Application of Ligature-Induced Periodontitis in Mice to Explore the Molecular Mechanism of Periodontal Disease

High-Frequency Ultrasound Characterization of Periodontal Soft Tissues Pre- and Post-Bacterial Inoculation

OBJECTIVE

Current diagnostic methods of inflammatory periodontal diseases, e.g., visual evaluation, periodontal probing, and radiographs, are either subjective or insensitive. Intra-oral high-frequency ultrasound was investigated to quantify inflammation by detecting tissue dimensional and perfusion changes.

METHODS

A cohort of 15-month-old mini-pigs, 4 female/male each, was analyzed. Pre-molars (PM) 3 and 4, as well as first molars (M1), were scanned. In bi-weekly time intervals all 4 quadrants were randomly enrolled and bacterial injection followed each quadrant scan in a weekly fashion. Soft tissue dimensions were obtained from B-mode images and statistically analyzed to identify correlations to inoculation time, i.e., response to bacterial loading, tooth type and sex, using analysis of variance and regression analysis. Color flow velocity and power-weighted color pixel density was obtained and statistically analyzed analogous to soft tissue.

RESULTS

Soft tissue thickness increased significantly post-inoculation at 1 and 2 mm below the free gingival margin for both genders and all observed teeth. The significance lasted for weeks 2, 4 and 6, except for female M1s (4 weeks). Color flow velocity was significantly higher compared with baseline for 6 weeks, except for male PM4 (2 weeks). Color flow power did not show significance for PM3 and 4, only in M1 (except male week 4). Significance also extended to tooth type and sex.

CONCLUSION

Periodontal tissue dimension and color flow velocity increased in correlation to bacterial inoculation. Further studies are needed to obtain an understanding of the underlying biology observed here. Eruption of dentition may have been a confounding factor for inflammation interpretation.

Association Between High Dietary Advanced Glycation End Products and Periodontitis

OBJECTIVE

The study aimed to provide evidence for a relationship between a high dietary intake of advanced glycation end products, and periodontitis.

MATERIALS AND METHODS

A total of 2334 adults from the National Health and Nutrition Examination Survey (NHANES) during 2003-2004 were included in this study. Binary regression analysis was conducted to measure the association between periodontitis and dietary advanced glycation end products (AGEs), and two adjusted models were constructed to further explore the relationship.

RESULTS

Participants with AGEs intake above 21.41 U/kcal had a higher prevalence of periodontitis compared to those with lower AGEs intake. After fully adjusting for associated factors, the odds ratios for periodontitis in relation to higher AGEs intake were 1.229 (95% confidence interval 1.015-1.488, p = .034), 1.349 (95% confidence interval 1.157-1.642, p = .003), and 1.331 (95% confidence interval 1.088-1.630 p = .006), respectively.

CONCLUSIONS

Our cross-sectional study reveals a strong association between periodontitis and AGEs.

CLINICAL RELEVANCE

An association between advanced glycation end products in the diet and periodontitis implies the importance of the quality of food intake for good oral health.

PRINCIPAL FINDINGS

The consumption of dietary advanced glycation end products is associated with an increased susceptibility to periodontitis development.

PRACTICAL IMPLICATIONS

These findings contribute to recognizing the harm of advanced glycation end products in various foods to periodontitis, and guiding clinical oral education.

Ginsenoside Rg1 regulating inflammatory response and bone-remodeling through Keap1/Nrf2 signaling pathway in rats with periodontitis

Periodontitis is a chronic inflammatory disease arising from local microorganisms and the host's own aberrant immune regulation. Ginsenoside Rg1(GS-Rg1) is an active extract of ginseng known for its anti-inflammatory and osteogenesis effects. However, GS-Rg1 has not been shown to treat periodontitis and its exact mechanism remains elucidated. Orthodontic wires inoculated with Porphyromonas gingivalis were wrapped around the gingiva of the first molar in rats to induce periodontitis. Inflammatory factor secretion was analyzed using RT-PCR and immunohistochemistry. The number of osteoclasts and secretion of osteogenic factors were analyzed using TRAP staining and immunofluorescence. The destruction of periodontal tissues was evaluated using Micro-CT and H&E staining. Keap1/Nrf2 pathway protein expression was analyzed using Western-Blot and RT-PCR. Applying GS-Rg1 significantly reduced the secretion of inflammatory factors IL-6 and increased the secretion of transforming growth factor TGF-β1. Additionally, GS-Rg1 decreased osteoclast numbers and increased RUNX2 and OCN expression. Furthermore, GS-Rg1 was found to enhance the expression of the related protein Nrf2 while reducing Keap1 expression. GS-Rg1 may effectively alleviate periodontitis through the Keap1/Nrf2 pathway. In conclusion, our study provided the first preclinical evidence to support GS-Rg1 as a potential therapeutic agent for treating periodontitis.

Ligature-induced periodontitis in a transgenic mouse model of Alzheimer's disease dysregulates neuroinflammation, exacerbates cognitive impairment, and accelerates amyloid pathology

A growing body of literature has identified periodontal disease among the modifiable risk factors for Alzheimer's disease (AD), but the mechanisms underlying this relationship is unknown. This study investigated this relationship using a ligature-induced preclinical periodontitis (Pd) model in non-transgenic (non-Tg) and 3xTg-AD mice. We found that ligature placement caused significant alveolar bone loss, with 3xTg-AD mice exhibiting exacerbated bone loss, suggesting AD-related genetic risk may amplify disease progression. Pd induced robust local inflammatory gene expression in both genotypes, but 3xTg-AD mice indicated a dysregulated immune response. Cognitive deficits were observed only in Pd-afflicted 3xTg-AD mice, specifically in hippocampus-mediated spatial memory and perirhinal cortex-mediated object recognition memory, while non-Tg mice remained unaffected. Neuroinflammatory responses varied by brain region, with the hippocampus and prefrontal cortex (PFC) showing the most pronounced changes. In these regions, 3xTg-AD mice exhibited significantly altered cytokine gene expression compared to non-Tg mice, particularly at later time points. Synaptic markers revealed vulnerabilities in 3xTg-AD mice, including reduced baseline Syp expression and dysregulated Synpo post-ligature. Pd transiently reduced glutamate receptor gene expression in both genotypes, with non-Tg mice showing persistent changes, potentially linked to preserved memory. Pd also accelerated amyloid-β (Aβ) deposition and sustained neurodegeneration in 3xTg-AD mice. Overall, this study shows that combining Pd and AD-related genetic risk exacerbates inflammation, cognitive impairment, synaptic dysfunction, Aβ pathology, and neurodegeneration. Neither insult alone was sufficient to produce these effects, highlighting the synergistic impact. These findings emphasize the need to explore anti-inflammatory interventions and downstream mechanisms to mitigate the confluence of these diseases.

Xanthine Derivative KMUP-3 Alleviates Periodontal Bone Resorption by Inhibiting Osteoclastogenesis and Macrophage Pyroptosis

AIM

This study investigated the function effects of KMUP-3, a self-developed synthetic xanthine-based derivative, in suppressing Porphyromonas gingivalis (Pg-LPS)-aggravated osteoclastogenesis and pyroptosis as a potential treatment for periodontitis.

METHODS

In vitro, the effects of Pg-LPS and KMUP-3 on osteoclast formation and macrophage pyroptosis were investigated using the receptor activator of nuclear factor-κB ligand (RANKL)-primed RAW264.7 macrophages. In vivo, the therapeutic effects of KMUP-3 were evaluated in a model of experimental periodontitis induced by gingival ligature placement.

RESULTS

We reveal that KMUP-3 suppressed osteoclastogenesis, inducible nitric oxide synthase activation, and reduced nitric oxide production enhanced by Pg-LPS in RANKL-primed RAW264.7 cells while also decreasing TLR4/NF-κB p65 pathway activation and decreased pro-inflammatory cytokine production; moreover, Pg-LPS promoted NLRP3 activation and exacerbated pyroptosis induction effects that were abolished by KMUP-3. Finally, KMUP-3 ameliorated alveolar bone loss and IL-1β levels in the gingival crevicular fluid in the rat ligature periodontitis model.

CONCLUSIONS

Our study demonstrated that KMUP-3 attenuates Pg-LPS-enhanced osteoclastogenesis and macrophage pyroptosis. Notably, KMUP-3 alleviates alveolar bone loss in experimental periodontitis rats and thus suggests its certain role in safeguarding against periodontal bone resorption.

STING regulates porphyromonas gingivalis lipopolysaccharide-induced pyroptosis and inflammatory response through the NF-κB/NLRP3 signaling pathway in human gingival fibroblasts

OBJECTIVE

The production of reactive oxygen species caused by antimicrobial response during periodontitis leads to the activation of NOD-like receptor protein 3 (NLRP3) inflammasome and pyroptosis. Stimulator of interferon genes (STING) has been found to be involved in regulating pyroptosis and inflammation in a variety of diseases. The present study aimed to investigate whether STING is involved in Porphyromonas gingivalis lipopolysaccharide (P.g LPS)-stimulated human gingival fibroblasts (HGFs) by regulating pyroptosis and inflammation.

DESIGN

After culturing and identifying HGFs, HGFs were treated with P.g LPS. Constructs of si-STING were transfected into HGFs, which were then stimulated with P.g LPS for 24 h. Subsequently, cell viability, pyroptosis, inflammation, oxidative stress and alterations in the STING/TANK-binding kinase 1 (TBK1)/interferon regulatory factor 3 (IRF3)/nuclear factor-kappaB (NF-κB)/NLRP3 signalling pathway were detected.

RESULTS

P.g LPS significantly enhanced STING expression in HGFs. Downregulation of STING rescued P.g LPS-enhanced pyroptosis, oxidative stress and inflammation in HGFs. Moreover, STING was found to bind directly to TBK1 to increase IRF3 phosphorylation and nuclear translocation of NF-κB, thus promoting NLRP3 inflammasome activation. Downregulation of STING rescued P.g LPS-enhanced TBK1/IRF3/NF-κB/NLRP3 pathway activation.

