Effect of variable moderate chronic stress on ligature-induced periodontal disease in Wistar rats

High Fat Diet Dysbiotic Mechanism of Decreased Gingival Blood Flow

The gut microbiome has a very important role in human health and its influence on the development of numerous diseases is well known. In this study, we investigated the effect of high fat diet (HFD) on the onset of dysbiosis, gingival blood flow decreases, and the periodontal matrix remodeling. We established a dysbiosis model (HFD group) and probiotic model by Lactobacillus rhamnosus GG (LGG) treatment for 12weeks. Fecal samples were collected 24h before mice sacrificing, while short chain fatty acids (SCFA) analysis, DNA extraction, and sequencing for metagenomic analysis were performed afterwards. After sacrificing the animals, we collected periodontal tissues and conducted comprehensive morphological and genetic analyses. While HFD reduced Bacteroidetes, SCFA, and gingival blood flow, this type of diet increased Firmicutes, lipopolysaccharide (LPS) binding protein, TLR4, pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6), matrix metalloproteinases (MMP-2 and MMP-9) expression, and also altered markers of bone resorption (OPG and RANKL). However, LGG treatment mitigated these effects. Thus, it was observed that HFD increased molecular remodeling via inflammation, matrix degradation, and functional remodeling and consequently cause reduced gingival blood flow. All of these changes may lead to the alveolar bone loss and the development of periodontal disease.

Effects of vitamin C local application on ligature-induced periodontitis in diabetic rats

Objective:

This study evaluated the effects of local vitamin C treatment on tissue advanced glycation end products (AGE), interleukin (IL)-6, 8-hydroxy-2-deoxyguanosine (8-OHdG), and matrix metalloproteinases (MMP)-8 in tissues; serum C-terminal telopeptide fragments (CTX); and alveolar bone loss (ABL) in rats.

Methodology:

35 male Sprague Dawley rats were divided equally into five groups: 1) control (C), 2) experimental periodontitis (P), 3) experimental diabetes (D), 4) experimental diabetes and experimental periodontitis (D + P), and 5) experimental diabetes–experimental periodontitis–locally applied vitamin C (D + P + LvitC). Diabetes was induced in rats with alloxan monohydrate, after which periodontitis was induced by ligature placement in the right mandibular first molar teeth for 11 days. In the treatment group, vitamin C was administered locally three times with two-days interval after ligature removal. The animals were sacrificed, and the samples were analyzed histometrically and immunohistochemically.

Results:

CTX, 8-OHdG, and AGE values significantly decreased in the treatment group compared to the D + P group. IL-6 and MMP-8 values decreased in the treatment group compared to the D + P group, but this is not significant. ABL was significantly reduced by the local delivery of vitamin C.

Conclusion:

This study reveals that vitamin C treatment may be beneficial to reduce serum CTX and gingival MMP-8 levels, oxidative stress, inflammation, and AGE accumulation in periodontal tissue. Vitamin C may be an immunomodulator and antioxidant locally applied in the treatment of periodontitis to reduce the adverse effects of diabetes in periodontal tissues.

Immune modulatory and antioxidant effects of locally administrated vitamin C in experimental periodontitis in rats

Background: Vitamin C is an important water-soluble vitamin with antioxidant and immune-modulatory actions. The aim of this study was to investigate the effects of locally applied vitamin C on alveolar bone resorption in rats with experimental periodontitis.Methods: Twenty-one male Sprague-Dawley rats divided into three groups with seven animals in each group: (1) control, (2) experimental periodontitis and 3) experimental periodontitis-local vitamin C treatment group. After ligature was removed, 50 μL vitamin C was locally administered into the subperiosteum of the buccal gingiva of periodontitis vitamin C (PvitC) group rats for three times in intervals of 2 days. At the end of the study, the animals were scarified, and serum and gingival samples were collected for analysis of serum IL-1β, oxidative stress index (OSI), CTX and malondialdehyde (MDA) levels and gingival MMP-8 immunostaining. Alveolar bone loss and attachment loss were determined based on measurements on histological sections obtained from rat mandibles.Results: Serum MDA and OSI levels which are related to the oxidative stress were significantly lower in the PvitC group as compared with those in the P group (p < .05). Serum CTX levels which are related to the bone resorption were significantly lower in the PvitC group as compared with those in the P group (p < .05). The numeric density of MMP-8-positive cells was significantly lower in the PvitC group compared to P group (p < .05). Alveolar bone loss and attachment loss were significantly lower in the PvitC group compared to P group (p < .05)Conclusions: The local vitamin C administration provided protection against inflammation-induced alveolar bone resorption by decreasing oxidative stress and inflammation-induced tissue breakdown vitamin C may be a therapeutic agent that can be used in periodontitis treatment.

