Diferencia en la expresión del ligando de receptor activador para el factor nuclear K B, en tejido tumoral frente a la infección por diferentes patógenos periodontales / Difference in receptor activator of nuclear factor K B expression in tumoral tissue by different periodontal pathogens

La enfermedad periodontal es una de las principales causas de pérdida dentaria. Clínicamente, esta patología, mediada por la desregulación del sistema inmune producto de una disbiosis ocurrida en el surco gingival, inicia con la inflamación de la encía y evoluciona con el daño irreversible de los tejidos que rodean el diente. El hueso alveolar es uno de los tejidos afectados esta patología, esto debido a la activación de osteoclastos por la sobreexpresión de la proteína RANKL en el huésped. El propósito de este trabajo es determinar el nivel de sobreexpresión de RANKL, en un modelo de células tumorales U2OS, frente a la infección con Porphyromonas gingivalis y Prevotella intermedia. Para identificar el nivel de RANKL, se definieron cuatro grupos: Un grupo control, no tratado; Grupo PG, tratado con P. gingivalis; Grupo PI, tratado con P. Intermedia; y un grupo PG+PI, tratado con ambas bacterias. El nivel relativo de la proteína RANKL fue determinado en el sobrenadante y en los extractos celulares de manera independiente, mediante la técnica Western blot. En sobrenadantes, el grupo PG mostró mayores niveles de RANKL comparados con PI (p < 0,05). En extractos celulares los niveles fueron mayores en el grupo PG+PI (p < 0,05). El grupo PI mostró los niveles más bajos de RANKL. La infección polimicrobiana resulta en una mayor expresión de RANKL en células tumorales U2OS, mientras que frente a la infección P. gingivalis, se observó mayor cantidad de RANKL soluble.

SUMMARY: Periodontal disease is one of the main causes of tooth loss. Clinically, this pathology, mediated by the deregulation of the immune system due to a dysbiosis occurred in the gingival sulcus, begins with the inflammation of the gum and evolves with the irreversible damage of the tissues that surround the tooth. Alveolar bone is one of the most affected tissues by this disease, due to the activation of osteoclasts by the upregulation of RANKL in the host. The aim of this study is to determine the increase of RANKL, in a U2OS tumor cells model, inoculated with Porphyromonas gingivalis and Prevotella intermedia. To identify the level of RANKL, four groups were defined: A control group, not treated; PG group, treated with P.gingivalis; PI group, treated with P. intermedia; and a PG+PI group, treated with both bacteria. The relative level of RANKL was determined in the supernatant and cell extracts independently, using the Western blot technique. In supernatants, the PG group showed higher RANKL levels compared to PI (p < 0.05). In cell extracts the levels were higher in the PG+PI group (p < 0.05.). The PI group showed the lowest levels of RANKL.Polymicrobial infection results in a greater expression of of soluble RANKL was observed.

The imbalance of Th17/Treg via STAT3 activation modulates cognitive impairment in P. gingivalis LPS-induced periodontitis mice.

Periodontitis is one of the most common oral diseases worldwide, and it is associated with various systemic diseases, including cognitive diseases. STAT3 regulates the inflammatory cascade and influences adaptive immunity by modulating Th17/Treg cell differentiation. In this study, we aimed to explore the effect of adaptive immunity inside and outside the brain on the association between periodontitis and cognitive impairment and understand the role of the STAT3 signaling pathway. We established Porphyromonas gingivalis LPS-induced periodontitis mice models by injecting P. gingivalis LPS into the gingival sulcus of mice. Behavioral tests showed that learning and memory abilities were impaired. The flow cytometry data showed an imbalance in the Th17/Treg ratio in the blood and brain samples of the mice. The expression of Th17-related cytokines (IL-1ß, IL-17A, IL-21, and IL-22) increased, whereas that of Treg-related cytokines (IL-2 and IL-10) decreased in both the blood and the brain. The level of LPS increased and the STAT3 signaling pathway was activated during this process. These effects were reversed by C188-9, a STAT3 inhibitor. In conclusion, P. gingivalis LPS-induced periodontitis may promote the occurrence and progression of cognitive impairment by modulating the Th17/Treg balance inside and outside the brain. The STAT3 signaling pathway may have immunoregulatory effects on the mouth-to-brain axis.