CONCLUSION

STING/TBK1/IRF3/NF-κB/NLRP3 is a key pathway governing pyroptosis, oxidative stress and inflammation of HGFs induced by LPS.

Exacerbating effects of Western dietary habits on experimentally induced periodontitis in rats

This study explored the impact of western diet (WD) on a ligature-induced periodontitis (PD) model. After either control diet (CD) or WD feeding for 16 weeks, male Wistar rats were allocated in six groups (n = 6). The first and second groups had no PD. The third and fourth groups had ligature-induced PD for 10 days, while the fifth and sixth groups had ligature-induced PD for 10 days, followed by ligature removal healing period for another 10 days. The CD contained 13.71% protein, 75.98% carbohydrate, and 10.31% fat, though WD composed of 14.7% protein, 40.7% carbohydrate, and 44.6% fat. After clinical evaluation, the maxillary alveolar bone and gingival tissues were collected for morphometric, microstructural, histological, and gene expression analyses. There were significant increases in the gingival bleeding index, periodontal probing depth, and tooth mobility in WD animals with PD and in the healing groups. The WD groups had a greater alveolar crest height, indicating greater bone resorption. Disruption of the bone microarchitecture by PD was exacerbated in WD-fed animals. The histological evaluation demonstrated a greater extent of gingival inflammation in the PD groups. The Tnf, Il6, Ctsk, and Tnfsf11/RANKL gene expression levels were increased in the WD groups, while the Bglap and Hif1a gene expression levels were decreased in the WD groups. Findings of the study are compelling preclinical evidence that WD deteriorates periodontal health and exacerbates periodontal disease and alveolar bone loss in experimental animals. Future clinical research is warranted to translate these preclinical findings.

Application of Single-Cell Genomics to Animal Models of Periodontitis and Peri-Implantitis

AIMS

This narrative review aims to synthesize current knowledge on integrating single-cell genomics technologies with animal models of periodontitis and peri-implantitis.

REVIEW

Single-cell RNA sequencing (scRNAseq) reveals cellular heterogeneity and specific cell roles in periodontitis and peri-implantitis, overcoming the limitations of bulk RNA sequencing. Under controlled conditions and genetic manipulation, animal models facilitate studying disease progression, gene functions and systemic disease links, aiding targeted therapy development. Knockout models have started to elucidate the impact of genetic mutations on periodontal disease and host responses. scRNAseq in animal models has been used to examine connections between periodontitis and systemic diseases, revealing altered immune environments and cellular interactions. Emerging studies are now applying these methods to animal models of peri-implantitis. Integrating these datasets into single-cell and spatially resolved atlases will enable future meta-analyses, providing deeper insights into disease mechanisms considering factors such as sex, strain, and age.

CONCLUSIONS

Integrating scRNAseq with animal models advances the understanding of periodontitis and peri-implantitis pathogenesis and precision therapies. The combined use of single-cell and spatial genomics and scRNAseq will further enhance data insights significantly for drug discovery and preclinical testing, making these technologies pivotal in validating animal models and translating findings into clinical practice.

Experimental Murine Periodontitis Increases Salivary Gland IgA-Producing B Cells Following Oral Dysbiosis

The oral microbiome is closely involved in the maintenance of host health and the development of systemic diseases. The salivary glands play an essential role in homeostasis in the oral cavity. Here, we investigated the effects of periodontal inflammation on salivary gland function and the oral microbiome. In experimental periodontitis model mice, an increase in IgA⁺ cells in the salivary glands were observed 1 week after treatment. Alteration of the oral microbiome was also induced in this model. Gene expression analysis of the salivary glands showed changes in the expression of genes related to B-cell maturation and plasma cell differentiation and an increase in the expression of genes related to macrophage activation upon experimental periodontitis induction. Furthermore, the relationship between disruption of oral microflora and salivary gland function was examined using a cohousing model in which experimental periodontitis model mice and untreated mice were reared in the same cage. We found that cohoused normal mice underwent alteration of the oral microbiome, with increases in IgA⁺ cells and macrophages in the salivary glands. In summary, our results suggest that, in the oral cavity, there is a close link between oral bacterial flora and immune cells in the salivary glands. Our results also show that localized inflammation disrupts the homeostasis in the oral cavity, inducing pathological conditions such as dysbiosis. Our study suggests the importance of the interaction among local oral inflammation, salivary gland function, and oral microflora, and provides new insights into the mechanisms by which oral health is maintained.

Inhibitory effects of Colocasia antiquorum var. esculenta varnish on inflammation and alveolar bone loss in a rat ligature-induced periodontitis model

We aimed to evaluate whether Colocasia antiquorum var. esculenta (CA) mixed with experimental varnish inhibits inflammation and alveolar bone loss in a rat ligature-induced periodontitis model. The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) were tested and cell viability of CA were also evaluated. The varnish mixed with CA (CAV) was applied to ligature site of Sprague-Dawley rats and alveolar bone loss and cytokines were measured. CA exhibited a MIC of 31.3 μg/mL and an MBC of 62.5 μg/mL against Porphyromonas gingivalis, with no cytotoxicity. The CAV group exhibited significantly lower levels of alveolar bone loss than the PC group (p<0.05). The expression of IL-1β, TNF-α, and IL-6 was significantly decreased, while that of Runx2 was significantly increased in the CAV than in the PC group (p<0.05). In conclusion, CAV demonstrated the potential to improve the symptoms of periodontitis.

Luteolin ameliorates periodontitis by modulating mitochondrial dynamics and macrophage polarization via the JAK2/STAT3 pathway

BACKGROUND

Periodontal disease (PD) is a chronic inflammatory condition affecting oral and systemic health. Luteolin (LUT), a natural flavonoid, has shown anti-inflammatory effects, but its therapeutic potential and mechanisms in PD remain unclear.

OBJECTIVE

This study aimed to investigate the effects of LUT on PD, focusing on its impact on mitochondrial dynamics, macrophage polarization, and the JAK2/STAT3 signaling pathway.

METHODS

A combination of network pharmacology analysis and in vivo and in vitro experiments was employed. The efficacy of LUT was evaluated using a ligature-induced rat PD model and LPS-stimulated THP-1-derived macrophages. Key assessments included micro-CT for bone loss, flow cytometry for macrophage polarization, and Western blot for pathway analysis.

RESULTS

LUT significantly reduced alveolar bone loss and enhanced M2 macrophage polarization, as indicated by increased CD206 and Arg1 expression. Additionally, it improved mitochondrial function by reducing ROS and restoring membrane potential, decreasing mitochondrial fission, and promoting mitochondrial fusion. Mechanistically, LUT inhibited JAK2/STAT3 phosphorylation, promoting anti-inflammatory effects.

CONCLUSION

These findings suggest that LUT ameliorates periodontal inflammation and bone loss by modulating mitochondrial dynamics, promoting M2 macrophage polarization, and suppressing the JAK2/STAT3 signaling pathway. This highlights LUT as a promising multitarget candidate for PD treatment.

Lockd Enhances Mandibular Mesenchymal Stem Cell Proliferation While Inhibiting Osteogenic Capability via Binding With SUZ12 in the Inflammatory Microenvironment

AIM

To investigate the role of lncRNA Lockd in mandibular mesenchymal stem cell (M-MSC) proliferation and osteogenic capability in the inflammatory microenvironment, focusing on its interaction with SUZ12.

MATERIALS AND METHODS

Using lncR Lockd knockdown/overexpression cell models and a murine periodontitis model, we explored Lockd's effects on M-MSC proliferation and osteogenic capability in the inflammatory microenvironment. Predictions from multiple databases and a series of rescue experiments revealed the regulatory role of the Lockd/SUZ12 signalling axis of M-MSC in the inflammatory microenvironment.

RESULTS

Lockd was found to stimulate M-MSC proliferation but impair osteogenic differentiation. The in vitro studies suggested that the activation of Lockd negatively inhibited the osteogenic differentiation process and may ultimately impact bone formation in periodontitis. Mechanistically, it was elucidated that Lockd interacts with SUZ12, a core component of the polycomb repressive complex 2 (PRC2), and may affect the PRC2 complex's role in osteogenic gene expression.

CONCLUSIONS

Lockd boosts the proliferation of M-MSCs but inhibits their osteogenic differentiation by interacting with SUZ12, potentially inhibiting osteogenic capability in the inflammatory microenvironment.

Indoxyl sulfate exacerbates alveolar bone loss in chronic kidney disease through ferroptosis

OBJECTIVES

The purpose of this study was to determine whether indoxyl sulfate (IS) is involved in alveolar bone deterioration and to elucidate the mechanism underlying alveolar bone loss in chronic kidney disease (CKD) patients.

MATERIALS AND METHODS

Mice were divided into the control group, CP group (ligature-induced periodontitis), CKD group (5/6 nephrectomy), and CKD + CP group. The concentration of IS in the gingival crevicular fluid (GCF) was determined by HPLC. The bone microarchitecture was evaluated by micro-CT. MC3T3-E1 cells were stimulated with IS, and changes in mitochondrial morphology and ferroptosis-related factors were detected. RT-PCR, western blotting, alkaline phosphatase activity assays, and alizarin red S staining were utilized to assess how IS affects osteogenic differentiation.

RESULTS

Compared with that in the other groups, alveolar bone destruction in the CKD + CP group was more severe. IS accumulated in the GCF of mice with CKD. IS activated the aryl hydrocarbon receptor (AhR) in vitro, inhibited MC3T3-E1 cell osteogenic differentiation, caused changes in mitochondrial morphology, and activated the SLC7A11/GPX4 signaling pathway. An AhR inhibitor attenuated the aforementioned changes induced by IS.

