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Alzheimer’s Imaging Consortium IC-P: Poster Presentations

Background: Rosiglitazone, a peroxisome proliferator-activated receptor [gamma] (PPAR[gamma]) agonist, has an anti-inflammatory effect in the brain, decreasing interleukin-1[beta] concentrations in hippocampus and restoring the age-related deficit in long-term potentiation. It also attenuates learning and memory deficits in a mouse model of Alzheimer’s disease. Evidence suggests that activation of microglia and astrocytes contribute to agerelated neuroinflammatory changes. In this study, relaxometry measurements were assessed in hippocampus of young and aged rats because there have been recent reports in the literature linking spin-lattice (T1) and spinspin (T2) relaxation times to astrocytic activation and microglial activation respectively. Methods: Male Wistar rats aged 3 and 18 months (n ¼ 5-6 per group) were treated either with 3 mg/day rosiglitazone maleate or with vehicle only for 56 days and MR images obtained under anesthesia using a 7-Tesla MRI scanner (Bruker) with slices selected to give optimal regions of interest in dorsal hippocampus (Fig. 1). Images were acquired using rapid acquisition with relaxation enhancement (RARE) and echotrain multi-slice-multi-echo (MSME) sequences, from which T1 and T2 maps were generated, respectively; and a fast imaging with steady-state precession (FISP) protocol, from which both T1 and T2 maps were generated. Data from manually-selected regions of interest were analyzed using software scripts in IDL language (ITTVIS). One- or two-way analyses of variance (ANOVA) with Fischer’s post-test were used to statistically assess the data. Tissue from the animals was examined for markers of astrogliosis and microglial activation. Results: T1 in hippocampus and cortex (p < 0.01, Fig. 2) were significantly increased with age whilst T2 in hippocampus (p < 0.05) and cortex (p < 0.01, Fig. 3) were significantly decreased with age. Treatment with rosiglitazone significantly attenuated the age-related T1 increase in both regions (p < 0.05, Fig. 2) and it increased T2 relaxation time in hippocampus of aged, but not young rats (p < 0.05, Fig. 3). Conclusions: The data demonstrate an age-related increase in T1 in hippocampus and cortex, which is attenuated by rosiglitazone; this correlates with astrocytosis (Fig. 4). We also show a decrease in T2 relaxation time in hippocampus and cortex, which correlates with an increase in microglial activation (Fig. 5), and report that rosiglitazone-treatment of aged rats increases hippocampal T2.

IC-P-006

IN VIVO AMYLOID PLAQUE DETECTION USING CONTRAST-ENHANCED MAGNETIC RESONANCE MICROSCOPY IN TRANSGENIC MICE

Alexandra Petiet1,2, Anne Bertrand2, Christopher Wiggins3, Diane Houitte2, Thomas Debeir1, Thomas Rooney1, Marc Dhenain2,3, 1 Sanofi-Aventis R&D, Vitry-sur-Seine, France; 2CNRS URA 2210, Mircen, Orsay, France; 3CEA, DSV, I2BM, Neurospin, Gif-sur-Yvette, France. Contact e-mail: [email protected] Background: Amyloid plaques have previously been identified in mouse models of Alzheimer’s disease (AD) using magnetic resonance micros-