Clostridium butyricum Alleviates Gut Microbiota Alteration-Induced Bone Loss after Bariatric Surgery by Promoting Bone Autophagy.

Bariatric surgery is the most common and effective treatment of severe obesity; however, these bariatric procedures always result in detrimental effects on bone metabolism by underlying mechanisms. This study aims to investigate the skeletal response to bariatric surgery and to explore whether Clostridium butyricum alleviates gut microbiota alteration-induced bone loss after bariatric surgery. Consequently, male SD rats received Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) surgery, respectively, followed by body weight recording. The bone loss after bariatric surgery was further determined by dual-energy X-ray absorptiometry (DXA), micro-CT measurement, histologic analyses, and Western blot. Besides, 16S rDNA gene sequencing was performed to determine the gut microbiota alteration after surgery, and intervention with fecal microbiota from RYGB donor was conducted in obese SD rats, followed by C. butyricum administration. Accordingly, rats in the RYGB and SG groups maintained sustained weight loss, and DXA and micro-CT measurement further demonstrated significant bone loss after bariatric surgery. Besides, histologic and Western blot analyses validated enhanced osteoclastogenesis and inhibited osteoblastogenesis and defective autophagy after surgery. The 16S rDNA gene sequencing suggested a significant alteration of gut microbiota composition in the RYGB group, and intervention with fecal microbiota from RYGB donor further determined that this kind of alteration contributed to the bone loss after RYGB. Meanwhile, C. butyricum might protect against this postoperative bone loss by promoting osteoblast autophagy. In summary, this study suggests novel mechanisms to clarify the skeletal response to bariatric surgery and provides a potential candidate for the treatment of bone disorder among bariatric patients. SIGNIFICANCE STATEMENT: The significance of this study is the discovery of obvious bone loss and defective autophagy after bariatric surgery. Besides, it is revealed that gut microbiota alterations could be the reason for impaired bone mass after bariatric surgery. Furthermore, Clostridium butyricum could alleviate the gut microbiota alteration-induced bone loss after bariatric surgery by promoting osteoblast autophagy.

Anti-Periodontitis Effect of Ethanol Extracts of Alpinia Katsumadai Seeds.

Oral microbes are intimately associated with many oral and systemic diseases. Ongoing research is seeking to elucidate drugs that prevent and treat microbial diseases. Various functions of Alpinia Katsumadai seed extracts have been reported such as their anti-viral, anti-oxidant, anti-inflammatory, anti-puritic, anti-emetic, and cytoprotective effects. Here, we investigated the anti-periodontitis effect of an ethanol extract of Alpinia Katsumadai seeds (EEAKSs) on dental plaque bacteria (DPB)-induced inflammation and bone resorption. DPB and Porphyromonas gingivalis (P. gingivalis) were cultured and lipopolysaccharide (LPS) was extracted. Prostaglandin E2 (PGE2) and cyclooxygenase 2 (COX-2) levels were estimated using ELISA. Cytotoxicity was also verified. Proteases were screened using a protease antibody array method. Osteoclastic bone resorption was also investigated. EEAKSs suppressed P. gingivalis growth on agar plates. LPS prepared from dental plaque bacteria (DPB-LPS) and P. gingivalis (PG-LPS) significantly increased PGE2 and COX2 levels in immortalized gingival fibroblasts (IGFs), immortalized human oral keratinocytes (IHOKs), and RAW264.7 macrophage cells. However, DPB-LPS and PG-LPS-induced PGE2 and COX-2 increases were effectively abolished by EEAKS treatment at non-cytotoxic concentrations. In the protease antibody array, matrix metalloproteinase (MMP)-2, MMP-3, MMP-7, kallikrein 10, cathepsin D, and cathepsin V levels were increased by PG-LPS stimulation. However, increases in protease levels except for cathepsin D were suppressed by EEAKS treatment. In addition, RANKL-induced osteoclast differentiation was significantly inhibited by EEAKS treatment, leading to reductions in resorption pit formation. These results suggest that EEAKSs exerted a beneficial oral health effect to help prevent DPB-mediated periodontal disease.

