Audrey Kraska

Age-associated cerebral atrophy in mouse lemur primates

We assessed the regional brain atrophy in mouse lemur primates from 4.7T T2-weighted magnetic resonance images. Thirty animals aged from 1.9 to 11.3 years were imaged. Sixty-one percent of the 23 animals older than 3 years involved in the study displayed an atrophy process. Cross-sectional analysis suggests that the atrophy follows a gradual pathway, starting in the frontal region then involving the temporal and/or the parietal part of the brain and finally the occipital region. Histological evaluation of five animals selected according to various stages of atrophy suggested that extracellular amyloid deposits and tau pathology cannot explain by themselves this atrophy and that intracellular amyloid deposition is more closely linked to this pathology. This study suggests that most of the age-related atrophy occurring in mouse lemurs is caused by one clinical, evolving, pathological process. The ability to follow this pathology non-invasively by MRI will allow to further characterize it and evaluate its relationship with neuropathological lesions that are involved in human diseases such as Alzheimer.

In Vivo Cross-sectional Characterization of Cerebral Alterations Induced by Intracerebroventricular Administration of Streptozotocin

Cerebral aging is often associated with the occurrence of neurodegenerative diseases leading to dementia. Animal models are critical to elucidate mechanisms associated to dementia and to evaluate neuroprotective drugs. Rats that received intracerebroventricular injection of streptozotocin (icv-STZ) have been reported as a model of dementia. In these animals, this drug induces oxidative stress and brain glucose metabolism impairments associated to insulin signal transduction failure. These mechanisms are reported to be involved in the pathogenesis of Alzheimers disease and other dementia. Icv-STZ rats also display memory impairments. However, little is known about the precise location of the lesions induced by STZ administration. In this context, the present study characterized the cerebral lesions induced by two-doses of icv-STZ by using high-field magnetic resonance imaging to easily and longitudinally detect cerebral abnormalities and by using immunohistochemistry to evaluate neuronal loss and neuroinflammation (astrocytosis and microgliosis). We showed that, at high doses, icv-STZ induces severe and acute neurodegenerative lesions in the septum and corpus callosum. The lesions are associated with an inflammation process. They are less severe and more progressive at low doses. The relevance of high and low doses of icv-STZ to mimic dementia and evaluate new drugs is discussed in the final part of this article.

Micro-MRI Study of Cerebral Aging: Ex Vivo Detection of Hippocampal Subfield Reorganization, Microhemorrhages and Amyloid Plaques in Mouse Lemur Primates

Mouse lemurs are non-human primate models of cerebral aging and neurodegeneration. Much smaller than other primates, they recapitulate numerous features of human brain aging, including progressive cerebral atrophy and correlation between regional atrophy and cognitive impairments. Characterization of brain atrophy in mouse lemurs has been done by MRI measures of regional CSF volume and by MRI measures of regional atrophy. Here, we further characterize mouse lemur brain aging using ex vivo MR microscopy (31 µm in-plane resolution). First, we performed a non-biased, direct volumetric quantification of dentate gyrus and extended Ammons horn. We show that both dentate gyrus and Ammons horn undergo an age-related reorganization leading to a growth of the dentate gyrus and an atrophy of the Ammons horn, even in the absence of global hippocampal atrophy. Second, on these first MR microscopic images of the mouse lemur brain, we depicted cortical and hippocampal hypointense spots. We demonstrated that their incidence increases with aging and that they correspond either to amyloid deposits or to cerebral microhemorrhages.

Age-associated evolution of plasmatic amyloid in mouse lemur primates: relationship with intracellular amyloid deposition

Alzheimers disease (AD) is the most common age-related neurodegenerative disorder. Amyloid-β peptide (Aβ) deposition in the brain is one of its hallmarks, and the measure of plasma Aβ is considered to be a biomarker for anti-amyloid drug efficacy in animal models of AD. However, age-associated plasmatic Aβ modulation in animal models is practically never addressed in the literature. Mouse lemur primates are used as a model of normal and AD-like cerebral aging. Here, we studied the effect of age on plasmatic Aβ in 58 mouse lemurs aged from 1 to 10 years. A subset of animals presented high plasmatic Aβ, and the proportion of animals with high plasmatic Aβ was higher in aged animals as compared with young ones. Histologic evaluation of the brain of some of these animals was carried out to assess extracellular and intracellular amyloid load. In aged lemurs, plasmatic Aβ was negatively correlated with the density of neurons accumulating deposits of Aβ.