CONCLUSIONS

IS activated the AhR/SLC7A11/GPX4 signaling pathway, inhibited osteogenesis in MC3T3-E1 cells, and participated in alveolar bone resorption in CKD model mice through ferroptosis.

Effects of periodontal disease on the reproductive performance and offspring of Wistar rats

BACKGROUND

Periodontitis can induce systemic inflammation, and it may affect the testicles and male reproductive performance. This study investigated the effects of periodontitis on the testicles, reproductive performance, and offspring development in male rats.

METHODS

Male Wistar rats were induced with periodontitis by ligating their first molars. After 14 days of inducing periodontal lesions, the animals were observed for an additional 54 days, corresponding to a complete cycle of spermatogenesis. Rats from the periodontitis group (GP, n = 12) and the control group (GC, n = 12) were paired with healthy females (n = 48) for 10 days, equivalent to 2 estrous cycles. Post-mating, the males underwent microtomographic, histological, and reproductive parameter assessments.

RESULTS

Microtomographic analysis revealed higher porosity around the first molar in GP (26 ± 6%) and greater distance between the amelocemental junction and the alveolar bone (1.37 [1.12-1.90] mm), indicative of bone resorption. GP also exhibited significant decreases in final body weight, reduced Sertoli and Leydig cell counts, and lowered testosterone levels compared to GC. Significant morphological alterations in sperm tails were observed in GP compared to GC.

CONCLUSIONS

Periodontitis adversely affected reproductive performance, evoking, and offspring development in male rats. These findings highlight the systemic impacts of periodontal disease on male reproductive health in an animal model.

PLAIN LANGUAGE SUMMARY

Our study investigated how periodontitis can affect male reproductive health in rats and offspring development. We induced periodontitis in male rats and, after a full cycle of sperm production, these rats were mated with healthy females. We observed that the rats with periodontitis had worse reproductive performance compared to the control group without periodontitis. Additionally, the offspring of the rats with periodontitis showed signs of compromised intrauterine development and a higher incidence of congenital malformations. These results highlight that the inflammation caused by periodontitis can have adverse effects beyond the mouth, significantly impacting male reproductive health and offspring development. These findings suggest the need for further research into the clinical implications of periodontitis on reproductive health.

Single-Cell and Spatial Multi-Omics Analysis Reveal That Targeting JAG1 in Epithelial Cells Reduces Periodontal Inflammation and Alveolar Bone Loss

Mucosal immunity plays a critical role in the pathogenesis of inflammatory immune diseases. This study leverages single-cell RNA sequencing, spatial transcriptomics, and spatial proteomics to compare the cellular mechanisms involved in periodontitis between humans and mice, aiming to develop precise strategies to protect the gingival mucosal barrier. We identified key conserved and divergent features in cellular landscapes and transcriptional profiles across the two species, underscoring the complexity of inflammatory responses and immune dynamics in periodontitis. Additionally, we revealed a novel regulatory mechanism by which epithelial cells modulate macrophage behavior and inflammation through the JAG1-Notch pathway. Validation through animal experiments revealed that JAG1 inhibition reduces inflammation in epithelial cells, mitigating periodontitis. Our findings advance the understanding of periodontal disease pathogenesis and highlight the importance of integrating human and animal model data to develop treatments aligned with human physiology, offering potential therapeutic targets for controlling inflammation and enhancing tissue regeneration.

Anti-inflammatory effectiveness of Peperomia pellucida (L.) Kunth in rats induced with periodontitis

Background

Periodontitis, marked by deep periodontal pocket depth (PPD), facilitates bacterial colonization and inflammation, necessitating adjunctive therapies. Although 0.2 % chlorhexidine (CHX) mouthwash is effective, its side effects have led to the search for alternative treatments. Peperomia pellucida (L.) Kunth, known as Pepper Elder, is a traditional medicinal plant with potential as an adjunctive herbal therapy for periodontitis.

Objective

This study aimed to investigate the anti-inflammatory efficacy of Peperomia pellucida extract in rats with induced periodontitis.

Methods

A post-test control group design was used in this laboratory experimental study. Four groups of Wistar strain Rattus norvegicus rats were utilized: a Pristine group (without periodontitis), a negative control group (induced periodontitis only), a positive control group (induced periodontitis and administered 0.2 % CHX), and an experimental group (induced periodontitis and administered 2.5 μL of Pepper Elder extract). Each treatment group received daily administration for one week. PPD measurements were taken on days 0, 3, 5, and 7. Blood serum was collected on day 7 for ELISA to measure IL-1β, TNF-α, IL-10, and IL-13 levels. Statistical analysis was performed using the Kruskal-Wallis test with a post hoc LSD and Mann-Whitney test.

Results

The extract-treated rats showed a decrease in PPD, with significant differences between the extract group and the negative control group (p < 0.05). TNF-α levels in the extract group differed significantly from the negative control group (p < 0.05) but not from the Pristine and positive control groups. IL-1β levels differed significantly only from the negative control group. IL-10 levels were significantly different from both the Pristine and negative control groups, while IL-13 levels differed significantly only from the negative control group.

Conclusion

Peperomia pellucida (L.) Kunth extract exhibits anti-inflammatory effects in rats with induced periodontitis.

Omega-3 fatty acids as a treatment option in periodontitis: Systematic review of preclinical studies

Background: Periodontitis presents as a chronic inflammatory disease that affects the gingival tissues and structures surrounding the tooth. However, the existing approaches for periodontitis do not allow complete control of the disease. In this regard, an active search is being carried out both in preclinical and clinical studies for new approaches based, among other things, on nutraceuticals. Aim: This systematic review aimed to summarize and systematize data from preclinical studies on the effects of the use of polyunsaturated omega-3 fatty acids in experimentally induced periodontitis. Methods: A systematic search for research articles was performed using electronic scientific databases. Only original in vivo experimental studies investigating the use of omega-3 polyunsaturated fatty acids in experimentally induced periodontitis were included. Quality and risk of bias assessment (Systematic Review Centre for Laboratory Animal Experimentation) and quality of evidence assessment (using the modified Grading of Recommendations Assessment, Development and Evaluation approach) were performed. Results: Nineteen studies were included in this systematic review. It has been shown that omega-3 polyunsaturated fatty acids may decrease the progression of periodontitis with amelioration of alveolar bone loss along with decreased pro-inflammatory response and inhibition of osteoclasts. Despite the promising results, most of the analyzed studies were characterized by low to moderate quality and a significant risk of bias. Conclusion: Based on the retrieved data, the possibility of extrapolating the obtained results to humans is limited, indicating the need for additional studies to elucidate the key patterns and mechanisms of action of omega-3 polyunsaturated fatty acids and their endogenous metabolites in experimentally induced periodontitis.

Epithelial RANKL Limits Experimental Periodontitis via Langerhans Cells

Due to its capacity to drive osteoclast differentiation, the receptor activator of nuclear factor kappa-β ligand (RANKL) is believed to exert a pathological influence in periodontitis. However, RANKL was initially identified as an activator of dendritic cells (DCs), expressed by T cells, and exhibits diverse effects on the immune system. Hence, it is probable that RANKL, acting as a bridge between the bone and immune systems, plays a more intricate role in periodontitis. Using ligature-induced periodontitis (LIP), rapid alveolar bone loss was detected that was later halted even though the ligature was still present. This late phase of LIP was also linked with immunosuppressive conditions in the gingiva. Further investigation revealed that the ligature prompted an immediate migration of RANK-expressing Langerhans cells (LCs) and EpCAM+ DCs, the antigen-presenting cells (APCs) of the gingival epithelium, to the lymph nodes, followed by an expansion of T regulatory (Treg) cells in the gingiva. Subsequently, the ligatured gingiva was repopulated by monocyte-derived RANK-expressing EpCAM+ DCs, while gingival epithelial cells upregulated RANKL expression. Blocking RANKL signaling with monoclonal antibodies significantly reduced the frequencies of Treg cells in the gingiva and prevented gingival immunosuppression. In addition, RANKL signaling facilitated the differentiation of LCs from bone marrow precursors. To further investigate the role of RANKL, we used K14-RANKL mice, in which RANKL is overexpressed by gingival epithelial cells. The elevated RANKL expression shifted the steady-state frequencies of LCs and EpCAM+ DCs within the epithelium, favoring LCs over EpCAM+ DCs. Following ligature placement, heightened levels of Treg cells were observed in the gingiva of K14-RANKL mice, and alveolar bone loss was significantly reduced. These findings suggest that RANKL-RANK interactions between gingival epithelial cells and APCs are crucial for suppressing gingival inflammation, highlighting a protective immunological role for RANKL in periodontitis that was overlooked due to its osteoclastogenic activity.

Periodontitis and diabetes in pregnant rats: Maternal-fetal outcomes

Aim

To evaluate the repercussions of periodontitis and diabetes association on rat pregnancy and newborns.

Methods

Diabetes was induced in female Wistar rats 24 h after birth through the administration of Streptozotocin. The diabetic condition of the rats was further confirmed in adulthood. After mating, the pregnant rats were distributed into four experimental groups (n = 12 rats/group): nondiabetic and diabetic with and without periodontitis. Periodontitis was induced by a ligature inserted into the first molar on day 0 of pregnancy. Body weight, water and feed consumption were evaluated weekly, and an oral glucose tolerance test was performed on day 17 of pregnancy. On day 21 of pregnancy, the animals were anesthetized and killed for organ removal. The hemimandibles were collected to analyze alveolar bone loss. Immunological and biochemical parameters were evaluated in the maternal blood samples, and reproductive performance was analyzed. The newborns were weighed, and anomalies evaluated.

Results

The group with diabetes and periodontitis had a greater degree of alveolar bone loss, along with higher relative pancreatic weight, blood glucose levels, triglyceride and inflammatory cytokine levels, hepatic transaminase activity, and embryonic losses. In addition, these newborns had increased body weight, placental weight, a greater number of ossification centers, and a higher rate of visceral and skeletal anomalies.

