Three-dimensional micro-computed tomographic imaging of alveolar bone in experimental bone loss or repair

Proton FLASH Radiotherapy Ameliorates Radiation-induced Salivary Gland Dysfunction and Oral Mucositis and Increases Survival in a Mouse Model of Head and Neck Cancer

Head and neck cancer radiotherapy often damages salivary glands and oral mucosa, severely negatively impacting patients' quality of life. The ability of FLASH proton radiotherapy (F-PRT) to decrease normal tissue toxicity while maintaining tumor control compared with standard proton radiotherapy (S-PRT) has been previously demonstrated for several tissues. However, its potential in ameliorating radiation-induced salivary gland dysfunction and oral mucositis and controlling orthotopic head and neck tumor growth has not been reported. The head and neck area of C57BL/6 mice was irradiated with a single dose of radiotherapy (ranging from 14-18 Gy) or a fractionated dose of 8 Gy × 3 of F-PRT (128 Gy/second) or S-PRT (0.95 Gy/second). Following irradiation, the mice were studied for radiation-induced xerostomia by measuring their salivary flow. Oral mucositis was analyzed by histopathologic examination. To determine the ability of F-PRT to control orthotopic head and neck tumors, tongue tumors were generated in the mice and then irradiated with either F-PRT or S-PRT. Mice treated with either a single dose or fractionated dose of F-PRT showed significantly improved survival than those irradiated with S-PRT. F-PRT-treated mice showed improvement in their salivary flow. S-PRT-irradiated mice demonstrated increased fibrosis in their tongue epithelium. F-PRT significantly increased the overall survival of the mice with orthotopic tumors compared with the S-PRT-treated mice. The demonstration that F-PRT decreases radiation-induced normal tissue toxicity without compromising tumor control, suggests that this modality could be useful for the clinical management of patients with head and neck cancer.

Hepatocyte growth factor is protective in early stage but bone-destructive in late stage of experimental periodontitis

BACKGROUND AND OBJECTIVE

Clinical studies found high levels of hepatocyte growth factor (HGF) expression in patients with periodontitis. Studies suggest that HGF plays an important role in periodontitis, is involved in inflammation, and modulates alveolar bone integrity in periodontitis. This study aims to investigate the effects and mechanisms of HGF in the progression of experimental periodontitis.

METHODS

We used silk thread ligation to induce periodontitis in HGF-overexpressing transgenic (HGF-Tg) and wild-type C57BL/6J mice. The effects of HGF overexpression on alveolar bone destruction were assessed by microcomputed tomography imaging at baseline and on days 7, 14, 21, and 28. We analyzed the cytokines (IL-6 and TNF-α) and lymphocytes in periodontitis tissues by enzyme-linked immunosorbent assay and flow cytometry. The effects of HGF on alveolar bone destruction were further tested by quantifying the systemic bone metabolism markers CTXI and PINP and by RNA sequencing for the signaling pathways involved in bone destruction. Western blotting and immunohistochemistry were performed to further elucidate the involved signaling pathways.

RESULTS

We found that experimental periodontitis increased HGF production in periodontitis tissues; however, the effects of HGF overexpression were inconsistent with disease progression. In the early stage of periodontitis, periodontal inflammation and alveolar bone destruction were significantly lower in HGF-Tg mice than in wild-type mice. In the late stage, HGF-Tg mice showed higher inflammatory responses and progressively aggravated bone destruction with continued stimulation of inflammation. We identified the IL-17/RANKL/TRAF6 pathway as a signaling pathway involved in the HGF effects on the progression of periodontitis.

CONCLUSION

HGF plays divergent effects in the progression of experimental periodontitis and accelerates osteoclastic activity and bone destruction in the late stage of inflammation.

Accelarated Orthodontic Treatment Using Microosteoperforations: A Comparative Study

Background

Accelerated orthodontic treatment has gained popularity in recent years as patients seek shorter treatment durations. Microosteoperforations (MOPs) have emerged as a minimally invasive technique to expedite tooth movement. This study aims to compare the effectiveness of MOPs in accelerating orthodontic treatment with conventional methods.

Materials and Methods

A randomized controlled trial was conducted on 60 orthodontic patients requiring dental alignment. The participants were divided into two groups: Group A (MOPs) and Group B (conventional orthodontic treatment). In Group A, MOPs were performed at the beginning of the treatment. Both groups received monthly orthodontic adjustments. Treatment duration, rate of tooth movement, and patient discomfort were measured and compared between the two groups.

Results

The study found that in Group A, the treatment duration was reduced by 30% compared to Group B (P < 0.05). The rate of tooth movement in the MOPs group was 1.5 times higher than the conventional group (P < 0.01). Additionally, patient-reported discomfort levels were similar between the two groups. No adverse events related to MOPs were observed during the study.

Conclusion

MOPs significantly accelerate orthodontic treatment, reducing treatment duration by 30% and increasing the rate of tooth movement by 1.5 times compared to conventional methods. Importantly, MOPs are well-tolerated by patients, making them a valuable option for expediting orthodontic treatment with minimal discomfort. This study highlights the potential benefits of integrating MOPs into orthodontic practice to improve treatment efficiency and patient satisfaction.

Oral Lactobacillus zeae exacerbates the pathological manifestation of periodontitis in a mouse model

INTRODUCTION

The worldwide prevalence of periodontitis is considerably high, and its pathogenic mechanisms must be investigated and understood in order to improve clinical treatment outcomes and reduce the disease prevalence and burden. The exacerbation of the host immune system induced by oral microbial dysbiosis and the subsequent tissue destruction are the hallmarks of the periodontitis. However, the oral bacteria involved in periodontitis are not fully understood. We used the Oxford Nanopore Technologies (ONT) sequencing system to analyze metagenomic information in subgingival dental plaque from periodontitis and non-periodontitis patients. The number of Lactobacillus zeae (L. zeae) in the periodontitis patients was 17.55-fold higher than in the non-periodontitis patients, suggesting that L. zeae is a novel periodontitis-associated pathogen. Although several Lactobacillus species are used in vivo as probiotics to treat periodontitis and compete with Porphyromonas gingivalis (P. gingivalis), the roles of L. zeae in periodontitis progression, and the relationship between L. zeae and P. gingivalis needs to be investigated.

METHODS

Both L. zeae and P. gingivalis were inoculated in the ligature-implant site of periodontitis mice. We collected mouse gingival crevicular fluid to analyze inflammatory cytokine secretion using a multiplex assay. Intact or sliced mouse maxilla tissue was used for micro-computed tomography analysis or hematoxylin and eosin staining, immunohistochemistry, and tartrate-resistant acid phosphatase staining to evaluate alveolar bone loss, neutrophil infiltration, and osteoclast activation, respectively.

RESULTS

We observed that L. zeae competed with P. gingivalis, and it increased inflammatory cytokine secretion at the ligature-implant site. Similar to P. gingivalis, L. zeae promoted ligature-induced neutrophile infiltration, osteoclast activation, and alveolar bone loss.

DISCUSSION

We, therefore, concluded that L. zeae accelerated the progression of periodontitis in the ligature-induced periodontitis mouse model.

Influence of antiresorptive/antiangiogenic therapy on changes in periodontal and oral tissue structures: a histomorphometrical analysis in rats

OBJECTIVE

The objective of this study was to investigate the influence of various antiresorptive and antiangiogenic medications on morphological changes in periodontal and oral tissue structures.

MATERIALS AND METHODS

Fifty-five Wistar rats randomly received dual application (i.e., at baseline and after 12-weeks) one of the following medications: (1) amino-bisphosphonate [zoledronate (Zo)], (2) RANKL inhibitor [denosumab (De)], (3) antiangiogenic [bevacizumab (Be)], (4) Zo + Be, (5) De + Be or (6) no medication [Control (Co)]. Periodontal and oral tissue biopsies were obtained at 17 (n = 21 animals, Phase 1, (De = 3, De + Be = 3, Zo = 5, Be = 3, Zo + Be = 2, Co = 5) and 29 (n = 34 animals, (De = 8, De + Be = 6, Zo = 2, Be = 7, Zo + Be = 4, Co = 7, Phase 2) weeks after the second drug application. The following outcomes were histomorphometrically assessed: periodontal space width in the coronal (PLS-C, mm) and apical sections (PLS- A), number of empty alveolar bone lacunae in the coronal, apical sections and at the apex at respective tooth sites (EL - C, EL- A, EL- Ap), mucosal thickness at edentulous alveolar ridge areas (MT, mm), and, when present, associated areas of inflammatory cell infiltrates (ICI, mm2).

RESULTS

Comparable mean PLS-C, PLS-A, ET-A, ET-C, ET-Ap, and MT values were observed in all experimental groups after Phases 1 and 2. The presence of ICI was identified in 3 animals in the Co group (Phase 1: 1, Phase 2: 2), and 17 animals in the test groups (Phase 1: 4; Phase 2: 14). The estimated ICI surface area was significantly higher in the Zo + Be group, followed by the Zo and Be groups compared to that measured in the Co group. The time (i.e., Phases 1 and 2) was not found to be a predictor for the extent of the ICI area. In all groups, the EL-C, EL-A, and EL-Ap values were significantly higher after Phase 2 compared to those assessed after Phase 1. The MT values were significantly reduced in all groups after Phase 2 compared to those measured after Phase 1.

CONCLUSIONS

The present evaluation was not able to find any morphological effects of different antiresorptive and antiangiogenic medications on periodontal and oral tissue structures. The presence of inflammatory cell infiltrates was more frequently observed in the animals administered with antiresorptive and antiangiogenic medications as well as combinations thereof.

CLINICAL RELEVANCE

Administration of antiresorptive and antiangiogenic medications may be capable of inducing inflammatory reactions in periodontal tissues.

