Obesity and Hyperlipidemia Modulate Alveolar Bone Loss in Wistar Rats

Induced Periodontitis in Rats With Three Ligature Types: An Exploratory Study

BACKGROUND

The placement of ligatures in the cervical area of rat molars is considered as a predictable model to induce periodontitis.

OBJECTIVES

The present explorative study aimed to compare the efficacy of metal wires (MWs), without or with sandblasting, versus silk ligatures (SLs) in inducing periodontal bone loss in rats.

MATERIALS AND METHODS

Twenty-four Wistar rats were randomly divided into three groups of eight rats that received three different types of ligatures (MW, sandblasted wire [SMW], and SL) around their first right mandibular molar, while the contralateral tooth was left without the ligature and served as a control. Bone loss was assessed by measuring the distance from the cementoenamel junction (CEJ) to the bone crest at the distal aspect of the first molar on central mesiodistal sections generated from micro-CT scans taken 24 and 35 days after ligature placement.

RESULTS

In the SL group, only in two rats the ligatures were retained until the end of the 24-day period; in all other animals, the ligatures were lost at some time point. In the SMW, the ligatures were retained only for the 24-day period. In the MW group, no ligatures were lost. Irrespective of the group or experimental period, the difference in the crestal bone level between ligated and control teeth was in most cases z < 0.20 mm, that is, in 19 out of 25 pairs of teeth. In a few cases, the bone crest was more apically located at the control teeth compared to the ligated ones (four cases each, during both 24- and 35-day experimental periods).

CONCLUSIONS

Bone loss was minimal during the experimental period, with no significant differences between the test and control teeth, or among the three types of ligatures. MWs, not even roughened, do not seem to be a better alternative to SLs for inducing bone loss in the experimental periodontitis model in the rat. This assumption, however, has to be confirmed in a larger, well-powered study.

A reliable deep-learning-based method for alveolar bone quantification using a murine model of periodontitis and micro-computed tomography imaging

OBJECTIVES

This study focuses on artificial intelligence (AI)-assisted analysis of alveolar bone for periodontitis in a mouse model with the aim to create an automatic deep-learning segmentation model that enables researchers to easily examine alveolar bone from micro-computed tomography (µCT) data without needing prior machine learning knowledge.

METHODS

Ligature-induced experimental periodontitis was produced by placing a small-diameter silk sling ligature around the left maxillary second molar. At 4, 7, 9, or 14 days, the maxillary bone was harvested and processed with a µCT scanner (µCT-45, Scanco). Using Dragonfly (v2021.3), we developed a 3D deep learning model based on the U-Net AI deep learning engine for segmenting materials in complex images to measure alveolar bone volume (BV) and bone mineral density (BMD) while excluding the teeth from the measurements.

RESULTS

This model generates 3D segmentation output for a selected region of interest with over 98 % accuracy on different formats of µCT data. BV on the ligature side gradually decreased from 0.87 mm3 to 0.50 mm3 on day 9 and then increased to 0.63 mm3 on day 14. The ligature side lost 4.6 % of BMD on day 4, 9.6 % on day 7, 17.7 % on day 9, and 21.1 % on day 14.

CONCLUSIONS

This study developed an AI model that can be downloaded and easily applied, allowing researchers to assess metrics including BV, BMD, and trabecular bone thickness, while excluding teeth from the measurements of mouse alveolar bone.

CLINICAL SIGNIFICANCE

This work offers an innovative, user-friendly automatic segmentation model that is fast, accurate, and reliable, demonstrating new potential uses of artificial intelligence (AI) in dentistry with great potential in diagnosing, treating, and prognosis of oral diseases.

Protective Effect of Bovine Milk Extracellular Vesicles on Alveolar Bone Loss

SCOPE

Bovine milk extracellular vesicles (MEVs) have demonstrated therapeutic potential in regulating bone cell activity. However, the outcome of their use on alveolar bone loss has not yet been demonstrated.

METHODS AND RESULTS

This study evaluates the effect of oral administration of MEVs on ovariectomized (OVX) mice. There is a reduced height of the alveolar bone crest in OVX mice by MEVs treatment, but the alveolar bone parameters are not altered. OVX mice are then submitted to a force-induced bone remodeling model by orthodontic tooth movement (OTM). MEVs-treated mice have markedly less bone remodeling movement, unlike the untreated OVX mice. Also, OVX mice treated with MEVs show an increased number of osteoblasts and osteocytes associated with higher sclerostin expression and reduce osteoclasts in the alveolar bone. Although the treatment with MEVs in OVX mice does not show differences in root structure in OTM, few odontoclasts are observed in the dental roots of OVX-treated mice. Compared to untreated mice, maxillary and systemic RANKL/OPG ratios are reduced in OVX mice treated with MEVs.

CONCLUSION

Treatment with MEVs results in positive bone cell balance in the alveolar bone and dental roots, indicating its beneficial potential in treating alveolar bone loss in the nutritional context.

Association of obesity and weight gain with alveolar bone loss: Results of the Northern Finland Birth Cohort 1966 study

AIM

To investigate whether long-term obesity, long-term central obesity and weight gain are associated with alveolar bone loss.

MATERIALS AND METHODS

A sub-population (n = 1318) of the Northern Finland Birth Cohort 1966 was categorized based on body mass index (BMI: normal weight, overweight and obesity) and waist circumference (WC: no central obesity, central obesity) at ages 31 and 46. These categories were combined to define whether the participants stayed in the same categories or passed on to a higher category (weight gain). Alveolar bone level (BL) data were collected at age 46.

RESULTS

The associations of long-term obesity and weight gain with BL ≥ 5 mm were stronger in smokers than in the total population and in never smokers. Males who passed on to higher BMI and WC categories showed a higher likelihood for BL ≥ 5 mm (range in relative risks [RRs] 1.3-2.2) than males who stayed in the same categories (range in RRs 0.7-1.1). The associations with BL ≥ 5 mm were weak or non-existent in females.

CONCLUSIONS

The relation between obesity and periodontal diseases seems more complex than previously presumed. The role of gender and smoking should be taken into account in future studies.