Longitudinal in vivo micro-anatomic follow-up of amyloid plaque load by MRI

polycarbonate. The average signal intensity of tissue surrounding the lateral ventricles was measured in 3T T1-weighted MRI images from ten subjects with AD in the ADNI database. The mixture found to replicate this tissue was made of 2% (w/v) agar dissolved in water, containing 0.01% (w/v) NaCl and a gadopentetate dimeglumine concentration of 0.0375 mM. A brain-shaped mold was filled with tissue-mimicking solution and the ventricle positioned in the middle of the brain. The completed phantom was scanned using the ADNI-specific MP-RAGE sequence. Images were analyzed using a fully-automated segmentation tool. Results: The signal intensity difference between the ventricle and agar solution successfully matched in-vivo signal intensity differences. At a resolution of 1.0 x1.0 x1.0 mm, a volume of 46.6 cm was reported, which is only 2.3% smaller than the actual volume. This result illustrates that the software used does a reasonable job of estimating ventricle volume. The use of the ventricle phantom allowed us to also pinpoint ventricular sub-regions where the algorithm failed. Conclusions: A life-sized MRI-compatible brain ventricle phantom was successfully created. Images acquired are available from the authors to groups wishing to use this data for validation. As enlargement of the ventricles is further established as a marker of disease progression and incorporated into clinical trials, careful validation using gold standards must be performed to ensure the integrity of the study.

Invivo detection of age-related cerebral glucose uptake alterations by PET in microcebus murinus primates

e Laval and Centre de Recherche Universit e Laval Robert Giffard, Quebec, Quebec, Canada; David Geffen School of Medicine at UCLA, Los Angeles, California, United States; 4 University of Alberta, Edmonton, Alberta, Canada; 5 Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States; New York University School of Medicine, Center for Brain Health, New York, New York, United States; 7 Rush University, Chicago, Illinois, United States; Boston University School of Medicine, Boston, Massachusetts, United States; Center for NeuroImaging Research CENIR and Universit e Pierre et Marie Curie, Paris, France; 10 University of Frankfurt/Main, Frankfurt, Germany; 11 McGill University, Montreal, Quebec, Canada; University of Eastern Finland, Kuopio, Finland; Wayne State University School of Medicine, 8D-University Health Center, Detroit, Michigan, United States; 14 Mayo Clinic and Foundation, Rochester, Minnesota, United States.

MRI evaluation of focal brain lesions in streptozotocin-treated animals: Comparison between rodents (rats) and primates (microcebus murinus)

STREPTOZOTOCIN-TREATED ANIMALS: COMPARISON BETWEEN RODENTS (RATS) AND PRIMATES (MICROCEBUS MURINUS) Audrey Kraska, Mathieu Santin, Marc Dhenain, Hantraye Philippe, Olene Dorieux, Marion Chaigneau, Martine Guillermier, Diane Houitte, Charl ene Josephine, Martine Perret, Nelly Joseph-Mathurin, Fabienne Aujard, Pierre Lestage, URA CEA-CNRS 2210 MIRCen, Fontenay-aux-Roses, Pantin, France; 2 Sanofi-Aventis, Chilly-Mazarin; 3 CNRS, Fontenay-aux-Roses; 4 URA CEA-CNRS 2210 MIRCen, Fontenay-aux-Roses; CNRS, Brunoy; URA CEA-CNRS 2210 MIRCen, Fontenay-aux-Roses; URA CEA-CNRS 2210 MIRCen, Fontenay-aux-Roses; 8 UMR 7179 CNRS-MNHN, Brunoy; 9 URA CEA-CNRS 2210 MIRCen, Fontenay-aux-Roses; UMR 7179 CNRS-MNHN, Brunoy; Institut de recherches Servier, Croissy-sur-Seine.

P1-16 Evolution avec l’âge de biomarqueurs plasmatiques de l’amyloïdose chez des souris APP/PS1dE9 modèles de la maladie d’Alzheimer et le primate Microcebus murinus