Nifedipine attenuates alveolar bone destruction and improves trabecular microarchitectures in mice with experimental periodontitis

Studies have shown that nifedipine exerts anti-inflammatory and immunosuppressive actions in addition to being a calcium channel blocker. The present study was performed to explore the influence of nifedipine on alveolar bone destruction in mice with experimental periodontitis by evaluating morphological information acquired from micro-computed tomography analysis. BALB/c mice were randomly assigned into four groups: control (C) group; experimental periodontitis (E) group; experimental periodontitis + 10 mg/kg dose of nifedipine (EN10) group; and experimental periodontitis + 50 mg/kg dose of nifedipine (EN50) group. Periodontitis was induced by oral inoculation with Porphyromonas gingivalis over a 3-week time period. Nifedipine significantly mitigated the loss of alveolar bone height as well as increase of root surface exposure induced by experimental periodontitis. Additionally, the reduction in the bone volume fraction associated with P. gingivalis infection was significantly recovered upon nifedipine treatment. Further, nifedipine attenuated P. gingivalis-induced deteriorations in the trabeculae-associated parameters. Significant difference was evident between Groups EN10 and EN50 in both the extent of alveolar bone loss and microstructural parameters assessed, except trabecular separation and trabecular number. Nifedipine appeared to have good performance in ameliorating bone loss in mice with induced periodontitis. Nifedipine may be utilized in the clinical management of periodontitis, though further research is indicated to verify the therapeutic effect.

Clostridium butyricum MIYAIRI 588 alleviates periodontal bone loss in mice with diabetes mellitus

The gut microbiota is a bridge linking periodontitis and systemic diseases, such as diabetes mellitus (DM). The probiotic Clostridium butyricum MIYAIRI 588 (CBM588) is reportedly an effective therapeutic approach for gut dysbiosis. Here, in a mouse model, we explored the therapeutic effect of CBM588 on periodontal bone destruction in DM and DM-associated periodontitis (DMP), as well as the underlying mechanism. Micro-computed tomography revealed that DM and DMP both aggravated periodontal bone destruction, which was alleviated by intragastric supplementation with CBM588. Moreover, 16S rRNA sequencing and untargeted metabolite analysis indicated that CBM588 ameliorated DMP-triggered dysbiosis and led to reduced oxidative stress associated with elevated 4-hydroxybenzenemethanol (4-HBA) in serum. Furthermore, in vitro and in vivo experiments found that the metabolite 4-HBA promoted nuclear factor erythroid 2-related factor 2 (Nrf2) signaling activation and modulated the polarization of macrophages, thus ameliorating inflammatory bone destruction in DMP. Our study demonstrates the protective effects of CBM588 in DM-induced mice, with and without ligature-induced periodontitis. The mechanism involves regulation of the gut microbiota and restoration of the integrity of the gut barrier to alleviate oxidative damage by elevating serum 4-HBA. This study suggests the possibility of CBM588 as a therapeutic adjuvant for periodontal treatment in diabetes patients.

Osteocyte RANKL Drives Bone Resorption in Mouse Ligature-Induced Periodontitis

Mouse ligature-induced periodontitis (LIP) has been used to study bone loss in periodontitis. However, the role of osteocytes in LIP remains unclear. Furthermore, there is no consensus on the choice of alveolar bone parameters and time points to evaluate LIP. Here, we investigated the dynamics of changes in osteoclastogenesis and bone volume (BV) loss in LIP over 14 days. Time-course analysis revealed that osteoclast induction peaked on days 3 and 5, followed by the peak of BV loss on day 7. Notably, BV was restored by day 14. The bone formation phase after the bone resorption phase was suggested to be responsible for the recovery of bone loss. Electron microscopy identified bacteria in the osteocyte lacunar space beyond the periodontal ligament (PDL) tissue. We investigated how osteocytes affect bone resorption of LIP and found that mice lacking receptor activator of NF-κB ligand (RANKL), predominantly in osteocytes, protected against bone loss in LIP, whereas recombination activating 1 (RAG1)-deficient mice failed to resist it. These results indicate that T/B cells are dispensable for osteoclast induction in LIP and that RANKL from osteocytes and mature osteoblasts regulates bone resorption by LIP. Remarkably, mice lacking the myeloid differentiation primary response gene 88 (MYD88) did not show protection against LIP-induced bone loss. Instead, osteocytic cells expressed nucleotide-binding oligomerization domain containing 1 (NOD1), and primary osteocytes induced significantly higher Rankl than primary osteoblasts when stimulated with a NOD1 agonist. Taken together, LIP induced both bone resorption and bone formation in a stage-dependent manner, suggesting that the selection of time points is critical for quantifying bone loss in mouse LIP. Pathogenetically, the current study suggests that bacterial activation of osteocytes via NOD1 is involved in the mechanism of osteoclastogenesis in LIP. The NOD1-RANKL axis in osteocytes may be a therapeutic target for bone resorption in periodontitis. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

GPR40 deficiency worsens metabolic syndrome-associated periodontitis in mice

BACKGROUND AND OBJECTIVE

G protein-coupled receptor 40 (GPR40) is a receptor for medium- and long-chain free fatty acids (FFAs). GPR40 activation improves type 2 diabetes mellitus (T2DM), metabolic syndrome (MetS), and the complications of T2DM and MetS. Periodontitis, a common oral inflammatory disease initiated by periodontal pathogens, is another complication of T2DM and MetS. Since FFAs play a key role in the pathogenesis of MetS which exacerbates periodontal inflammation and GPR40 is a FFA receptor with anti-inflammatory properties, it is important to define the role of GPR40 in MetS-associated periodontitis.

MATERIALS AND METHODS

We induced MetS and periodontitis by high-fat diet and periodontal injection of lipopolysaccharide (LPS), respectively, in wild-type and GPR40-deficient mice and determined alveolar bone loss and periodontal inflammation using micro-computed tomography, histology, and osteoclast staining. We also performed in vitro study to determine the role of GPR40 in the expression of proinflammatory genes.

RESULTS

The primary outcome of the study is that GPR40 deficiency increased alveolar bone loss and enhanced osteoclastogenesis in control mice and the mice with both MetS and periodontitis. GPR40 deficiency also augmented periodontal inflammation in control mice and the mice with both MetS and periodontitis. Furthermore, GPR40 deficiency led to increased plasma lipids and insulin resistance in control mice but had no effect on the metabolic parameters in mice with MetS alone. For mice with both MetS and periodontitis, GPR40 deficiency increased insulin resistance. Finally, in vitro studies with macrophages showed that deficiency or inhibition of GPR40 upregulated proinflammatory genes while activation of GPR40 downregulated proinflammatory gene expression stimulated synergistically by LPS and palmitic acid.

CONCLUSION

GPR40 deficiency worsens alveolar bone loss and periodontal inflammation in mice with both periodontitis and MetS, suggesting that GPR40 plays a favorable role in MetS-associated periodontitis. Furthermore, GPR40 deficiency or inhibition in macrophages further upregulated proinflammatory and pro-osteoclastogenic genes induced by LPS and palmitic acid, suggesting that GPR40 has anti-inflammatory and anti-osteoclastogenic properties.

The Presence of Periodontitis Exacerbates Non-Alcoholic Fatty Liver Disease via Sphingolipid Metabolism-Associated Insulin Resistance and Hepatic Inflammation in Mice with Metabolic Syndrome

Clinical studies have shown that periodontitis is associated with non-alcoholic fatty liver disease (NAFLD). However, it remains unclear if periodontitis contributes to the progression of NAFLD. In this study, we generated a mouse model with high-fat diet (HFD)-induced metabolic syndrome (MetS) and NAFLD and oral P. gingivalis inoculation-induced periodontitis. Results showed that the presence of periodontitis increased insulin resistance and hepatic inflammation and exacerbated the progression of NAFLD. To determine the role of sphingolipid metabolism in the association between NAFLD and periodontitis, we also treated mice with imipramine, an inhibitor of acid sphingomyelinase (ASMase), and demonstrated that imipramine treatment significantly alleviated insulin resistance and hepatic inflammation, and improved NAFLD. Studies performed in vitro showed that lipopolysaccharide (LPS) and palmitic acid (PA), a major saturated fatty acid associated with MetS and NAFLD, synergistically increased the production of ceramide, a bioactive sphingolipid involved in NAFLD progression in macrophages but imipramine effectively reversed the ceramide production stimulated by LPS and PA. Taken together, this study showed for the first time that the presence of periodontitis contributed to the progression of NAFLD, likely due to alterations in sphingolipid metabolism that led to exacerbated insulin resistance and hepatic inflammation. This study also showed that targeting ASMase with imipramine improves NAFLD by reducing insulin resistance and hepatic inflammation.

High-fat diet-induced metabolic syndrome increases ligature-induced alveolar bone loss in mice

BACKGROUND

It has been well documented that metabolic syndrome (MetS) increases severity of periodontitis. In this study, we determined the effect of high-fat diet (HFD)-induced MetS on alveolar bone loss in a mouse model with ligature-induced periodontitis. To understand how MetS increases bone loss, we tested our hypothesis that palmitic acid (PA), a most abundant saturated fatty acid in the HFD, interacts with lipopolysaccharide (LPS) to promote osteoclastogenesis.

METHODS

We induced MetS by feeding mice HFD for 18 weeks and induced periodontitis with ligature placement. After treatments, we assessed alveolar bone loss using micro-computed tomography and determined osteoclastogenesis using tartrate-resistant acid phosphatase (TRAP) staining. To explore the mechanisms, we treated macrophages with PA, LPS or both and analyzed the osteoclast formation and cytokine expression in macrophages.

RESULTS

While ligature robustly induced periodontitis in mice with or without MetS, the mice with MetS had more bone loss than those without MetS. PA and LPS cooperatively induced osteoclast formation and stimulated the expression of inflammatory cytokines involved in osteoclastogenesis potentially via a FAT/CD36-dependent mechanism in macrophages.

CONCLUSIONS

HFD-induced MetS increases alveolar bone loss in mice with ligature-induced periodontitis, and PA and LPS cooperatively stimulate osteoclast formation and proinflammatory gene expression in macrophages.

IL-1β and TNF-α play an important role in modulating the risk of periodontitis and Alzheimer's disease

BACKGROUND

Systemic activation of the immune system can exert detrimental effects on the central nervous system. Periodontitis, a chronic disease of the oral cavity, is a common source of systemic inflammation. Neuroinflammation might be a result of this to accelerate progressive deterioration of neuronal functions during aging or exacerbate pre-existing neurodegenerative diseases, such as Alzheimer's disease. With advancing age, the progressive increase in the body's pro-inflammatory status favors the state of vulnerability to both periodontitis and Alzheimer's disease. In the present study, we sought to delineate the roles of cytokines in the pathogenesis of both diseases.