Conclusion

The combination of maternal diabetes and periodontitis negatively impacts maternal parameters and fetal development. The findings reinforce the importance of maintaining maternal oral health to ensure the general health of the offspring, especially in cases where diabetes is present.

Current clinical framework on nitric oxide role in periodontal disease and blood pressure

OBJECTIVES

In this review, we explored potential associations between NO and its derivatives, nitrite and nitrate, with periodontal and cardiovascular diseases, with special emphasis on the former. By providing a state-of-the-art and integrative understanding of this topic, we aimed to shed light on the potential role of these three nitrogen oxides in the periodontitis-hypertension nexus, identify knowledge gaps, and point out critical aspects of the experimental methodologies.

MATERIALS AND METHODS

A comprehensive literature review was conducted on human salivary and plasma concentrations of nitrate and nitrite, and their impact on periodontal and cardiovascular health.

RESULTS

A nitrate-rich diet increases nitrate and nitrite levels in saliva and plasma, promoting oral health by favorably altering the oral microbiome. Chlorhexidine (CHX) mouthrinses disrupt the nitrate-nitrite-NO pathway, reducing NO bioavailability, and potentially affecting blood pressure. This is because CHX eliminates nitrate-reducing bacteria, which are essential for NO production. Although endogenous NO production may be insufficient, the nitrate-nitrite-NO pathway plays a critical role in maintaining appropriate endothelial function, which is balanced by the microbiome and dietary nitrate intake. Dietary nitrate supplementation may lead to beneficial changes in the oral microbiome, thereby increasing the NO bioavailability. However, NO bioavailability can be compromised by reactive oxygen species (ROS) and the uncoupling of endothelial nitric oxide synthase (eNOS), leading to further ROS generation and creating a detrimental cycle. Studies on NO and periodontal disease have shown increased nitrite concentrations in patients with periodontal disease, although these studies have some methodological limitations. In terms of blood pressure, literature suggests that CHX mouthrinses may reduce the capacity of nitrate-reducing bacteria, potentially leading to an increase in blood pressure.

CONCLUSIONS

Several studies have suggested an association between NO levels and the development of cardiovascular and periodontal diseases. However, the exact mechanisms linking these diseases remains to be fully elucidated.

CLINICAL RELEVANCE

Nitric oxide (NO) is a signaling molecule that plays a crucial role in several physiological processes such as vascular homeostasis, inflammation, immune cell activity, and pathologies such as hypertension and periodontitis.

Development and applications of peri-implantitis mouse models

OBJECTIVE

Peri-implantitis is one of the most common complications of implants. However, its pathogenesis has not been clarified. In recent years, mouse models are gradually being used in the study of peri-implantitis. This review aims to summarize the methods used to induce peri-implantitis in mice and their current applications.

METHOD

Articles of peri-implantitis mouse models were collected. We analyzed the various methods of inducing peri-implantitis and their application in different areas.

RESULTS

Most researchers have induced peri-implantitis by silk ligatures. Some others have induced peri-implantitis by Pg gavage and LPS injection. Current applications of peri-implantitis mouse models are in the following areas: investigation of pathogenesis and exploration of new interventions, comparison of peri-implantitis with periodontitis, the interaction between systemic diseases and peri-implantitis, etc. CONCLUSION: Silk ligature for 2-4 weeks, Pg gavage for 6 weeks, and LPS injection for 6 weeks all successfully induced peri-implantitis in mice. Mice have the advantages of mature gene editing technology, low cost, and short time to induce peri-implantitis. It has applications in the study of pathogenesis, non-surgical treatments, and interactions with other diseases. However, compared with large animals, mice also have a number of disadvantages that limit their application.

Genetic analysis of impaired healing responses after periodontal therapy in type 2 diabetes: Clinical and in vivo studies

OBJECTIVE

This study aims to investigate the mechanisms underlying the impaired healing response by diabetes after periodontal therapy.

BACKGROUND

Outcomes of periodontal therapy in patients with diabetes are impaired compared with those in patients without diabetes. However, the mechanisms underlying impaired healing response to periodontal therapy have not been sufficiently investigated.

MATERIALS AND METHODS

Zucker diabetic fatty (ZDF) and lean (ZL) rats underwent experimental periodontitis by ligating the mandibular molars for one week. The gingiva at the ligated sites was harvested one day after ligature removal, and gene expression was comprehensively analyzed using RNA-Seq. In patients with and without type 2 diabetes (T2D), the corresponding gene expression was quantified in the gingiva of the shallow sulcus and residual periodontal pocket after non-surgical periodontal therapy.

RESULTS

Ligation-induced bone resorption and its recovery after ligature removal were significantly impaired in the ZDF group than in the ZL group. The RNA-Seq analysis revealed 252 differentially expressed genes. Pathway analysis demonstrated the enrichment of downregulated genes involved in the peroxisome proliferator-activated receptor (PPAR) signaling pathway. PPARα and PPARγ were decreased in mRNA level and immunohistochemistry in the ZDF group than in the ZL group. In clinical, probing depth reduction was significantly less in the T2D group than control. Significantly downregulated expression of PPARα and PPARγ were detected in the residual periodontal pocket of the T2D group compared with those of the control group, but not in the shallow sulcus between the groups.

CONCLUSIONS

Downregulated PPAR subtypes expression may involve the impaired healing of periodontal tissues by diabetes.

Occlusal trauma aggravates periodontitis through the plasminogen/plasmin system

OBJECTIVES

Periodontitis is a common oral disease that is aggravated by occlusal trauma. Fibrin is a protein that participates in blood clotting and is involved in several human diseases. The deposition of fibrin in periodontal tissues can induce periodontitis, while mechanical forces may regulate the degradation of fibrin. Our study investigated how occlusal trauma aggravating periodontitis through regulating the plasminogen/plasmin system and fibrin deposition.

MATERIALS AND METHODS

This study included 84 C57BL/6 mice in which periodontitis was induced with or without occlusal trauma. Micro-computed tomography was used to assess bone resorption. Fibrin, fibrinogen, plasminogen, plasmin, tissue plasminogen activator (t-PA), and urokinase plasminogen activator (u-PA) levels were measured using Frazer-Lendrum staining, quantitative reverse transcription polymerase chain reaction, enzyme-linked immunosorbent assay, western blotting, immunofluorescence staining, and immunohistochemistry staining.

RESULTS

Occlusal trauma aggravated inflammation and bone resorption. The periodontitis group showed significant fibrin deposition. Occlusal trauma increased fibrin deposition and neutrophil aggregation. The periodontitis with occlusal trauma group had decreased fibrinogen, t-PA, and u-PA expression and plasmin and fibrin degradation product levels, as well as increased plasminogen levels.

CONCLUSION

Occlusal trauma promotes excessive fibrin deposition by suppressing the plasminogen/plasmin system, thus exacerbating periodontitis.

A Flagellin-Adjuvanted Trivalent Mucosal Vaccine Targeting Key Periodontopathic Bacteria

Periodontal disease (PD) is caused by microbial dysbiosis and accompanying adverse inflammatory responses. Due to its high incidence and association with various systemic diseases, disease-modifying treatments that modulate dysbiosis serve as promising therapeutic approaches. In this study, to simulate the pathophysiological situation, we established a "temporary ligature plus oral infection model" that incorporates a temporary silk ligature and oral infection with a cocktail of live Tannerella forsythia (Tf), Pophyromonas gingivalis (Pg), and Fusobacterium nucleatum (Fn) in mice and tested the efficacy of a new trivalent mucosal vaccine. It has been reported that Tf, a red complex pathogen, amplifies periodontitis severity by interacting with periodontopathic bacteria such as Pg and Fn. Here, we developed a recombinant mucosal vaccine targeting a surface-associated protein, BspA, of Tf by genetically combining truncated BspA with built-in adjuvant flagellin (FlaB). To simultaneously induce Tf-, Pg-, and Fn-specific immune responses, it was formulated as a trivalent mucosal vaccine containing Tf-FlaB-tBspA (BtB), Pg-Hgp44-FlaB (HB), and Fn-FlaB-tFomA (BtA). Intranasal immunization with the trivalent mucosal vaccine (BtB + HB + BtA) prevented alveolar bone loss and gingival proinflammatory cytokine production. Vaccinated mice exhibited significant induction of Tf-tBspA-, Pg-Hgp44-, and Fn-tFomA-specific IgG and IgA responses in the serum and saliva, respectively. The anti-sera and anti-saliva efficiently inhibited epithelial cell invasion by Tf and Pg and interfered with biofilm formation by Fn. The flagellin-adjuvanted trivalent mucosal vaccine offers a novel method for modulating dysbiotic bacteria associated with periodontitis. This approach leverages the adjuvant properties of flagellin to enhance the immune response, aiming to restore a balanced microbial environment and improve periodontal health.

