsCRP) and interleukins 6 and 1ß (IL-6 and IL-1ß). Plasma was analyzed for changes in systemic inflammatory markers, including hsCRP. We confirmed adherence with erythrocyte fatty acid measurement. Forty-six participants completed the trial. While similar at baseline, the proportion of DHA in red blood cell plasma membranes increased from 3.6% ± 0.9% to 6.2% ± 1.6% in the intervention group but did not change among controls. DHA supplementation decreased mean pocket depth (-0.29 ± 0.13; p = .03) and gingival index (-0.26 ± 0.13; p = .04). Plaque index and bleeding on probing did not change. Significant adjusted differences were found between DHA and control for both gingival crevicular fluid hsCRP (-5.3 ng/mL, standard error [SE] = 2.4, p = .03) and IL-1ß (-20.1 pg/mL, SE = 8.2, p = .02) but not IL-6 (0.02 pg/mL, SE = 0.71, p = .98) or systemic hsCRP (-1.19 mg/L, SE = 0.90, p = .20). In this randomized controlled trial, aspirin-triggered DHA supplementation significantly improved periodontal outcomes in people with periodontitis, indicating its potential therapeutic efficacy (clinicaltrials.gov NCT01976806).

Recent advances in host defense mechanisms/therapies against oral infectious diseases and consequences for systemic disease.

The innate and adaptive immune systems are both crucial to oral disease mechanisms and their impact on systemic health status. Greater understanding of these interrelationships will yield opportunities to identify new therapeutic targets to modulate disease processes and/or increase host resistance to infectious or inflammatory insult. The topics addressed reflect the latest advances in our knowledge of the role of innate and adaptive immune systems and inflammatory mechanisms in infectious diseases affecting the oral cavity, including periodontitis and candidiasis. In addition, several potential links with systemic inflammatory conditions, such as cardiovascular disease, are explored. The findings elucidate some of the defense mechanisms utilized by host tissues, including the role of IL-17 in providing immunity to oral candidiasis, the antimicrobial defense of mucosal epithelial cells, and the pro-resolution effects of the natural inflammatory regulators, proresolvins and lipoxins. They also describe the role of immune cells in mediating pathologic bone resorption in periodontal disease. These insights highlight the potential for therapeutic benefit of immunomodulatory interventions that bolster or modulate host defense mechanisms in both oral and systemic disease. Among the promising new therapeutic approaches discussed here are epithelial cell gene therapy, passive immunization against immune cell targets, and the use of proresolvin agents.

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-1ß 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.