copy. Because of their high iron content, plaques typically appear as hypointense spots on T2-weighted scans. One of the challenges in imaging plaques is to achieve high-enough resolution and contrast to detect these 50-mm large lesions. While most high-field systems can reach high resolution, the lack of contrast between the plaques and the parenchyma often impedes their detection. Methods: Transgenic mice over-expressing mutations of the human genes responsible for familial forms of AD were studied. A total of eight APP/PS1 mice and seven wild-type mice were used for the in vivo study. The mice were injected in the lateral ventricles with a non-specific gadolinium(Gd)-based contrast agent (CA). Within 6 hours after injections, the animals were imaged in a 7 T Siemens system (Syngo MR VB15) using a 3D turbo spin-echo sequence (resolution ¼ 503503200 mm, scan time ¼ 2.5 hours). A total of six APP mice were used for the ex vivo study where the extracted brains were fixed and stained with a Gd CA for at least 24 hours, then imaged (3D FLASH gradient-echo sequence, resolution ¼ 653653200 mm and scan time ¼ 1 hour, or resolution ¼ 23323390 mm and scan time ¼ 12 hours). Results: There was a continuous diffusion of the CA into the parenchyma for up to 40 min after injection, until it reached a plateau and remained in the brain for at least 5 hours. The images showed that prior to injection of CA, no plaques were detectable in the cortex or hippocampus, whereas some were clearly visible after injection of CA. The ex vivo results showed that 50-mm large plaques could be detected after staining with the CA. However, individual plaques were only well-defined at high resolution, enabling quantification of the plaque load which was about 10% in the cortex. Conclusions: This study shows that amyloid plaques can be detected both in vivo and ex vivo using a non-specific Gd-contrast agent. The level of detail achieved should be sufficient for pharmacology studies. IC-P-007

MEMORY LOSS IN YOUNG APPSWE/PS1DE9 MICE AND ASSOCIATED CHANGES IN BRAIN METABOLISM ANALYZED USING A 3-D VOXELBASED APPROACH

Anne-Sophie He´rard1, Thierry Delzescaux1, Sylvie Cornet2, Jessica Lebenberg1, Pierre-Etienne Chabrier2, Philippe Hantraye1, Marc Dhenain1, 1CEA-MIRCen-CNRS URA 2210, Fontenay-Aux-Roses, France; 2SCRAS-IHB, Les Ulis, France. Contact e-mail: anne-sophie. [email protected] Background: APPswe/PS1dE9 is a mouse model of Alzheimer’s disease that starts to develop amyloid plaques by the age of 4 months. This study evaluated early alterations of spatial memory and brain glucose metabolism in this mouse strain. The latter biomarker is of great interest in translational studies, as it can be evaluated both in animals and humans. Methods: APPswe/PS1dE9-transgenic (Tg) and C57BL/6 J amyloid free control (WT) mice were studied at 4.5 months, i.e. at the very beginning of amyloid deposition. Spatial memory was evaluated using the Morris water maze (nTg ¼ 14; nWT ¼ 14). During the training (4 trials/day for 4 days) the latency and distance to reach platform (PF) were evaluated. For the memory retention test, the PF was removed and mice were allowed to navigate for 60 seconds. The time spent in the target quadrant, the distance moved, the number of crossing into PF zone, and the swim speed were evaluated (Ethovision videotracking system, Noldus). Glucose uptake was quantified in awake mice (nTg ¼ 6; nWT ¼ 7) by [14C]-2-deoxyglucose autoradiography of the whole brain (20-mm serial sections). 3D autoradiographic brain volumes were reconstructed using BrainRAT (freely available software, http://www.brainvisa.info) and statistical analyses were performed without any a priory hypothesis using SPM5. Cerebral amyloid deposits were examined in the same animals (BAM10 immunostaining and Congo red). Results: APPswe/PS1dE9 mice displayed significant spatial memory alterations that could be detected in training (increased distance and latencies to reach the PF) and retention sessions (reduced time spent in the quadrant). Despite these alterations, SPM analysis of glucose metabolism revealed no statistically significant hypometabolic voxels in Tg as compared to WT animals. On the contrary, hypermetabolic voxels were identified bilaterally. They were located in lateral olfactory tracts and in the somatosensory and motor parietal cortex (increases of 12.0%/

Alzheimer’s Imaging Consortium IC-P: Poster Presentations 13.7% and 13.9%/13.0% for the left and right sides of these structures). Conclusions: Although young Tg mice displayed spatial memory impairment, no obvious hypometabolic brain regions was detected. Strikingly, Tg mice even present with discrete areas of hypermetabolism in the somatosensory and motor parietal cortex and in olfactory areas. The fine relationship between these behavioral and metabolic changes remains to be elucidated. IC-P-008