Platr3/NUDT21/NF-κB Axis Mediates P. gingivalis-Suppressed Cementoblast Mineralization

Porphyromonas gingivalis (P. gingivalis) is one of the major pathogens causing periodontitis and apical periodontitis (AP). Long noncoding RNA (lncRNA) can regulate cellular mineralization and inflammatory diseases. The aim of this study was to investigate the role and mechanism of lncRNA in P. gingivalis-stimulated cementoblast mineralization. In vivo, C57BL/6 mice were divided into the healthy, the AP, and AP + P. gingivalis groups (n = six mice per group). Micro computed tomography, immunohistochemistry staining, and fluorescence in situ hybridization were used to observe periapical tissue. In vitro, cementoblasts were treated with osteogenic medium or P. gingivalis. Pluripotency associated transcript 3 (Platr3), interleukin 1 beta (IL1B), and osteogenic markers were analyzed by quantitative real-time polymerase chain reaction and western blot. RNA pull-down and RNA immunoprecipitation assays were used to detect proteins that bind to Platr3. RNA sequencing was performed in Platr3-silenced cementoblasts. In vivo, P. gingivalis promoted periapical tissue destruction and IL1B expression, but inhibited Platr3 expression. In vitro, P. gingivalis facilitated IL1B expression (P < 0.001), whereas suppressed the expression of Platr3 (P < 0.001) and osteogenic markers (P < 0.01 or 0.001). In contrast, Platr3 overexpression alleviated the repressive effect of P. gingivalis on cementoblast mineralization (P < 0.01 or 0.001). Furthermore, Platr3 bound to nudix hydrolase 21 (NUDT21) and regulated the nuclear factor-κB (NF-κB) signaling pathway. Knocking down NUDT21 suppressed osteogenic marker expression and activated the above signaling pathway. Collectively, the results elucidated that Platr3 mediated P. gingivalis-suppressed cementoblast mineralization through the NF-κB signaling pathway by binding to NUDT21.

Histological and Biochemical Evaluation of Silibinin in Treatment of Periodontitis Induced in Rats with Liver Cirrhosis

AIM

This study aimed to evaluate the impact of silibinin as a therapeutic agent on ligature-induced periodontitis in rats with liver cirrhosis.

MATERIALS AND METHODS

Twenty-five Wistar rats were enrolled in this study. Group A (Control) included eight rats. The other 17 rats received CCl4 to develop cirrhosis, which was confirmed by sacrificing one of the rats and performing a histological examination of its liver tissue. Periodontitis was induced in the remaining 16 rats then they were allocated into (n = 8) group B-periodontitis with cirrhosis and group C-silibinin-treated group, 5 times/week starting from week 11 till week 14. Animals of the three groups were euthanized, and biochemical analysis comprising of liver functions assessment (serum levels of glutamate-pyruvate transaminase, serum levels of glutamate-oxalate transaminase, TIMP1) and oxidative stress index [MDA, nitric oxide (NO), superoxide dismutase (SOD), and catalase (CAT)] and histological examination were conducted by the end of week 14.

RESULTS

Group C revealed a more organized orientation of the periodontal ligament (PDL) collagen fibers with a marked regain of the alveolar bone height compared to group B. Biochemical analysis confirmed the potent therapeutic effect of silibinin manifested by a significant improvement in the biochemical parameters: tissue inhibitor of metalloproteinase-1, MDA, NO levels, and antioxidant enzymes.

CONCLUSION

Group B was associated with the most unfavorable biochemical findings and the maximum periodontal destruction. Group C demonstrated a positive osteogenic capacity and a noteworthy improvement in biochemical findings, which were comparable to those of group A, which displayed normal and healthy findings.

CLINICAL SIGNIFICANCE

The study highlights the potential use of silibinin as a natural remedy with minimal side effects for treating periodontitis in rats with liver cirrhosis. The findings could be translated to human clinical trials, which may lead to new treatment strategies using silibinin as a targeted therapy or as adjunctive therapy to conventional periodontal treatment for patients with liver cirrhosis who are more susceptible to periodontitis. How to cite this article: Shawky HA, Ahmed NM, Essawy MM, et al. Histological and Biochemical Evaluation of Silibinin in Treatment of Periodontitis Induced in Rats with Liver Cirrhosis. J Contemp Dent Pract 2024;25(7):631-638.

The Role of Pericyte Migration and Osteogenesis in Periodontitis

A ligature-induced periodontitis model was established in wild-type and CD146CreERT2; RosatdTomato mice to explore the function of pericytes in alveolar bone formation. We found that during periodontitis progression and periodontal wound healing, CD146+/NG2+ pericytes were enriched in the periodontal tissue areas, which could migrate to the alveolar bone surface and colocalize with ALP+/OCN+ osteoblasts. Chemokine C-X-C motif receptor 4 (CXCR4) inhibition using AMD3100 blocked CD146-Cre+ pericyte migration and osteogenesis, as well as further exacerbated periodontitis-associated bone loss. Next, primary pericytes were sorted out by magnetic-activated cell sorting and demonstrated that C-X-C motif chemokine ligand 12 (CXCL12) promotes pericyte migration and osteogenesis via CXCL12-CXCR4-Rac1 signaling. Finally, the local administration of an adeno-associated virus for Rac1 overexpression in NG2+ pericytes promotes osteoblast differentiation of pericytes and increases alveolar bone volume in periodontitis. Thus, our results provided the evidence that pericytes may migrate and osteogenesis via the CXCL12-CXCR4-Rac1 axis during the pathological process of periodontitis.

The bidirectional effect of neutrophils on periodontitis model in mice: A systematic review

OBJECTIVE

To evaluate the regulatory role of neutrophils as the first line of host immune defense in the periodontal microenvironment of mice.

METHODS

A systematic search was performed using PubMed, Web of Science, and ScienceDirect databases for articles published between 2012 and 2023. In this review, articles investigating the effect of neutrophils on alveolar bone resorption in a mouse model of periodontitis were selected and evaluated according to eligibility criteria. Important variables that may influence outcomes were analyzed.

RESULTS

Eleven articles were included in this systematic review. The results showed that because of their immune defense functions, the functional homeostasis of local neutrophils is critical for periodontal health. Neutrophil deficiency aggravates alveolar bone loss. However, several studies have shown that excessive neutrophil infiltration is positively correlated with alveolar bone resorption caused by periodontitis in mice. Therefore, the homeostasis of neutrophil function needs to be considered in the treatment of periodontitis.

CONCLUSIONS

Pooled analysis suggests that neutrophils play a bidirectional role in periodontal tissue remodeling in mouse periodontitis models. Therefore, targeted regulation of local neutrophil function provides a novel strategy for the treatment of periodontitis.

Effect of chondroitin sulfate modified polyethyleneimine on mediating oligodeoxynucleotide YW002 in the treatment of periodontitis

PURPOSE

In a previous study, we found that oligodeoxynucleotide (ODN) YW002 could induce the activity of alkaline phosphatase of early osteogenesis in human periodontal membrane stem cells, and downregulate the synthesis of nitric oxide in RAW 264.7 cells in the late inflammatory stage, laying the experimental foundation for the subsequent application of ODN YW002 in periodontitis. However, free ODN does not easily adhere to cells and is easily hydrolyzed by nuclease, so the immune effect of ODN is greatly reduced. Therefore, the nano-drug delivery system provides a method for efficient delivery and uptake of ODN.

METHODS

We synthesized a polyethyleneimine (PEI) modified chondroitin sulfate (CS) derivative (PEI-CS) via Michael addition to deliver ODN YW002. We aimed to evaluate whether PEI-CS could effectively deliver YW002 to RAW 264.7 cells and if it can regulate inflammation in vitro. PEI-CS/YW002 nanocomplexes were locally injected into a mouse periodontitis model, and the therapeutic effects were evaluated by microcomputed tomography (micro-CT) and hematoxylin-eosin (H&E) staining.

RESULTS

The results indicated that PEI-CS had good biocompatibility and could form a stable nanocomplex with YW002 at a mass ratio of 4 : 1. Moreover, PEI-CS could deliver YW002 into RAW 246.7 cells and markedly decreased the expression levels of interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α. Histological evaluation and micro-CT scanning showed that PEI-CS/YW002 nanocomplexes effectively inhibited periodontitis and reduced alveolar bone resorption in mice.

CONCLUSION

Our study has underscored the potential of PEI-CS/YW002 nanocomplexes as promising agents for the prevention and treatment of periodontitis due to their potent anti-inflammatory effects.

Experimental models for peri-implant diseases: a narrative review

OBJECTIVES

Peri-implant diseases, being the most common implant-related complications, significantly impact the normal functioning and longevity of implants. Experimental models play a crucial role in discovering potential therapeutic approaches and elucidating the mechanisms of disease progression in peri-implant diseases. This narrative review comprehensively examines animal models and common modeling methods employed in peri-implant disease research and innovatively summarizes the in vitro models of peri-implant diseases.

MATERIALS AND METHODS

Articles published between 2015 and 2023 were retrieved from PubMed/Medline, Web of Science, and Embase. All studies focusing on experimental models of peri-implant diseases were included and carefully evaluated.

RESULTS

Various experimental models of peri-implantitis have different applications and advantages. The dog model is currently the most widely utilized animal model in peri-implant disease research, while rodent models have unique advantages in gene knockout and systemic disease induction. In vitro models of peri-implant diseases are also continuously evolving to meet different experimental purposes.

CONCLUSIONS

The utilization of experimental models helps simplify experiments, save time and resources, and promote advances in peri-implant disease research. Animal models have been proven valuable in the early stages of drug development, while technological advancements have brought about more predictive and relevant in vitro models.

CLINICAL RELEVANCE

This review provides clear and comprehensive model selection strategies for researchers in the field of peri-implant diseases, thereby enhancing understanding of disease pathogenesis and providing possibilities for developing new treatment strategies.