METHODS

To examine the impacts of periodontitis on the onset and progression of Alzheimer's disease, 6-month-old female 3 × Tg-AD mice and their age-matched non-transgenic mice were employed. Periodontitis was induced using two different experimental models: heat-killed bacterial-induced periodontitis and ligature-induced periodontitis. To delineate the roles of pro-inflammatory cytokines in the pathogenesis of periodontitis and Alzheimer's disease, interleukin 1 beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) were also injected into the buccal mandibular vestibule of mice.

RESULTS

Here, we show that IL-1β and TNF-α were two of the most important and earliest cytokines upregulated upon periodontal infection. The systemic upregulation of these two cytokines promoted a pro-inflammatory environment in the brain contributing to the development of Alzheimer's disease-like pathology and cognitive dysfunctions. Periodontitis-induced systemic inflammation also enhanced brain inflammatory responses and subsequently exacerbated Alzheimer's disease pathology and cognitive impairment in 3 × Tg-AD mice. The role of inflammation in connecting periodontitis to Alzheimer's disease was further affirmed in the conventional magnetization transfer experiment in which increased glial responses resulting from periodontitis led to decreased magnetization transfer ratios in the brain of 3 × Tg-AD mice.

CONCLUSIONS

Systemic inflammation resulting from periodontitis contributed to the development of Alzheimer's disease tau pathology and subsequently led to cognitive decline in non-transgenic mice. It also potentiated Alzheimer's disease pathological features and exacerbated impairment of cognitive function in 3 × Tg-AD mice. Taken together, this study provides convincing evidence that systemic inflammation serves as a connecting link between periodontitis and Alzheimer's disease.

The Fungal Metabolite (+)-Terrein Abrogates Inflammatory Bone Resorption via the Suppression of TNF-α Production in a Ligature-Induced Periodontitis Mouse Model

Current periodontal treatment focuses on the mechanical removal of the source of infection, such as bacteria and their products, and there is no approach to control the host inflammatory response that leads to tissue destruction. In order to control periodontal inflammation, we have previously reported the optimization of (+)-terrein synthesis methods and the inhibitory effect of (+)-terrein on osteoclast differentiation in vitro. However, the pharmacological effect of (+)-terrein in vivo in the periodontitis model is still unknown. In this study, we investigated the effect of synthetic (+)-terrein on inflammatory bone resorption using a ligature-induced periodontitis mouse model. Synthetic (+)-terrein (30 mg/kg) was administered intraperitoneally twice a week to the mouse periodontitis model. The control group was treated with phosphate buffer. One to two weeks after the induction of periodontitis, the periodontal tissues were harvested for radiological evaluation (micro-CT), histological evaluation (HE staining and TRAP staining), and the evaluation of inflammatory cytokine production in the periodontal tissues and serum (quantitative reverse-transcription PCR, ELISA). The synthetic (+)-terrein-treated group suppressed alveolar bone resorption and the number of osteoclasts in the periodontal tissues compared to the control group (p < 0.05). In addition, synthetic (+)-terrein significantly suppressed both mRNA expression of TNF-α in the periodontal tissues and the serum concentration of TNF-α (both p < 0.05). In conclusion, we have demonstrated that synthetic (+)-terrein abrogates alveolar bone resorption via the suppression of TNF-α production and osteoclast differentiation in vivo. Therefore, we could expect potential clinical effects when using (+)-terrein on inflammatory bone resorption, including periodontitis.

Efficacy of a Novel Pleiotropic MMP-Inhibitor, CMC2.24, in a Long-Term Diabetes Rat Model with Severe Hyperglycemia-Induced Oral Bone Loss

Purpose

CMC2.24, a novel 4-(phenylaminocarbonyl)-chemically-modified-curcumin, is a pleiotropic MMP-Inhibitor of various inflammatory/collagenolytic diseases including periodontitis. This compound has demonstrated efficacy in host modulation therapy along with improved resolution of inflammation in various study models. The objective of current study is to determine the efficacy of CMC2.24 in reducing the severity of diabetes, and its long-term role as an MMP-inhibitor, in a rat model.

Methods

Twenty-one adult male Sprague-Dawley rats were randomly distributed into three groups: Normal (N), Diabetic (D) and Diabetic+CMC2.24 (D+2.24). All three groups were orally administered vehicle: carboxymethylcellulose alone (N, D), or CMC2.24 (D+2.24; 30mg/kg/day). Blood was collected at 2-months and 4-months' time-point. At completion, gingival tissue and peritoneal washes were collected/analyzed, and jaws examined for alveolar bone loss by micro-CT. Additionally, sodium hypochlorite(NaClO)-activation of human-recombinant (rh) MMP-9 and its inhibition by treatment with 10μM CMC2.24, Doxycycline, and Curcumin were evaluated.

Results

CMC2.24 significantly reduced the levels of lower-molecular-weight active-MMP-9 in plasma. Similar trend of reduced active-MMP-9 was also observed in cell-free peritoneal and pooled gingival extracts. Thus, treatment substantially decreased conversion of pro- to actively destructive proteinase. Normalization of the pro-inflammatory cytokine (IL-1ß, resolvin-RvD1), and diabetes-induced osteoporosis was observed in presence of CMCM2.24. CMC2.24 also exhibited significant anti-oxidant activity by inhibiting the activation of MMP-9 to a lower-molecular-weight (82kDa) pathologically active form. All these systemic and local effects were observed in the absence of reduction in severity of hyperglycemia.

Conclusion

CMC2.24 reduced activation of pathologic active-MMP-9, normalized diabetic osteoporosis, and promoted resolution of inflammation but had no effect on the hyperglycemia in diabetic rats. This study also highlights the role of MMP-9 as an early/sensitive biomarker in the absence of change in any other biochemical parameter. CMC2.24 also inhibited significant activation of pro-MMP-9 by NaOCl (oxidant) adding to known mechanisms by which this compound treats collagenolytic/inflammatory diseases including periodontitis.

Platelet-rich fibrin combined with new bone graft material for mandibular defect repair: A in vivo study on rabbits

Insufficient bone mass is still a difficult point to be solved in oral implantation, so new bone graft materials are continuously researched and discussed in clinical practice in order to obtain better bone augmentation. In order to explore whether platelet-rich fibrin (PRF) can promote the formation of new bone in mineralized collagen (MC), MC/PRF and pure MC were implanted into the bilateral mandibular defect model in rabbits, respectively. Micro-CT scan and histological evaluation of the target area at 4, 8, and 12 weeks after operation. The results of Micro-CT three-dimensional reconstruction analysis showed that the ratio of bone volume to total volume (BV/TV), trabecular bone number (Tb.N), trabecular bone thickness (Tb.Th) and trabecular bone separation (Tb.Sp) and residual material volume fraction (RMVF) in the MC/PRF group were better than those in the MC group (p<0.05). The results of HE and Masson staining showed that the new bone formation and material degradation rate of the MC/PRF group were better than those of the MC group. The results suggest that PRF can accelerate the formation of new bone in MC, and provide new ideas for the clinical application of new bone graft materials.

Development of an Orally Active Small-Molecule Inhibitor of Receptor Activator of Nuclear Factor-κB Ligand

Receptor activator of nuclear factor-κB (RANK) and its ligand, RANKL, play pivotal roles in bone remodeling. The monoclonal antibody denosumab successfully inhibited the maturation of osteoclasts (OCs) by binding to RANKL in the clinic. We continued our efforts to develop small-molecule inhibitors of RANKL. In this work, 41 β-carboline derivatives were synthesized based on previously synthesized compound Y1599 to improve its drug-like properties. Compound Y1693 was identified as a potent RANKL inhibitor that improved absorption-distribution-metabolism-excretion properties and effectively prevented RANKL-induced osteoclastogenesis and bone resorption. Furthermore, Y1693 also suppressed the expression of OC marker genes. Moreover, Y1693 demonstrated good tolerability and efficacy in an orally administered mouse model of osteoporosis as well as the ability to rescue alveolar bone loss in vivo caused by periodontal disease. Collectively, the above findings may provide a valuable direction for the development of novel antiresorptive therapies that target RANKL.

Systemic Dietary Hesperidin Modulation of Osteoclastogenesis, Bone Homeostasis and Periodontal Disease in Mice

This study aimed to evaluate the effects of hesperidin (HE) on in vitro osteoclastogenesis and dietary supplementation on mouse periodontal disease and femoral bone phenotype. RAW 264.7 cells were stimulated with RANKL in the presence or absence of HE (1, 100 or 500 µM) for 5 days, and evaluated by TRAP, TUNEL and Western Blot (WB) analyses. In vivo, C57BL/6 mice were given HE via oral gavage (125, 250 and 500 mg/kg) for 4 weeks. A sterile silk ligature was placed between the first and second right maxillary molars for 10 days and microcomputed tomography (μCT), histopathological and immunohistochemical evaluation were performed. Femoral bones subjected or not to dietary HE (500 mg/kg) for 6 and 12 weeks were evaluated using μCT. In vitro, HE 500 µM reduced formation of RANKL-stimulated TRAP-positive(+) multinucleated cells (500 µM) as well as c-Fos and NFATc1 protein expression (p < 0.05), markers of osteoclasts. In vivo, dietary HE 500 mg/kg increased the alveolar bone resorption in ligated teeth (p < 0.05) and resulted in a significant increase in TRAP+ cells (p < 0.05). Gingival inflammatory infiltrate was greater in the HE 500 mg/kg group even in the absence of ligature. In femurs, HE 500 mg/kg protected trabecular and cortical bone mass at 6 weeks of treatment. In conclusion, HE impaired in vitro osteoclastogenesis, but on the contrary, oral administration of a high concentration of dietary HE increased osteoclast numbers and promoted inflammation-induced alveolar bone loss. However, HE at 500 mg/kg can promote a bone-sparing effect on skeletal bone under physiological conditions.

Ligature-induced periodontitis mouse model protocol for studying Saccharibacteria

This protocol outlines the process of preparing Saccharibacteria (TM7) and applying ligature with and without TM7 onto a mouse molar, and measuring the subsequent bone resorption and inflammation. This ligature model is particularly useful in studying the pathogenicity of specific bacteria that do not typically colonize the mouse oral cavity. This is especially true in the case of TM7 bacteria that prefer to grow on the surface of other bacteria. For complete details on the use and execution of this protocol, please refer to Chipashvili et al. (2021).

