Extracts of Prevotella intermedia and Actinobacillus actinomycetemcomitans inhibit alkaline phosphatase activity in osteoblastic cells in vitro

The oral microbiome in young women at different stages of periodontitis: Prevotella dominant in stage III periodontitis

Objective

Periodontitis progression is related to the dynamic dysbiosis of oral microbiome. We identified the dominant bacteria and the potential pathway in young women with stage-III periodontitis.

Materials and methods

Samples of subgingival plaque were collected from 26 young women with periodontitis (20 with stage-I and 6 with stage-III). Using 16S rRNA-sequencing, we determined the variation in oral bacterial communities of the two groups, and identified the dominant bacteria of each group. We used the Kyoto Encyclopedia of Genes and Genomes (KEGG) database to evaluate the signaling pathways related to the difference in oral bacterial composition. The role of the dominant bacteria of stage-III periodontitis was investigated in vivo and in vitro using an endoplasmic reticulum stress inhibitor.

Results

Young women with stage-I periodontitis had higher values for the Chao1 Index, Observed Species and Phylogenetic Diversity Whole Tree Index than those for women with stage-III periodontitis. β-diversity analyses revealed that samples could be divided into different groups according to the periodontitis stage. The most representative biomarkers of stage-III periodontitis in young women were bacteria of the phylum Bacteroidetes, its order, family and genera Bacteroidales, Prevotellaceae and Prevotella. The KEGG database revealed that the change in oral bacterial composition of young women with stage-III periodontitis may be related to protein processing in an endoplasmic reticulum pathway. Salubrinal (an endoplasmic reticulum stress regulator) controlled expression of Runx2, Col1a1, Ocn in mouse bone-marrow mesenchymal cells. Salubrinal administration showed that moderate endoplasmic reticulum stress inhibited alveolar bone loss in periodontitis induced by Prevotella intermedia lipopolysaccharide.

Conclusion

Differences between periodontitis stages were noted and bacteria of Prevotella species were abundant in young women with stage-III periodontitis. This phenomenon was related to protein processing in an endoplasmic reticulum pathway.

Effect of total sonicated Aggregatibacter actinomycetemcomitans fragments on gingival stem/progenitor cells

Background

Aggregatibacter-actinomycetemcomitans (A.actinomycetemcomitans) are strongly associated with localized-aggressive-periodontitis (LAgP). The study’s aim was to test for the first time the effect of total sonicated A.actinomycetemcomitans-bacterial-fragments on gingival mesenchymal stem/progenitor cells’ (G-MSCs) proliferation and regenerative gene expression in-vitro.

Material and Methods

G-MSCs were isolated, characterized, expanded and stimulated by total sonicated A.actinomycetemcomitans-bacterial-fragments (0 (negative-control), 15, 60, 120 and 240µg/ml; serovar-b; n=6/group). Cellular proliferation and NF-κβ (NFKB1), Alkaline Phosphatase (ALPL), Collagen-I (COL1A1), Collagen-III (COL3A1), Osteonectin (SPARC) and Osteopontin (SPP1) m-RNA expression were assessed via reverse-transcription-polymerase-chain-reaction (RT-PCR) at 24, 48 and 72 hours and CFUs-ability evaluated at twelve days.

Results

G-MSCs demonstrated stem/progenitor cells’ characteristics. A.actinomycetemcomitans-bacterial-fragments (up to 72 hours) resulted in marked G-MSCs’ proliferation over-time (p<0.001) and elevated NFKB1 (p=0.017), COL1A1 (p=0.025), SPARC (p=0.025), decreased ALPL (p=0.017), with no significant differences for COL3A1 and SPP1 expression or stimulation times (p>0.05; Friedman-test). Longer-term stimulation for twelve days reduced G-MSCs’ CFUs.

Conclusions

Sonicated A.actinomycetemcomitans-bacterial-fragments’ exert beneficial short-term effects on G-MSCs’ proliferative and non-mineralized tissue forming aptitude. Results shed new light on the importance of periodontal treatment for LAgP patients, using power driven sonic/ultrasonic devices, which, in addition to reducing the subgingival microbial load, produces cell-stimulatory A.actinomycetemcomitans-bacterial-fragments, with positive attributes on tissue reparative/regenerative responses of tissue resident stem/progenitor cells in their niche.

Key words:Ultrasonic, Aggregatibacter actinomycetemcomitans, stem cells, gingiva, Aggressive periodontitis.

Capnocytophaga spp. involvement in bone infections: a review

Capnocytophaga are commensal gliding bacteria that are isolated from human and animal oral flora and are responsible for infections both in immunocompromised and immunocompetent hosts. Accumulation of microbial plaque, loss of collagen attachment, and alveolar bone resorption around the tooth can lead to local Capnocytophaga spp. bone infections. These capnophilic bacteria, from oral sources or following domestic animal bites, are also causative agents of bacteraemia and systemic infections as well as osteomyelitis, septic arthritis, and infections on implants and devices. The present literature review describes the main aetiologies of bone infections due to Capnocytophaga spp., the cellular mechanisms involved, methods used for diagnosis, antimicrobial susceptibility, and effective treatments.