Multitasking by the OC Lineage during Bone Infection: Bone Resorption, Immune Modulation, and Microbial Niche.

Bone infections, also known as infectious osteomyelitis, are accompanied by significant inflammation, osteolysis, and necrosis. Osteoclasts (OCs) are the bone-resorbing cells that work in concert with osteoblasts and osteocytes to properly maintain skeletal health and are well known to respond to inflammation by increasing their resorptive activity. OCs have typically been viewed merely as effectors of pathologic bone resorption, but recent evidence suggests they may play an active role in the progression of infections through direct effects on pathogens and via the immune system. This review discusses the host- and pathogen-derived factors involved in the in generation of OCs during infection, the crosstalk between OCs and immune cells, and the role of OC lineage cells in the growth and survival of pathogens, and highlights unanswered questions in the field.

Root canal contamination or exposure to lipopolysaccharide differentially modulate prostaglandin E 2 and leukotriene B 4 signaling in apical periodontitis.

Purpose To evaluate the kinetics of apical periodontitis development in vivo , induced either by contamination of the root canals by microorganisms from the oral cavity or by inoculation of bacterial lipopolysaccharide (LPS) and the regulation of major enzymes and receptors involved in the arachidonic acid metabolism. Methodology Apical periodontitis was induced in C57BL6 mice (n=96), by root canal exposure to oral cavity (n=48 teeth) or inoculation of LPS (10 µL of a suspension of 0.1 µg/µL) from E. coli into the root canals (n= 48 teeth). Healthy teeth were used as control (n=48 teeth). After 7, 14, 21 and 28 days the animals were euthanized and tissues removed for histopathological and qRT-PCR analyses. Histological analysis data were analyzed using two-way ANOVA followed by Sidak's test, and qRT-PCR data using two-way ANOVA followed by Tukey's test (α=0.05). Results Contamination by microorganisms led to the development of apical periodontitis, characterized by the recruitment of inflammatory cells and bone tissue resorption, whereas inoculation of LPS induced inflammatory cells recruitment without bone resorption. Both stimuli induced mRNA expression for cyclooxygenase-2 and 5-lipoxygenase enzymes. Expression of prostaglandin E 2 and leukotriene B 4 cell surface receptors were more stimulated by LPS. Regarding nuclear peroxisome proliferator-activated receptors (PPAR), oral contamination induced the synthesis of mRNA for PPARδ, differently from inoculation of LPS, that induced PPARα and PPARγ expression. Conclusions Contamination of the root canals by microorganisms from oral cavity induced the development of apical periodontitis differently than by inoculation with LPS, characterized by less bone loss than the first model. Regardless of the model used, it was found a local increase in the synthesis of mRNA for the enzymes 5-lipoxygenase and cyclooxygenase-2 of the arachidonic acid metabolism, as well as in the surface and nuclear receptors for the lipid mediators prostaglandin E2 and leukotriene B4.

Are Probiotics the New Calcium and Vitamin D for Bone Health?

PURPOSE OF REVIEW: Calcium and vitamin D supplementation is recommended for patients at high risk of fracture and/or for those receiving pharmacological osteoporosis treatments. Probiotics are micro-organisms conferring a health benefit on the host when administered in adequate amounts, likely by influencing gut microbiota (GM) composition and/or function. GM has been shown to influence various determinants of bone health. RECENT FINDINGS: In animal models, probiotics prevent bone loss associated with estrogen deficiency, diabetes, or glucocorticoid treatments, by modulating both bone resorption by osteoclasts and bone formation by osteoblast. In humans, they interfere with 25-hydroxyvitamin D levels, and calcium intake and absorption, and slightly decrease bone loss in elderly postmenopausal women, in a quite similar magnitude as observed with calcium ± vitamin D supplements. A dietary source of probiotics is fermented dairy products which can improve calcium balance, prevent secondary hyperparathyroidism, and attenuate age-related increase of bone resorption and bone loss. Additional studies are required to determine whether probiotics or any other interventions targeting GM and its metabolites may be adjuvant treatment to calcium and vitamin D or anti-osteoporotic drugs in the general management of patients with bone fragility.