Experimental Periodontitis Deteriorated Atherosclerosis Associated With Trimethylamine N-Oxide Metabolism in Mice

Background

Periodontitis is considered a risk factor for atherosclerosis, but the mechanism is not clear. It was reported that oral administration of Porphyromonas gingivalis altered the gut microbiota in mice. Gut dysbiosis and the intestinal metabolite trimethylamine N-oxide (TMAO) were verified to be associated with atherosclerosis. Therefore, the possible TMAO-related mechanism between periodontitis and atherosclerosis needs to be explored.

Methods

Experimental periodontitis was established by oral administration of P. gingivalis for 2 months in ApoE^−/− mice. Mouse hemi-mandibles were scanned using Micro-CT. Quantification of TMAO was performed using liquid chromatography–tandem mass spectrometry. Mouse feces were collected and the bacterial DNA was extracted, then the gut microbiota was analyzed using 16S rRNA genes. Atherosclerotic lesion areas were quantified. Livers, small intestines, and large intestines were analyzed for gene expression.

Results

Aggravated atherosclerosis plaques were found in experimental periodontitis mice. Plasma TMAO, a pathogenic factor of atherosclerosis, was initially found to be increased in periodontitis mice. Changes in the composition and abundance of the intestinal microflora of periodontitis mice were found. Flavin monooxygenase 3 (FMO3), the catalyzing enzyme of TMAO in the liver, was significantly increased, accompanied by an increase of IL-6 in liver, the abnormal intestinal integrity and enhanced plasma LPS. The IL-6 and LPS were verified to be able to increase FMO3 in HepG2 cells.

Conclusion

Our research discovered that experimental periodontitis in ApoE^−/− mice induced gut dysbiosis and an increase in TMAO. These results suggest a possible mechanism by which periodontitis may accelerate atherosclerosis by influencing the intestinal microbes and the metabolism, which were triggered by inflammation of the liver and intestine.

Avaliação da perda óssea utilizando diferentes parâmetros na análise microtomográfica. Estudo em ratos

Resumo Introdução o desafio no uso do Micro-Ct tem sido estabelecer e padronizar padrões adequados para escaneamento e tratamento das imagens, para que se obtenha o máximo desempenho do equipamento, e permitir a comparação dos achados entre diferentes estudos. Objetivo o presente estudo tem como objetivo comparar a porcentagem de volume ósseo em regiões com perda óssea periodontal utilizando diferentes metodologias para definição da área a ser analisada (ROI). Material e método dez ratos foram submetidos à indução de doença periodontal, e, após a eutanásia, as mandíbulas foram escaneadas com cortes de 9 μ e 18 μm de espessura, com passo de rotação de 0.3mm. As imagens foram reconstituídas utilizando o software NRecon, e em seguida, utilizando o software CTAnalyser – CTAn, foram definidas as áreas de interesse (ROI) ao redor dos segundos molares. A primeira área de interesse (ROI1) foi definida em um padrão retangular que se restringiu às regiões interproximais e furca, onde a área total de tecido ósseo foi obtida somando os resultados dos 3 ROIs. A segunda área (ROI2) foi definida no sentido corono/apical ao redor do segundo molar até suas limitações proximais com os dentes vizinhos, onde a porcentagem de tecido ósseo pertencente às raízes foram excluídas das avaliações. As análises foram realizadas com cinco diferentes valores de thresholds (130-50, 130-60, 130-70, 130-80, 130-90 e 130-100). Resultado a análise entre os diferentes ROIs demonstrou que em ambas as análises foi observada a tendência a menor porcentagem de tecido ósseo quanto maior o contraste de tons de cinza utilizado, no entanto, nos resultados obtidos no ROI2 essa diferença não foi estatisticamente significante. Conclusão com os resultados obtidos pode se concluir que a utilização de diferentes thresholds para quantificação óssea, em áreas onde houve doença periodontal, pode trazer resultados divergentes; a definição da área de interesse interfere com os resultados obtidos e que a obtenção de uma área de interesse com a remoção das raízes mostrou-se menos susceptível à variação dos parâmetros de escaneamento.

Inhibition of acid sphingomyelinase by imipramine abolishes the synergy between metabolic syndrome and periodontitis on alveolar bone loss

BACKGROUND AND OBJECTIVE

Clinical studies have shown that metabolic syndrome (MetS) exacerbates periodontitis. However, the underlying mechanisms remain largely unknown. Since our animal study has shown that high-fat diet-induced MetS exacerbates lipopolysaccharide (LPS)-stimulated periodontitis in mouse model and our in vitro study showed that acid sphingomyelinase (aSMase) plays a key role in the amplification of LPS-triggered pro-inflammatory response by palmitic acid (PA) in macrophages, we tested our hypothesis that inhibitor of aSMase attenuates MetS-exacerbated periodontitis in animal model. Furthermore, to explore the potential underlying mechanisms, we tested our hypothesis that aSMase inhibitor downregulates pro-inflammatory and pro-osteoclastogenic gene expression in macrophages in vitro.

MATERIAL AND METHODS

We induced MetS and periodontitis in C57BL/6 mice by feeding high-fat diet (HFD) and periodontal injection of A. actinomycetemcomitans LPS, respectively, and treated mice with imipramine, a well-established inhibitor of aSMase. Micro-computed tomography (micro-CT), tartrate-resistant acid phosphatase staining, histological and pathological evaluations as well as cell cultures were performed to evaluate alveolar bone loss, osteoclast formation, periodontal inflammation and pro-inflammatory gene expression.

RESULTS

Analysis of metabolic parameter showed that while HFD induced MetS by increasing bodyweight, insulin resistance, cholesterol and free fatty acids, imipramine reduced free fatty acids but had no significant effects on other metabolic parameters. MicroCT showed that either MetS or periodontitis significantly reduced bone volume fraction (BVF) of maxilla and the combination of MetS and periodontitis further reduced BVF. However, imipramine increased BVF in mice with both MetS and periodontitis to a level similar to that in mice with periodontitis alone, suggesting that imipramine abolished the synergy between MetS and periodontitis on alveolar bone loss. Consistently, results showed that imipramine inhibited osteoclast formation and periodontal inflammation in mice with both MetS and periodontitis. To elucidate the mechanisms by which imipramine attenuates MetS-exacerbated periodontitis, we showed that imipramine inhibited the upregulation of pro-inflammatory cytokines and transcription factor c-FOS as well as ceramide production by LPS plus PA in macrophages.

CONCLUSION

This study has shown that imipramine as an inhibitor of aSMase abolishes the synergy between MetS and periodontitis on alveolar bone loss in animal model and inhibits pro-inflammatory and pro-osteoclastogenic gene expression in macrophages in vitro. This study provides the first evidence that aSMase is a potential therapeutic target for MetS-exacerbated periodontitis.

Quercetin Preserves Oral Cavity Health by Mitigating Inflammation and Microbial Dysbiosis

Failure to attenuate inflammation coupled with consequent microbiota changes drives the development of bone-destructive periodontitis. Quercetin, a plant-derived polyphenolic flavonoid, has been linked with health benefits in both humans and animals. Using a systematic approach, we investigated the effect of orally delivered Quercetin on host inflammatory response, oral microbial composition and periodontal disease phenotype. In vivo, quercetin supplementation diminished gingival cytokine expression, inflammatory cell infiltrate and alveolar bone loss. Microbiome analyses revealed a healthier oral microbial composition in Quercetin-treated versus vehicle-treated group characterized by reduction in the number of pathogenic species including Enterococcus, Neisseria and Pseudomonas and increase in the number of non-pathogenic Streptococcus sp. and bacterial diversity. In vitro, Quercetin diminished inflammatory cytokine production through modulating NF-κB:A20 axis in human macrophages following challenge with oral bacteria and TLR agonists. Collectively, our findings reveal that Quercetin supplement instigates a balanced periodontal tissue homeostasis through limiting inflammation and fostering an oral cavity microenvironment conducive of symbiotic microbiota associated with health. This proof of concept study provides key evidence for translational studies to improve overall health.

Suppression of alveolar bone resorption by salubrinal in a mouse model of periodontal disease

AIMS

The relationship between stress to endoplasmic reticulum (ER) and periodontitis has been known, and ER stress induced by Porphyromonas gingivalis results in the loss of alveolar bone. Salubrinal is a small synthetic compound and attenuates ER stress through inhibition of de-phosphorylation of eukaryotic translation initiation factor 2 alpha (eIF2α). In this study, we examined whether salubrinal attenuates periodontitis in a mouse model of experimental periodontal disease.

MATERIALS AND METHODS

We evaluated loss of alveolar bone and attachment levels in periodontium using micro-computed tomography (μCT) and hematoxylin-eosin (HE) staining, respectively. Furthermore, we measured osteoclast numbers using tartrate-resistant acid phosphatase (TRAP) staining and osteoblast numbers using HE staining for bone resorption and for bone formation, respectively. To examine the inhibitory effects of salubrinal against pro-inflammatory cytokines, we measured TNF-α and IL1-β score in periodontium using immunohistostaining.

KEY FINDINGS

The results revealed that salubrinal suppressed loss of alveolar bone and attachment levels in periodontium induced by periodontitis. It decreased osteoclast numbers and increased osteoblasts. It also suppressed the expression levels of TNF-α in periodontium.

SIGNIFICANCE

These results show that salubrinal alleviates periodontitis through suppression of alveolar bone resorption and the pro-inflammatory cytokine, and promotion of the bone formation. Since salubrinal has been shown to have these beneficial effects for periodontal disease, it may provide a novel therapeutic possibility for the disease.

Angiopoietin-like protein 2 deficiency promotes periodontal inflammation and alveolar bone loss

BACKGROUND

Human periodontitis is a highly prevalent inflammatory disease that leads to connective tissue degradation, alveolar bone resorption, and tooth loss. Angiopoietin-like 2 (ANGPTL2) regulates chronic inflammation in various diseases and is functionally involved in maintaining tissue homeostasis and promoting tissue regeneration, but there is limited information about its function in periodontitis. Here we investigated the expression and explicit role of ANGPTL2 in periodontitis.

