The Role Of Psychological Stress On The Oxygen Metabolism In Periodontitis

ObjectivePeriodontal disease is one of the major causes of tooth loss in the world. Although psychological stress is known to aggravate periodontal pathology, the exact mechanisms remain to be elucidated. In this proposal, we explore the role of decreased tissue oxygenation in periodontal pathology in the context of stress. Results from these studies will provide valuable insight into the role of oxygen in stress-induced periodontal pathology and its ability to ameliorate it, leading to future studies in oxygen regulated pathways. The insights gain will help to develop novel strategies to promote periodontal health.MethodsForty-eight male Wistar rats in SPF grade were randomly divided into 4 groups.1) Normal control group:The rats were treated with normal feeding, and the periodontal tissues were not received with special treatment; 2) Experimental periodontitis group:The periodontitis models were induced by wrapping 3/0 silk ligature around the left maxillary second molar of rats, inoculated with putative periodontopathic bacteria; 3) Stress-stimulating group: The rats were only treated with stress-stimulating; 4) Periodontal model with stress-stimulating group:The periodontitis models were induced by wrapping 3/0 silk ligature around the left maxillary second molar of rats, inoculated with putative periodontopathic bacteria, and then the rats were treated with stress-stimulating. The rats were sacrificed at the end of 1,4,6 and 8 wk after the operation. The gingival index (GI) and the attachment loss (AL) were measured before the rats were euthanized. The histological change of periodontal tissues was observed under microscope after the samples were stained with hematoxylin and eosin (H&E). Furthermore, the HIF-la levels in the periodontal tissue were examined by immunohistochemistry. Results1. Gingival index: There was no significant difference between the GI in stress-stimulating group and normal control group during the experiment (P>0.05); The GI in experimental periodontitis group and periodontal model with stress-stimulating group were significantly higher than normal control group at the end of 4,6 and 8 wk (P<0.01); The GI in periodontal model with stress-stimulating group was significantly higher than experimental periodontitis group at the end of 4, 6 and 8 wk (P<0.01).2. Attachment loss:The AL in experimental periodontitis group and periodontal model with stress-stimulating group were significantly higher than normal control group and stress-stimulating group during the experiment(P<0.01); There was no significant difference in AL between the stress-stimulating group and normal control group during the experiment(P>0.05); The AL in periodontal model with stress-stimulating group was significantly higher than experimental periodontitis group at the end of 4,6 and 8 wk (P<0.01).3. Histological changes:There was no significant change in periodontal tissues between normal control group and stress-stimulating group; The experimental periodontitis group showed a moderate periodontal inflammation damage; while periodontal destruction in the periodontal model with stress-stimulating group were more serious than other experimental groups. Connective epithelium was separated from the surface of teeth root and migrated apically. A lot of inflammatory cells were observed in the deeper periodontal tissue. The structure of periodontal membrane was destroyed with collagen fibers edema and denaturalization. Many active osteoclasts and osteoclastic resorption were observed on the surface of alveolar bone, and the height of alveolar bone was decreased.,4. HIF-la immunohistochemical staining results:The average rate of positive cells in normal control group and stress-stimulating group showed no significant difference during the experiment(P>0.05); The average rate of positive cells in experimental periodontitis group and periodontal model with stress-stimulating group were significantly higher than normal control group and stress-stimulating group (P<0.01); The average rate of positive cells in periodontal model with stress-stimulating group was significantly higher than experimental periodontitis group at the end of 4,6 and 8 wk (P<0.01).Conclusions1. The periodontitis models were successfully induced in rats by ligature inoculated with putative periodontopathic bacteria.2. Stress-stimulating does not cause periodontitis in rats.3. Stress-stimulating can aggravate experimental periodontitis in rats.4. Stress-stimulating may aggravate periodontitis by decreased tissue oxygenation in rats.