Bone microbial contamination influences autogenous grafting in sinus augmentation

BACKGROUND

The oral occurrence of putative microbial pathogens in humans has been documented in health and disease. The presence of periodontopathogens in patients with a history of periodontal disease may have a negative impact on bone regeneration. This investigation was conducted to confirm the presence of periodontal pathogens in bone particles harvested intraorally for maxillary sinus augmentation and to assess the clinical and radiographic outcomes 6 to 12 months after bone augmentation.

METHODS

Culture and polymerase chain reaction (PCR)-based identification were performed by paper-point sampling of intraorally harvested bone particles in a group of 12 maintenance patients undergoing maxillary sinus augmentation. Radiographs were taken to assess and compare bone healing and volume gain at baseline and at 6 to 12 months after augmentation.

RESULTS

The presence of periodontal pathogens (Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans [previously Actinobacillus actinomycetemcomitans], Prevotella intermedia, Tannerella forsythia [previously T. forsythensis], Fusobacterium nucleatum, Parvimonas micra [previously Peptostreptococcus micros or Micromonas micros], Campylobacter rectus, enteric Gram-negative rods, and Dialister pneumosintes) was identified in 10 of 12 patients (83%) by culture, PCR, or both and was associated with greater bone volume loss at 6 months postaugmentation. The PCR-positive triad, P. gingivalis, A. actinomycetemcomitans, and P. intermedia, was associated with pronounced volume loss of the grafted sinus at 6 months.

CONCLUSIONS

To the best of our knowledge, this is the first study to confirm osseous microbial contamination with major periodontopathogens in individuals undergoing maxillary sinus augmentation with a history of periodontitis. The effect on the grafting outcome translated into bone volume loss in the grafted sinus 6 months postaugmentation. Specific microbial contamination may have an impact on osteogenesis in osseous regeneration.

Prolonged exposure to bacterial toxins downregulated expression of toll-like receptors in mesenchymal stromal cell-derived osteoprogenitors

Background

Human mesenchymal stromal cells (MSCs, also known as mesenchymal stem cells) are multipotent cells with potential therapeutic value. Owing to their osteogenic capability, MSCs may be clinically applied for facilitating osseointegration in dental implants or orthopedic repair of bony defect. However, whether wound infection or oral microflora may interfere with the growth and osteogenic differentiation of human MSCs remains unknown. This study investigated whether proliferation and osteogenic differentiation of MSCs would be affected by potent gram-positive and gram-negative derived bacterial toxins commonly found in human settings.

Results

We selected lipopolysaccharide (LPS) from Escherichia coli and lipoteichoic acid (LTA) from Streptococcus pyogenes as our toxins of choice. Our findings showed both LPS and LTA did not affect MSC proliferation, but prolonged LPS challenge upregulated the osteogenic differentiation of MSCs, as assessed by alkaline phosphatase activity and calcium deposition. Because toll-like receptors (TLRs), in particularly TLR4 and TLR2, are important for the cellular responsiveness to LPS and LTA respectively, we evaluated their expression profiles serially from MSCs to osteoblasts by quantitative PCR. We found that during osteogenic differentiation, MSC-derived osteoprogenitors gradually expressed TLR2 and TLR4 by Day 12. But under prolonged incubation with LPS, MSC-derived osteoprogenitors had reduced TLR2 and TLR4 gene expression. This peculiar response to LPS suggests a possible adaptive mechanism when MSCs are subjected to continuous exposure with bacteria.

Conclusion

In conclusion, our findings support the potential of using human MSCs as a biological graft, even under a bacterial toxin-rich environment.

Lipopolysaccharide alters decorin and biglycan synthesis in rat alveolar bone osteoblasts: consequences for bone repair during periodontal disease

A prime pathogenic agent associated with periodontitis is lipopolysaccharide (LPS) derived from Porphyromonas gingivalis. This study investigated the effects of P. gingivalis LPS on osteoblasts, which are responsible for alveolar bone repair. Bone cells were obtained from explants of rat alveolar bone chips and cultured with 0–200 ng ml⁻¹ of P. gingivalis LPS. Porphyromonas gingivalis LPS significantly increased cell proliferation and inhibited osteoblast differentiation, as judged by reduced alkaline phosphatase activity. Analysis of biglycan mRNA and protein levels indicated that P. gingivalis LPS significantly delayed the normally high expression of biglycan during the early stages of culture, which are associated with cell proliferation and early differentiation of progenitor cells. In the presence of P. gingivalis LPS, decorin expression by the alveolar bone cells was reduced during periods of culture relating to collagen fibrillogenesis and mineral deposition. Analysis of glycosaminoglycan chains conjugated to these proteoglycans suggested that in the presence of P. gingivalis LPS, dermatan sulfate persisted within the matrix. This study suggests that P. gingivalis LPS influences the expression and processing of decorin and biglycan in the matrix, altering alveolar bone cell activity and osteoblast phenotype development. The consequences of this altered expression in relation to hindering bone repair as part of the cycle of events during periodontal disease are discussed.