Induction of Periodontitis Using Bacterial Strains Isolated from the Human Oral Microbiome in an Experimental Rat Model

Periodontal disease is that condition resulting in the destruction of periodontal tissues, bone resorption, and tooth loss, the etiology of which is linked to immunological and microbiological factors. The aim of this study was to evaluate the potential trigger of periodontal disease in a rat model using bacterial species incriminated in the pathology of human periodontitis and to establish their optimal concentrations capable of reproducing the disease, with the idea of subsequently developing innovative treatments for the condition. In this study, we included 15 male Wistar rats, aged 20 weeks, which we divided into three groups. In each group, we applied ligatures with gingival retraction wire on the maxillary incisors. The ligature and the gingival sac were contaminated by oral gavage with a mixture of fresh cultures of Aggregatibacter actinomycetemcomitans (A.a), Fusobacterium nucleatum (F.n) and Streptococcus oralis (S.o) in concentrations of 108, 109, and 1010 CFU/mL each for 5 days a week for 4 weeks. During the clinical monitoring period of 28 days, overlapped with the period of oral contamination, we followed the expression of clinical signs specific to periodontitis. We also monitored the evolution of body weight and took weekly samples from the oral cavity for the microbiological identification of the tested bacteria and blood samples for hematological examination. At the end of the study, the animals were euthanized, and the ligated incisors were taken for histopathological analysis. The characteristic symptomatology of periodontal disease was expressed from the first week of the study and was maintained until the end, and we were able to identify the bacteria during each examination. Hematologically, the number of neutrophils decreased dramatically (p < 0.0001) in the case of the 109 group, unlike the other groups, as did the number of lymphocytes. Histopathologically, we identified neutrophilic infiltrate in all groups, as well as the presence of coccobacilli, periodontal tissue hyperplasia, and periodontal lysis. In the 109 group, we also observed pulpal tissue with necrotic bone fragments and pyogranulomatous inflammatory reaction. By corroborating the data, we can conclude that for the development of periodontal disease using A.a, F.n, and S.o, a concentration of 109 or 1010 CFU/mL is required, which must necessarily contaminate a ligature thread applied to the level of the rat's dental pack.

Osteoporosis and Alveolar Bone Health in Periodontitis Niche: A Predisposing Factors-Centered Review

Periodontitis is a periodontal inflammatory condition that results from disrupted periodontal host-microbe homeostasis, manifested by the destruction of tooth-supporting structures, especially inflammatory alveolar bone loss. Osteoporosis is characterized by systemic deterioration of bone mass and microarchitecture. The roles of many systemic factors have been identified in the pathogenesis of osteoporosis, including endocrine change, metabolic disorders, health-impaired behaviors and mental stress. The prevalence rate of osteoporotic fracture is in sustained elevation in the past decades. Recent studies suggest that individuals with concomitant osteoporosis are more vulnerable to periodontal impairment. Current reviews of worse periodontal status in the context of osteoporosis are limited, mainly centering on the impacts of menopausal and diabetic osteoporosis on periodontitis. Herein, this review article makes an effort to provide a comprehensive view of the relationship between osteoporosis and periodontitis, with a focus on clarifying how those risk factors in osteoporotic populations modify the alveolar bone homeostasis in the periodontitis niche.

Is Obesity a Risk Factor for Periodontal Disease in Adults? A Systematic Review

There is inconclusive evidence about the link between the severity and prevalence of periodontitis in obese adults. Therefore, this systematic review aims to explore the possibility of significant evidence on the association between obesity and periodontitis and to determine the necessity to consider obesity as a risk factor for periodontitis. We followed the PRISMA protocol, and studies that met the eligibility criteria were included in this review. The risk of bias in individual studies was also evaluated. This review included 15 observational studies (9 cross-sectional studies, 2 case-control, and 4 cohort studies). The total study subjects from these studies were 6603 (males = 3432; females = 3171). Most studies showed a significant association between obesity and periodontitis. Among these studies, a few showed obese females to be at a higher risk, and one study found no association between obesity and periodontal disease at all. Based on the evidence obtained from this review, the body mass index (BMI) should be routinely assessed in patients to assess the risk for periodontal disease and to offer personalized management of periodontitis. Based on the findings of this review, we recommend the need to initiate awareness among clinicians and implement dental hygiene care prevention measures for obese patients.

Protective Effect of Virgin Coconut Oil on Osteopenia Induced by High Refined Carbohydrate-Containing Diet in Mice

Background: Obesity leads to chronic low-grade inflammation, promoting detrimental effects on bone. The consumption of virgin coconut oil (VCO) is associated with benefits related to meta-inflammation. We evaluated the effect of VCO supplementation on osteopenia promoted by diet-induced obesity in mice. Methods: Male BALB/c mice were fed a control (C) or highly refined carbohydrate-containing (HC) diet for eight weeks. After that, the HC diet group was supplemented with three doses of VCO for four weeks. Results: The HC diet increased the adiposity and leptin levels associated with augmented systemic inflammatory cells improved with VCO supplementation. The HC diet reduced the trabecular bone in the tibia, lumbar vertebrae, distal and proximal femur, as well as the bone mineral density of the femur and alveolar bone. The VCO supplementation reverted bone osteopenia by increasing the trabecular bone in different sites and improving femur and alveolar bone microarchitecture. Although the reduced number of osteoblasts in the alveolar bone of the HC diet group was not significantly enhanced by VCO supplementation, the reduced Alp expression in the HC diet group was enhanced in the VCO group. These beneficial effects were associated with lowering the Rankl/Opg ratio. Conclusion: VCO supplementation might be an effective strategy to attenuate bone osteopenic effects induced by obesity.