Bone Flap Resorption Associated with Indolent Propionibacterium acnes Infection After Cranioplasty: Case Report with Pathological Analysis.

BACKGROUND: Autologous bone resorption is a frequent complication of cranioplasty, often necessitating reoperation. The etiology of this phenomenon is unknown, although it has recently been associated with indolent Propionibacterium acnes infection. CASE DESCRIPTION: A 59-year-old man initially presented with a traumatic acute subdural hematoma treated with emergent decompressive hemicraniectomy and hematoma evacuation. His bone flap was cryopreserved. He underwent cranioplasty with autologous bone 3 months later. Over the subsequent 14 months, serial imaging demonstrated progressive bone flap resorption, ultimately requiring repeat cranioplasty with a custom allograft. Although there was no evidence of infection at the time of repeat cranioplasty, routine culture swabs were taken and grew P. acnes after the patient had been discharged home. Pathologic analysis of the fragments of the original bone flap that were removed demonstrated osteonecrosis with marrow fibrosis but no evidence of inflammation or infection. He was treated with 6 weeks of intravenous antibiotics and had no evidence of infection at 8-month follow-up. CONCLUSIONS: Indolent P. acnes infection can precipitate autologous bone flap resorption. While the mechanism of this is unknown, pathologic analysis of a partially resorbed bone flap in the setting of an indolent P. acnes infection found no evidence of an infectious process or inflammation within the bone. Further studies are needed to elucidate the mechanism of action of P. acnes in bone flap resorption.

Post-antibiotic gut dysbiosis-induced trabecular bone loss is dependent on lymphocytes.

Recent studies in mouse models have shown that gut microbiota significantly influences bone health. We demonstrated that 2-week oral treatment with broad spectrum antibiotics followed by 4 weeks of recovery of the gut microbiota results in dysbiosis (microbiota imbalance)-induced bone loss in mice. Because gut microbiota is critical for the development of the immune system and since both microbiota and the immune system can regulate bone health, in this study, we tested the role of the immune system in mediating post-antibiotic dysbiosis-induced bone loss. For this, we treated wild-type (WT) and lymphocyte deficient Rag2 knockout (KO) mice with ampicillin/neomycin cocktail in water for 2 weeks followed by 4 weeks of water without antibiotics. This led to a significant bone loss (31% decrease from control) in WT mice. Interestingly, no bone loss was observed in the KO mice suggesting that lymphocytes are required for dysbiosis-induced bone loss. Bray-Curtis diversity metrics showed similar microbiota changes in both the WT and KO post-antibiotic treated groups. However, several operational taxonomic units (OTUs) classified as Lactobacillales were significantly higher in the repopulated KO when compared to the WT mice, suggesting that these bacteria might play a protective role in preventing bone loss in the KO mice after antibiotic treatment. The effect of dysbiosis on bone was therefore examined in the WT mice in the presence or absence of oral Lactobacillus reuteri treatment for 4 weeks (post-ABX treatment). As hypothesized, mice treated with L. reuteri did not display bone loss, suggesting a bone protective role for this group of bacteria. Taken together, our studies elucidate an important role for lymphocytes in regulating post-antibiotic dysbiosis-induced bone loss.

Frontline Science: Characterization and regulation of osteoclast precursors following chronic Porphyromonas gingivalis infection.