ALTERATIONS OF BRAIN GLUCOSE METABOLISM IN AGED APP/PS1 MICE: AN ORIGINAL VOXEL-BASED STATISTICAL ANALYSIS USING BRAINRAT AND SPM

Anne-Sophie He´rard1, Albertine Dubois2, Nicolas Souedet1, Benoıˆt Delatour3, Philippe Hantraye1, Marc Dhenain1, Thierry Delzescaux1, 1 CEA-MIRCen-CNRS URA 2210, Fontenay-Aux-Roses, France; 2 CEA-SHFJ-INSERM U803, Orsay, France; 3Universite´ Paris SudNAMC-CNRS UMR 8620, Orsay, France. Contact e-mail: anne-sophie. [email protected] Background: Glucose brain metabolism is a widely used clinical biomarker in Alzheimer’s disease (AD), usually examined on 2D post mortem autoradiographic data in AD animal models. We propose an innovative method to analyze these data in 3D without a priori anatomical information, to derive brain metabolic activity maps using voxel-based approach in APP/PS1 mice. Results will be discussed relative to previous findings in this field. Methods: Uptake of [14C]-2-deoxyglucose was measured in adult awake APP/PS1 (64 6 1 weeks, n ¼ 4) and PS1 (65 6 2 weeks, n ¼ 3) transgenic mice. Glucose uptake was evaluated by autoradiography on the right hemisphere while the left hemisphere was processed for Congo red staining. Data acquisition was performed with a digital camera (blockface photographs) and a high resolution flatbed scanner (autoradiography, histology). Blockface, autoradiographic and histological post mortem volumes were 3D-reconstructed using BrainRAT in-house software (freely available, http://brainvisa.info) while statistical analysis was achieved using SPM5. Results: We successfully combined BrainRAT (computerized procedures for acquisition and 3D reconstruction of anatomic and functional volumes) and SPM5 (voxel-wise statistical analysis) methodologies to data sets mapping brain metabolic activity in a transgenic mouse model of AD. We were able to extract accurate parametric mapping of both hypoand hypermetabolic regions in the APP/PS1 animals relative to PS1 controls. Decreased glucose uptake was observed within cortex (cingulate -36%, retrosplenial -26%, somatosensory -23%), striatum (-22%), thalamus (-29%) and hippocampus (-25%). Increased glucose uptake was also detected within other cortical areas (piriform þ22%, perirhinal þ19%), amygdala (þ23%), dorsal endopiriform (þ34%) and accumbens (þ20%) nuclei, dentate gyrus (þ25%) and dorsal hippocampus (þ26%). Conclusions: We have demonstrated the ability to robustly and automatically reconstruct post mortem functional volumes. We also provided accurate cerebral glucose uptake mapping in a murine AD model, in 3D, without a priori hypotheses. We offer an efficient and standardized method to compare local changes in mice cerebral glucose utilization across ages, lines or drugs. Furthermore, our work demonstrates the possibility of using functional brain imaging and dedicated software to help bridge the gap, in translational studies, between features of neurodegenerative diseases in human beings and animal models.Acknowledgements: Sanofi-Aventis for sharing the mouse strains. IC-P-009

IN VIVO OPTICAL AND PET DETECTIONS OF FIBRILLAR TAU LESIONS IN A MOUSE MODEL OF TAUOPATHIES

Masahiro Maruyama1, Jun Maeda1, Bin Ji1, Ming-Rong Zhang1, Takashi Okauchi1, Maiko Ono1, Satoko Hattori1, John Q. Trojanowski2, Virginia M.-Y. Lee.2, Toshimitsu Fukumura1, Makoto Higuchi1, Tetsuya Suhara1, 1National Institute of Radiological Sciences, Chiba, Japan; 2 University of Pennsylvania, Philadelphia, PA, USA. Contact e-mail: [email protected]