Obesity, Bone Loss, and Periodontitis: The Interlink

Obesity and periodontitis are both common health concerns that have given rise to considerable economic and societal burden worldwide. There are established negative relationships between bone metabolism and obesity, obesity and diabetes mellitus (DM), and DM and periodontitis, to name a few, with osteoporosis being considered a long-term complication of obesity. In the oral cavity, bone metabolic disorders primarily display as increased risks for periodontitis and alveolar bone loss. Obesity-driven alveolar bone loss and mandibular osteoporosis have been observed in animal models without inoculation of periodontopathogens. Clinical reports have also indicated a possible association between obesity and periodontitis. This review systematically summarizes the clinical periodontium changes, including alveolar bone loss in obese individuals. Relevant laboratory-based reports focusing on biological interlinks in obesity-associated bone remodeling via processes like hyperinflammation, immune dysregulation, and microbial dysbiosis, were reviewed. We also discuss the potential mechanism underlying obesity-enhanced alveolar bone loss from both the systemic and periodontal perspectives, focusing on delineating the practical considerations for managing periodontal disease in obese patients.

Periodontal disease affects oral cancer progression in a surrogate animal model for tobacco exposure

For decades, the link between poor oral hygiene and the increased prevalence of oral cancer has been suggested. Most recently, emerging evidence has suggested that chronic inflammatory diseases from the oral cavity (e.g., periodontal disease), to some extent, play a role in the development of oral squamous cell carcinoma (OSCC). The present study aimed to explore the direct impact of biofilm‑induced periodontitis in the carcinogenesis process using a tobacco surrogate animal model for oral cancer. A total of 42 Wistar rats were distributed into four experimental groups: Control group, periodontitis (Perio) group, 4‑nitroquinoline 1‑oxide (4‑NQO) group and 4NQO/Perio group. Periodontitis was stimulated by placing a ligature subgingivally, while oral carcinogenesis was induced by systemic administration of 4NQO in the drinking water for 20 weeks. It was observed that the Perio, 4NQO and 4NQO/Perio groups presented with significantly higher alveolar bone loss compared with that in the control group. Furthermore, all groups receiving 4NQO developed lesions on the dorsal surface of the tongue; however, the 4NQO/Perio group presented larger lesions compared with the 4NQO group. There was also a modest overall increase in the number of epithelial dysplasia and OSCC lesions in the 4NQO/Perio group. Notably, abnormal focal activation of cellular differentiation (cytokeratin 10‑positive cells) that extended near the basal cell layer of the mucosa was observed in rats receiving 4NQO alone, but was absent in rats receiving 4NQO and presenting with periodontal disease. Altogether, the presence of periodontitis combined with 4NQO administration augmented tumor size in the current rat model and tampered with the protective mechanisms of the cellular differentiation of epithelial cells.

Pharmacological Therapies for the Management of Inflammatory Bone Resorption in Periodontal Disease: A Review of Preclinical Studies

Periodontitis, a highly prevalent multicausal chronic inflammatory and destructive disease, develops as a result of complex host-parasite interactions. Dysbiotic bacterial biofilm in contact with the gingival tissues initiates a cascade of inflammatory events, mediated and modulated by the host's immune response, which is characterized by increased expression of several inflammatory mediators such as cytokines and chemokines in the connective tissue. If periodontal disease (PD) is left untreated, it results in the destruction of the supporting tissues around the teeth, including periodontal ligament, cementum, and alveolar bone, which lead to a wide range of disabilities and poor quality of life, thus imposing significant burdens. This process depends on the differentiation and activity of osteoclasts, the cells responsible for reabsorbing the bone tissue. Therefore, the inhibition of differentiation or activity of these cells is a promising strategy for controlling bone resorption. Several pharmacological drugs that target osteoclasts and inflammatory cells with immunomodulatory and anti-inflammatory effects, such as bisphosphonates, anti-RANK-L antibody, strontium ranelate, cathepsin inhibitors, curcumin, flavonoids, specialized proresolving mediators, and probiotics, were already described to manage inflammatory bone resorption during experimental PD progression in preclinical studies. Meantime, a growing number of studies have described the beneficial effects of herbal products in inhibiting bone resorption in experimental PD. Therefore, this review summarizes the role of several pharmacological drugs used for PD prevention and treatment and highlights the targeted action of all those drugs with antiresorptive properties. In addition, our review provides a timely and critical appraisal for the scientific rationale use of the antiresorptive and immunomodulatory medications in preclinical studies, which will help to understand the basis for its clinical application.

Effects of periodontitis and periodontal treatment on systemic inflammatory markers and metabolic profile in obese and non-obese rats

BACKGROUND

Little is known about a synergistic effect of periodontitis and obesity on systemic biomarkers and a possible effect periodontal treatment may exert. This study aimed to evaluate the impact of periodontitis and periodontal treatment on systemic inflammation and metabolic profile in obese and non-obese rats.

METHODS

60 male Wistar rats were randomly divided in six groups differentiated by diet and periodontal status: no periodontitis (G1 and G4), untreated ligature-induced periodontitis (G2 and G5) and treated ligature-induced periodontitis (G3 and G6). Groups G4, G5 and G6 were exposed to cafeteria diet to induce obesity. Periodontitis was induced by silk ligatures over 4 weeks (G2, G3, G5, G6). Rats in G3 and G6 received scaling and root planning and were followed for additional 4 weeks. After sacrifice, serum levels of C-reactive protein (CRP), interleukin (IL)-1β, IL-6, IL-10, IL-17a, tumor necrosis factor alfa (TNF-α), glucose, triglycerides, and total cholesterol (TC) were compared between groups.

RESULTS

CRP was significantly higher in obese rats with than without periodontitis (G5 = 10.15μg/L vs. G4 = 4.47μg/L, p = 0.01). No beneficial effects of periodontal treatment were observed for CRP levels, IL-6, IL-1β, IL-17a, TNF-α, glucose and triglycerides. Treated periodontitis (G6) exhibited significantly lower TC than the periodontitis group (G5) in obese rats.

CONCLUSION

Periodontitis increased serum CRP in obese rats, indicating a synergistic role of periodontitis in the systemic inflammatory burden triggered by obesity. The treatment of induced periodontitis reduced TC levels in obese rats. This article is protected by copyright. All rights reserved.