Effects of IL-34 and anti-IL-34 neutralizing mAb on alveolar bone loss in a ligature-induced model of periodontitis

Macrophage colony-stimulating factor (M-CSF) and interleukin-34 (IL-34) are ligands for the colony-stimulating factor-1  receptor (CSF-1r) expressed on the surface of monocyte/macrophage lineage cells. The importance of coordinated signaling between M-CSF/receptor activator of the nuclear factor kappa-Β ligand (RANKL) in physiological and pathological bone remodeling and alveolar bone loss in response to oral bacterial colonization is well established. However, our knowledge about the IL-34/RANKL signaling in periodontal bone loss remains limited. Recently published cohort studies have demonstrated that the expression patterns of IL-34 are dramatically elevated in gingival crevicular fluid collected from patients with periodontitis. Therefore, the present study aims to evaluate the effects of IL-34 on osteoclastogenesis in vitro and in experimental ligature-mediated model of periodontitis using male mice. Our initial in vitro study demonstrated increased RANKL-induced osteoclastogenesis of IL-34-primed osteoclast precursors (OCPs) compared to M-CSF-primed OCPs. Using an experimental model of ligature-mediated periodontitis, we further demonstrated elevated expression of IL-34 in periodontal lesions. In contrast, M-CSF levels were dramatically reduced in these periodontal lesions. Furthermore, local injections of mouse recombinant IL-34 protein significantly elevated cathepsin K activity, increased the number of tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts and promoted alveolar bone loss in periodontitis lesions. In contrast, anti-IL-34 neutralizing monoclonal antibody significantly reduced the level of alveolar bone loss and the number of TRAP-positive osteoclasts in periodontitis lesions. No beneficial effects of locally injected anti-M-CSF neutralizing antibody were observed in periodontal lesions. This study illustrates the role of IL-34 in promoting alveolar bone loss in periodontal lesions and proposes the potential of anti-IL34 monoclonal antibody (mAb)-based therapeutic regimens to suppress alveolar bone loss in periodontitis lesions.

Therapeutic Effects of Hinokitiol through Regulating the SIRT1/NOX4 against Ligature-Induced Experimental Periodontitis

Hinokitiol (HKT) is one of the essential oil components found in the heartwood of Cupressaceae plants, and has been reported to have various bioactive effects, including anti-inflammatory effects. However, the improving effect of HKT on periodontitis, which is characterized by periodontal tissue inflammation and alveolar bone loss, has not been clearly revealed. Therefore, we investigated the periodontitis-alleviating effect of HKT and the related molecular mechanisms in human periodontal ligament cells. According to the study results, HKT downregulated SIRT1 and NOX4, which were increased by Porphyromonas gingivalis Lipopolysaccharide (PG-LPS) stimulation and were found to regulate pro-inflammatory mediators and oxidative stress through SIRT1/NOX4 signals. Additionally, by increasing the expression of osteogenic makers such as alkaline phosphatase, osteogenic induction of human periodontal ligament (HPDL) cells, which had been reduced by PG-LPS, was restored. Furthermore, we confirmed that NOX4 expression was regulated through regulation of SIRT1 expression with HKT. The in vitro effect of HKT on improving periodontitis was proven using the periodontal inflammation model, which induces periodontal inflammation using ligature, a representative in vivo model. According to in vivo results, HKT alleviated periodontal inflammation and restored damaged alveolar bone in a concentration-dependent manner in the periodontal inflammation model. Through this experiment, the positive effects of HKT on relieving periodontal tissue inflammation and recovering damaged alveolar bone, which are important treatment strategies for periodontitis, were confirmed. Therefore, these results suggest that HKT has potential in the treatment of periodontitis.

Periodontitis exacerbation during pregnancy in mice: Role of macrophage migration inhibitory factor as a key inductor

OBJECTIVE

The present study was designed to investigate the role of macrophage migration inhibitory factor (MIF) in the exacerbation of pregestational periodontal disease (PGPD).

BACKGROUND

Periodontitis (PT) is a severe stage of periodontal disease characterized by inflammation of the supporting tissues of the teeth, which usually worsens during pregnancy. MIF is a proinflammatory cytokine that is significantly elevated in periodontitis, both at the beginning and at the end of pregnancy. Although periodontitis usually presents with greater severity during pregnancy, the participation of MIF in the evolution of periodontitis has not been established.

METHODS

To analyze the relevance of MIF in the exacerbation of PGPD, we employed a model of PGPD in WT and Mif-/- mice, both with a BALB/c genetic background. PT was induced with nylon suture ligatures placed supramarginally around the second upper right molar. For PGPD, PT was induced 2 weeks before mating. We evaluated histological changes and performed histometric analysis of the clinical attachment loss, relative expression of MMP-2 and MMP-13 by immunofluorescence, and relative expression of the cytokines mif, tnf-α, ifn-γ, and il-17 by quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

Our data revealed that periodontal tissue from PGPD WT mice produced a twofold increase in MIF compared with PT WT mice. Moreover, the evolution of periodontitis in Mif-/- mice was less severe than in PGDP WT mice. Periodontal tissue from Mif-/- mice with PGPD produced 80% less TNF-α and no IFN-γ, as well as 50% lower expression of matrix metalloproteinase (MMP)-2 and 25% less MMP-13 compared to WT PGDP mice.

CONCLUSIONS

Our study suggests that MIF plays an important role in the exacerbation of periodontitis during pregnancy and that MIF is partially responsible for the inflammation associated with the severity of periodontitis during pregnancy.

The IL-33/ST2 axis is protective against acute inflammation during the course of periodontitis

Periodontitis, which is induced by repeated bacterial invasion and the ensuing immune reactions that follow, is the leading cause of tooth loss. Periodontal tissue is comprised of four different components, each with potential role in pathogenesis, however, most studies on immune responses focus on gingival tissue. Here, we present a modified ligature-induced periodontitis model in male mice to analyze the pathogenesis, which captures the complexity of periodontal tissue. We find that the inflammatory response in the peri-root tissues and the expression of IL-6 and RANKL by Thy-1.2- fibroblasts/stromal cells are prominent throughout the bone destruction phase, and present already at an early stage. The initiation phase is characterized by high levels of ST2 (encoded by Il1rl1) expression in the peri-root tissue, suggesting that the IL-33/ST2 axis is involved in the pathogenesis. Both Il1rl1- and Il33-deficient mice exhibit exacerbated bone loss in the acute phase of periodontitis, along with macrophage polarization towards a classically activated phenotype and increased neutrophil infiltration, indicating a protective role of the IL-33/ST2 axis in acute inflammation. Thus, our findings highlight the hidden role of the peri-root tissue and simultaneously advance our understanding of the etiology of periodontitis via implicating the IL-33/ST2 axis.

Nel-like Molecule Type 1 Combined with Gold Nanoparticles Modulates Macrophage Polarization, Osteoclastogenesis, and Oral Microbiota in Periodontitis

The disruption of host-microbe homeostasis and uncontrolled inflammatory response have been considered as vital causes for developing periodontitis, subsequently leading to an imbalance between the bone and immune system and the collapse of bone homeostasis. Consequently, strategies to modulate the immune response and bone metabolization have become a promising approach to prevent and treat periodontitis. In this study, we investigated the cooperative effects of Nel-like molecule type 1 (Nell-1) and gold nanoparticles (AuNPs) on macrophage polarization, osteoclast differentiation, and the corresponding functions in an experimental model of periodontitis in rats. Nell-1-combined AuNPs in in vitro studies were found to reduce the production of inflammatory factors (TNF-α, p < 0.0001; IL-6, p = 0.0012), modulate the ratio of M2/M1 macrophages by inducing macrophage polarization into the M2 phenotype, and inhibit cell fusion, maturation, and activity of osteoclasts. Furthermore, the local application of Nell-1-combined AuNPs in in vivo studies resulted in alleviation of damages to the periodontal and bone tissues, modulation of macrophage polarization and the activity of osteoclasts, and alteration of the periodontal microbiota, in which the relative abundance of the probiotic Bifidobacterium increased (p < 0.05). These findings reveal that Nell-1-combined AuNPs could be a promising drug candidate for the prevention and treatment of periodontitis. However, Nell-1-combined AuNPs did not show organ toxicity or impair the integrity of intestinal epithelium but alter the gut microbiota, leading to the dysbiosis of gut microbiota. The adverse impact of changes in gut microbiota needs to be further investigated. Nonetheless, this study provides a novel perspective and direction for the biological safety assessment of biomaterials in oral clinical applications.

A pilot study on the expression of circadian clock genes in the alveolar bone of mice with periodontitis

This study aimed to investigate the expression of circadian clock genes in mouse alveolar bone, and the possible reasons for these changes. Fifty C57 mice were orally inoculated with P. gingivalis, establishing a model of periodontitis using healthy mice as controls. The alveolar bone of both groups was taken for micro-computed tomography scanning to measure the amount of attachment loss, and the relative expression of mRNA in each clock gene and periodontitis related inflammatory factor was detected by real-time fluorescence quantitative polymerase chain reaction (qRT-PCR). After the establishment of the mouse model, the height of alveolar bone in the periodontitis group was significantly lower than that in the normal group (p < 0.05). The relative transcriptional level of Bmal1, Per2, and Cry1 mRNA was in the circadian rhythm in the normal group (p ≤ 0.05), while in the periodontitis group, its circadian rhythm disappeared and the transcriptional level characteristics were changed. Interleukin (IL)-6, tumor necrosis factor-alpha (TNF-α), and interferon (IFN-γ) mRNA transcriptional level were elevated in the periodontitis group compared to the normal group. In conclusion, the mRNA transcriptional level of Bmal1, Per2, and Cry1 in alveolar bone of normal mice has circadian rhythm, but the rhythm disappears under the condition of periodontitis, and the cause of its occurrence may be related to inflammatory cytokines.

Periodontal ligament-associated protein-1 promotes osteoclastogenesis in mice by modulating TGF-β1/Smad1 pathway

BACKGROUND

Periodontal ligament-associated protein-1 (PLAP-1), an important target molecule of osteoarthritis research, may affect alveolar bone resorption. The aim of our study was to comprehensively and systematically detect the effect of PLAP-1 on alveolar bone resorption and the underlying mechanism in PLAP-1 knockout mouse models.

METHODS

We used a PLAP-1 knockout (C57BL/6N-Plap-1-/- ) mouse model to investigate the effect of PLAP-1 on osteoclast differentiation and the underlying mechanism by adding Porphyromonas gingivalis lipopolysaccharide to stimulate bone marrow-derived macrophages. The effect of PLAP-1 on alveolar bone resorption and the underlying mechanism were studied using a ligature periodontitis model, with microcomputed tomography imaging, immunochemistry, and immunofluorescence.