Hyperhomocysteinemia: an instigating factor for periodontal disease

Hyperhomocysteinemia (HHcy) affects bone remodeling, since a destructive process in cortical alveolar bone has been linked to it; however, the mechanism remains at large. HHcy increases proinflammatory cytokines viz. TNF-α, IL-1b, IL-6, and IL-8 that leads to a cascade that negatively impacts methionine metabolism and homocysteine cycling. Further, chronic inflammation decreases vitamins B12, B6, and folic acid that are required for methionine homocysteine homeostasis. This study aims to investigate a HHcy mouse model (cystathionine β-synthase deficient, CBS^+/-) for studying the potential pathophysiological changes, if any, in the periodontium (gingiva, periodontal ligament, cement, and alveolar bone). We compared the periodontium side-by-side in the CBS^+/- model with that of the wild-type (C57BL/6J) mice. Histology and histomorphometry of the mandibular bone along with gene expression analyses were carried out. Also, proangiogenic proteins and metalloproteinases were studied. To our knowledge, this research shows, for the first time, a direct connection between periodontal disease during CBS deficiency, thereby suggesting the existence of disease drivers during the hyperhomocysteinemic condition. Our findings offer opportunities to develop diagnostics/therapeutics for people who suffer from chronic metabolic disorders like HHcy.

Blood Oxidative Stress Modulates Alveolar Bone Loss in Chronically Stressed Rats

We aimed to investigate the effects of chronic stress (CS) on experimental periodontitis (EP) in rats. For this, 28 Wistar rats were divided into four groups: control, ligature-induced experimental periodontitis (EP), chronic stress (CS; by physical restraint model) and CS+EP (association of chronic stress and ligature-induced periodontitis). The experimental period lasted 30 days, including exposure to CS every day and ligature was performed on the 15th experimental day. After 30 days, the animals were submitted to the behavioral test of the elevated plus maze (EPM). Next, rats were euthanized for blood and mandible collection in order to evaluate the oxidative biochemistry (by nitric oxide (NO), reduced-glutathione activity (GSH), and thiobarbituric acid reactive substance levels (TBARS)) and alveolar bone characterization (by morphometric, micro-CT, and immunohistochemistry), respectively. The behavioral parameters evaluated in EPM indicated higher anxiogenic activity in the CS and CS+EP, groups, which is a behavioral reflex of CS. The results showed that CS was able to change the blood oxidative biochemistry in CS and CS+EP groups, decrease GSH activity in the blood, and increase the NO and TBARS concentrations. Thus, CS induces oxidative blood imbalance, which can potentialize or generate morphological, structural, and metabolic damages to the alveolar bone.

Immune modulatory and antioxidant effects of melatonin in experimental periodontitis in rats