METHODS

Immunohistochemistry and quantitative real-time PCR (qRT-PCR) were used to detect the ANGPTL2 expression in periodontal tissues and periodontal ligament cells (PDLCs). A ligature-induced periodontitis model was generated in wild-type and ANGPTL2 knockout mice. qRT-PCR and enzyme-linked immunosorbent assay were used to assess the production of inflammatory cytokines and matrix metalloproteinases (MMPs) in cultured PDLCs. Western blot was performed to detect proteins in relevant signaling pathways.

RESULTS

Increased ANGPTL2 expression was observed in inflamed periodontal tissues and PDLCs. ANGPTL2 deficiency promoted alveolar bone loss with enhanced osteoclastogenesis and inflammatory reactions in ligature-induced periodontitis. Downregulation of ANGPTL2 remarkably enhanced expression levels of interleukin (IL)-6, IL-8, MMP1, and MMP13 in Porphyromonas gingivalis lipopolysaccharide-induced PDLCs, whereas ANGPTL2-overexpressing PDLCs showed opposite trends. ANGPTL2 downregulation activated STAT3 and nuclear factor-κB pathways and blocked Akt signaling under inflammatory environment. Treatment with a STAT3 inhibitor partially suppressed the inflammatory reaction of PDLCs mediated by ANGPTL2 knockdown.

CONCLUSIONS

Our study provides the first evidence of an anti-inflammatory effect of ANGPTL2 in murine periodontitis. The findings demonstrate the critical and protective role of ANGPTL2 in alveolar bone loss and periodontal inflammation.

B-Cell Deficiency Exacerbates Inflammation and Bone Loss in Ligature-Induced Experimental Periodontitis in Mice

Objective

Periodontitis, one of the most prevalent chronic oral infectious diseases in humans, is induced by the breakdown in the balance between the biofilm and host immune system. Previous studies have shown the presence of large numbers of B cells in periodontitis lesions, implicating that B lymphocytes play a predominant role during the pathogenesis of periodontitis. This study aimed to investigate the role of all B cells in the initiation of periodontitis.

Methods

Experimental periodontitis was induced in B cell-deficient (CD19Cre) mice and wild-type (WT) control mice by 5-0 silk ligation around the maxillary second molar. Four weeks after ligation, alveolar bone loss was determined by micro-computed tomography. The levels of inflammatory cytokines and receptor activator of NF-κB ligand (RANKL)/osteoprotegerin in periodontal lesions were analyzed using real-time quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, and immunohistochemistry. Lymphocyte populations in the cervical lymph nodes and spleen and among the peripheral blood mononuclear cells were detected by flow cytometry.

Results

B-cell deficiency resulted in increased severity of alveolar bone loss in mouse experimental periodontitis, which was associated with increased osteoclast activity and upregulated RANKL expression in the periodontal lesions. In addition, gingiva cytokine expression profiles were shifted to T helper type 1 (Th1) and Th17 in the CD19Cre mice with ligature-induced periodontitis compared with WT mice. In addition, a reduced CD4⁺/CD8⁺ T cell ratio was observed in the CD19Cre mice.

Conclusion

B-cell deficiency exacerbates the inflammation and alveolar bone loss in ligature-induced experimental periodontitis in mice, implicating that B cells may overall play a protective role in the initiation of periodontitis.

Ablation of transient receptor potential vanilloid subtype 1-expressing neurons in rat trigeminal ganglia aggravated bone resorption in periodontitis with diabetes

OBJECTIVES

We aimed to investigate the contribution of neurons expressing transient receptor potential vanilloid subtype 1 (TRPV1) to alveolar bone homeostasis in periodontitis with diabetes.

DESIGN

Diabetes was induced by streptozotocin injection in Sprague-Dawley rats. Resiniferatoxin was injected into left trigeminal ganglia to ablate TRPV1-expressing neurons. 3-0 silks were tied around left maxillary second molars to induce experimental periodontitis. Alveolar bone was assessed by micro-computed tomography and tartrate-resistant acid phosphatase staining. Macrophages were detected by immunohistochemistry staining.

RESULTS

TRPV1 expression in trigeminal ganglia was increased in diabetic rats compared to non-diabetic counterparts. Local ablation of TRPV1 eliminated facial heat hyperalgesia but aggravated alveolar bone damage and osteoclastogenesis in experimental periodontitis in both diabetic and non-diabetic rats. Immunohistochemistry staining presented enhanced macrophage infiltration and M1 macrophage polarization in periodontal lesions in TRPV1-ablated groups.

CONCLUSIONS

These findings demonstrated that TRPV1 expression in trigeminal ganglia could be enhanced in diabetic condition, and the integrity of TRPV1-expressing neurons in trigeminal ganglia exerted a neuroprotective effect against alveolar bone resorption and inflammation in diabetic periodontitis.

A Novel Modified-Curcumin Promotes Resolvin-Like Activity and Reduces Bone Loss in Diabetes-Induced Experimental Periodontitis

PURPOSE

Clinically, it is challenging to manage diabetic patients with periodontitis. Biochemically, both involve a wide range of inflammatory/collagenolytic conditions which exacerbate each other in a "bi-directional manner." However, standard treatments for this type of periodontitis rely on reducing the bacterial burden and less on controlling hyper-inflammation/excessive-collagenolysis. Thus, there is a crucial need for new therapeutic strategies to modulate this excessive host response and to promote enhanced resolution of inflammation. The aim of the current study is to evaluate the impact of a novel chemically-modified curcumin 2.24 (CMC2.24) on host inflammatory response in diabetic rats.

METHODS

Type I diabetes was induced by streptozotocin injection; periodontal breakdown then results as a complication of uncontrolled hyperglycemia. Non-diabetic rats served as controls. CMC2.24, or the vehicle-alone, was administered by oral gavage daily for 3 weeks to the diabetics. Micro-CT was used to analyze morphometric changes and quantify bone loss. MMPs were analyzed by gelatin zymography. Cell function was examined by cell migration assay, and cytokines and resolvins were measured by ELISA.

RESULTS

In this severe inflammatory disease model, administration of the pleiotropic CMC2.24 was found to normalize the excessive accumulation and impaired chemotactic activity of macrophages in peritoneal exudates, significantly decrease MMP-9 and pro-inflammatory cytokines to near normal levels, and markedly increase resolvin D1 (RvD1) levels in the thioglycolate-elicited peritoneal exudates (tPE). Similar effects on MMPs and RvD1 were observed in the non-elicited resident peritoneal washes (rPW). Regarding clinical relevance, CMC2.24 significantly inhibited the loss of alveolar bone height, volume and mineral density (ie, diabetes-induced periodontitis and osteoporosis).

CONCLUSION

In conclusion, treating hyperglycemic diabetic rats with CMC2.24 (a tri-ketonic phenylaminocarbonyl curcumin) promotes the resolution of local and systemic inflammation, reduces bone loss, in addition to suppressing collagenolytic MMPs and pro-inflammatory cytokines, suggesting a novel therapeutic strategy for treating periodontitis complicated by other chronic diseases.

Influence of the treatment with the antineoplastic agents 5-fluorouracil and cisplatin on the severity of experimental periodontitis in rats

PURPOSE

The determination on how antineoplastic agents interfere on the progression of periodontitis is critical for improvement and even development of novel therapeutic approaches for periodontal management. This study evaluated the influence of chemotherapy with 5-fluorouracil (5-FU) or cisplatin (CIS) on healthy periodontal tissues and on the progression of experimental periodontitis (EP).

METHODS

One hundred forty-four male rats were divided into six groups (n = 24). Each group was treated with physiological saline solution (PSS) 0.9%, 5-FU, or CIS. Experimental periodontitis (EP) was induced by ligature placement. Animals were euthanized at 7, 15, and 30 days after treatment. Data were statistically analyzed (p ≤ 0.05).

RESULTS

The groups with EP and treated with 5-FU or CIS showed lower percentage of bone volume in the furcation region and higher percentage of alveolar bone loss, higher number of TRAP-positive cells, and lower number of PCNA-positive cells when compared group with EP and treated with PSS (p ≤ 0.05). Groups with EP and treated with 5-FU or CIS showed high immunolabelling pattern of RANKL, TNF-α, and IL-1β, moderate of BAX, and low of HIF-1α. Histological analysis showed severe tissue breakdown in the groups with EP and treated with 5-FU or CIS.

CONCLUSIONS

Chemotherapy with antineoplastic agents 5-FU and CIS increased the intensity and duration of the inflammation and compromised tissue repair by reduction in cellular and vascular turnover. The more severe periodontal breakdown was caused by 5-FU.

Local administration of ReveromycinA ointment suppressed alveolar bone loss in mice

ReveromycinA (RMA) was developed and is a unique agent for inhibiting osteoclast activity. In a previous study, we experimentally induced periodontal disease in a high-turnover osteoporosis osteoprotegerin-knockout mice (OPG KO) model and found that intraperitoneal administration of RMA inhibited alveolar bone resorption. We prepared a novel RMA-containing ointment for topical non-invasive administration in the oral cavity, in preparation for possible future clinical application. And we investigated whether this ointment can inhibit alveolar bone resorption in an experimental mouse model of periodontal disease. We examined wild-type (WT) and OPG KO mice ligated with wire around contact points on the left first and second molars to cause food impaction and induce experimental periodontal disease. RMA was administered three times a day. Using micro-computed tomography, we measured the volume of alveolar bone loss and also performed histological analysis. Our findings showed that localized administration of RMA containing ointment resulted in suppressed alveolar bone resorption, reduced osteoclast count, and lower immunostaining scores of inflammation sites compared with controls in both OPG KO and WT mice. Localized application of the specific osteoclast suppressor RMA in ointment form in the oral cavity could be a novel treatment for periodontitis that inhibits alveolar bone resorption locally.

Quantitative morphometric analysis of molar teeth and alveolar bone using micro-computed tomography in aged mice

OBJECTIVES

Irreversible morphological regressions of the teeth or related structures in older people can diminish their overall health. However, research on human aging in dentistry is complicated by several confounding factors. In this study, we conducted a morphometric analysis of the mandibular second molars and surrounding alveolar bone in C57BL/6 mice to evaluate age-related changes in the oral cavity.