Obesity influences the proteome of periodontal ligament tissues following periodontitis induction in rats

BACKGROUND AND OBJECTIVES

Many studies have been conducted to better understand the molecular mechanism involved with periodontitis progression. There has been growing interest in the potential impact of obesity on periodontitis onset and progression, but the mechanisms involved remain to be elucidated. The present study was designed to determine the impact of obesity on experimentally induced periodontitis in rats and identify novel pathways involved.

METHODS

Sixteen Holtzman rats were distributed into two groups (n = 8): ligature-induced periodontitis (P) and obesity plus ligature-induced periodontitis (OP). Obesity was induced by a high-fat diet for 70 days, whereas periodontitis was induced for 20 days, with a cotton thread placed around the upper first molars bilaterally. Alveolar bone loss was measured by microtomographic analysis and histologically by histometry on the hemimaxillae. The protein composition of the periodontal ligament was evaluated by proteomic analysis.

RESULTS

Data analysis (body weight, adipose tissue weight, and blood test) confirmed obesity induction, whereas bone loss was confirmed by micro-CT and histologic analyses. Proteome analysis from the periodontal ligament tissues (PDL) identified 819 proteins, 53 exclusive to the P group, 28 exclusive to the OP group, and 738 commonly expressed. Validation was performed by immunohistochemistry for selected proteins (spondin1, vinculin, and TRAP).

CONCLUSION

Histologically, it was found that obesity did not significantly affect bone loss resulting from periodontitis. However, the present study's findings indicated that obesity affects the proteome of PDL submitted to experimental periodontitis, allowing for identifying potential targets for personalized approaches.

Soy isoflavones alleviate periodontal destruction in ovariectomized rats

OBJECTIVE

The purpose of this study was to investigate whether soy isoflavone supplementation is effective in preventing periodontal destruction exacerbated by estrogen deficiency (ED) and its potential mechanism.

BACKGROUND

The progression of periodontitis is affected by host factors, such as smoking, diabetes mellitus, and steroid use. Bone loss in periodontitis can be aggravated by ED.

METHODS

A rat model of experimental periodontitis (EP) with ED was established by silk ligature and inoculation with Porphyromonas gingivalis, and some EP rats were subjected to bilateral ovariectomy (OVX). The treatment groups received an intravenous injection of 17-β-estradiol (E₂ B) or soy isoflavones (SI) by gavage. The rats were euthanized, and the maxillary jaws, gingiva, and serum were harvested. Tight junction protein and interleukin (IL)-17 expression, reactive oxygen species (ROS) level, and periodontal destruction were assessed. In addition, we determined whether grainyhead-like 2 (GRHL2) is required for enhancing the epithelial barrier by SI in an in vitro P. gingivalis infection model.

RESULTS

Estrogen deficiency impaired the expression of genes encoding tight junction proteins in the gingiva, increased IL-17 level, and accelerated alveolar bone resorption. SI treatment alleviated tight junction protein expression, decreased IL-17 and ROS levels, and prevented the absorption of alveolar bone. Furthermore, GRHL2 expression was significantly induced by SI in human oral keratinocytes-1 (HOK-1) cells; GRHL2 knockdown impaired the expression of OCLN and ZO-1 induced by SI treatment.

CONCLUSION

Soy isoflavones alleviates periodontitis in OVX rats, as observed by the increased expression of tight junction proteins, and reduced IL-17 level and alveolar bone loss. The in vitro studies suggested that the enhancement of oral epithelial barrier by SI treatment was partially dependent on GRHL2.

Gut-Bone Axis: A Non-Negligible Contributor to Periodontitis

Periodontitis is a polymicrobial infectious disease characterized by alveolar bone loss. Systemic diseases or local infections, such as diabetes, postmenopausal osteoporosis, obesity, and inflammatory bowel disease, promote the development and progression of periodontitis. Accumulating evidences have revealed the pivotal effects of gut microbiota on bone health via gut-alveolar-bone axis. Gut pathogens or metabolites may translocate to distant alveolar bone via circulation and regulate bone homeostasis. In addition, gut pathogens can induce aberrant gut immune responses and subsequent homing of immunocytes to distant organs, contributing to pathological bone loss. Gut microbial translocation also enhances systemic inflammation and induces trained myelopoiesis in the bone marrow, which potentially aggravates periodontitis. Furthermore, gut microbiota possibly affects bone health via regulating the production of hormone or hormone-like substances. In this review, we discussed the links between gut microbiota and periodontitis, with a particular focus on the underlying mechanisms of gut-bone axis by which systemic diseases or local infections contribute to the pathogenesis of periodontitis.

Impact of endodontic and periodontal diseases and treatments on the aorta and liver of obese and non-obese rats

AIM

To evaluate the impact of the presence and treatment of periodontal disease (PD) and apical periodontitis (AP) on the aorta and liver of obese and non-obese rats.

METHODOLOGY

One hundred and forty Wistar rats were divided into two groups, according to the diet administered: normal diet (-n), without obesity; and cafeteria diet (-c), with induced obesity. These groups were divided into seven subgroups according to the specific experimental protocols: naïve control (NC); AP; AP with treatment (APt); PD; PE with treatment (PDt); AP and PD (APPD); and AP and PD with treatment (APPDt). AP and PD lesions were induced for four weeks. Four weeks after treatments, the animals were euthanatized, and the aorta and liver were dissected for histological evaluation. For the comparison of the thickness of the aorta between groups, the Kruskal-Wallis test was used, followed by the Mann-Whitney test. For the analysis of other variables related to the aorta and liver outcomes, logistic regression was carried out.

RESULTS

Both PD and AP were associated with the development of histological alterations in the aortic arch, with no significant difference between obese and non-obese animals (p = .17). The aorta thickness was increased significantly (p < .05) with the combination of PD and AP in obese rats (APPDt-c group) compared with the other groups (NC-n, APt-n, APt-c and AP-c). The logistic regression models revealed that the untreated (OR = 7.78; 95%CI = 2.4-25) and treated (OR = 2.9; 95%CI = 1.0-8.4) groups were significantly more likely to have endothelial alterations compared with the control groups (p = .002). Obesity (OR = 16.5; 95%CI = 3.4-81.3) was the only predictor variable of liver steatosis (p < .001).