RESULTS

The in vitro analysis results demonstrated that PLAP-1 knockout significantly inhibited osteoclast differentiation under both normal and inflammatory conditions. Bioinformatic analysis, immunofluorescence, and co-immunoprecipitation showed colocalization and interaction between PLAP-1 and transforming growth factor beta 1 (TGF-β1). The phosphorylation of Smad1 was reduced in the PLAP-1 knockout cells compared with that in the cells from wild-type mice. The in vivo analysis results demonstrated that PLAP-1 knockout decreased bone resorption and the levels of osteoclast differentiation markers in experimental periodontitis compared with those in wild-type mice. Immunofluorescence staining confirmed colocalization of PLAP-1 and TGF-β1 in the experimental periodontitis model. The phosphorylation level of Smad1 was significantly reduced in PLAP-1 knockout mice compared with that in wild-type mice.

CONCLUSIONS

This study revealed that the knockout of PLAP-1 inhibits osteoclast differentiation and decreases alveolar bone resorption through the TGF-β1/Smad1 signaling pathway, which could serve as an innovative target for the prevention and treatment of periodontitis.

Chronological analysis of periodontal bone loss in experimental periodontitis in mice

OBJECTIVES

Periodontal disease is understood to be a result of dysbiotic interactions between the host and the biofilm, causing a unique reaction for each individual, which in turn characterizes their susceptibility. The objective of this study was to chronologically evaluate periodontal tissue destruction induced by systemic bacterial challenge in known susceptible (BALB/c) and resistant (C57BL/6) mouse lineages.

MATERIAL AND METHODS

Animals, 6-8 weeks old, were allocated into three experimental groups: Negative control (C), Gavage with sterile carboxymethyl cellulose 2%-without bacteria (Sham), and Gavage with carboxymethyl cellulose 2% + Porphyromonas gingivalis (Pg-W83). Before infection, all animals received antibiotic treatment (sulfamethoxazole/trimethoprim, 400/80 mg/5 mL) for 7 days, followed by 3 days of rest. Microbial challenge was performed 3 times per week for 1, 2, or 3 weeks. After that, the animals were kept until the completion of 42 days of experiments, when they were euthanized. The alveolar bone microarchitecture was assessed by computed microtomography.

RESULTS

Both C57BL/6 and BALB/c mice exhibited significant bone volume loss and lower trabecular thickness as well as greater bone porosity compared to the (C) and (Sham) groups after 1 week of microbial challenge (p < .001). When comparing only the gavage groups regarding disease implantation, time and lineage, it was possible to observe that within 1 week of induction the disease was more established in BALB/c than in C57BL/6 (p < .05).

CONCLUSIONS

Our results reflected that after 1 week of microbial challenge, there was evidence of alveolar bone loss for both lineages, with the loss observed in BALB/c mice being more pronounced.

Metronidazole-loaded polydopamine nanomedicine with antioxidant and antibacterial bioactivity for periodontitis

Aim: This study focused on treating periodontitis with bacterial infection and local over accumulation of reactive oxygen species. Materials & methods: Polydopamine nanoparticles (PDA NPs) were exploited as efficient carriers for encapsulated metronidazole (MNZ). The therapeutic efficacy and biocompatibility of PDA@MNZ NPs were investigated through both in vitro and in vivo studies. Results: The nanodrug PDA@MNZ NPs were successfully fabricated, with well-defined physicochemical characteristics. In vitro, the PDA@MNZ NPs effectively eliminated intracellular reactive oxygen species and inhibited the growth of Porphyromonas gingivalis. Moreover, the PDA@MNZ NPs exhibited synergistic therapy for periodontitisin in vivo. Conclusion: PDA@MNZ NPs were confirmed with exceptional antimicrobial and antioxidant functions, offering a promising avenue for synergistic therapy in periodontitis.

Mouse gingival single-cell transcriptomic atlas identified a novel fibroblast subpopulation activated to guide oral barrier immunity in periodontitis

Periodontitis, one of the most common non-communicable diseases, is characterized by chronic oral inflammation and uncontrolled tooth supporting alveolar bone resorption. Its underlying mechanism to initiate aberrant oral barrier immunity has yet to be delineated. Here, we report a unique fibroblast subpopulation activated to guide oral inflammation (AG fibroblasts) identified in a single-cell RNA sequencing gingival cell atlas constructed from the mouse periodontitis models. AG fibroblasts localized beneath the gingival epithelium and in the cervical periodontal ligament responded to the ligature placement and to the discrete topical application of Toll-like receptor stimulants to mouse maxillary tissue. The upregulated chemokines and ligands of AG fibroblasts linked to the putative receptors of neutrophils in the early stages of periodontitis. In the established chronic inflammation, neutrophils, together with AG fibroblasts, appeared to induce type 3 innate lymphoid cells (ILC3s) that were the primary source of interleukin-17 cytokines. The comparative analysis of Rag2-/- and Rag2-/-Il2rg-/- mice suggested that ILC3 contributed to the cervical alveolar bone resorption interfacing the gingival inflammation. We propose the AG fibroblast-neutrophil-ILC3 axis as a previously unrecognized mechanism which could be involved in the complex interplay between oral barrier immune cells contributing to pathological inflammation in periodontitis.

Systemic Type 2 Inflammation-Associated Atopic Dermatitis Exacerbates Periodontitis

INTRODUCTION

Atopic dermatitis (AD) is a prevalent and chronic inflammatory skin disease characterized by Th2 cell-mediated type 2 inflammation. Emerging evidence indicated that AD patients exhibit an increased incidence of oral disorders. In the present study, we sought mechanistic insights into how AD affects periodontitis.

METHODS

Onset of AD was induced by 2,4-dinitrochlorobenzene (DNCB). Furthermore, we induced periodontitis (P) in AD mice. The effect of AD in promoting inflammation and bone resorption in gingiva was evaluated. Hematoxylin and eosin staining, tartrate-resistant acid phosphatase staining, immunofluorescence assay, and flow cytometry were used to investigate histomorphology and cytology analysis, respectively. RNA sequencing of oral mucosa is used tissues to further understand the dynamic transcriptome changes. 16S rRNA microbial analysis is used to profile oral microbial composition.

RESULTS

Compared to control group, mice in AD group showed inflammatory signatures and infiltration of a proallergic Th2 (Th2A)-like subset in oral mucosa but not periodontitis, as identified by not substantial changes in mucosa swelling, alveolar bone loss, and TRAP+ osteoclasts infiltration. Similarly, more Th2A-like cell infiltration and interleukin-4 levels were significantly elevated in the oral mucosa of DNCB-P mice compared to P mice. More importantly, AD exacerbates periodontitis when periodontitis has occurred and the severity of periodontitis increased with aggravation of dermatitis. Transcriptional analysis revealed that aggravated periodontitis was positively correlated with more macrophage infiltration and abundant CCL3 secreted. AD also altered oral microbiota, indicating the re-organization of extracellular matrix.

CONCLUSIONS

These data provide solid evidence about exacerbation of periodontitis caused by type 2 dermatitis, advancing our understanding in cellular and microbial changes during AD-periodontitis progression.

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).

Evaluation of morphological, histological, and immune-related cellular changes in ligature-induced experimental periodontitis in mice

Background/purpose

The ligature-induced periodontitis model is an effective approach to induce inflammation and bone loss similar to that of human periodontitis. Previous clinical and in vitro studies have shown the involvement of lymphocytes in periodontitis, while, the local and systemic profile of immune cells associated with periodontitis in the ligature-induced periodontitis model in mice remains unclear.

Materials and methods

Experimental periodontitis was constructed in mice by ligating around the maxillary second molars for 14 and 28 days, respectively. Alveolar bone loss was assessed by micro-computed tomography (micro-CT). Hematoxylin and eosin (H&E) and tartrate-resistant acid phosphatase (TRAP) staining were used to evaluate the histological changes in the periodontal tissues. B and T cells in the cervical lymph nodes, spleen, and peripheral blood were analyzed by flow cytometry.

Results

The 14-day ligation effectively induced significant periodontal inflammation and alveolar bone loss in C57BL/6J mice, which were progressive and maintained for a relatively long-term period until day 28. In addition, CD3+ T cells and CD19+ B cells were the dominant population in both health and disease, and the B cell population within the cervical lymph nodes (LN) increased significantly under periodontitis condition, while, no significant differences of the T and B cell population among the spleen and peripheral blood were observed.

Conclusion

The ligature-induced periodontitis mice model was established to perform a longitudinal assessment of changes in periodontal tissues morphologically and histologically, meanwhile, explore the local and systemic changes of the predominant immune-associated cells.

Periodontitis promotes bacterial extracellular vesicle-induced neuroinflammation in the brain and trigeminal ganglion

Gram-negative bacteria derived extracellular vesicles (EVs), also known as outer membrane vesicles, have attracted significant attention due to their pathogenic roles in various inflammatory diseases. We recently demonstrated that EVs secreted by the periodontopathogen Aggregatibacter actinomycetemcomitans (Aa) can cross the blood-brain barrier (BBB) and that their extracellular RNA cargo can promote the secretion of proinflammatory cytokines, such as IL-6 and TNF-α, in the brain. To gain more insight into the relationship between periodontal disease (PD) and neuroinflammatory diseases, we investigated the effect of Aa EVs in a mouse model of ligature-induced PD. When EVs were administered through intragingival injection or EV-soaked gel, proinflammatory cytokines were strongly induced in the brains of PD mice. The use of TLR (Toll-like receptor)-reporter cell lines and MyD88 knockout mice confirmed that the increased release of cytokines was triggered by Aa EVs via TLR4 and TLR8 signaling pathways and their downstream MyD88 pathway. Furthermore, the injection of EVs through the epidermis and gingiva resulted in the direct retrograde transfer of Aa EVs from axon terminals to the cell bodies of trigeminal ganglion (TG) neurons and the subsequent activation of TG neurons. We also found that the Aa EVs changed the action potential of TG neurons. These findings suggest that EVs derived from periodontopathogens such as Aa might be involved in pathogenic pathways for neuroinflammatory diseases, neuropathic pain, and other systemic inflammatory symptoms as a comorbidity of periodontitis.