Bone destruction in inflammatory osteolytic diseases including periodontitis is related to excessive activity of osteoclasts (OC), which originate from precursor cells of the myeloid lineage, termed osteoclast precursors (OCP). In contrast to ample knowledge that we currently have on mature OC, little is known about OCP and their regulation during bacterial infection. Therefore, this study aimed to identify and characterize OCP following chronic infection with a periodontal bacteria Porphyromonas gingivalis (Pg). We used a microosmotic pump to continually release Pg subcutaneously in a murine model. Two weeks after Pg infection, the frequency of CD11b+c-fms+Ly6Chi population is significantly elevated within the bone marrow, spleen, and peripheral blood. In vitro and in vivo studies identified these cells as the OCP-containing population and Pg infection significantly enhanced the osteoclastogenic activity of these cells. Furthermore, mRNA sequencing analysis indicated a unique gene and pathway profile in CD11b+c-fms+Ly6Chi population following Pg infection, with changes in genes and pathways related to OC differentiation, cell proliferation and apoptosis, inflammatory response, phagocytosis, and immunity, as well as antigen processing and presentation. Moreover, using IL-6 knockout mice, we found that IL-6 is important for Pg-induced accumulation of CD11b+c-fms+Ly6Chi population from the bone marrow and periphery. Our results provide new insight into the characterization and regulation of OCP following a chronic bacterial infection. This knowledge is relevant to the understanding of the pathogenesis of bacteria-induced bone loss, and to the identification of potential therapeutic targets of bone loss diseases.

Root canal contamination or exposure to lipopolysaccharide differentially modulate prostaglandin E 2 and leukotriene B 4 signaling in apical periodontitis

Abstract Purpose To evaluate the kinetics of apical periodontitis development in vivo , induced either by contamination of the root canals by microorganisms from the oral cavity or by inoculation of bacterial lipopolysaccharide (LPS) and the regulation of major enzymes and receptors involved in the arachidonic acid metabolism. Methodology Apical periodontitis was induced in C57BL6 mice (n=96), by root canal exposure to oral cavity (n=48 teeth) or inoculation of LPS (10 µL of a suspension of 0.1 µg/µL) from E. coli into the root canals (n= 48 teeth). Healthy teeth were used as control (n=48 teeth). After 7, 14, 21 and 28 days the animals were euthanized and tissues removed for histopathological and qRT-PCR analyses. Histological analysis data were analyzed using two-way ANOVA followed by Sidak's test, and qRT-PCR data using two-way ANOVA followed by Tukey's test (α=0.05). Results Contamination by microorganisms led to the development of apical periodontitis, characterized by the recruitment of inflammatory cells and bone tissue resorption, whereas inoculation of LPS induced inflammatory cells recruitment without bone resorption. Both stimuli induced mRNA expression for cyclooxygenase-2 and 5-lipoxygenase enzymes. Expression of prostaglandin E 2 and leukotriene B 4 cell surface receptors were more stimulated by LPS. Regarding nuclear peroxisome proliferator-activated receptors (PPAR), oral contamination induced the synthesis of mRNA for PPARδ, differently from inoculation of LPS, that induced PPARα and PPARγ expression. Conclusions Contamination of the root canals by microorganisms from oral cavity induced the development of apical periodontitis differently than by inoculation with LPS, characterized by less bone loss than the first model. Regardless of the model used, it was found a local increase in the synthesis of mRNA for the enzymes 5-lipoxygenase and cyclooxygenase-2 of the arachidonic acid metabolism, as well as in the surface and nuclear receptors for the lipid mediators prostaglandin E2 and leukotriene B4.

MyD88 and IL-1R signaling drive antibacterial immunity and osteoclast-driven bone loss during Staphylococcus aureus osteomyelitis.

