Effects Of Severe Periodontitis On Learning And Memory Function And Expression Of Inflammatory Factors In Rats Induced By A?

Objective: To investigate the effects of periodontal tissue inflammation on the development of learning and memory impairment induced by A beta and the expression of inflammatory factors in the brainMethod: Ninety-six male SD rats were randomly divided into three groups: control group(n = 12)and control group(n = 36)with A? 1?l control(A? 1?l group,n = 12)and A? 2?l control group(A? 2?l group,n = 12)and model control group(A?5?l group,n =12)] and experimental group of 48(including blank experimental group(CP group,n = 12),A?1?l experimental group(CP+A?1?l group,n = 12),A?2?l experimental group(CP+ A?2?l group,n = 12)and model experimental group(CP+ A? 5?l group,n = 12)].In the experimental group,48 rats were established with severe periodontitis(CP)model,and then the rats in the experimental group except the blank experimental group(36 rats in total)were injected with A?25-35 in the hippocampus together with the rats in the control group.Each rat in the A?1 ?l group and the CP+A?1 ?l group each rat hippocampus injection of 1?l A?25-35;A?2?l group and CP+ A? 2?l group each rat hippocampus injected2?l A?25-35;A?5?l group and CP+ A? 5?l group each rat hippocampus injection of 5?l A?25-35 sporadic Alzheimer's Disease(sporadic Alzheimer's Disease,SAD)animal model.From the 14 th day after injection of A?25-35 into the hippocampus,the Morris water maze test was used to examine the effects of severe periodontitis and hippocampal injection of A?25-35 on the spatial learning and memory function of rats,and after the end of the test,The next day,space exploration experiments were conducted.After the end of space exploration,all rats were sacrificed by euthanasia and whole brain,cerebral cortex and hippocampus brain tissue and maxillary bilateral alveolar bone were obtained;pathological sections of brain tissue were made,The paraffin slices were made from the maxilla on one side of the SD rats,and the histological changes were observed after HE staining.The other side was photographed with a micro focal camera after methylene blue staining,and the absorption of the alveolar bone was observed.The pathological sections of the brain tissue were made.The morphology and density of theneurons in the hippocampus CA3 region were observed by HE staining.The ELISA method was used to detect the neurons in the hippocampus of the rats.The protein content of IL-1,IL-6,CRP,TNF-? and A?1-40 in cerebral cortex and hippocampus..Results:(1)pathological sections of periodontal tissues showed no significant changes in alveolar bone and periodontal tissue in blank control group and control group.In the experimental group,the symptoms of severe periodontitis were found in the experimental group of SD rats.The alveolar ridge of the upper second molar of the experimental group was reduced,the surface of the epithelium was erosive,some of the epithelial nailed process was reticular,a large number of inflammatory cells were infiltrated,the collagen fibers proliferated,and osteoclasts were seen.Observation of digital photos showed that the alveolar height of maxillary second molars in all experimental groups was significantly decreased,and the root furcation was exposed.The bone resorption reached the tip of the root 1/3.(2)Analysis of Morris water maze test data in each group showed that compared with the blank group,A?5?l group and CP+A?5?l group had long escape latency,poor learning and memory ability,and significant statistical difference;The escape latency of A?1?l group,CP+A?1?l group,A?2?l group and CP+A?2?l group were different,but the difference was not statistically significant;the difference in escape latency between experimental group and control group was not statistically significant..In addition,no significant difference was found in the swimming speed of rats in each group.(3)The results of this experiment show that the presence of IL-1,IL-6,CRP,TNF-?,and A?1-40 can be detected in all cerebral cortex and hippocampal brain tissue samples.Compared with the blank group,the contents of the above four inflammatory factors and A?1-40 were increased in all the control groups and the experimental group in the hippocampus and cerebral cortex,and most of the increase was statistically significant.Compared with the control group,almost all experimental groups in the hippocampus and cerebral cortex above four inflammatory factors and A?1-40 levels were increased and part of the increase was statistically significant.(4)HE staining of paraffin sections in brain tissue showed that the number of hippocampal neurons in the blank group and CPgroup was abundant,the structure was complete,and the nucleolus were clearly visible.Compared with the blank group,thenumber of neurons in the cells were decreased,some cells had obvious deep staining,nuclear condensation,cell space increased,and the number of neurons in CA3 area decreased significantly than that in the blank group,and the difference was statistically significant.But the othe group rats hippocampus Neurons can only be seen in a small number of cells with deep staining and nucleus pyknosis.Conclusion: The effect of severe periodontitis on the learning and memory impairment induced by A? in rats is not obvious,but severe periodontitis may promoting the increase and accumulation of inflammatory factors in the brain of SD rats,suggesting that severe periodontitis may have an effect on the occurrence and development of Alzheimer's disease.