Elucidating On The Biological Effects And Mechasnims Of Mesenchymal Stem Cell Derived Exosome To Adult Hippocampal Neurogenesis As Well As The Therapeutic Effects To Alzheimer's Disease

Background:Neurodegenerative diseases is characterized as divastating irrevasible neural dysfunctions risked by ageing.Typically as Alzheimer's disease,the atrophy ocurrs within hippocampus and brain cortex that caused by accelerating neural death would engage the learning and memory dysfunctions and seriously affect the wellbeing of the patients.Unforturnately,until now the therapies targeting on the main cirpurit of AD have not been developed due to the insufficient understanding for its etiologies.In adult mammalian brain,there exist a group of neural stem cells(NSCs),which maintaining the continous self-renew and differentiation for regulating the neural plasticity of the animal.Thus,developing the resolution to harness such NSCs as the regenerative tools for treating AD and other neurodegnerative diseases is importan task for scientists.Mesenchymal stem cells(MSCs)is another somatic stem cells featured with immune regulation,stable self-renew and multiple lineage commitment.Currently,convergent evidence indicates that exosome derived from MSCs is the biological underpining for their ability to trigger cell-cell interactions.However,whether MSCs exosome could also exerts the promoting effects to adult neurogenesis,initiate the neural repair and thereby reduce the behavioral dysfunctions in AD animal models are yet to be identified.Furthermore,understanding the biological mechanisms ofthe MSCs exosome on their therapeutic effects to AD animal model would enlight the new pathway for clarifying the molecular target and faciliate the drug development of AD.Objective:Exosome plays as the critical biological fundamental for the biological effects of mesenchymal stem cells(MSCs).Current study aims to explore the protein and peptide functions human MSCs derived exosomes,and thereby investigate their neurobiological effects.Moreover,this study further detected the therapeutic effects and the underlying mechanisms of MSCs derived exosome to Alzheimer's disease(AD)model.The key issues need to resolve in this study are as following:1.What the enriched component and functions in proteomics of MSCs exosome?2.Whether MSCs exosome could exert the pro-neurogenic effects?3.Whether MSCs exosome could improve the behavioral patterns after the neuraldamage?4.What are the functions of MSCs exosome to AD animal model?5.Whether MSCs exosome could recover the hippocampal functions in AD model?6.What is the key molecular mechanism underlying the effects of MSCs exosome to ADmodel?Methods:Following methodologies were utilized in this study:1.In this study,h UC-MSCs was prepared and used for collecting exosome andperform the proteomic analysis.2.The flow cytometry technique was used for detecting the cell surface marker ofthe h UC-MSCs.ELISA and western blot was used for detecting the target proteinlevel.3.Behavioral tests and immunofluorescence were used for detecting the effects ofexosome to cognition,antidepressant behavior and hippocampal neurogenesis.4.The acute and AD animal model was created by injecting STZ and beta-amyloidin hippocampal site,respectively.5.Gene knockdown by si RNA was also used for detecting the molecular mechanismunderlying the effects of MSCs exosome to AD model.Results:MSCs was prepared by separate and culture h UC-MSCs and the exosomes was collected.The flow cytometry analysis demonstrated that h UC-MSCs high expressed the CD105,CD44 and CD29 and low expressed CD35 and CD45,which are identified as the MSCs cell surface marker.Moreover,the cultural h UC-MSCs have the differentiation ability with adipogenesis and osteogenesis.Proteomic analysis indicates most of the proteins and peptides in MSCs exosome have the function in metabolic regulation.It was found that MSCs exosomes contained 942 protein components,and sixty-seven of these have not been previously reported.Injecting of MSCs exosomes resulted in the elevation of the adiponectin in both central and peripheral level.Moreover,MSCs exosome could improve the growth of hippocampal NSCs and accelerate the neural differentiation.Although no behavioral effects under physiologiocal level,MSCs exosome could attenuate the behavioral dysfunctions in STZ injected mice in associating with its effects to enhance the hippocampal neurogenesis.In Abeta injected AD model,treatment of MSCs effectively ameliorated the cognitive deficits as well as the depressive/anxiety mood.Furthermore,MSCs exosome significantly accelerated the growth of newborn neurons in AD model.ELISA analysis indicates that MSCs exosome dramatically increased the BDNF level,and Dil staining combined with BDNF antibody also confirmed that MSCs exosome contain the BDNF.Knockdown of BDNF expression with si RNA could compromise the effects of MSCs exosome to AD induced behavioral dysfunctions.Conclusion:MSCs exosome was enriched with large amount of the metabolic regulating factors,which might be the fundamental for improve hippocampal neurogenesis.Under acute stress,MSCs exosome could effectively enhance hippocampal neurogenesis and improve the behavioral pattern.In AD model,MSCs exosome established the obvious behavioral protection.Moreover,the effects of MSCs exosome to increase hippocampal neurogenesis might be the potential neurobiological mechanism.BDNF-mediated signaling is the key regulator of MSCs exosome to improve behavioral performance in AD model.