Staphylococcus aureus is able to infect virtually all organ systems and is a frequently isolated etiologic agent of osteomyelitis, a common and debilitating invasive infection of bone. Treatment of osteomyelitis requires invasive surgical procedures and prolonged antibiotic therapy, yet is frequently unsuccessful due to extensive pathogen-induced bone damage that can limit antibiotic penetration and immune cell influx to the infectious focus. We previously established that S. aureus triggers profound alterations in bone remodeling in a murine model of osteomyelitis, in part through the production of osteolytic toxins. However, staphylococcal strains lacking osteolytic toxins still incite significant bone destruction, suggesting that host immune responses are also major drivers of pathologic bone remodeling during osteomyelitis. The objective of this study was to identify host immune pathways that contribute to antibacterial immunity during S. aureus osteomyelitis, and to define how these immune responses alter bone homeostasis and contribute to bone destruction. We specifically focused on the interleukin-1 receptor (IL-1R) and downstream adapter protein MyD88 given the prominent role of this signaling pathway in both antibacterial immunity and osteo-immunologic crosstalk. We discovered that while IL-1R signaling is necessary for local control of bacterial replication during osteomyelitis, it also contributes to bone loss during infection. Mechanistically, we demonstrate that S. aureus enhances osteoclastogenesis of myeloid precursors in vitro, and increases the abundance of osteoclasts residing on bone surfaces in vivo. This enhanced osteoclast abundance translates to trabecular bone loss, and is dependent on intact IL-1R signaling. Collectively, these data define IL-1R signaling as a critical component of the host response to S. aureus osteomyelitis, but also demonstrate that IL-1R-dependent immune responses trigger collateral bone damage through activation of osteoclast-mediated bone resorption.

Probiotic Lactobacillus reuteri Prevents Postantibiotic Bone Loss by Reducing Intestinal Dysbiosis and Preventing Barrier Disruption.

Antibiotic treatment, commonly prescribed for bacterial infections, depletes and subsequently causes long-term alterations in intestinal microbiota composition. Knowing the importance of the microbiome in the regulation of bone density, we investigated the effect of postantibiotic treatment on gut and bone health. Intestinal microbiome repopulation at 4-weeks postantibiotic treatment resulted in an increase in the Firmicutes:Bacteroidetes ratio, increased intestinal permeability, and notably reduced femoral trabecular bone volume (approximately 30%, p < 0.01). Treatment with a mucus supplement (a high-molecular-weight polymer, MDY-1001 [MDY]) prevented the postantibiotic-induced barrier break as well as bone loss, indicating a mechanistic link between increased intestinal permeability and bone loss. A link between the microbiome composition and bone density was demonstrated by supplementing the mice with probiotic bacteria. Specifically, Lactobacillus reuteri, but not Lactobacillus rhamnosus GG or nonpathogenic Escherichia coli, reduced the postantibiotic elevation of the Firmicutes:Bacteroidetes ratio and prevented femoral and vertebral trabecular bone loss. Consistent with causing bone loss, postantibiotic-induced dysbiosis decreased osteoblast and increased osteoclast activities, changes that were prevented by both L. reuteri and MDY. These data underscore the importance of microbial dysbiosis in the regulation of intestinal permeability and bone health, as well as identify L. reuteri and MDY as novel therapies for preventing these adverse effects. © 2018 American Society for Bone and Mineral Research.

Streptococcus gordonii induces bone resorption by increasing osteoclast differentiation and reducing osteoblast differentiation.

Streptococcus gordonii is commonly found in the periapical endodontic lesions of patients with apical periodontitis, a condition characterized by inflammation and periapical bone loss. Since bone metabolism is controlled by osteoclastic bone resorption and osteoblastic bone formation, we investigated the effects of S. gordonii on the differentiation and function of osteoclasts and osteoblasts. For the determination of bone resorption activity in vivo, collagen sheets soaked with heat-killed S. gordonii were implanted on mouse calvaria, and the calvarial bones were scanned by micro-computed tomography. Mouse bone marrow-derived macrophages (BMMs) were stimulated with M-CSF and RANKL for 2 days and then differentiated into osteoclasts in the presence or absence of heat-killed S. gordonii. Tartrate-resistant acid phosphatase staining was performed to determine osteoclast differentiation. Primary osteoblast precursors were differentiated into osteoblasts with ascorbic acid and ß-glycerophosphate in the presence or absence of heat-killed S. gordonii. Alkaline phosphatase staining and alizarin red S staining were conducted to determine osteoblast differentiation. Western blotting was performed to examine the expression of transcription factors including c-Fos, NFATc1, and Runx2. Heat-killed S. gordonii induced bone destruction in a mouse calvarial implantation model. The differentiation of RANKL-primed BMMs into osteoclasts was enhanced in the presence of heat-killed S. gordonii. Heat-killed S. gordonii increased the expression of c-Fos and NFATc1, which are essential transcription factors for osteoclast differentiation. On the other hand, heat-killed S. gordonii inhibited osteoblast differentiation and reduced the expression of Runx2, an essential transcription factor for osteoblast differentiation. S. gordonii exerts bone resorptive activity by increasing osteoclast differentiation and reducing osteoblast differentiation, which may be involved in periapical bone resorption.

