Diabetes Medication Metformin Inhibits Osteoclast Formation and Activity in In Vitro Models for Periodontitis

Diabetes and periodontitis are comorbidities and may share common pathways. Several reports indicate that diabetes medication metformin may be beneficial for the periodontal status of periodontitis patients. Further research using appropriate cell systems of the periodontium, the tissue that surrounds teeth may reveal the possible mechanism. Periodontal ligament fibroblasts anchor teeth in bone and play a role in the onset of both alveolar bone formation and degradation, the latter by inducing osteoclast formation from adherent precursor cells. Therefore, a cell model including this type of cells is ideal to study the influence of metformin on both processes. We hypothesize that metformin will enhance bone formation, as described for osteoblasts, whereas the effects of metformin on osteoclast formation is yet undetermined. Periodontal ligament fibroblasts were cultured in the presence of osteogenic medium and 0.2 or 1 mM metformin. The influence of metformin on osteoclast formation was first studied in PDLF cultures supplemented with peripheral blood leukocytes, containing osteoclast precursors. Finally, the effect of metformin on osteoclast precursors was studied in cultures of CD14+ monocytes that were stimulated with M-CSF and receptor activator of Nf-κB ligand (RANKL). No effects of metformin were observed on osteogenesis: not on alkaline phosphatase activity, Alizarin red deposition, nor on the expression of osteogenic markers RUNX-2, Collagen I and Osteonectin. Metformin inhibited osteoclast formation and accordingly downregulated the genes involved in osteoclastogenesis: RANKL, macrophage colony stimulating factor (M-CSF) and osteoclast fusion gene DC-STAMP. Osteoclast formation on both plastic and bone as well as bone resorption was inhibited by metformin in M-CSF and RANKL stimulated monocyte cultures, probably by reduction of RANK expression. The present study unraveling the positive effect of metformin in periodontitis patients at the cellular level, indicates that metformin inhibits osteoclast formation and activity, both when orchestrated by periodontal ligament fibroblasts and in cytokine driven osteoclast formation assays. The results indicate that metformin could have a systemic beneficiary effect on bone by inhibiting osteoclast formation and activity.

Analysis of the cells isolated from epithelial cell rests of Malassez through single-cell limiting dilution

The epithelial cell rests of Malassez (ERM) are essential in preventing ankylosis between the alveolar bone and the tooth (dentoalveolar ankylosis). Despite extensive research, the mechanism by which ERM cells suppress ankylosis remains uncertain; perhaps its varied population is to reason. Therefore, in this study, eighteen unique clones of ERM (CRUDE) were isolated using the single-cell limiting dilution and designated as ERM 1–18. qRT-PCR, ELISA, and western blot analyses revealed that ERM-2 and -3 had the highest and lowest amelogenin expression, respectively. Mineralization of human periodontal ligament fibroblasts (HPDLF) was reduced in vitro co-culture with CRUDE ERM, ERM-2, and -3 cells, but recovered when an anti-amelogenin antibody was introduced. Transplanted rat molars grown in ERM-2 cell supernatants produced substantially less bone than those cultured in other cell supernatants; inhibition was rescued when an anti-amelogenin antibody was added to the supernatants. Anti-Osterix antibody staining was used to confirm the development of new bones. In addition, next-generation sequencing (NGS) data were analysed to discover genes related to the distinct roles of CRUDE ERM, ERM-2, and ERM-3. According to this study, amelogenin produced by ERM cells helps to prevent dentoalveolar ankylosis and maintain periodontal ligament (PDL) space, depending on their clonal diversity.

Atypical Peripheral Ossifying Fibroma of the Mandible

Peripheral ossifying fibroma (POF) is a benign localized lesion originating from gingival and alveolar oral mucosa. Its origin can be cells of periodontal ligament. The lesions usually develop in women in their twenties. POF is a complex clinical and histological diagnosis due to its shared characteristics with many other conditions. In this paper, we presented a case of an atypical peripheral ossifying fibroma (POF) in the left lateral part of the mandible in a 70-year-old male patient who had two semicircular bridges supported on four implants in the upper and lower jaws. A review of CBCT and orthopedic imaging showed no visible intraosseous changes. Histological analysis revealed the diagnosis of POF. The case in question is interesting, as elaborated on in the discussion section of this paper because POF is usually found in female patients aged between 20 and 30 years.

Nrf2 Activation Is Involved in Cyclic Mechanical Stress-Stimulated Osteogenic Differentiation in Periodontal Ligament Stem Cells via PI3K/Akt Signaling and HO1-SOD2 Interaction

Nuclear factor erythroid-2-related factor-2 (Nrf2), the major transcriptional regulator in antioxidant response and cellular defense, had the vital effect on regulating osteogenic differentiation. Our previous study revealed that Nrf2 activation was involved in cyclic mechanical stress-stimulated osteogenic differentiation in the human periodontal ligament stem cells (PDLSCs). However, the mechanisms of Nrf2 underlying this process remained unclear. The goal of the study was to explore the mechanisms of Nrf2 in PDLSCs during cyclic mechanical stress-stimulated osteogenic differentiation via the tandem mass tag (TMT)-based liquid chromatography tandem-mass spectrometry (LC-MS/MS) analysis. And we applied tert-Butylhydroquinone (t-BHQ), the Nrf2 activator, to the orthodontic rats and detected the expression levels of the osteogenesis markers by immunohistochemistry (IHC) staining. Our results showed that Nrf2 activation in PDLSCs was involved in cyclic mechanical stress-stimulated osteogenic differentiation via phosphoinositide 3 kinase (PI3K)/protein kinase B (Akt) pathway. The protein-protein interaction between Akt and Nrf2 was detected. And the protein-protein interaction between heme oxygenase 1 (HO1) and superoxide dismutase 2 (SOD2), the downstream antioxidants of Nrf2, was associated with cyclic mechanical stress-stimulated osteogenic differentiation. T-BHQ enhanced the expression levels of the osteogenesis markers in orthodontic rats. Nrf2 might possess the potential to be a feasible molecular target in orthodontics.

