Mechanism Of Pathological ?-synuclein Spreading Via The Urogenital Nerves Initiating Multiple System Atrophy-like Syndromes In Mice

BackgroundMultiple system atrophy?MSA?is an unexplained,rare,fatal late-onset neurodegenerative disorder with no effective treatment.The main clinical symptoms are autonomic dysfunction,levodopa non-sensitive Parkinson's symptoms and cerebellar ataxia.It is often highlighted by one systemic impairment,and with the superposition of other symptoms.So far,the pathogenesis of MSA remains unclear.MSA has common pathological features with Parkinson's disease?PD?,dementia with Lewy bodies?DLB?,and pure autonomic failure?PAF?,ie,abnormal deposition of?-synuclein??-syn?in the nervous system and formation of inclusions in cells.These diseases are collectively referred to as?-synucleinopathy.Studies using cell and animal models have found that?-syn fibers can induce abnormal folding of normal?-syn like prion,form inclusions,and spread between cells.Therefore,some scholars have suggested that the formation and transmission of?-syn positive inclusions in the central nervous system may be a common pathological mechanism of?-synucleinopathy.Clinical statistics show that about65%of MSA patients have urinary dysfunction earlier than dyskinesia,and erectile dysfunction in male patients is usually the first symptom,which occurs before urinary symptoms.The incidence of urinary frequency and urinary incontinence in the early stage of MSA is 88%-100%,and the incidence of male sexual dysfunction is 74%-84%.The pathological changes of MSA are widespread,and the?-syn positive inclusions in the oligodendrocytes of the nervous system are characteristic lesions.Autopsy of MSA patients found that in addition to the caudate nucleus,putamen,globus pallidus,substantia nigra,pons,and cerebellar Purkinje cells,?-syn positive inclusions were also detected in periaqueductal gray matter?PAG?,pontinemicturition center?PMC?,sacral parasympathetic nucleus?SPN?,intermediate lateral column?IML?,and Onuf nucleus,etc.The presence of?-syn positive inclusions has also been detected in the relevant autonomic conduction pathways,which may be responsible for early urogenital dysfunction in MSA patients.Therefore,we hypothesized that?-syn positive inclusions may be retrogradely spread from the bladder detrusor?DET?nerve endings along the urogenital related autonomic nerve pathway to the brain leading to MSA-like syndromes.ObjectiveIn this study,we constructed a transgenic mouse model to investigate whether?-syn positive inclusions can be retrogradely transmitted to the brain along the urogenital related autonomic nerve pathways,simulating autonomic dysfunction and dyskinesia in MSA patients,and further exploring the possible pathogenesis of MSA.Methods1.Eight MSA patients,6 PD patients,6 progressive supranuclear palsy?PSP?patients,and 6 normal controls were enrolled in this study and the bladder DET specimens were collected.The presence of?-syn positive inclusions were measured by immunohistochemical staining.2.The?-syn preformed fibrils?PFFs?was prepared and its morphology was identified by transmission electron microscopy.3.We injected?-syn PFFs into DET of TgM83^+/-mice and evaluated them by combining immunohistochemical assays,urodynamic examination,external anal sphincter?EAS?electromyography?EMG?,and behavioral test.Results1.Immunohistochemical staining of patient specimens showed that?-syn positive inclusions were present in the DET nerve endings of MSA patients,but not in the DET of PD,PSP,and normal controls.2.The histological results of the mouse model showed that the deposition of?-syn positive inclusions was detected in the urogenital autonomic nerve pathways of mice after injection of?-syn PFFs.3.The results of the mouse model behavioral tests show that abnormal EAS EMG and urodynamic abnormalities can be detected in the experimental group in the early stage,followed by behavioral dysfunction.Conclusion1.In the transgenic mouse model,?-syn positive inclusios can spread retrogradely to the brain along the urogenital related autonomic nerve pathways.2.In the transgenic mouse model,the transmission of?-syn positive inclusions along the urogenital related autonomic nerve pathwaye mimics the autonomic dysfunction and dyskinesia of MSA patients.