CONCLUSION

Histological alterations in the aortic arch of obese and non-obese rats were observed in the presence of periodontal disease and apical periodontitis. The combination of PD and AP increased the aorta thickness in obese rats. A reduction of vascular endothelial lesions was observed with the treatments of PD and AP.

Plaque control alleviated renal damage that was aggravated by experimental periodontitis in obese rats

OBJECTIVE

This study aimed to evaluate the influence of experimental periodontitis on renal damage in obese rats.

MATERIALS AND METHODS

Thirty-two male Sprague Dawley rats were randomly allocated into 4 groups with 8 animals each: obese rats (obese group), obese rats with periodontitis (periodontitis obese group), obese rats with periodontitis that underwent plaque control (plaque-control obese group), and healthy rats (healthy group). Rats were fed a high-fat diet to establish an obesity model. Experimental periodontitis was induced by local ligation with silk around the bilateral maxillary second molars. The plaque control was accomplished by removing ligations and local wiping with an antiseptic rinse. Histology was used to observe the gingival inflammation and clinical attachment level (CAL) to further assess bone loss and to also observe renal structure. Serum creatinine, urea nitrogen, and kidney injury molecule-1 (KIM-1) levels were measured to evaluate renal function. Renal Toll-like receptor 4 (TLR4), nuclear factor-kappa B (NF-κB), serum C-reactive protein (CRP), lipopolysaccharides (LPS), and interleukin-1β (IL-1β) were measured to evaluate renal and systemic inflammation.

RESULTS

Periodontal histology showed that in the periodontitis obese group, the epithelial barrier was considerably eroded by inflammatory cells, which infiltrated into the subepithelial connective tissue and lamina propria. A periodontal pocket was forming accompanied by the loss of attachment. The extent of infiltration of inflammatory cells and the CAL were significantly higher than those of the obese group (p < .001). In the plaque-control obese group, although the inflammatory condition was significantly improved than in the periodontitis obese group, the clinical attachment level with the presence of fiber hyperplasia could not be restored. Renal histology showed that renal tubular structural damage was aggravated in the periodontitis obese group, including vacuolar degeneration, exfoliation of the proximal tubular epithelial cell lining, multifocal loss of the brush border, and movement of several nuclei from the basement membrane to the lumen. These alterations were improved in the plaque-control obese group. Kidney TLR4 and NF-κB mRNA levels increased significantly in the periodontitis obese group compared to the obese group (p = .015 and p = .015, respectively) and decreased significantly in the plaque-control obese group (p = .028 and p = .021, respectively). Kidney TLR4 and NF-κB protein expression in the plaque-control obese group were significantly lower than those in the periodontitis obese group (p < .001 and p = .043, respectively). Serum creatinine and KIM-1 levels significantly decreased in the plaque-control obese group compared to the periodontitis obese group (p = .001 and p = .002, respectively). At 21 weeks (1 week after periodontal ligation), serum CRP levels in the periodontitis obese group were significantly higher than that in the healthy group (p = .017). Other serum inflammatory markers (LPS and IL-1β) did not change significantly.

CONCLUSION

Experimental periodontitis induced dysfunction and structural destruction of the kidney in obese rats. Plaque control relieved renal damage.

Distinguish fatty acids impact survival, differentiation and cellular function of periodontal ligament fibroblasts

Alveolar bone (AB) remodeling is necessary for the adaption to mechanical stimuli occurring during mastication and orthodontic tooth movement (OTM). Thereby, bone degradation and assembly are strongly regulated processes that can be altered in obese patients. Further, increased fatty acids (FA) serum levels affect bone remodeling cells and we, therefore, investigated whether they also influence the function of periodontal ligament fibroblast (PdLF). PdLF are a major cell type regulating the differentiation and function of osteoblasts and osteoclasts localized in the AB. We stimulated human PdLF (HPdLF) in vitro with palmitic (PA) or oleic acid (OA) and analyzed their metabolic activity, growth, survival and expression of osteogenic markers and calcium deposits. Our results emphasize that PA increased cell death of HPdLF, whereas OA induced their osteoblastic differentiation. Moreover, quantitative expression analysis of OPG and RANKL revealed altered levels in mechanically stimulated PA-treated HPdLF. Furthermore, osteoclasts stimulated with culture medium of mechanical stressed FA-treated HPdLF revealed significant changes in cell differentiation upon FA-treatment. For the first time, our results highlight a potential role of specific FA in the function of HPdLF-modulated AB remodeling and help to elucidate the complex interplay of bone metabolism, mechanical stimulation and obesity-induced alterations.

Pam2CSK4 (TLR2 agonist) induces periodontal destruction in mice

Lipoproteins are important bacterial immunostimulating molecules capable of inducing receptor activator of nuclear factor-κB (RANKL) and osteoclast formation in vitro and in vivo . Although these molecules are present in periodontopathogenic bacteria, their role in periodontitis is not known. In this study, we used Pam2CSK4 (PAM2), a synthetic molecule that mimics bacterial lipoprotein, to investigate the effects of lipoproteins on periodontitis in mice. C57BL/6 male mice were randomly divided into three experimental groups: 1) Negative control group: animals received vehicle injection; 2) Positive control group: animals received injection of Escherichia coli lipopolysaccharide (LPS); 3) PAM2 group: animals received PAM2 injection. All the injections were performed bilaterally every other day into the palatal mucosa between first and second molars. After twenty-four days, the animals were euthanized to assess alveolar bone volume (micro-CT), cellular and extracellular composition in the gingiva (stereometric analysis), and osteoclast numbers (TRAP staining). Treatment with either PAM2 or LPS induced gingival inflammation, as demonstrated by increased infiltration of inflammatory cells and enhanced angiogenesis, associated with a smaller number of fibroblasts and decreased extracellular matrix. Importantly, treatment not only with LPS but also with PAM2 resulted in a larger number of TRAP+ multinucleated osteoclasts and significant loss of alveolar bone. Collectively, our data demonstrate that PAM2 can induce gingival inflammation and bone loss in mice, broadening the avenues of investigation into the role of lipoproteins in the pathogenesis of periodontal disease.

