Developing a Porcine Model to Study the Glymphatic System

The glymphatic system is a brain-wide solute clearance system that has developed in the brain to clear metabolic waste during sleep. This clearance is mediated by advective fluxes of cerebrospinal fluid (CSF) along perivascular spaces (PVS) and through the brain. The movement of CSF from the PVS and through the brain is dependent on the polarised expression of aquaporin-4 (AQP4) at astrocyte endfeet, that project to form the outer PVS boundary. The capacity of the glymphatic system to clear proteins like amyloid-beta (Aß) and tau has generated great interest in exploiting this system therapeutically in the context of Alzheimer’s disease (AD). However, much of the knowledge on the glymphatic system, more specifically, the microscopic machinery and processes, have been studied and described exclusively in rodents. To this end, apart from several magnetic resonance imaging studies confirming the existence of macroscopic glymphatic phenomena in humans i.e. advective movement of gadobutrol from the CSF into the brain, the microscopic aspects of the glymphatic system remain largely unexplored in the large gyrencephalic brain. Thus, the aims of this thesis were to develop a large animal model to study the glymphatic system and further use this model to study the glymphatic system in the context of neuropathology, which in this case took the form of sub-dural haematoma, and amyloid-beta (re)-circulation in the context of AD. To achieve this, a cisterna magna (CM) cannulation surgery was translated from rodents to pigs, such that it would be possible to introduce fluorescent tracers into the porcine CSF in vivo and explore the glymphatic pathways. Initially, to characterise these pathways whole brains were extracted intact after fluorescent tracer circulation and processed using several advanced imaging readouts, including macroscopy, along with confocal, light sheet and electron microscopy. Imaging data revealed: 1) The folded architecture of the gyrencephalic brain helped direct upstream CSF distribution, 2) PVS-mediated CSF influx into the brain is steadfast in the pig brain, as in rodents, and could be traced in deep sub-cortical structures and down to a capillary level, 3) PVS influx sites are 4-fold more extensive in pigs than in rodents. Taken together these data indicate not only a conservation of the glymphatic system and its machinery from rodents to pigs but a more developed system in the large mammal. In the context of suspected sub-acute subdural haematoma (SDH) a brain-wide impairment in glymphatic influx amounted, raising important questions concerning the consequence of undiagnosed SDH for glymphatic function and brain clearance. In the context of AD the acute introduction of Aß1-42 into the CSF was found to impair glymphatic function, highlighting the consequences of Aß recirculation for brain clearance. Interestingly, upon closer examination it was found that Aß did not penetrate into the brain as was the case with inert protein tracers, but instead remained localised to pial and penetrating arteries. This localisation was elastin specific and only occured with Aß (1-40/1-42) but not dextran or bovine serum albumin. This outcome appears to reflect an Aß entrapment system that prevents the recirculation of Aß into the brain, but further work is necessary to unravel its potential as a clearance pathway for Aß from the CSF to protein transporters at the endothelial cell layer. In an attempt to study this in vivo a porcine cranial window model was generated in order to image PVS transport in the large gyrencephalic brain. While low resolution imaging was indeed possible, brain motion proved a challenge not yet overcome. We hope that in the future, through mitigating brain motion, it will be possible to study PVS transport, the glymphatic system, and this potential Aß entrapment pathway, in the brain of a large mammal in vivo

Direct Cannula Implantation in the Cisterna Magna of Pigs

The glymphatic system is a waste clearance system in the brain that relies on the flow of cerebrospinal fluid (CSF) in astrocyte-bound perivascular spaces and has been implicated in the clearance of neurotoxic peptides such as amyloid-beta. Impaired glymphatic function exacerbates disease pathology in animal models of neurodegenerative diseases, such as Alzheimer's, which highlights the importance of understanding this clearance system. The glymphatic system is often studied by cisterna magna cannulations (CMc), where tracers are delivered directly into the cerebrospinal fluid (CSF). Most studies, however, have been carried out in rodents. Here, we demonstrate an adaptation of the CMc technique in pigs. Using CMc in pigs, the glymphatic system can be studied at a high optical resolution in gyrencephalic brains and in doing so bridges the knowledge gap between rodent and human glymphatics