Melatonin is an important antioxidant, and through its anti-inflammatory effects it can control immune responses, oxidative stress, and defense cell infiltration. Periodontitis is a disease of the oral cavity and the generation of free radicals is an important consideration in this disease. Therefore, we examined the immune-modulatory and antioxidant roles of melatonin in the treatment of periodontitis. In all, 30 male Wistar rats were randomly divided into three groups: the control group, the periodontitis-induced (PED) group, and the periodontitis+melatonin treatment (MEL+PED) group. The control group received no treatment, whereas periodontitis was induced in both the PED and the MEL+PED groups, with the MEL+PED group being treated with systemic melatonin. For the periodontitis-induced groups, the rats' mandibular first molar teeth were ligatured (3-0 cotton) in a submarginal position for 4 weeks, and then the ligature was removed. After removal of the ligature, melatonin was administered only to the MEL+PED group (an ip dose of 10mg/kg body wt for 15 days at 11:00 PM each day). In the histological examination, the MEL+PED group, which received the melatonin, showed reduced inflammatory cytokines (IL-1β, from 97.47 to 84.24pg/ml; TNF-α, from 0.22530 to 0.22519pg/ml), regulated oxidative stress parameters (MDA, from 41,458 to 30,708nmol/g; GSH, from 18,166 to 25,858nmol/mg), and less periodontal tissue destruction (CEJ-PL, lingual, from 244.54 to 140.57μm; buccal, from 235.6 to 158.93μm; and CEJ-BC, lingual, from 383.65 to 287.76μm; buccal, from 391.92 to 296.12μm). From these findings we conclude that, even when periodontitis was induced, melatonin reduced the oxidative damage in the rats' periodontal tissue by inhibiting the inflammatory effects and by restoring the antioxidants.

Methodological model of chronic stress associated with ligature-induced periodontitis in rats: a radiographic study

This study evaluated the time efficiency of stress associated with ligature-induced periodontitis in rats. Sixty adult Wistar rats, housed in temperature-controlled rooms and receiving water and food ad libitum, were randomly separated into stress (n = 30) or control groups (n = 30). All animals were anesthetized, and nylon ligatures were placed at the gingival margin level of the maxillary right second molars. After the induction of periodontitis, rats in the stress group were subjected to physical restraint for 12 hours daily. The animals were euthanized after 7, 15 and 30 days by anesthetic overdose (10 animals per group per period). The right hemimaxillae were stored in formalin solution for 48 hours. Parallel radiographic images of the hemimaxillae were taken and processed following standard procedures. Radiographic examination was performed by a blinded and previously calibrated investigator. Bone height level was measured, and data were submitted to analysis of variance and post hoc Bonferroni tests (p < 0.05). Rats in the stress group had greater bone loss than those in the control group at 7 and 15 days post-induction (p < 0.05). After 30 days, there was no statistically significant difference between the groups (p > 0.05). Restraint stress modulates the short-term progression of periodontal disease in rats. Therefore, the 12-hour daily physical restraint stress model in rats applied for up to 15 days is suitable for the investigation of the combined effect of ligation and restraint stress on periodontal degradation.

Effect of neonatal clomipramine in the pathogenesis of ligature-induced periodontitis in Lewis rats

OBJECTIVE

The aim of this study was to verify the association between an endogenous depression model and the development of ligature-induced periodontitis in rats.

MATERIAL AND METHODS

Nine male Lewis rats received 30 mg/kg clomipramine from neonatal day 8 to day 21 (depressed group), while 13 control Lewis rats were left untouched (control group). On day 150, ligatures were placed around the 2nd upper molars in both groups, i.e. the contralateral molar of the intra-group control. On day 190, the rats were killed and the maxillae were defleshed. The distance between the cemento-enamel junction and the alveolar bone crest was measured by a blinded examiner using standardized digital photographs.

RESULTS

The depressed rats showed hyperactivity in open field on day 142 and greater attempts to escape on day 143 compared to controls. The other behavioral data did not show statistically significant differences between the groups (Mann-Whitney, p>0.05). In teeth with ligature, mean alveolar bone loss varied from 0.51 to 0.60 and from 0.63 to 0.64 mm for tests and controls, respectively (t-test, p>0.05). In teeth without ligature, these values varied from 0.38 to 0.43 and 0.42 to 0.45 mm in the test and control groups, respectively (t-test, p>0.05).

CONCLUSION

Induced depression did not alter ligature-induced bone loss in Lewis rats.