Periodontal status, vascular reactivity, and platelet aggregation changes in rats submitted to hypercholesterolemic diet and periodontitis

BACKGROUND AND OBJECTIVES

Periodontitis can corroborate with development and progression of atherosclerosis and a possible bidirectional interaction between both pathologies has been hypothesized. The aim of this work was to study the interactions between diet-induced hypercholesterolemia and ligature-induced periodontitis in Wistar rats submitted to both conditions.

MATERIAL AND METHODS

Animals were divided into four experimental groups: C (control: standard diet without periodontitis), Perio (periodontitis plus standard diet), HC (high cholesterol diet without periodontitis), and HC + Perio (high cholesterol diet plus periodontitis). The diets were offered for 45 days and a silk ligature was applied in the lower first molars of Perio and HC-Perio animals on day 34 and maintained for 11 days until euthanasia. The mandibles were excised, and alveolar bone loss was determined by macroscopic and micro-tomographic (µ-CT) imaging. Blood samples were obtained, and platelet aggregation was induced in plasma rich in platelets by adenosine diphosphate (ADP) and collagen. Endothelium-dependent vascular reactivity and protein expression of endothelial (eNOS), phosphorylated endothelial (peNOS), and inducible (iNOS) nitric oxide synthases were evaluated in aorta samples.

RESULTS

The HC diet combined with periodontitis (HC + Perio group) was associated with an increased alveolar bone loss, when compared to the other groups. Both in Perio and HC groups, platelet aggregation induced by ADP or collagen was increased, while maximum aortic relaxation induced by acetylcholine was decreased. Periodontitis or HC diet alone decreased the expression of peNOS and HC diet increased the expression of iNOS. In contrast, no additive or synergistic effects were found in vascular reactivity or in platelet aggregation when the two conditions were associated (HC + Perio group).

CONCLUSION

Hypercholesterolemia accelerated the process of bone loss induced by periodontitis while a high cholesterol diet or periodontitis individually increased platelet aggregation and vascular reactivity in rats without additive or synergistic effects, when associated.

Salivary Cytokine Biomarker Concentrations in Relation to Obesity and Periodontitis

Systemic low-grade inflammation is associated with obesity. Our aim was to examine the association between obesity and salivary biomarkers of periodontitis. Salivary interleukin (IL)-1-receptor antagonist (IL-1Ra), IL-6, IL-8, IL-10, and tumor necrosis factor (TNF)-α concentrations were measured from 287 non-diabetic obese (body mass index (BMI) of >35 kg/m²) individuals and 293 normal-weight (BMI of 18.5–25 kg/m²) controls. Periodontal status was defined according to a diagnostic cumulative risk score (CRS) to calculate the risk of having periodontitis (CRS I, low risk; CRS II, medium risk; CRS III, high risk). In the whole population, and especially in smokers, higher IL-8 and lower IL-10 concentrations were detected in the obese group compared to the control group, while in non-smoking participants, the obese and control groups did not differ. IL-1Ra and IL-8 concentrations were higher in those with medium or high risk (CRS II and CRS III, p < 0.001) of periodontitis, whereas IL-10 and TNF-α concentrations were lower when compared to those with low risk (CRS I). In multivariate models adjusted for periodontal status, obesity did not associate with any salivary cytokine concentration. In conclusion, salivary cytokine biomarkers are not independently associated with obesity and concentrations are dependent on periodontal status.

Aberrant Periodontal and Systemic Immune Response of Overweight Rodents to Periodontal Infection

This study aimed to explore periodontal and systemic immune response of overweight hosts to periodontitis. Forty C57 BL/6J male mice were divided into high (HF) or low fat (LF) diet groups and fed with the two diets, respectively, for 8 weeks. Each diet group was then divided into periodontitis (P) or control (C) groups (n = 10 per group) for 10-day ligation or sham-ligation. Overweight-related parameters including body weight were measured. Alveolar bone loss (ABL) was morphometrically analyzed and periodontal osteoclasts were stained. Periodontal immune response including leukocyte and macrophage number and inflammatory cytokines were analyzed by histology and quantitative PCR. Serum cytokine and lipid levels were quantified using electrochemiluminescence immunoassays, enzyme-linked immunosorbent assays, and biochemistry. It was found that HF group had 14.4% body weight gain compared with LF group (P < 0.01). ABL and periodontal osteoclast, leukocyte, and macrophage number were higher in P group than C group regardless of diet (P < 0.05). ABL and periodontal osteoclast number were not affected by diet regardless of ligation or sham-ligation. Leukocyte and macrophage number and protein level of tumor necrosis factor α (TNF-α) in periodontium and serum interleukin-6 level were downregulated by HF diet in periodontitis mice (P < 0.05). Periodontal protein level of TNF-α was highly correlated with serum interleukin-6 and low-density lipoprotein cholesterol levels (P < 0.01). These findings indicated that impaired immune response occurs both periodontally and systemically in preobesity overweight individuals. Given a well-reported exacerbating effect of obesity on periodontitis, overweight, if let uncontrolled, might place the individuals at potential risk for future periodontal tissue damage.

Gingival mesenchymal stem cells attenuate pro-inflammatory macrophages stimulated with oxidized low-density lipoprotein and modulate lipid metabolism

OBJECTIVE

To examine the effects of gingival mesenchymal stem cells (GMSCs) on inflammatory macrophages upon oxidized low-density lipoprotein (ox-LDL) stimulation and evaluate therapeutic potential of GMSCs on mouse model of periodontitis associated with hyperlipidemia.

METHODS

in vitro, GMSCs were co-cultured with macrophages for 48 h in the absence or presence of M1 polarizing conditions and oxidized low-density lipoprotein in the transwell system. The supernatants were collected for ELISA. M1 and M2 markers of macrophages were analyzed by flow cytometry and PCR, and lipid accumulation was assessed by oil red O staining. in vivo, eighteen mice were divided into three groups (n = 6): Group A (periodontally healthy mice as control), Group B (periodontitis mice with hyperlipidemia), Group C (periodontitis mice with hyperlipidemia with the transplantation of GMSCs). The serum levels of cholesterol and inflammatory factors were measured by automatic analyzer. Bone regeneration was evaluated by Masson staining.