Regional Brain Analysis of Modified Amino Acids and Dipeptides during the Sleep/Wake Cycle

Sleep is a state in which important restorative and anabolic processes occur. Understanding changes of these metabolic processes during the circadian rhythm in the brain is crucial to elucidate neurophysiological mechanisms important for sleep function. Investigation of amino acid modifications and dipeptides has recently emerged as a valuable approach in the metabolic profiling of the central nervous system. Nonetheless, very little is known about the effects of sleep on the brain levels of amino acid analogues. In the present study, we examined brain regional sleep-induced alterations selective for modified amino acids and dipeptides using Ultra-high performance liquid chromatography-MS/MS (UHPLC-MS/MS) based metabolomics. Our approach enabled the detection and identification of numerous amino acid-containing metabolites in the cortex, the hippocampus, the midbrain, and the cerebellum. In particular, analogues of the aromatic amino acids phenylalanine, tyrosine and tryptophan were significantly altered during sleep in the investigated brain regions. Cortical levels of medium and long chain N-acyl glycines were higher during sleep. Regional specific changes were also detected, especially related to tyrosine analogues in the hippocampus and the cerebellum. Our findings demonstrate a strong correlation between circadian rhythms and amino acid metabolism specific for different brain regions that provide previously unknown insights in brain metabolism

PDGF-B Is Required for Development of the Glymphatic System

The glymphatic system is a highly polarized cerebro-spinal fluid (CSF) transport system that facilitates the clearance of neurotoxic molecules through a brain-wide network of perivascular pathways. Herein we have mapped the development of the glymphatic system in mice. Perivascular CSF transport first emerges in hippocampus in newborn mice, and a mature glymphatic system is established in the cortex at 2 weeks of age. Formation of astrocytic endfeet and polarized expression of aquaporin 4 (AQP4) consistently co-incided with the appearance of perivascular CSF transport. Deficiency of platelet-derived growth factor B (PDGF-B) function in the PDGF retention motif knockout mouse line Pdgfb(ret/ret) suppressed the development of the glymphatic system, whose functions remained suppressed in adulthood compared with wild-type mice. These experiments map the natural development of the glymphatic system in mice and define a critical role of PDGF-B in the development of perivascular CSF transport

LA SUPER AMBIANCE KANGOUROU

Titre uniforme : [Black and blue]Titre uniforme : [Black and blue]Titre uniforme : [Laura]Titre uniforme : [Laura]Collection : Super collection kangourouComprend : SOUVENIR DE LA NOUVELLE-ORLEANS / Sidney BECHET ; Sidney BECHET, saxo-soprano, Teddy BUCKNER, trompette, et des instrumentistes de jazz - BLUE PANASSIE / Lionel HAMPTON ; Lionel HAMPTON, vibraphone - Claude BOLLING, piano, et Instrumentistes de jazz - REHEARSAL BLUES / Dizzie GILLESPIE ; Dizzy GILLESPIE, trompette et instrumentistes de jazz - NIGHT LIFE IN POMPEI / Earl HINES ; Earl HINES, piano, et instrumentistes de jazz - BLUES FOR KICKS / NICHOLAS ; Albert NICHOLAS, clarinette et instrumentistes de jazz - LAURA / RAKSIN - MERCER ; Gerry MULLIGAN, saxo-baryton et instrumentistes de jazz - I REMEMBER HARLEM / Roy ELDRIDGE ; Roy ELDRIDGE, trompette, et instrumentistes de jazz - LONESOME ROAD / AUSTIN ; Jonah JONES, trompette, Sidney BECHET, saxo - soprano, et instrumentistes de jazz - BLACK AND BLUE / RAZAF - WALLER ; Buck CLAYTON, trompette, et instrumentistes de jazz - JAY JAY BLUES / JOHNSON ; Milt JACKSON, vibraphone, et instrumentistes de jazzBnF-Partenariats, Collection sonore - BelieveContient une table des matière