Cerebrovascular and Blood-Brain Barrier Impairments in Machado-Joseph Disease

• Autor(a) principal: Lobo, Diana Filipa Duarte
• Data de Publicação: 2017
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/25829
• topic: MMachado-Joseph Disease (MJD); Neurodegenerative disease; Blood-brain barrier (BBB); Blood-Cerebrospinal Fluid Barrier (BCSFB); Tight Junction (TJ); Dynamic Contrast Enhanced-Magnetic Resonance Imaging (DCE-MRI); Domínio/Área Científica::Engenharia e Tecnologia::Outras Engenharias e Tecnologias

Central Nervous System (CNS)-barriers are essential to maintain brain homeostasis, protection and nutrition. Blood-brain barrier (BBB) is mainly constituted by brain endothelial cells, pericytes and astrocytes that restrict the communication between blood and the brain parenchyma. Blood-cerebrospinal fluid barrier (BCSFB) controls molecular exchange between and the cerebrospinal fluid in the epithelial cells of choroid plexus. Both barriers express tight junction (TJ) proteins that limit the paracellular permeability between adjacent cells. In several neurodegenerative diseases, BBB dysfunction has been associated with neuroinflammation and TJs disruption with consequent enhancement of pathogenesis. Machado-Joseph Disease (MJD), also a neurodegenerative disorder, is caused by an expansion in CAG repeats in MJD1 gene that codifies for mutant ataxin-3 protein and causes neurodegeneration and neuroinflammation. The aim of this work was to evaluate the cerebrovascular and CNS-barriers integrity in MJD. To accomplish that, we first assessed BBB permeability by quantifying the Evans blue (EB) extravasation in the brain of a transgenic mouse model of MJD. In a second experiment, we aimed at investigating which mechanisms were involved in BBB disruption, by analyzing: the presence of mutant ataxin-3 in cerebellar blood vessels, fibrin extravasation across BBB, and the expression of TJ-associated proteins. Finally, perfusion and vascular permeability were evaluated by Dynamic Contrast Enhanced-Magnetic Resonance Imaging (DCE-MRI). The results of this work showed that BBB is disrupted in this MJD mouse model, which was demonstrated by Evans blue and fibrin extravasation. Both barriers showed alterations in TJs expression. Occludin was cleaved in both barriers, claudin-5 was upregulated in BBB, whereas ZO-1 showed a tendency to be decreased in BCSFB. Furthermore, it was demonstrated the presence of ataxin-3 aggregates in cerebellar blood vessels. Finally, DCE-MRI confirmed an increased blood volume and higher vascular permeability in MJD mice. In conclusion, this work demonstrated that cerebrovasculature and CNS-barriers are impaired in MJD.