Effects of Selective Alveolar Decortication on the Periodontal Complex

Background Modification of bone turnover has been reported following selective alveolar decortication but the molecular signals in the periodontal ligament space (PDL) remain unanswered. The objective of this study was to understand how selective alveolar decortication affects the biological reactions in the periodontal ligament. Methods Selective alveolar decortication in wild-type mice (n=25) was performed on mandibular right buccal cortical plate adjacent to the mandibular right third molar and euthanized at 3, 7, 14 and 28 days. We also performed selective alveolar decortication in Lrp5ACT (n=5) mice and Ad-Dkk1 treated mice (n=5), and euthanized at 7 days. The periodontium around the mandibular third molars were examined using histology, immunohistochemical analyses for osteogenic markers, TGF-β, RANKL, TRAP and alkaline phosphatase activity. Results The expression of osteogenic markers in the wild-type PDL was maintained during healing time period after selective alveolar decortication. Increased osteoclast activity in the wild-type mice was observed at 3 and 7 days after selective alveolar decortication. The PDL in Lrp5G171V (Lrp5ACT) mice and adenovirus Dkk1 (Ad-Dkk1) treated mice also showed insignificant changes in the expression of osteogenic markers following selective alveolar decortication. In Lrp5ACT mice where there was a reduction of bone resorption, selective alveolar decortication caused a dramatic increase in osteoclast activity. Conclusions Selective alveolar decortication affects only bone turnover, but not the expression of osteogenic markers in the PDL.

Radiographic outcome of root canal treatment in dogs: 281 teeth in 204 dogs (2001–2018)

OBJECTIVE To evaluate the radiographic outcome of root canal treatment (RCT) in dogs and compare outcomes with those reported for a previous study performed at the same institution in 2002. ANIMALS 204 dogs representing 281 teeth that underwent RCT. PROCEDURES The medical record database of a veterinary teaching hospital was searched to identify dogs that underwent RCT between 2001 and 2018. Only dogs that had undergone at least 1 radiographic recheck appointment a minimum of 50 days after RCT were included in the study. Dental radiographs were reviewed. Treatment was considered successful if the periapical periodontal ligament space was within reference limits and preexisting external inflammatory root resorption (EIRR), if present, had stabilized. Treatment was considered to show no evidence of failure (NEF) if preoperative EIRR had stabilized and any preoperative periapical lucency (PAL) remained the same or had decreased in size but had not completely resolved. Treatment was considered to have failed if EIRR or a PAL developed after RCT, if a preoperative PAL increased in size, or if preexisting EIRR progressed. RESULTS Follow-up time ranged from 52 to 3,245 days (mean, 437 days). RCT was classified as successful for 199 (71%) teeth, NEF for 71 (25%) teeth, and failed for 11 (4%) teeth. CONCLUSIONS AND CLINICAL RELEVANCE Results showed that almost 2 decades after RCT outcome in dogs was first evaluated, during which time numerous advances in dental materials and techniques had been made, the success rate of RCT was virtually unchanged.

Comprehensive analysis of the long noncoding RNA-associated competitive endogenous RNA network in the osteogenic differentiation of periodontal ligament stem cells

Backgroud The mechanism implicated in the osteogenesis of human periodontal ligament stem cells (PDLSCs) has been investigated for years. Previous genomics data analyses showed that long noncoding RNA (lncRNA), microRNA (miRNA) and messenger RNA (mRNA) have significant expression differences between induced and control human PDLSCs. Competing for endogenous RNAs (ceRNA), as a widely studied mechanism in regenerative medicine, while rarely reported in periodontal regeneration. The key lncRNAs and their ceRNA network might provide new insights into molecular therapies of periodontal regeneration based on PDLSCs. Results Two networks reflecting the relationships among differentially expressed RNAs were constructed. One ceRNA network was composed of 6 upregulated lncRNAs, 280 upregulated mRNAs, and 18 downregulated miRNAs. The other network contained 33 downregulated lncRNAs, 73 downregulated mRNAs, and 5 upregulated miRNAs. Functional analysis revealed that 38 GO terms and 8 pathways related with osteogenesis were enriched. Twenty-four osteogenesis-related gene-centred lncRNA-associated ceRNA networks were successfully constructed. Among these pathways, we highlighted MAPK and TGF-beta pathways that are closely related to osteogenesis. Subsequently, subnetworks potentially linking the GO:0001649 (osteoblast differentiation), MAPK and TGF-beta pathways were constructed. The qRT-PCR validation results were consistent with the microarray analysis. Conclusion We construct a comprehensively identified lncRNA-associated ceRNA network might be involved in the osteogenesis of PDLSCs, which could provide insights into the regulatory mechanisms and treatment targets of periodontal regeneration.