RESULTS

When co-cultured with GMSCs, the M1 markers of Tumor Necrosis Factor (TNF) -α, Interleukin (IL) -6, Interleukin (IL) -1β, CD86, and Human Leukocyte Antigen (HLA) -DR were significantly reduced. In contrast, M2 markers such as Interleukin(IL) -10 and CD206 were moderately increased. Similar results were obtained in the cell culture supernatants. In animal experiment, GMSCs suppressed the expression of sterol regulatory element binding transcription factor 1c (SREBP-1c) and elevated the levels of peroxisome proliferator-activated receptor alpha (PPARα) and peroxisome proliferator activator receptor- coactivator 1(PGC-1α) in the liver, attenuated cholesterol dysfunction via the downregulation of low-density lipoprotein (LDL) and total cholesterol (TC), and the upregulation of high-density lipoprotein (HDL), and decreased the levels of TNF-α and IL-6. Moreover, GMSC treatment improved bone regeneration.

CONCLUSION

GMSCs inhibit the activation of M1 macrophages, regulate lipid metabolism and reduce inflammatory response, and promote bone regeneration in mouse model of periodontitis associated with hyperlipidemia.

Characterization of ligature-induced experimental periodontitis

We sought to better characterize the progression of periodontal tissue breakdown in rats induced by a ligature model of experimental periodontal disease (PD). A total of 60 male Sprague-Dawley rats were evenly divided into an untreated control group and a PD group induced by ligature bilaterally around first and second maxillary molars. Animals were sacrificed at 1, 3, 5, 7, 14, and 21 days after the induction of PD. Alveolar bone loss was evaluated by histomorphometry and microcomputed tomography (μCT). The immune-inflammatory process in the periodontal tissue was assessed using descriptive histologic analysis and quantitative polymerase chain reaction (qPCR). This ligature model resulted in significant alveolar bone loss and increased inflammatory process of the periodontal tissues during the initial periods of evaluation (0-14 days). A significant increase in the gene expression of pro-inflammatory cytokines, interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), and proteins involved in osteoclastogenesis, receptor activator of nuclear factor-k B ligand (RANKL) and osteoprotegerin (OPG) was observed in the first week of analysis. In the later periods of evaluation (14-21 days), no significant alterations were noted with regard to inflammatory processes, bone resorption, and expression of cytokine genes. The ligature-induced PD model resulted in progressive alveolar bone resorption with two different phases: Acute (0-14 days), characterized by inflammation and rapid bone resorption, and chronic (14-21 days) with no significant progression of bone loss. Furthermore, the gene expressions of IL-6, IL-1β, TNF-α, RANKL, and OPG were highly increased during the progress of PD in the early periods. RESEARCH HIGHLIGHTS: Ligature-induced bone resorption in rats occurred in the initial periods after disease induction The bone resorption was characterized by two distinct phases: Acute (0-14 days), with pronounced inflammation and alveolar bone loss Chronic phase (14-21 days): No further disease progression Several pro-inflammatory cytokines were increased during the progress of periodontitis.

Characterization of a diet-induced obesity rat model for periodontal research

OBJECTIVES

Obesity is associated with periodontitis, but the mechanisms underlying this association have yet to be unraveled. The present investigation was to evaluate a common rat model, in which obesity is induced by high-fat, high-sucrose diet (HFSD), for its applicability in periodontal research.

MATERIALS AND METHODS

Ten male Wistar rats were fed a 3-month HFSD along with a matching control group. Afterwards, the body weight, adipocyte morphology, leptin and adiponectin levels in adipose tissue, gingiva, and serum as well as the serum levels of triglyceride, cholesterol, and glucose were analyzed. For statistical analyses, parametric and non-parametric tests were applied (p < 0.05).

RESULTS

Body weight was significantly higher in the HFSD group after dieting as compared to control. HFSD caused a significant increase in serum triglyceride, low-density lipoprotein cholesterol, and leptin levels and a significant decrease in high-density lipoprotein cholesterol. Furthermore, adipose tissue from HFSD rats exhibited significantly larger adipocytes, displayed a significant upregulation of leptin and, surprisingly, elevated adiponectin levels, which is in contrast to chronic obesity in humans. Although leptin and adiponectin were also observed in gingival biopsies, no obvious differences between the groups were found.

CONCLUSIONS

Although this rat diet-induced obesity model is characterized by changes typical of obesity, it also has limitations, which have to be considered when data, especially with regard to adipokines, are extrapolated to humans.

CLINICAL RELEVANCE

The rodent diet-induced obesity model may be useful for unraveling pathomechanisms underlying the association between obesity and periodontal destruction but conclusions have to be drawn with caution.

Impact of obesity and aging on crestal alveolar bone height in mice

Obesity and aging are associated with periodontitis, which represents a chronic inflammatory disease of the tooth-supporting tissues, i.e. the periodontium. However, if both risk factors also have a negative impact on crestal alveolar bone in a clinically healthy periodontium, has yet to be elucidated and was analyzed in this in-vivo study. Eight C57BL/6 mice were fed a normal diet during the entire study. Half of these mice were sacrificed at week 19 (group 1: younger lean mice), whereas the other half of the animals were sacrificed at week 25 (group 2: older lean mice). In addition, four mice were fed a high-fat diet until their sacrifice at week 19 (group 3: younger obese mice). Mandibles and maxillae were scanned by micro-computed tomography and, subsequently, the distance between the cementoenamel junction and alveolar bone crest (CEJ-ABC) at all molars was determined. Levels of interleukin-6, cyclooxygenase-2, visfatin and adiponectin in gingival samples were quantified by real-time PCR. For statistical analyses, the Mann-Whitney-U test was applied (p<0.05). As compared to lean mice, obese animals presented a significantly increased CEJ-ABC distance, i.e. reduced alveolar bone crest height, at week 19. The alveolar bone loss was mainly found at the first molars of the mandibles. In animals fed a normal diet, the alveolar bone crest height in the mandibles and maxillae was significantly lower in the older mice as compared to the younger animals. Furthermore, gingival cyclooxygenase-2 and visfatin expressions were higher in the obese versus lean mice and in the older versus younger mice. This in-vivo investigation shows that obesity and older age can result in reduced alveolar bone crest height and suggests that they represent risk factors even in a clinically healthy periodontium.