Blue Light-Emitting Diode Irradiation Without a Photosensitizer Alters Oral Microbiome Composition of Ligature-Induced Periodontitis in Mice

Objective: This study investigated the suppressive effects of blue light-emitting diode (LED) irradiation on bone resorption and changes in the oral microbiome of mice with ligature-induced periodontitis. Background: Wavelength of blue light has antimicrobial effects; however, whether blue LED irradiation alone inhibits the progression of periodontitis remains unclear. Methods: Nine-week-old male mice ligated ligature around the right maxillary second molar was divided into ligation alone (Li) and ligation with blue LED irradiation (LiBL) groups. The LiBL group underwent blue LED (wavelength, 455 nm) irradiation four times in a week at 150 mW/cm2 without a photosensitizer on the gingival tissue around the ligated tooth at a distance of 5 mm for 5 min. The total energy density per day was 45 J/cm2. Bone resorption was evaluated using micro-computed tomography at 8 days. Differences in the oral microbiome composition of the collected ligatures between the Li and LiBL groups were analyzed using next-generation sequencing based on the 16S rRNA gene from the ligatures. Results: Blue LED irradiation did not suppress bone resorption caused by ligature-induced periodontitis. However, in the LiBL group, the α-diversity, number of observed features, and Chao1 were significantly decreased. The relative abundances in phylum Myxococcota and Bacteroidota were underrepresented, and the genera Staphylococcus, Lactococcus, and Lactobacillus were significantly overrepresented by blue LED exposure. Metagenomic function prediction indicated an increase in the downregulated pathways related to microbial energy metabolism after irradiation. The co-occurrence network was altered to a simpler structure in the LiBL group, and the number of core genera decreased. Conclusions: Blue LED irradiation altered the composition and network of the oral microbiome of ligature-induced periodontitis in mice.

A New Way to Model Periodontitis in Laboratory Animals

The prevalence of periodontal diseases is increasing, tends to increase with age and is considered as one of the main causes of tooth loss. To assess the effectiveness of new methods of treatment of periodontal diseases, studies on laboratory animals can be promising.

THE AIM OF THE STUDY

to develop a new method of accelerated modeling of experimental periodontitis on laboratory animals.

MATERIAL AND METHODS

The study was carried out on 22 female rats. A wire ligature was applied to the cervical area of the incisors of the animals in an eight-shaped manner. Plaque obtained from a patient with periodontitis was placed under the wire, and nicotine and ethyl alcohol solutions were injected under the gingival mucosa. A complex index has been proposed to assess inflammation. At the end of the experiment the animals were euthanized, their jaws were dissected into dentoalveolar blocks and further descriptive histologic analysis was performed.

RESULTS

On the second day the gingiva of the rats acquired a cyanotic-pink color, on the fourth day the consistency of the gingiva became friable, mobility appeared in the lower incisors. Complex index of inflammation in animals of the main group: before the study-9, on the 7th day-195. Gingival preparations showed signs of exudative inflammation. In alveolar processes-irreversible resorption of bone structures. The difference of indicators in animals before and after the experiment was statistically significant (p < 0.05).

CONCLUSION

The new experimental model of periodontitis is reproduced in a short period of time, provides intensive development of inflammation, leads to disruption of the integrity of epithelial and connective tissue attachment, destruction of alveolar bone.

TRPC expression in human periodontal ligament cells and the periodontal tissue of periodontitis mice: a preliminary study

BACKGROUND

Transient receptor potential canonical (TRPC) channels are non-selective cationic channels with permeability to Ca2+ and Na+. Despite their importance, there are currently few studies on TRPC in the periodontal ligament (PDL) and bone cells in the dental field. To provide biological information regarding TRPC in PDL cells and periodontal tissue, we evaluated TRPC channels expression in the osteoblast differentiation of PDL cells and periodontitis-induced tissue. Human PDL cells were cultured in osteogenic differentiation media for 28 days, and the expression of Runx2, osteocalcin (OCN), and TRPC1, 3, 4, and 6 was evaluated by real-time PCR. In ligature-induced periodontitis mice, the alveolar bone and osteoid areas, the osteoclast number, and the expression of Runx2, OCN, TRPC3, and TRPC6 was evaluated by H&E staining, TRAP staining, and immunohistochemistry, respectively.

RESULTS

In the PDL cell differentiation group, TRPC6 expression peaked on day 7 and TRPC3 expression generally increased during differentiation. During the 28 days of periodontitis progression, alveolar bone loss and osteoclast numbers increased compared to the control group during the experimental period and the osteoid area increased from day 14. TRPC6 expression in the periodontitis group increased in the PDL area and in the osteoblasts compared to the control group, whereas TRPC3 expression increased only in the PDL area on days 7 and 28.

CONCLUSIONS

These results indicate changes of TRPC3 and TRPC6 expression in PDL cells that were differentiating into osteoblasts and in periodontitis-induced tissue, suggesting the need for research on the role of TRPC in osteoblast differentiation or periodontitis progression.

Mouse gingival single-cell transcriptomic atlas: An activated fibroblast subpopulation guides oral barrier immunity in periodontitis

Periodontitis, one of the most common non-communicable diseases, is characterized by chronic oral inflammation and uncontrolled tooth supporting alveolar bone resorption. Its underlying mechanism to initiate aberrant oral barrier immunity has yet to be delineated. Here, we report a unique fibroblast subpopulation activated to guide oral inflammation (AG fibroblasts) identified in a single-cell RNA sequencing gingival cell atlas constructed from the mouse periodontitis models. AG fibroblasts localized beneath the gingival epithelium and in the cervical periodontal ligament responded to the ligature placement and to the discrete application of Toll-like receptor stimulants to mouse maxillary tissue. The upregulated chemokines and ligands of AG fibroblasts linked to the putative receptors of neutrophils in the early stages of periodontitis. In the established chronic inflammation, neutrophils together with AG fibroblasts appeared to induce type 3 innate lymphoid cells (ILC3s) that were the primary source of interleukin-17 cytokines. The comparative analysis of Rag2-/- and Rag2γc-/- mice suggested that ILC3 contributed to the cervical alveolar bone resorption interfacing the gingival inflammation. We propose that AG fibroblasts function as a previously unrecognized surveillant to initiate gingival inflammation leading to periodontitis through the AG fibroblast-neutrophil-ILC3 axis.

Synoviolin alleviates GSDMD-mediated periodontitis by suppressing its stability

INTRODUCTION

Inflammasome and pyroptosis play important roles in periodontitis. Gasdermin D (GSDMD), a key factor in pyroptosis, is cleaved by caspase-1 and regulated by ubiquitination. Synoviolin is a ubiquitin E3 ligase that interacts with GSDMD. In this study, the effects of Synoviolin on inflammasome activation and periodontitis were explored.

METHODS

The expression of IL-1β, GSDMD, and Synoviolin in peripheral blood mononuclear cells from patients with periodontitis was determined. The interaction between GSDMD and Synoviolin was studied. The cytokine level in gingival tissues and the distance from the cementoenamel junction to the alveolar bone crest were measured in mice with Synoviolin deficiency in myeloid cells.

RESULTS

We reported that elevated mRNA and protein levels of IL-1β and GSDMD, decreased levels of Synoviolin mRNA and protein, and decreased ubiquitination of GSDMD were associated with periodontitis. Synoviolin interacted with GSDMD. Synoviolin-deficient bone marrow-derived macrophages had increased IL-1β and IL-18 secretion after ATP stimulation. Mice with Synoviolin deficiency in myeloid cells had more severe periodontitis and upregulated IL-1β and IL-18.

CONCLUSIONS

Therefore, we conclude that Synoviolin suppresses inflammasome activation and periodontitis by regulating GSDMD stability.

Sirt6 Activation Ameliorates Inflammatory Bone Loss in Ligature-Induced Periodontitis in Mice

Periodontitis is an inflammatory disease caused by microorganisms that induce the destruction of periodontal tissue. Inflamed and damaged tissue produces various inflammatory cytokines, which activate osteoclasts and induce alveolar bone loss and, eventually, tooth loss. Sirt6 expression suppresses inflammation and bone resorption; however, its role in periodontitis remains unclear. We hypothesized that Sirt6 has a protective role in periodontitis. To understand the role of Sirt6 in periodontitis, we compared periodontitis with ligature placement around the maxillary left second molar in 8-week-old control (C57BL/6J) male mice to Sirt6-overexpressing Tg (Sirt6Tg) mice, and we observed the resulting phenotypes using micro-CT. MDL801, a Sirt6 activator, was used as a therapy for periodontitis through oral gavage. Pro-inflammatory cytokines and increased osteoclast numbers were observed in alveolar bone tissue under periodontitis surgery. In the same condition, interestingly, protein levels from Sirt6 were the most downregulated among sirtuins in alveolar bone tissue. Based on micro-CT and CEJ-ABC distance, Sirt6Tg was observed to resist bone loss against ligature-induced periodontitis. Furthermore, the number of osteoclasts was significantly reduced in Sirt6Tg-ligated mice compared with control-ligated mice, although systemic inflammatory cytokines did not change. Consistent with this observation, we confirmed that bone loss was significantly reduced when MDL801, a Sirt6 activator, was included in the ligation mouse model. Our findings demonstrate that Sirt6 activation prevents bone loss against ligature-induced periodontitis. Thus, a Sirt6 activator may provide a new therapeutic approach for periodontitis.