Effects of lipopolysaccharide extracted from Prevotella intermedia on bone formation and on the release of osteolytic mediators by fetal mouse osteoblasts in vitro

Prevotella intermedia, a Gram-negative obligate anaerobic black-pigmented oral bacterium, belongs to a small group of microorganisms that is closely associated with the initiation of periodontal diseases. Lipopolysaccharide (LPS), an outer membrane component, is one of the main virulence factors of this bacterium. The aim of this study was to examine the effects of Prev. intermedia lipopolysaccharide, extracted by the hot-phenol-water method, on differentiation (alkaline phosphatase activity) and mineralisation (calcium incorporation) of fetal mouse calvarial cells in vitro and to determine the release of the important osteolytic factors nitric oxide, interleukin-6 (IL-6) and matrix metalloproteinases by these cells after treatment with different concentrations of Prev. intermedia lipopolysaccharide (0.2-25 microg/ml). By gelatin zymography, we also characterized the matrix metalloproteinases released by these osteoblasts. Treatment with Prev. intermedia lipopolysaccharide dose-dependently inhibited bone formation by reducing alkaline phosphatase activity and calcium incorporation and induced the release of nitric oxide, IL-6 and the latent proforms of MMP-2 and MMP-9 by fetal mouse osteoblasts in organoid culture. These results indicate that the lipopolysaccharide from Prev. intermedia not only participates in periodontal tissue destruction and alveolar bone resorption, but also inhibits bone formation.

Microbial analysis of bone collected during implant surgery: a clinical and laboratory study

Dental implant surgery produces bone debris which can be used to correct bone defects in the "simultaneous-augmentation" technique. However, this debris is potentially contaminated with oral bacteria. Therefore, this study examined bone debris collected during dental implant surgery in order 1) to identify the microbial contaminants and 2) to compare the effects of two different aspiration protocols on the levels of microbial contamination. Twenty-four partially dentate patients were randomly allocated into two equal groups and underwent bone collection using the Frios Bone Collector during surgery to insert two endosseous dental implants. In group S (using a stringent aspiration protocol), bone collection occurred within the surgical site only. In group NS (utilizing a non-stringent aspiration protocol), bone collection and tissue fluid control was achieved using the same suction tip. Bone samples were immediately transported for microbial analysis. Colonial and microscopic morphology, gaseous requirements and identification kits were utilized for identification of the isolated microbes. Twenty-eight species were identified including a number associated with disease, in particular, Enterococcus faecalis and Staphylococcus epidermidis as well as the anaerobes Actinomyces odontolyticus, Eubacterium sp., Prevotella intermedia, Propionibacterium propionicum and Peptostreptococcus asaccharolyticus. In group S (stringent aspiration protocol), significantly fewer organisms were found than in group NS, the non-stringent aspiration protocol (P=0.001). Gram-positive cocci dominated the isolates from both groups. It is concluded that if bone debris is collected for implantation around dental implants, it should be collected with a stringent aspiration protocol (within the surgical site only) to minimize bacterial contaminants.

The role of immune responses in bone loss during periodontal disease

A network of cytokines and other soluble mediators unites the immune system and bone; bacterial infections induce immune responses which may perturb this network. Periodontal diseases are Gram-negative infections resulting in bone loss in the jaw. Evidence is presented that immune responses to these infections produces net resorption of bone.

Inhibition of osteoblastic cell differentiation by lipopolysaccharide extract from Porphyromonas gingivalis

Lipopolysaccharide from Porphyromonas gingivalis (P-LPS), an important pathogenic bacterium, is closely associated with inflammatory destruction of periodontal tissues. P-LPS induces the release of cytokines and local factors from inflammatory cells, stimulates osteoclastic-cell differentiation, and causes alveolar bone resorption. However, the effect of P-LPS on osteoblastic-cell differentiation remains unclear. In this study, we investigated the effect of P-LPS extract prepared by the hot-phenol-water method, on the differentiation of primary fetal rat calvaria (RC) cells, which contain a subpopulation of osteoprogenitor cells, into osteoblastic cells. P-LPS extract significantly inhibited bone nodule (BN) formation and the activity of alkaline phosphatase (ALPase), an osteoblastic marker, in a dose-dependent manner (0 to 100 ng of P-LPS extract per ml). P-LPS extract (100 ng/ml) significantly decreased BN formation to 27% of the control value and inhibited ALPase activity to approximately 60% of the control level on days 10 to 21 but did not affect RC cell proliferation and viability. P-LPS extract time-dependently suppressed the expression of ALPase mRNA, with an inhibitory pattern similar to that of enzyme activity. The expression of mRNAs for osteocalcin and osteopontin, matrix proteins related to bone metabolism, was markedly suppressed by P-LPS extract. Furthermore, P-LPS extract increased the expression of mRNAs for CD14, LPS receptor, and interleukin-1beta in RC cells. These results indicate that P-LPS inhibits osteoblastic-cell differentiation and suggest that LPS-induced bone resorption in periodontal disease may be mediated by effects on osteoblastic as well as osteoclastic cells.

