Duodenal alpha‐Synuclein Pathology and Enteric Gliosis in Advanced Parkinson's Disease

ABSTRACT Background The role of the gut-brain axis has been recently highlighted as a major contributor to Parkinson’s Disease (PD) physiopathology, with numerous studies investigating bidirectional transmission of pathological protein aggregates, such as α-Synuclein (αSyn), in the context of neurodegenerative disease. However, little and often conflictual evidence is available from human studies due to patient heterogeneity, sampling variability, and the employment of antibodies with affinity for different αSyn epitopes. Objectives We aimed to investigate the enteric nervous system (ENS) in PD by characterizing αSyn alterations and glial responses in duodenum biopsies of PD patients by employing topography-specific sampling and conformation-specific αSyn antibodies. Methods 18 Patients with symptomatic PD who underwent Duodopa Percutaneous Endoscopic Gastrostomy and Jejunal Tube (PEG-J) procedure, as well as 18 age- and -sex-matched Healthy Control subjects undergoing routine diagnostic endoscopy, were included in the study. A mean of 4 duodenal wall biopsies were sampled from each patient. Immunohistochemistry was performed for anti-aggregated αSyn (5G4) and GFAP antibodies. Morphometrical-semi-quantitative analysis was performed to characterize αSyn-5G4+ and GFAP+ density and size. Results Elevated immunoreactivity for aggregated α-Syn was identified in all biopsies of PD patients compared to controls. αSyn-5G4+ colocalized with neuronal marker β-III-tubulin. Evaluation of enteric glia cells revealed an increased size and density when compared with controls, suggesting reactive gliosis. Conclusions Duodenal biopsy may represent a feasible and reliable tool for characterizing PD pathology in the GI tract and discerning patients from controls. Future studies are required to confirm these findings in a prodromal or early PD phase.