P9

Background: Intracellular inclusions of pathological tau fibrils are hallmark lesions in Alzheimer’s disease (AD) and associated tauopathies, and there has been a growing interest in the mechanistic links between fibrillar tau accumulation and neuronal deterioration. In-vivo visualization of tau lesions would thus serve the preclinical and clinical needs for pursuing the molecular etiology of neurodegenerative disorders and evaluating candidate disease-modifying therapies. This notion has led us to develop imaging agents capable of capturing tau aggregates in a living mouse model of tauopathies. Methods: An array of fluorescent chemicals were screened by assaying their in-vitro binding to recombinant tau fibrils and neuronal tau inclusions on brain sections from patients with diverse tauopathies and mice transgenic for the pathogenic P301S mutant tau. The selected compounds were intravenously injected into the tau transgenics, and ex-vivo labelings of tau lesions with these agents in excised brain samples were microscopically assessed. Pulse-laser optical and positron emission tomographic (PET) systems were then applied to in-vivo detections of tau pathologies in the transgenic mice with near-infrared fluorescent and 11C-labeled compounds, respectively. The PET data were also supplemented by in-vitro and ex-vivo autoradiographic analyses. Results: Chemical properties of the compounds such as structural dimensions and hydrophilicities were associated with their affinities for tau inclusions in a wide range of tauopathies as well as transgenics. A class of chemicals sharing the common core structure enabled ex-vivo visualization of aggregates in the transgenic mice. One of these putative imaging agents was suitable for the near-infrared optics, and was proven to bind to tau aggregated in living mouse brains based on the intensity and lifetime of its fluorescent signals. Two other compounds of the same group were radiolabeled with 11C, and were demonstrated to allow both autoradiographic and PET detections of tau lesions in the transgenics. Conclusions: The present neuroimaging approaches using mouse models of the diseases provide insights into the structural basis of molecular interactions between tau fibrils and exogenous compounds, which would facilitate the development of diagnostic and therapeutic agents for AD and non-AD tauopathies. IC-P-010

DIAGNOSTIC UTILITY OF PLATELET AMYLOID PRECURSOR PROTEIN RATIO, RED BLOOD CELLS AND PLASMA BETA AMYLOID (Ab 1-42) LEVELS IN LATE-ONSET ALZHEIMER’S DISEASE

Ben Ashok1, B’joe Baben1, Vasudevan Devanathan2, Senthil Kumar3, Jeyakumar Rajadhas4, 1Sri Ramachandra Medical College, Chennai, India; 2 Kamakshi Memorial Hospital, Chennai, India; 3Central Leather Research Institute, Chennai, India; 4Stanford University, Stanford, CA, USA. Contact e-mail: [email protected] Background: Alzheimer’s disease (AD) is a severe neurodegenerative disease with a characteristic progressive decline in cognitive functions and dementia. It is believed that the majority of all AD patients are affected by the sporadic form, caused by the combined effects of several risk factors. Increasing evidence suggests that abnormal processing of amyloid precursor protein (APP) may play an important role in the pathogenesis of AD. The present study focused on finding reliable biochemical markers in peripheral venous blood and their relation to AD. Methods: The biochemical markers, platelets APP ratio, red blood cells (RBC), and plasma beta amyloid (Ab 1-42) were quantitated in 40 probable/possible sporadic AD patients and 60 non demented age matched healthy controls. Results: The present study found a reduction in platelet APP ratio. The magnetitude of the APP ratio reduction is proportional to the severity of the cognitive loss in AD. The mean plasma Ab1-42 levels were higher in AD compared to age matched healthy subjects. In erythrocytes the mean RBC Ab1-42 levels were found to be decreased in AD but there was substantial individual variability and overlap in plasma and RBC Ab1-42 levels between these groups. Conclusions: Since platelet APP ratio is decreased at different stages of AD and abnormal APP processing is related to the neuropathological changes in AD brain, the present study suggests that the APPr may assist in the early diagnosis of AD in individuals at risk for the disease