Prilocaine induces apoptosis in osteoblastic cells

PURPOSE

To determine whether prilocaine, a local anesthetic, induces apoptosis in osteoblastic cells.

METHODS

After reaching subconfluence, human osteoblastic Saos-2 and MG63 cells and mouse osteoblastic MC3T3-E1 cells were exposed for 48 hr to varying concentrations of prilocaine up to 10 mM and the cytotoxicity of the cells was analyzed by phase-contrast microscopy and WST-1 assay. Saos-2 cells treated for 48 hr with 5 mM prilocaine were stained with Hoechst 33342 and nuclear fragmentation was examined under a fluorescence microscope. DNA was extracted from the cells treated with 5 mM prilocaine and DNA ladder formation (a hallmark of apoptosis) was analyzed by agarose gel electrophoresis.

RESULT

Prilocaine induced cell death in Saos-2 cells in a dose- and time-dependent manner up to the concentration of 10 mM. Marked nuclear condensation and fragmentation of chromatin were observed in the prilocaine-treated cells. DNA ladder formation also was induced by prilocaine treatment. Prilocaine-induced DNA ladder formation was dose-dependent with maximal effect at a concentration of 5 mM and was time-dependent from 12 to 48 hr. DNA ladder formation was also induced by prilocaine treatment in human osteoblastic MG63 cells and mouse osteoblastic MC3T3-E1 cells. Cycloheximide prevented prilocaine-induced apoptosis in Saos-2 cells in a dose-dependent fashion up to 20 microM as determined by WST-1 assay and DNA ladder formation in agarose gel electrophoresis.

CONCLUSION

Osteoblastic cells treated with prilocaine exhibit both morphological and biochemical features indicative of apoptosis. The apoptotic mechanisms involve transcriptional regulation of specific proteins or protein synthesis.

Extracts of Actinobacillus actinomycetemcomitans induce apoptotic cell death in human osteoblastic MG63 cells

Whether an extracellular component of periodontal-disease-causing bacteria induces apoptotic cell death in bone-related cells is unknown. To study the effects on osteoblasts of extracts obtained from sonicated Actinobacillus actinomycetemcomitans and Prevotella intermedia, we cultured human osteoblastic cell lines MG63 and Saos-2 cells and mouse osteoblastic cell line MC3T3-E1 cells in the presence of such extracts. The addition of the extracts from Actinobacillus actinomycetemcomitans induced cell death in MG63 cells in a dose- and time-dependent fashion over the concentration range of 0.1 to 10 microg/mL. By contrast, the extracts from Prevotella intermedia did not induce cell death in these cells, even in the presence of 10 microg/mL protein. By using the Hoechst 33342 staining technique, we observed marked nuclear condensation and fragmentation of chromatin in MG63 cells treated with the extracts of Actinobacillus actinomycetemcomitans. DNA ladder formation, a hallmark of apoptosis, also was detected in MG63 cells treated with extracts from Actinobacillus actinomycetemcomitans. In MG63 cells, DNA ladder formation was dose-dependent, with a maximal effect at a concentration of 10 microg/mL, and time-dependent, from 12 to 48 hrs. However, the extracts from Prevotella intermedia did not induce DNA fragmentation in MG63, Saos-2, or MC3T3-E1 cells. The extracts from Actinobacillus actinomycetemcomitans did not induce cell death and DNA fragmentation in Saos-2 and MC3T3-E1 cells. Sonicated extracts of Actinobacillus actinomycetemcomitans that had been treated with heat and trypsin did not induce DNA ladder formation in MG63 cells, suggesting that the apoptosis-inducing factors are proteinaceous. Cycloheximide prevented the Actinobacillus actinomycetemcomitans-induced DNA ladder formation in MG63 cells in a dose-dependent fashion, suggesting that new gene transcription and protein synthesis are regulated for Actinobacillus actinomycetemcomitans-induced apoptosis in MG63 cells. Our results indicate that apoptosis in alveolar bone cells induced by Actinobacillus actinomycetemcomitans plays an important role in periodontal diseases.