Histometric analysis of ligature-induced periodontitis in rats: a comparison of histological section planes

The purpose of this study was to analyze the histometry of ligature-induced periodontitis in rats at different histological section depths. Sixteen male adult Wistar rats were randomly assigned to two groups: ligature and control. In the ligature group, rats received a sterile 4/0 silk ligature around the maxillary right 2nd molar. Thirty serial sections containing the 1st and 2nd molars, in which the coronal and root pulp, cementoenamel junction (CEJ) in the mesial side of the 2nd molar, interproximal alveolar bone and connective fiber attachment were clearly visible, were selected for histometric analysis. The histological sections were clustered in groups of 10 sections corresponding the buccal (B), central (C) and lingual (L) regions of the of periodontal tissue samples. The distance between the CEJ in the mesial side of the 2nd molar and the attached periodontal ligament fibers (CEJ-PL) as well as the distance between the CEJ and the alveolar bone crest (CEJ-BC) were determined. From CEJ-PL and CEJ-BC distances measured for each specimen, the measurements obtained in the B, L and C regions were recorded individually and together. Data were submitted to statistical analysis. Significant differences (p<0.001) were observed between the control and ligature groups regarding CEJ-PL (0.05 mm and 0.26 mm, respectively) and CEJ-BC (0.47 mm and 0.77 mm, respectively) measurements. Regarding the depth of the buccal, central and lingual planes, the means of CEJ-PL and CEJ-BC of both groups showed no statistically significant differences (p>0.05). In conclusion, the selection of 10 serial sections of the central region of periodontal tissue samples at any depth can be considered as representative for the evaluation of periodontal ligament fiber attachment and bone loss in ligature-induced periodontitis in rats.

Comparison of histometric and morphometric analyses of bone height in ligature-induced periodontitis in rats

The purpose of this study was to compare histologic and morphometric procedures of bone height measurement. Microscopic measurements are the most frequent methods in periodontal studies with animals, but have limited capacity to identify bone levels associated with both healthy tissues and periodontal disease. Ligatures were placed in the maxillary left second molars of 10 male 60-day-old Wistar rats for 30 days. Left and right maxillary sides of 5 rats were processed for histologic analysis (H), sectioned buccolingually, and stained with HE. The maxillae of the other 5 rats were defleshed and used for morphometric analysis (M). Histometric measurements from the cementoenamel junction to the bone crest were performed. Standardized photographs were used for morphometric analysis. The t test was used for dependent or independent samples (alpha = 0.05%). Distances from cementoenamel junction to bone crest were 0.95 +/- 0.25 and 1.07 +/- 0.30 mm for H and M, respectively. Buccal measurements were 0.92 +/- 0.16 and 1.08 +/- 0.35 mm for H and M. The values obtained using H and M for areas without ligatures were 0.44 +/- 0.15 and 0.47 +/- 0.11 mm for lingual measurements and 0.23 +/- 0.08 and 0.41 +/- 0.10 mm for buccal measurements. No significant differences were found between the two methods in the detection of bone height associated with the placement of ligatures in rats.

Effect of methotrexate on alveolar bone loss in experimental periodontitis in Wistar rats

OBJECTIVE

Interleukin-1 (IL-1) and tumor necrosis factor (TNF) are pro-inflammatory cytokines directly related with tissue destruction in the pathogenesis of periodontitis. Inhibitory effects on IL-1 and TNF production have been attributed to the folate analog methotrexate. The purpose of this study was to evaluate the effect of methotrexate on the pathogenesis of alveolar bone loss in experimental periodontitis in rats.

METHODS

Ligature-induced experimental periodontitis was created in 44 Wistar rats. The animals were randomly divided into four groups and treated with methotrexate (0.1, 0.5, and 1.0 mg x kg(-1)) or saline. Morphometrical registration of alveolar bone loss was carried out after 28 days of ligature placement to determine the effect of methotrexate on the progression of experimental periodontitis.

RESULTS

Intra-group comparisons showed significantly higher alveolar bone loss mean values in maxillary sides with ligature (paired sample t-test; p<0.05). Mean alveolar bone loss was not different between groups and was independent of the dosage (range 0.63-0.67 mm, one-way ANOVA; p>0.05).

CONCLUSION

Although methotrexate has important cytokine-inhibitory properties, its possible use in modulating the host immune-inflammatory response in periodontal disease was not confirmed.