Establishment And Evaluation Of β-Amyloid Oligomers-Induced Alzheimer’s Disease Model In Cynomolgus Monkey

BackgroundAlzheimer’s disease is the largest neurodegenerative disease in humans.It is a chronic disease characterized by progressive cognitive impairment and impaired memory,accompanied by various mental and behavioral disorders and personality changes,and gradually deteriorated over time.Nowadays,with the acceleration of aging,the incidence and prevalence of AD are increasing day by day,and it increases exponentially with age.The report "Dementia: A Public Health Focus" published by WHO and ADI in 2012 points out that the incidence of AD is 7.7 million people per year.At present,the cause and mechanism of AD have not been clarified,and there are still no specific therapeutic drugs,which has caused heavy psychological and economic burden to society and families.Therefore,the preparation of animal models that simulate human AD characteristics is very important for the study of AD.Non-human primates have highly similar genetic structure and physiological functions to human beings.The behavior and pathological changes of cynomolgus monkeys AD model induced by Aβ 1-42 Oligomers simulate the basic characteristics of human AD,and provide an effective model carrier for future research on the pathogenesis,early diagnosis,treatment and prevention of AD.ObjectiveThe AD model of cynomolgus monkeys was induced by intracerebral injection of Abeta 1-42 Oligomers using stereotaxic CED technique.The effectiveness of the model as an AD animal model was evaluated from the perspective of neuropathology and cognitive memory behavior.That is to evaluate the pathological changes of brain Aβ deposition,abnormal phosphorylation of tau protein,inflammatory reaction and changes of cognitive memory after modeling,so as to establish the basic animal model of AD and the evaluation technology of preclinical transformation.Methods1.Siemens 1.5T MR superconducting scanner was used for cranial MRI to determine the stereotactic coordinates.According to the stereotaxic data of MRI,Aβ1-42 Oligomers were injected into the brain parenchyma of cynomolgus monkeys by CED technology to construct AD model.The location of injection area and drug diffusion after injection were observed combined with Gd-DTPA contrast agent.2.To optimize the synthesis of Aβ1-42 Oligomers,and to identify the aggregation of Aβ 1-42 peptide by Western Blot.3.Brain tissue was obtained by autopsy,and the changes of pathological parameters of AD model were analyzed by immunohistochemistry.4.Based on the Wisconsin General Test Apparatus(WGTA)principle,a DMTS device for non-human primate cognitive behavior was developed independently to test and evaluate the changes of working memory behavior of cynomolgus monkeys in the process of modeling.Results1.After injecting the mixture of Aβ 1-42 Oligomers and Gd-DTPA labelled solution into the brain,MRI scan showed that the injection solution was spherical,uniform and widely spread around the injection target,without causing local brain edema or injury,and no abnormal drug reflux along the needle path.2.WB identification showed that soluble Aβ 1-42 Oligomers were the main injected into the brain.Among them,the aggregation forms of Aβ 1-42 peptide mainly include low molecular weight oligomers and monomers,and no fibrous substances were found.3.Immunohistochemical staining analysis of brain tissue after autopsy showed that compared with the normal control group,a large number of Aβ deposits were observed in temporal cortex,striatum and hippocampus 8 months after the fourth injection of Aβ 1-42 Oligomers,which were dispersed and granular.At the same time,abnormal phosphorylated tau protein aggregation in the temporal cortex,striatum and hypothalamus can be observed in late neurofibrillary tangles and filaments.There was no obvious deposition of Aβ and abnormal tau tangle in the control group.In addition,compared with the control group,the activated astrocyte marker GFAP and microglia marker Iba1 associated with neuroinflammation were observed in the brain of the animals injected with Aβ 1-42 Oligomers.The staining was deepened and the number of cells was increased significantly,and the morphology was complex.A large number of ChAT positive cells were observed in the basal nucleus of the forebrain in all animal brain tissues.4.The results of DMTS cognitive function evaluation showed that the correct rate of delayed test decreased in varying degrees from baseline to the 6th injection of Aβ 1-42 Oligomers in normal group and DM group.Compared with baseline,the correct rate of delayed test in normal group and DM group decreased significantly after injection of Aβ 1-42 Oligomers(P < 0.05).There was no significant difference in the correct rate of delayed test between normal group and DM group in baseline,after the first,second,third,fourth and fifth injection of Aβ 1-42 Oligomers(P > 0.05).The correct rate of delayed test in DM group at 10 s,15 s and 30 s after the 6th injection was significantly lower than that in normal group,and the difference was statistically significant(P < 0.05).ConclusionIn this study,the stereotaxic CED technique was used to inject Aβ 1-42 Oligomers into the brain to establish a clinical AD-like model of elderly cynomolgus monkeys.The DMTS cognitive behavioral device based on WGTA can effectively evaluate the changes of working memory in animals.After the induction of Aβ 1-42 Oligomers,a large number of Aβ plaque deposits,tau pathological tangles and neuroinflammation were formed in the brain of animals,which showed a significant decline in cognitive and memory ability and successfully duplicated the characteristics of clinical AD.Therefore,bilateral intermittent infusion of Aβ 1-42 Oligomers into the brain parenchyma of non-human primates can reproduce the key features of human AD,in order to provide a unique model carrier and evaluation strategy for the study of the etiology,pathogenesis and therapeutic intervention of AD.