METHODS

The animals were divided into five groups based on their age: 4 weeks (juvenile mice; n=5); 20 weeks (n=7), 50 weeks (n=5), 77 weeks (n=7), and 100 weeks (n=5); changes were evaluated using micro-computed tomography.

RESULTS

The molars of juvenile mice had sharp and pointed cusps and presented maximum heights. With age and occlusal wear, the cusp heights demonstrated a significant decrease (up to 75%) until the last stage of life. Conversely, apparent lesions were not observed on the basal portion of the crown, even in the most heavily worn teeth. The roots of the molars continued to grow in length at 4 weeks of age. Alveolar bone resorption begins to occur in middle age and continues throughout life. The proportion of vertical bone loss reached approximately 40% of the entire root length, demonstrating a remarkable increase between weeks 77 and 100.

CONCLUSIONS

Overall, these morphological changes were similar to those observed in humans. Therefore, it might be appropriate to use aged mice as an experimental model for basic and clinical research in geriatric dentistry.

Pathological and Therapeutic Approach to Endotoxin-Secreting Bacteria Involved in Periodontal Disease

It is widely recognized that periodontal disease is an inflammatory entity of infectious origin, in which the immune activation of the host leads to the destruction of the supporting tissues of the tooth. Periodontal pathogenic bacteria like Porphyromonas gingivalis, that belongs to the complex net of oral microflora, exhibits a toxicogenic potential by releasing endotoxins, which are the lipopolysaccharide component (LPS) available in the outer cell wall of Gram-negative bacteria. Endotoxins are released into the tissues causing damage after the cell is lysed. There are three well-defined regions in the LPS: one of them, the lipid A, has a lipidic nature, and the other two, the Core and the O-antigen, have a glycosidic nature, all of them with independent and synergistic functions. Lipid A is the "bioactive center" of LPS, responsible for its toxicity, and shows great variability along bacteria. In general, endotoxins have specific receptors at the cells, causing a wide immunoinflammatory response by inducing the release of pro-inflammatory cytokines and the production of matrix metalloproteinases. This response is not coordinated, favoring the dissemination of LPS through blood vessels, as well as binding mainly to Toll-like receptor 4 (TLR4) expressed in the host cells, leading to the destruction of the tissues and the detrimental effect in some systemic pathologies. Lipid A can also act as a TLRs antagonist eliciting immune deregulation. Although bacterial endotoxins have been extensively studied clinically and in a laboratory, their effects on the oral cavity and particularly on periodontium deserve special attention since they affect the connective tissue that supports the tooth, and can be linked to advanced medical conditions. This review addresses the distribution of endotoxins associated with periodontal pathogenic bacteria and its relationship with systemic diseases, as well as the effect of some therapeutic alternatives.

Hyperglycemia modulates M1/M2 macrophage polarization via reactive oxygen species overproduction in ligature-induced periodontitis

BACKGROUND AND OBJECTIVE

Periodontitis in diabetic patients is characterized by enhanced inflammation and aggravated tissue damage in comparison with that in non-diabetic counterparts. The progression of periodontal damage under diabetic condition can be partly ascribed to hyperglycemia-induced disturbance between immune activation and inflammation resolution, where macrophages are capable of participating given their plasticity in response to different stimuli. Herein, we aimed to investigate the changes of macrophage polarization in periodontitis under diabetic condition and the underlying mechanism.

MATERIALS AND METHODS

Type-1 diabetes was induced by the injection of streptozotocin (STZ, 60 mg/kg) in Sprague-Dawley rats. Rats in N-acetyl cysteine (NAC)-treated groups received NAC dissolved in drinking water (200 mg/kg/day). Experimental periodontitis was induced by ligating 3-0 silk around left maxillary second molars for 4 weeks. Alveolar bone destruction was tested by micro-computed tomography and tartrate-resistant acid phosphatase (TRAP) staining. M1/M2 macrophage polarization in periodontal tissue was detected by immunohistochemistry staining. RAW264.7 were cultured in normal glucose (5.5 mM) or high glucose environment (25 mM) with or without NAC (8 mmol/L). LPS (100 ng/ml) and IL-4 (20 ng/ml) were used to induce M1 macrophages and M2 macrophages, respectively. M1/M2 macrophage polarization was detected by qRT-PCR, immunofluorescent staining, and flow cytometry. Reactive oxygen species (ROS) accumulation was detected by fluorogenic probes. RANKL (100 ng/ml) were applied to induce osteoclastogenic differentiation of RAW264.7, and osteoclast formation was examined by TRAP staining.

RESULTS

Rats with diabetes displayed enhanced macrophages infiltration and M1 macrophage polarization in periodontal lesions compared with vehicle-treated rats. Under LPS or IL-4 stimulation, high glucose culture of RAW264.7 elevated ROS level and increased the expression of M1 macrophage markers (iNOS, TNF-α, and IL-6) whereas decreased the expression of M2 macrophage markers (Arg-1 and CD206). Supernatants of high glucose-treated M1/M2 macrophages enhanced osteoclast formation compared to normal glucose-cultured cells. Decreasing ROS level via NAC partially reversed the effect of high glucose on M1/M2 macrophage polarization. Meanwhile, daily intake of NAC in rodent models inhibited M1 macrophage polarization, which subsequently ameliorated alveolar bone loss and decreased osteoclast numbers in periodontitis in diabetic rats.

CONCLUSION

These findings demonstrated that hyperglycemia could polarize macrophage toward M1 macrophages via overproducing ROS under inflammatory condition, which might take responsibility for aggravated periodontal damage in periodontitis under diabetic condition. Inhibiting M1 macrophages and restoring M2 macrophages by ROS scavenger is hopefully a potential adjunct treatment strategy for diabetic periodontitis.

Gram-positive bacteria cell wall-derived lipoteichoic acid induces inflammatory alveolar bone loss through prostaglandin E production in osteoblasts

Periodontitis is an inflammatory disease associated with severe alveolar bone loss and is dominantly induced by lipopolysaccharide from Gram-negative bacteria; however, the role of Gram-positive bacteria in periodontal bone resorption remains unclear. In this study, we examined the effects of lipoteichoic acid (LTA), a major cell-wall factor of Gram-positive bacteria, on the progression of inflammatory alveolar bone loss in a model of periodontitis. In coculture of mouse primary osteoblasts and bone marrow cells, LTA induced osteoclast differentiation in a dose-dependent manner. LTA enhanced the production of PGE₂ accompanying the upregulation of the mRNA expression of mPGES-1, COX-2 and RANKL in osteoblasts. The addition of indomethacin effectively blocked the LTA-induced osteoclast differentiation by suppressing the production of PGE₂. Using ex vivo organ cultures of mouse alveolar bone, we found that LTA induced alveolar bone resorption and that this was suppressed by indomethacin. In an experimental model of periodontitis, LTA was locally injected into the mouse lower gingiva, and we clearly detected alveolar bone destruction using 3D-μCT. We herein demonstrate a new concept indicating that Gram-positive bacteria in addition to Gram-negative bacteria are associated with the progression of periodontal bone loss.

Effects of Limosilactobacillus fermentum CCFM1139 on experimental periodontitis in rats

Periodontitis is a polymicrobial inflammatory disease often characterized by the excessive colonization of Porphyromonas gingivalis and Fusobacterium nucleatum, which causes alveolar bone resorption and advanced oral inflammation. This study aimed to evaluate the effect of Limosilactobacillus fermentum CCFM1139 on experimental periodontitis induced following ligature and infection with P. gingivalis and F. nucleatum in vivo. The results showed that L. fermentum CCFM1139 significantly reduced weight loss associated with periodontal inflammation (p < 0.05), while decreasing both the P. gingivalis and F. nucleatum populations within the oral cavity of rats (p < 0.05) and regulating the expression of tumor necrosis factor-alpha, interleukin (IL)-1 beta, and IL-8 in the periodontal tissue (p < 0.05). Microcomputed tomography (micro-CT) and histopathological examination revealed that L. fermentum CCFM1139 supplementation reduced the level of alveolar bone loss and bone porosity and increased bone volume (p < 0.05) in the experimental animals. Furthermore, L. fermentum CCFM1139 exhibited promising effects in preventing the deepening of the periodontal pocket and the increase in the gap between adjacent molars. Thus L. fermentum CCFM1139 was shown to have solid potential as an oral probiotic for protection against periodontitis suggesting that this may be a good candidate in the production of a new functional food for improving periodontitis.

Effects of a β2-adrenergic receptor blocker on experimental periodontitis in spontaneously hypertensive rats

AIMS

Recent studies have reported a relationship between periodontal disease and hypertension, and previous evidence suggests that the sympathetic nervous system plays an important role in the control of bone metabolism. This study sought to evaluate the effect of the beta-2 adrenergic receptor (β2-AR) blocker butoxamine on experimental periodontitis in a rat model.

MATERIALS AND METHODS

Wistar-Kyoto and spontaneously hypertensive rats (n = 6 per group) were orally administered butoxamine 1 mg/kg/day and experimental periodontitis was induced by applying an orthodontic ligature wire. The rats were sacrificed after 4 weeks and the residual alveolar bone was measured using micro-computed tomography (micro-CT) imaging analysis software for histological analysis.

KEY FINDINGS

Micro-CT imaging analysis showed a higher ratio of residual alveolar bone, BV/TV, and Tb.N in both Wistar-Kyoto and spontaneously hypertensive rats treated with butoxamine compared with the corresponding control rats. In histological analysis, compared with the Wistar-Kyoto and spontaneously hypertensive rat control groups, the corresponding butoxamine-treated groups showed a lower ratio of attachment level, lower values of osteoclast number and surface.

SIGNIFICANCE

β2-AR blockers maintained the alveolar bone mass and attachment level by suppressing osteoclast activity. Thus, β2-AR blockers may be effective in preventing periodontitis.

