A Pilot Study Of Exosomes In Alzheimer's Disease

Background:AD is a progressive degenerative disease characterized by memory loss,multiple cognitive disorders and mental retardation,which seriously affects the quality of life of patients.At present,the diagnosis of AD needs to be combined with clinical symptoms,signs,intelligence scale,cerebrospinal fluid biomarkers,Positron Emission Computed Tomography(PET)and so on.However,because lumbar puncture is an invasive operation,clinical implementation is more difficult;the radiation of PET and its high price limit its application.At present,most of them are based on clinical symptoms,signs and intelligence scale.More and more studies have shown that AD patients have neuropathological and biomarker changes before clinical symptoms.There is no effective drug for the treatment of AD,which has no obvious effect on the improvement of symptoms in patients with advanced stage.This brings a lot of difficulties to patients and their families.Therefore,there is an urgent need for better biomarkers to provide help for the diagnosis of AD.Exosomes are nano-sized extracellular vesicles(EVs)secreted by most cell types and abundantly present in body fluids,including blood,saliva,urine,cerebrospinal fluid,and breast milk.The exosomes can freely cross the BBB and reach the urine through the kidney.Studies have shown that exosomes can spread toxic A? and hyperphosphorylated tau between cells,contributing to neuronal loss in Alzheimer's Disease(AD).Therefore,we think that the exosomes extracted from plasma and urine can reflect the change of brain environment to some extent,which is beneficial to the early diagnosis of AD.Objective:Explore the difference of morphology,quantity and pathological protein level of plasma and urinary exosomes in AD patients with matched healthy controls to determine whether plasma and urinary exosomes can provide some basis for early diagnosis of AD.Methods:In this study,the plasma samples of 30 AD patients aged 50-80 years old in Neurology of Henan Provincial people's Hospital was collected,and the plasma samples of 30 normal persons matched with the sex,age,education level and region of AD patients was collected from physical examination center.At the same time,the urine samples of another 30 AD patients aged 50-80 years old was collected,and the urine samples of 30 normal persons matched with the sex,age,education level and region of AD patients was collected.All the subjects were examined by magnetic resonance imaging(MRI)and intelligence scale,such as,Montreal Cognitive Assessment(Mo CA)and Mini-mental State Examination(MMSE).The disease stage of AD patients was judged to be moderate to severe.Enzyme-linked immunosorbent assay(ELISA)was used to detect the levels of pathological protein P-S396-tau and A?1-42(standardized by CD63)in plasma and urine of patients with AD and healthy controls.The morphology and quantity of exosomes of were observed and analyzed by transmission electron microscope(TEM)and nanoparticle tracking analysis(NTA).Results:There was no significant difference in the level of CD63 protein in plasma exosomes between patients with AD and healthy controls(p = 0.514>0.05).The levels of pathological protein P-S396-Tau and A?1-42 standardized by CD63 were significantly higher than those in healthy control group(p = 0.002< 0.05,p = 0.043< 0.05).The diameter of plasma exosomes in AD patients was smaller than that in healthy control group and the difference was statistically significant(p = 0.048< 0.05).The number of plasma exosomes with a diameter range of 30 nm and 150 nm in AD patients was generally larger than that in healthy subjects,but the difference was not statistically significant(P = 0.167> 0.05).There was no significant difference in the level of CD63 protein in urine exosomes between AD and healthy controls(p = 0.191> 0.05).The levels of P-S396-tau and A ? 1-42 standardized by CD63 were significantly higher than those in healthy control group(p = 0.024<0.05,p = 0.040<0.05).The number of urinary exocrine in AD patients was more than that in matched healthy controls and the difference was statistically significant(P = 0.049<0.05).The mode level of urinary exosomes diameter in patients with AD was generally larger than that in healthy subjects,but the difference was not statistically significant(p = 0.272>0.05).Conclusion:The differences in levels of P-S396-tau and A?1-42,the quantity of exosomes in urinary and plasma exosomes between AD patients and healthy controls may provide a basis for early diagnosis of AD.Compared with the matched healthy control group,the levels of pathological protein P-S396-tau and A?1-42 in blood exosomes of AD patients were higher,and the diameter of exosomes was smaller.Compared with the matched healthy control group,the levels of pathological proteins P-S396-tau and A?1-42 in urinary exosomes of patients with AD were higher and the number of exosomes was relatively higher.These differences may provide a basis for the early diagnosis of AD and contribute to the further research of AD.