title: MRI and MRS alterations in the preclinical phase of murine prion disease: association with neuropathological and behavioural changes.
abstract: Prion diseases are fatal chronic neurodegenerative diseases. Previous qualitative magnetic resonance imaging (MRI) and spectroscopy (MRS) studies report conflicting results in the symptomatic stages of the disease, but little work has been carried out during the earlier stages of the disease. Here we have used the murine ME7 model of prion disease to quantitatively investigate MRI and MRS changes during the period prior to the onset of overt clinical signs (20+ weeks) and have correlated these with pathological and behavioural abnormalities. Using in vivo MRI, at the later stages of the preclinical period (18 weeks) the diffusion of tissue water was significantly reduced, coinciding with significant microglial activation and behavioural hyperactivity. Using in vivo MRS, we found early (12 weeks) decreases in the ratio of N-acetyl aspartate to both choline (NAA/Cho) and creatine (NAA/Cr) in the thalamus and hippocampus, which were associated with early behavioural deficits. Ex vivo MRS of brain extracts confirmed and extended these findings, showing early (8-12 weeks) decreases in both the neuronal metabolites NAA and glutamate, and the metabolic metabolites lactate and glucose. Increases in the glial metabolite myo-inositol were observed at later stages when microglial and astrocyte activation is substantial. These changes in MRI and MRS signals, which precede overt clinical signs of disease, could provide insights into the pathogenesis of this disease and may enable early detection of pathology.
authors.affiliation: Experimental Neuroimaging Group, Department of Physiology, Anatomy and Genetics, University of Oxford, Sherrington Building, Parks Rd., Oxford, OX1 3PT, UK.
authors.forename: Kerry A
authors.initials: KA
authors.lastname: Broom
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Anthony
authors.forename: John P
authors.initials: JP
authors.lastname: Lowe
authors.forename: Julian L
authors.initials: JL
authors.lastname: Griffin
authors.forename: Helen
authors.initials: H
authors.lastname: Scott
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Blamire
authors.forename: Peter
authors.initials: P
authors.lastname: Styles
authors.forename: V Hugh
authors.initials: VH
authors.lastname: Perry
authors.forename: Nicola R
authors.initials: NR
authors.lastname: Sibson
mesh_terms: D000818:Animals; D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000032:analysis / Q000378:metabolism; D001253:Astrocytes / Q000378:metabolism; D001834:Body Water / Q000502:physiology; D001921:Brain / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology; D002794:Choline / Q000032:analysis / Q000378:metabolism; D003401:Creatine / Q000032:analysis / Q000378:metabolism; D004058:Diffusion; D004195:Disease Models, Animal; D018450:Disease Progression; D005911:Gliosis / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D005947:Glucose / Q000378:metabolism; D018698:Glutamic Acid / Q000032:analysis / Q000378:metabolism; D006948:Hyperkinesis / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D007294:Inositol / Q000378:metabolism; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D051379:Mice; D008810:Mice, Inbred C57BL; D017628:Microglia / Q000378:metabolism; D017096:Prion Diseases / Q000175:diagnosis* / Q000473:pathology* / Q000503:physiopathology
chemical_list: D001224:Aspartic Acid; D018698:Glutamic Acid; D007294:Inositol; C000179:N-acetylaspartate; D005947:Glucose; D003401:Creatine; D002794:Choline