Electrosprayed minocycline hydrochloride-loaded microsphere/SAIB hybrid depot for periodontitis treatment

Minocycline hydrochloride (MINO) has been one of the most frequently used antibiotics in the treatment of periodontitis due to its antibacterial activity and osteogenesis effects; however, high levels of MINO administered during the treatment halt the formation of new bone. Therefore, the purpose of the present study was to prepare a MINO-microsphere/sucrose acetate isobutyrate (SAIB) hybrid depot to reduce the burst release of MINO and ensure antibacterial and osteogenesis effects of MINO in the treatment of periodontitis. Uniform microspheres, approximately 5 µm size, with a slightly rough surface and different MINO loading (10, 12, and 14%) were prepared, and the microspheres were added into SAIB, after which the burst release significantly decreased from 66.18 to 2.92%, from 71.82 to 3.82%, and from 73.35 to 4.45%, respectively, and the release from all the MINO-microspheres/SAIB hybrid depots lasted for 77 days. In addition, cytotoxicity test showed that the MINO-microsphere with 12% drug loading promoted the proliferation of osteoblasts the most and was subsequently used in vivo experiments. Moreover, in the model of ligatured-induced periodontitis in SD rats, the MINO-microsphere/SAIB hybrid depot not only significantly increased the alveolar bone height and bone volume but also reduced the inflammation of the periodontal tissue. Additionally, it also inhibited the expression of the receptor activator of nuclear factor-kappa B ligand (RANKL) and promoted the expression of osteoprotegerin (OPG).. These results indicated that the MINO-microsphere/SAIB hybrid depot might be promising in the treatment of periodontitis.

Diabetes fuels periodontal lesions via GLUT1-driven macrophage inflammaging

Hyperglycemia induces chronic low-grade inflammation (inflammaging), which is a newly identified contributor to diabetes-related tissue lesions, including the inflammatory bone loss in periodontitis. It is also a secondary senescent pattern mediated by an increased burden of senescent cells and senescence-associated secretory phenotype (SASP). Macrophage is a key SASP-spreading cell and may contribute to the maintenance of SASP response in the periodontal microenvironment. Using a transgenic diabetic model (BLKS/J-Lepr^db/lepr^db mice) we identified striking senescence of the periodontium in young (18-wk)-diabetic mice accompanied by amassed p16⁺-macrophages and enhanced early SASP response. Exposed to high glucose in vitro, bone marrow-derived macrophage (BMDM) revealed a strong GLUT1 mRNA response driving the elevated-glucose uptake. GLUT1 is a representative and facilitative glucose transporter in macrophages with potential roles in hyperglycemia-induced inflammation. In this study, both GLUT1 and the downstream GTPase Rheb expression upregulated in the gingiva of diabetic mice with impaired condition. Furthermore, SASP release and p16/p21 signaling were proven to be triggered by mTOR phosphorylation in BMDM and antagonized by restricting glucose uptake in GLUT1^-/- BMDM. Taken together, our findings suggest that elevated-GLUT1 sensor responded to high glucose is important for macrophage senescence and SASP response, generated as a result of hyperglycemia, and it is a potential molecular mechanism for the exacerbation of periodontitis in diabetes.

Febuxostat Attenuates the Progression of Periodontitis in Rats

INTRODUCTION

Periodontitis is a lifestyle-related disease that is characterized by chronic inflammation in gingival tissue. Febuxostat, a xanthine oxidase inhibitor, exerts anti-inflammatory and antioxidant effects.

OBJECTIVE

The present study investigated the effects of febuxostat on periodontitis in a rat model.

METHODS

Male Wistar rats were divided into 3 groups: control, periodontitis, and febuxostat-treated periodontitis groups. Periodontitis was induced by placing a ligature wire around the 2nd maxillary molar and the administration of febuxostat (5 mg/kg/day) was then initiated. After 4 weeks, alveolar bone loss was assessed by micro-computed tomography and methylene blue staining. The expression of osteoprotegerin (OPG), a bone resorption inhibitor, was detected by quantitative RT-PCR and immunological staining, and the number of osteoclasts in gingival tissue was assessed by tartrate-resistant acid phosphatase staining. The mRNA and protein expression levels of the proinflammatory cytokines, tumor necrosis factor-alpha (TNF-α), and interleukin-1 beta (IL-1β), in gingival tissue were measured using quantitative RT-PCR and immunological staining. Oxidative stress in gingival tissue was evaluated by the expression of 4-hydroxy-2-nonenal (4-HNE), and 8-hydroxy-2-deoxyguanosine (8-OHdG). To clarify the systemic effects of periodontitis, blood pressure and glucose tolerance were examined.

RESULTS

In rats with periodontitis, alveolar bone resorption was associated with reductions in OPG and increases in osteoclast numbers. The gingival expression of TNF-α, IL-1β, 4-HNE, and 8-OHdG was up-regulated in rats with periodontitis. Febuxostat significantly reduced alveolar bone loss, proinflammatory cytokine levels, and oxidative stress. It also attenuated periodontitis-induced glucose intolerance and blood pressure elevations.

CONCLUSION

Febuxostat prevented the progression of periodontitis and associated systemic effects by inhibiting proinflammatory mediators and oxidative stress.

Timing of Mouse Molar Formation Is Independent of Jaw Length Including Retromolar Space

For humans and other mammals to eat effectively, teeth must develop properly inside the jaw. Deciphering craniodental integration is central to explaining the timely formation of permanent molars, including third molars which are often impacted in humans, and to clarifying how teeth and jaws fit, function and evolve together. A factor long-posited to influence molar onset time is the jaw space available for each molar organ to form within. Here, we tested whether each successive molar initiates only after a minimum threshold of space is created via jaw growth. We used synchrotron-based micro-CT scanning to assess developing molars in situ within jaws of C57BL/6J mice aged E10 to P32, encompassing molar onset to emergence. We compared total jaw, retromolar and molar lengths, and molar onset times, between upper and lower jaws. Initiation time and developmental duration were comparable between molar upper and lower counterparts despite shorter, slower-growing retromolar space in the upper jaw, and despite size differences between upper and lower molars. Timing of molar formation appears unmoved by jaw length including space. Conditions within the dental lamina likely influence molar onset much more than surrounding jaw tissues. We theorize that molar initiation is contingent on sufficient surface area for the physical reorganization of dental epithelium and its invagination of underlying mesenchyme.

Guidelines for Micro-Computed Tomography Analysis of Rodent Dentoalveolar Tissues

Micro–computed tomography (μCT) has become essential for analysis of mineralized as well as nonmineralized tissues and is therefore widely applicable in the life sciences. However, lack of standardized approaches and protocols for scanning, analyzing, and reporting data often makes it difficult to understand exactly how analyses were performed, how to interpret results, and if findings can be broadly compared with other models and studies. This problem is compounded in analysis of the dentoalveolar complex by the presence of four distinct mineralized tissues: enamel, dentin, cementum, and alveolar bone. Furthermore, these hard tissues interface with adjacent soft tissues, the dental pulp and periodontal ligament (PDL), making for a complex organ. Drawing on others' and our own experience analyzing rodent dentoalveolar tissues by μCT, we introduce techniques to successfully analyze dentoalveolar tissues with similar or disparate compositions, densities, and morphological characteristics. Our goal is to provide practical guidelines for μCT analysis of rodent dentoalveolar tissues, including approaches to optimize scan parameters (filters, voltage, voxel size, and integration time), reproducibly orient samples, define regions and volumes of interest, segment and subdivide tissues, interpret findings, and report methods and results. We include illustrative examples of analyses performed on genetically engineered mouse models with phenotypes in enamel, dentin, cementum, and alveolar bone. The recommendations are designed to increase transparency and reproducibility, promote best practices, and provide a basic framework to apply μCT analysis to the dentoalveolar complex that can also be extrapolated to a variety of other tissues of the body. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Acid-induced demineralisation of human enamel as a function of time and pH observed using X-ray and polarised light imaging

Acid-induced enamel demineralisation affects many individuals either by exposure to acidic diets, acidic gas pollution (dental erosion) or to dental plaque acids (dental caries). This study aimed to develop in situ X-ray and light imaging methods to determine progression of enamel demineralisation and the dynamic relationship between acid pH and mineral density. Hourly digital microradiograph time-lapse sequences showed the depth of enamel demineralisation in 500 µm thick sections progressed with time from the surface towards the dentine following a power-law function, which was 21% faster than the lateral demineralisation progression after exposure for 85 h to lactic acid (10%, pH 2.2). The minimum greyscale remaining (mineral content) within the induced enamel lesion followed an exponential decay, while the accumulated total greyscale loss with time was linear, which showed a constant anisotropic mineral release within the enamel architecture. This 85 h demineralisation method studied by polarised light microscopy time-lapse sequences showed that once the demineralisation front reached the enamel Hunter-Schreger bands, there was preferential demineralisation along those bands. Mineral density loss was linear with increasing pH acidity between pH 5.2 and pH 4.0 (with 0.4 pH increments) when incubated over a 3-week period exposed to 0.5% lactic acid. At pH 4.0, there was complete mineral loss in the centre of the demineralised area after the 3-week period and the linear function intercepted the x-axis at ~ pH 5.5, near the critical pH for hydroxyapatite (HAp). These observations showed how intrinsic enamel structure and pH affected the progression of demineralisation. STATEMENT OF SIGNIFICANCE: Hydroxyapatite crystallites (HAp) in human enamel dissolve when exposed to an acidic environment but little is known about how the intrinsic structures in enamel and pH influence the demineralisation kinetics. We have developed a time-lapse in situ microradiography method to quantify microscopic anisotropic mineral loss dynamics in response to an acid-only caries model. Correlation with polarised light microscopy time-lapse sequences showed that larger structures in enamel also influence demineralisation progression as demineralisation occurred preferentially along the Hunter-Schreger bands (decussating prismatic enamel). The pH-controlled enamel mineral release in a linear manner quantifying the relationship between HAp orientation and acid solubility. These findings should direct the development of improved anti-demineralisation/ remineralisation treatments to retain/ restore the natural intrinsic enamel structure.

A 2-plane micro-computed tomographic alveolar bone measurement approach in mice

Purpose

This study introduces a standardized 2-plane approach using 8 landmarks to assess alveolar bone levels in mice using micro-computed tomography.

Materials and Methods

Bone level differences were described as distance from the cemento-enamel junction (CEJ) to alveolar bone crest (ABC) and as percentages of vertical bone height and vertical bone loss, comparing mice infected with Porphyromonas gingivalis (Pg) to controls. Eight measurements were obtained per tooth: 2 in the sagittal plane (mesial and distal) and 6 in the coronal plane (mesiobuccal, middle-buccal, distobuccal, mesiolingual, middle-lingual, and distolingual).