Introduction Les modeles animaux de la maladie d’Alzheimer sont necessaires a la comprehension de la physiopathologie et a l’evaluation de traitements potentiels. Les biomarqueurs tels que le peptide Aβ retrouve dans le plasma de modeles animaux peuvent permettre d’evaluer l’efficacite de ces traitements ainsi que de suivre l’evolution de la pathologie chez des modeles spontanes ou induits. Le but de notre etude etait de developper l’utilisation de l’Aβ plasmatique comme biomarqueur chez des souris transgeniques modeles d’amyloidose et chez un modele de vieillissement spontane, le primate microcebe murin. Materiel et methodes La concentration du peptide Aβ a ete evaluee chez des souris APPswe/PS1dE9 et chez des microcebes âges de 1 a 8 ans (n=27). Les souris, âgees de 16 a 116 semaines, etaient issues de differents fonds genetiques (B6C3F1 (n=20) et C57Bl6 (n=23). Les prelevements sanguins ont ete effectues sur des tubes EDTA, centrifuges (2000g ; 10min, 4°c). Le surnageant a ete collecte dans des tubes en polypropylene. Un cocktail d’inhibiteurs de proteases (Complete Mini Roche) a ete ajoute aux echantillons de plasma. La detection de l’Aβ40 et 42 a ete effectuee avec des kits ELISA commerciaux (BioSource). Resultats Nous avons observe une difference significative entre les taux d’Aβ plasmatique chez des souris APPswe/ PS1dE9 de differents fonds genetiques. Par exemple, les taux d’Aβ40 etaient respectivement de 988±75 et 591±37 pg/ml chez les souris B6C3F1 et C57BL/6J. Cependant, les taux d’Aβ40 et 42 plasmatiques chez les souris n’etaient pas modifies avec l’âge ou l’evolution de la pathologie. Chez le microcebe, aucune difference significative des taux d’Aβ40 n’a pu etre observee entre les animaux jeunes et âges (41.7±2.4 et 52.3±7.5 pg/ml). Cependant, une plus grande heterogeneite etait presente chez les microcebes âges, ceci pouvant etre un indicateur d’un vieillissement pathologique de type Alzheimer chez certains animaux. Conclusion La detection des taux d’Aβ plasmatique est un outil simple et tres precis chez la souris transgenique et le primate. Cet outil peut permettre de suivre les effets de traitements. Il pourra egalement permettre de selectionner des animaux pour l’etude du vieillissement pathologique chez le microcebe. Remerciements Association France-Alzheimer, National Institute on Aging (R01-AG020197).

O2-2 Détection par IRM haute résolution de plaques amyloïdes chez un primate : Le microcèbe

Introduction Le developpement de biomarqueurs pour diagnostiquer et suivre l’evolution de la maladie d’Alzheimer (MA) est un enjeu majeur pour la recherche. Chez les modeles murins de la MA, l’imagerie par RMN permet de detecter les plaques amyloides [1 ; 2]. Ces lesions apparaissent comme des spots hypointenses sur des images ponderees en T2*. Avant d’appliquer cette technique en clinique, il est necessaire de la developper chez un modele phylogenetiquement proche de l’homme. Nous avons donc cherche a mettre en evidence ces lesions par IRM chez un Primate : le microcebe murin [3]. Materiel et methodes Les cerveaux de 12 microcebes âges de 1 a 10 ans (n=6 jeunes et n=6 âges (âges moyens=2,5 et 7,5 ans respectivement)) ont ete incubes dans une solution de Gadolinium 2,5 mmol.l-1 (Dotarem® (Guerbet) dilue au 200eme) [4]. Des images ponderees en T2* ont ete enregistrees sur un spectrometre Clinique de 7T (Siemens, gradient 80mT/m, TR/TE=200/20 ms ; temps d’acquisition=5h ; resolution=(31×31×120)μm3). Les images ont ete analysees grâce au logiciel Anatomist. Une etude immunohistologique des cerveaux a ete realisee pour detecter l’amyloidose (coupes de 40μm, Ac 4G8(SIGNET)). Resultats Des lesions hypointenses ont ete detectees dans le cortex et l’hippocampe des microcebes. Le nombre de ces lesions etait plus important chez les animaux âges par rapport aux jeunes (Moyenne=4,83 et 0,17 chez les vieux et les jeunes ; U=0.5 ; p Conclusion L’IRM haute resolution permet de detecter des depots amyloides chez les microcebes. Les spots hypointenses ne correspondant pas aux plaques amyloides pourraient etre des alterations vasculaires. Une correlation entre le nombre de lesions hypointenses et l’âge a aussi ete mise en evidence. L’IRM permet donc de detecter des biomarqueurs du vieillissement cerebral chez les microcebes. Remerciements Association France-Alzheimer, National Institute on Aging (R01-AG020197).

Links between cerebral atrophy, behavioral alterations and neuropathological changes in mouse lemur primates

BEHAVIORAL ALTERATIONS AND NEUROPATHOLOGICAL CHANGES IN MOUSE LEMUR PRIMATES Marc Dhenain, Audrey Kraska, Nadine Mestre-Frances, Olene Dorieux, Fanny Petit, Emmanuel Bourrin, Anne-Sophie Herard, Evelyne Chenu, Andreas Volk, Martine Perret, Philippe Hantraye, Fabienne Aujard, Jean-Luc Picq, URA CEA CNRS 2210, Fontenay aux Roses, France; URA CEA CNRS 2210, Orsay, France; INSERM U710EPHE, Montpellier, France; Institut Curie, Orsay, France; CNRS UMR 7179, MNHN, Brunoy, France; E.A. 2027, Université Paris 8, St Denis, France. Contact e-mail: Marc.Dhenain@cea.fr