A dysbiotic microbiome triggers TH17 cells to mediate oral mucosal immunopathology in mice and humans.

Periodontitis is one of the most common human inflammatory diseases, yet the mechanisms that drive immunopathology and could be therapeutically targeted are not well defined. Here, we demonstrate an expansion of resident memory T helper 17 (TH17) cells in human periodontitis. Phenocopying humans, TH17 cells expanded in murine experimental periodontitis through local proliferation. Unlike homeostatic oral TH17 cells, which accumulate in a commensal-independent and interleukin-6 (IL-6)-dependent manner, periodontitis-associated expansion of TH17 cells was dependent on the local dysbiotic microbiome and required both IL-6 and IL-23. TH17 cells and associated neutrophil accumulation were necessary for inflammatory tissue destruction in experimental periodontitis. Genetic or pharmacological inhibition of TH17 cell differentiation conferred protection from immunopathology. Studies in a unique patient population with a genetic defect in TH17 cell differentiation established human relevance for our murine experimental studies. In the oral cavity, human TH17 cell defects were associated with diminished periodontal inflammation and bone loss, despite increased prevalence of recurrent oral fungal infections. Our study highlights distinct functions of TH17 cells in oral immunity and inflammation and paves the way to a new targeted therapeutic approach for the treatment of periodontitis.

Osteomicrobiology: A New Cross-Disciplinary Research Field.

The mutualistic interaction between the gut microbiota (GM) and its host profoundly shapes many aspects of our physiology. The composition and activity of the gut microbiota is modulated by environmental factors such as dietary habits and antibiotic treatments. In rodents, studies demonstrate that the GM is a crucial regulator of bone metabolism and that modulation of the GM composition by probiotic interventions can prevent castration-induced bone loss. Short-term colonization of germ-free mice with GM results in an activation of CD4+T cells, resulting in increased levels of pro-inflammatory cytokines in bone and thereby activation of osteoclastic bone resorption. Besides these immune-mediated effects on bone mass, the GM is involved in nutritional uptake and may, thereby, regulate overall body growth and bone sizes possibly mediated via altered IGF-I levels. We recently introduced a new term "osteomicrobiology" for the rapidly emerging research field of the role of the microbiota in bone health. This research field is aimed to bridge the gaps between bone physiology, gastroenterology, immunology, and microbiology. Future studies will determine if the GM is a novel therapeutic target for osteoporosis and if the GM composition might be used as a biomarker for fracture prediction.

Oral pathogenesis of Aggregatibacter actinomycetemcomitans.

Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) is a Gram-negative, facultative anaerobic bacillus that causes periodontal diseases such as localized aggressive periodontitis (LAP) and. consequently. bone resorption. The potential virulence factors of this organism are powerful leukotoxin, lipopolysaccharide (LPS), cell surface-associated materials, enzymes, and less well-defined virulence factors that will modulate the activity of the host defenses. This organism can induce bone resorption by various virulence factors in periodontal disease. In this review article, we reviewed the pathogenic roles of A. actinomycetemcomitans in periodontal disease and the mechanism which can induce bone resorption. Findings from several studies indicate that the interaction between virulence factors and the host immune system's response often progress bone resorption in periodontal disease. In this organism, GroEL, DnaK, HtpG, LTX, CDT, LPS, and cell surface-associated materials produce cytokines when exposed to the immune system. The produced cytokines are the main cause of tissue destruction and bone resorption in A. actinomycetemcomitans inflammation in periodontal disease.

Association Between Gut Microbiota and Bone Health: Potential Mechanisms and Prospective.