Results

Significant differences in the CEJ-to-ABC distance between Pg-infected mice and controls were found in the coronal plane (middle-lingual, mesiobuccal, and distolingual for the first molar; and mesiobuccal, middle-buccal, and distolingual for the second molar). In the sagittal plane, the distal measurement of the second molar was different. The middle-buccal, mesiobuccal, and distolingual sites of the first and second molars showed vertical bone loss relative to controls; the second molar middle-lingual site was also different. In the sagittal plane, the mesial sites of the first and second molars and the distal site of the second molar showed loss. Significantly different vertical bone height percentages were found for the mesial and distal sites of the second molar (sagittal plane) and the middle-lingual and distolingual sites of the first molar(coronal plane).

Conclusion

A reliable, standardized technique for linear periodontal assessments in mice is described. Alveolar bone loss occurred mostly on the lingual surface of the coronal plane, which is often omitted in studies.

Inhibition of Cathepsin K Alleviates Autophagy-Related Inflammation in Periodontitis-Aggravating Arthritis

Rheumatoid arthritis (RA) and periodontitis share many epidemiological and pathological features, with emerging studies reporting a relationship between the two diseases. Recently, RA and periodontitis have been associated with autophagy. In the present study, we investigated the effects of cathepsin K (CtsK) inhibition on RA with periodontitis in a mouse model and its immunological function affecting autophagy. To topically inhibit CtsK periodontitis with arthritis in the animal model, adeno-associated virus (AAV) transfection was performed in periodontal and knee joint regions. Transfection of small interfering RNA (siRNA) was performed to inhibit CtsK in RAW264.7 cells. The effects of CtsK inhibition on the autophagy pathway were then evaluated in both in vivo and in vitro experiments. RA and periodontitis aggravated destruction and inflammation in their respective lesion areas. Inhibition of CtsK had multiple effects: (i) reduced destruction of alveolar bone and articular tissue, (ii) decreased macrophage numbers and inflammatory cytokine expression in the synovium, and (iii) alleviated expression of the autophagy-related transcription factor EB (TFEB) and microtubule-associated protein 1A/1B-light chain 3 (LC3) at the protein level in knee joints. Inhibition of CtsK in vitro reduced the expression of autophagy-related proteins and related inflammatory factors. Our data revealed that the inhibition of CtsK resisted the destruction of articular tissues and relieved inflammation from RA with periodontitis. Furthermore, CtsK was implicated as an imperative regulator of the autophagy pathway in RA and macrophages.

A new anabolic compound, LLP2A-Ale, reserves periodontal bone loss in mice through augmentation of bone formation

BACKGROUND

Currently, there are no effective medications to reverse periodontal disease (PD)-induced bone loss. The objective of this study was to test a new anabolic compound, LLP2A-Ale, or with the combination treatment of mesenchymal stromal cell (MSC), in the treatment of bone loss secondary to PD.

METHODS

PD was induced in mice by placing a ligature around the second right molar. At one week after disease induction, the mice were treated with placebo, LLP2A-Ale, MSCs, or combination of LLP2A-Ale + MSCs, and euthanized at week 4.

RESULTS

We found that PD induced alveolar bone loss that was associated with reduced bone formation. LLP2A-Ale alone or in combination with MSCs sustained alveolar bone formation and reversed alveolar bone loss. Additionally, PD alone caused systemic inflammation and increased the circulating levels of G-CSF, IP-10, MIP-1a, and MIP2, which were suppressed by LLP2A-Ale +/- MSCs. LLP2A-Ale +/- MSCs increased bone formation at the peripheral skeletal site (distal femur), which was otherwise suppressed by PD.

CONCLUSION

Our findings indicated that LLP2A-Ale treatment rescued alveolar bone loss caused by PD, primarily by increasing bone formation. LLP2A-Ale also attenuated the circulating levels of a series of inflammatory cytokines and reversed the PD-induced suppression of systemic bone formation.

Photobiomodulation as adjunctive therapy for guided bone regeneration. A microCT study in osteoporotic rat model

Regeneration of diseased bone is challenging. Guided bone regeneration (GBR) has been applied to favor the bone repair. Photobiomodulation (PBM) is also a recognized therapy able to improve bone repair in healthy and diseased individuals. Thus, with the hypothesis that PBM therapy could improve the GBR of diseased bone, this study evaluated the effect of PBM as adjunctive therapy to GBR in osteoporotic rats. Osteoporosis was induced in rats using the oophorectomy model. Then, 5-mm calvaria bone defects were created and treated according to the experimental groups, as follows: with no further treatment (Control); conventional GBR (Membrane), GBR and PBM applied with 3 s, 4 J/cm² and 0.12 J per point (PBM-1) and GBR and PBM applied with 10s, 14 J/cm², 0.4 J per point (PBM-2). PBM therapy (808 nm, 40 mW, 1.42 W/cm²) was applied immediately, 48 and 96 h postoperatively. Four and eight weeks later, the samples were harvested and processed for micro-computerized tomography (Micro CT). Data were statistically compared (p < 0.05). From 4 to 8 weeks mostly significant changes were observed in the PBM groups. The bone volume fraction and number of trabeculae of the PBM groups, especially the PBM-1, were significantly higher than those of Control (p < 0.0001). The values of thickness and separation of the trabeculae and structural model index of the PBM groups were significantly smaller than Control (p < 0.0001). The connectivity density was significantly higher on Membrane and PBM groups than Control (p < 0.0004). The application of PBM as adjunctive therapy to GBR results in enhanced bone formation and maturation in comparison to the conventional GBR in the regeneration of lesions of osteoporotic bone in rats. Overviewing the challenges that face bone regeneration in patients with osteoporosis, our findings open new perspectives on the treatment of bone defects under osteoporotic conditions.

Effects of ınjectable platelet-rich fibrin in experimental periodontitis in rats

Injectable platelet-rich fibrin (i-PRF) is an effective biological material that positively contributes to angiogenesis, wound healing, inflammation, regeneration processes, etc. This research aimed to evaluate the effect of i-PRF in rats with experimental periodontitis. Following the development of ligature-induced periodontitis, 24 Wistar albino rats were divided into three groups. Group-1: scaling and root planing (only-SRP); Group-2: SRP + i-PRF; Group-3: only- i-PRF. Heart blood from six donors was used for the i-PRF application. i-PRF was administered as a subgingival injection in the relevant groups on the 1st, 3rd, and 7th days. The tissues were evaluated histopathologically and immunohistochemically. Also, bone structures were examined using micro-CT. According to the data obtained, no statistically significant difference was observed among the groups in terms of bone resorption, inflammation, bone volume, bone levels (mesial/distal), and IL-1β, IFN-ɤ, TNF-α, VEGF values (p > 0.05). However, bone mineral density was statistically significantly different among the groups (Group3 > Group2 > Group1) (p < 0.0001). Subgingival injection of only-i-PRF showed promising results in periodontitis treatment but contribution to SRP has not been proved according to this study results. The study results suggested that the i-PRF application was as effective as SRP in reducing bone loss, modulating inflammatory process, and effecting cytokines in experimental periodontitis. The significant effect of i-PRF on bone mineral density was the most remarkable result.

Oral dysbiosis induced by Porphyromonas gingivalis is strain-dependent in mice

Background:Porphyromonas gingivalis strain W83, one of the most widely investigated, is considered virulent in the context of periodontitis. The recently isolated P. gingivalis TDC60 has been reported to be highly pathogenic, although it has not yet been investigated in a mouse periodontitis model by oral gavage.

Aim: Our aim was to compare the virulence of both strains by evaluating their impact on alveolar bone loss and the composition of oral microbiota.

Methods: We inoculated by oral gavage C57BL/6 mice with either one of the two P. gingivalis strains and compared to a sham-treated group, without antibiotics pre-treatment. The mandibular alveolar bone of treated mice and controls were assessed, one month after the final inoculation, by microCT measurements. Moreover, at this time, we characterized their oral microbiota by 16S rRNA gene sequencing.

Results: While P. gingivalis W83 successfully initiated periodontitis, TDC60-treated mice only experienced moderate lesions. Furthermore, only W83-treated mice exhibited a specific distinct microbiota, with significantly lower richness and evenness than other samples, and decreased proportions of taxa usually found in healthy individuals.

Conclusion: This association between alveolar bone loss and a major persistent shift of the oral microbiota gives insights into virulence discrepancies among these bacterial strains.

Osteogenic effects of bioabsorbable magnesium implant in rat mandibles and in vitro

BACKGROUND

Bone augmentation or grafting is often required for placement of dental implants or surgical reconstruction of bony defects. Bioabsorbable magnesium implant was shown to promote osteogenesis in long bones. The objectives of this study were to determine osteogenic effects of pure magnesium (Mg) in rat mandible and underlying mechanisms.

METHODS

Pure Mg was implanted in sockets after rat mandibular incisors were extracted. Titanium (Ti) was used as control. Systemic effects were determined by serum Mg level and histologic analyses of liver and kidney. Local Mg concentration was measured by microscopy-energy-dispersive spectroscopy (SEM-EDS). Alveolar bone was analyzed by micro-computed tomography (micro-CT) and histology. Osteogenic effects of 0.8 to 20 mM magnesium chloride (MgCl₂ ) on periosteum-derived cells (PDCs) were evaluated by proliferation, alizarin red staining and quantitative RT-PCR assays.

RESULTS

Systemic effects were similar in Mg and Ti groups. Higher local Mg concentration was detected in Mg group (P < 0.05). Micro-CT showed higher alveolar bone volume (2- and 6-weeks post-operation) and denser cancellous bone (2 weeks post-operation) in Mg group, with significant amount of new subperiosteal bone formation on lateral alveolar bone surfaces by H&E staining. In PDC culture, proliferation rates, osteogenic gene expression for runt related transcription factor 2 (Runx2), bone sialoprotein (Bsp) and osteocalcin (Ocn), as well as calcium nodule formation rose significantly in 5, 10, and 20 mM MgCl₂ groups.

CONCLUSIONS

Rapid osteogenesis (especially subperiosteal) is induced by pure Mg in rat mandibular alveolar bone. Osteogenic capacity of PDCs is enhanced by higher Mg ion concentrations in vitro.