Diet versus jaw bones: Lessons from experimental models and potential clinical implications

The consumption of different types of diets influences not only body health but the bone remodeling process as well. Nutritional components can directly affect maxillary and mandibular alveolar bone microarchitecture. In this review, we focus on the current knowledge regarding the influence of diets and dietary supplementation on alveolar bone. Accumulating evidence from experimental models suggests that carbohydrate- and fat-rich diets are detrimental for alveolar bone, whereas protective effects are associated with consumption of calcium, ω-3, and bioactive compounds. Little is known about the effects of protein-free and protein-rich diets, boron, vitamin C, vitamin E, zinc, and caffeine on alveolar bone remodeling. Adipokines and direct effects of nutritional components on bone cells are proposed mechanisms linking diet and bone. Results from animal models substantiate the role of nutritional components on alveolar bone. It is a well-built starting point for clinical studies on nutritional monitoring and intervention for patients with alveolar bone disorders, especially those who are treatment refractory.

Effects of rosuvastatin on inducible nitric oxide synthase in rats with hyperlipidaemia and periodontitis

BACKGROUND AND OBJECTIVE

Nitric oxide is a free radical that is synthesized from l-arginine by nitric oxide synthase (NOS). The level of inducible NOS (iNOS) in gingiva with periodontitis is higher than that in healthy gingiva. The aim of this study was to evaluate the effects of rosuvastatin administration on alveolar bone loss (ABL) and iNOS(+) cell counts in gingival tissues in rats with ligature-induced experimental periodontitis with/without hyperlipidaemia.

MATERIAL AND METHODS

The rats were randomly divided into seven groups: Hy (cholesterol-added diet/water administration); HyP (cholesterol-added diet/periodontitis/water administration); HyPR (cholesterol-added diet/periodontitis/rosuvastatin administration); P (standard diet/periodontitis/water administration); PR (standard diet/periodontitis/rosuvastatin administration); C (standard diet/water administration); and R (standard diet/rosuvastatin administration). Experimental periodontitis was induced with silk ligatures, and rosuvastatin/water was administered to rats by oral gavage for the last 2 weeks of the 8-week study. After the rats were killed in week 8, histomorphometric and histological analyses were performed. Immunostained iNOS(+) cells were counted in the gingival samples and the Mann-Whitney U-test was used for statistical analysis.

RESULTS

The experimental groups exhibited increases in total cholesterol and low-density lipoprotein, except for Groups C and R. The cholesterol-added diet induced ABL in Group Hy. Of the periodontitis groups, the lowest ABL was found in Group PR. While there was a significant difference in ABL between Groups P (0.82 ± 0.15 mm) and PR (0.70 ± 0.21 mm) receiving a standard diet (P < .05), no difference was observed between Groups HyP (0.77 ± 0.07 mm) and HyPR (0.76 ± 0.11 mm) receiving a cholesterol-added diet (P ˃ .05). Rosuvastatin significantly reduced expression of iNOS in Groups PR (18.40 ± 2.31%) and HyPR (24.00 ± 4.83%) compared with Group P (30.90 ± 2.42%; P < .001). However, a larger number of iNOS(+) cells was found in Group HyPR than in Group PR (P < .001).

CONCLUSION

Administration of rosuvastatin reduced gingival iNOS expression in ligature-induced periodontitis with/without hyperlipidaemia. It also led to significant differences in ABL in rats with periodontitis, except when periodontitis was associated with hyperlipidaemia. These findings could provide an important contribution in further studies to evaluate the role of rosuvastatin as a host modulatory agent in the pathogenesis of periodontal diseases.

Rheumatoid Arthritis Exacerbates the Severity of Osteonecrosis of the Jaws (ONJ) in Mice. A Randomized, Prospective, Controlled Animal Study

Rheumatoid arthritis (RA), an autoimmune inflammatory disorder, results in persistent synovitis with severe bone and cartilage destruction. Bisphosphonates (BPs) are often utilized in RA patients to reduce bone destruction and manage osteoporosis. However, BPs, especially at high doses, are associated with osteonecrosis of the jaw (ONJ). Here, utilizing previously published ONJ animal models, we are exploring interactions between RA and ONJ incidence and severity. DBA1/J mice were divided into four groups: control, zoledronic acid (ZA), collagen-induced arthritis (CIA), and CIA-ZA. Animals were pretreated with vehicle or ZA. Bovine collagen II emulsified in Freund's adjuvant was injected to induce arthritis (CIA) and the mandibular molar crowns were drilled to induce periapical disease. Vehicle or ZA treatment continued for 8 weeks. ONJ indices were measured by micro-CT (µCT) and histological examination of maxillae and mandibles. Arthritis development was assessed by visual scoring of paw swelling, and by µCT and histology of interphalangeal and knee joints. Maxillae and mandibles of control and CIA mice showed bone loss, periodontal ligament (PDL) space widening, lamina dura loss, and cortex thinning. ZA prevented these changes in both ZA and CIA-ZA groups. Epithelial to alveolar crest distance was increased in the control and CIA mice. This distance was preserved in ZA and CIA-ZA animals. Empty osteocytic lacunae and areas of osteonecrosis were present in ZA and CIA-ZA but more extensively in CIA-ZA animals, indicating more severe ONJ. CIA and CIA-ZA groups developed severe arthritis in the paws and knees. Interphalangeal and knee joints of CIA mice showed advanced bone destruction with cortical erosions and trabecular bone loss, and ZA treatment reduced these effects. Importantly, no osteonecrosis was noted adjacent to areas of articular inflammation in CIA-ZA mice. Our data suggest that ONJ burden was more pronounced in ZA treated CIA mice and that RA could be a risk factor for ONJ development. © 2016 American Society for Bone and Mineral Research.