Context: It has been well established that the human gut microbiome plays a critical role in the regulation of important biological processes and the mechanisms underlying numerous complex diseases. Although researchers have only recently begun to study the relationship between the gut microbiota and bone metabolism, early efforts have provided increased evidence to suggest an important association. Evidence Acquisition: In this study, we attempt to comprehensively summarize the relationship between the gut microbiota and bone metabolism by detailing the regulatory effects of the microbiome on various biological processes, including nutrient absorption and the intestinal mucosal barrier, immune system functionality, the gut-brain axis, and excretion of functional byproducts. In this review, we incorporate evidence from various types of studies, including observational, in vitro and in vivo animal experiments, as well as small efficacy clinic trails. Evidence Synthesis: We review the various potential mechanisms of influence for the gut microbiota on the regulation of bone metabolism and discuss the importance of further examining the potential effects of the gut microbiota on the risk of osteoporosis in humans. Furthermore, we outline some useful tools/approaches for metagenomics research and present some prominent examples of metagenomics association studies in humans. Conclusion: Current research efforts, although limited, clearly indicate that the gut microbiota may be implicated in bone metabolism, and therefore, further exploration of this relationship is a promising area of focus in bone health and osteoporosis research. Although most existing studies investigate this relationship using animal models, human studies are both needed and on the horizon.

Staphylococcus Aureus Induces Osteoclastogenesis via the NF-κB Signaling Pathway.

BACKGROUND Osteomyelitis is one of the refractory diseases encountered in orthopedics, while Staphylococcus aureus (S. aureus) is the most common causative organism in osteomyelitis. However, the precise mechanisms underlying the bone loss caused by S. aureus infection have not been well defined. Here, we investigated the effect of S. aureus on osteoclast differentiation and the probable molecular mechanism. MATERIAL AND METHODS RAW 264.7 cells were treated for 5 days with live S. aureus, inactivated S. aureus, and S. aureus filtrate. Then, the formation of osteoclast-like cells and resorption pits was observed, and the expression of osteoclast-specific genes (TRAP, MMP-9, cathepsin K, CTR and Atp6v0d2) was detected by real-time PCR. Moreover, key proteins in the signaling pathway associated with osteoclast differentiation were detected with Western blot. RESULTS The data showed that live S. aureus, inactivated S. aureus, and S. aureus filtrate induced osteoclast formation, promoted bone resorption, and increased the expression of osteoclast-specific genes in a dose-dependent manner in the absence RANKL. In addition, we found that the S. aureus-induced osteoclastogenesis was related to the degradation of IκB-a, phosphorylation of NF-κB p65, and increased expression of NFATc1. Thus, we used JSH-23 to inhibit NF-κB transcriptional activity. The effect of the S. aureus-induced osteoclastogenesis and the expression of osteoclast-specific genes and NFATc1 were inhibited, which indicated that the NF-κB signaling pathway plays a role in S. aureus-induced osteoclastogenesis. CONCLUSIONS This study demonstrated that S. aureus induces osteoclastogenesis through its cell wall compound and secretion of small soluble molecules, and the NF-κB signaling pathway plays a role in this process.

Diabetes Enhances IL-17 Expression and Alters the Oral Microbiome to Increase Its Pathogenicity.

Diabetes is a risk factor for periodontitis, an inflammatory bone disorder and the greatest cause of tooth loss in adults. Diabetes has a significant impact on the gut microbiota; however, studies in the oral cavity have been inconclusive. By 16S rRNA sequencing, we show here that diabetes causes a shift in oral bacterial composition and, by transfer to germ-free mice, that the oral microbiota of diabetic mice is more pathogenic. Furthermore, treatment with IL-17 antibody decreases the pathogenicity of the oral microbiota in diabetic mice; when transferred to recipient germ-free mice, oral microbiota from IL-17-treated donors induced reduced neutrophil recruitment, reduced IL-6 and RANKL, and less bone resorption. Thus, diabetes-enhanced IL-17 alters the oral microbiota and renders it more pathogenic. Our findings provide a mechanistic basis to better understand how diabetes can increase the risk and severity of tooth loss.