EMIM 2018 ControlCenter

Online Program Overview Session: PW-13

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Neuroimaging I | Disease Models

Session chair: Stefanie Dedeurwaerdere - Braine l'Alleud, Belgium; Fabien Chaveau - Lyon, France
 
Shortcut: PW-13
Date: Thursday, 22 March, 2018, 11:30 AM
Room: Banquet Hall | level -1
Session type: Poster Session

Abstract

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# 146

18F-VC701-PET and MRI in the in vivo neuroinflammation assessment of a mouse model of Multiple Sclerosis (#418)

S. Belloli1, 2, 3, L. Zanotti4, V. Murtaj2, 5, 6, C. Mazzon7, G. Di Grigoli1, 2, C. Monterisi2, 6, V. Masiello2, L. Iaccarino8, A. Cappelli9, P. L. Poliani10, L. S. Politi11, R. M. Moresco1, 2, 6

1 CNR, IBFM, Segrate (MI), Italy
2 IRCCS San Raffaele Sientific Institute, Experimental Imaging Center, Milan, Italy
3 University of Milano-Bicocca, Milan Center for Neuroscience (NeuroMI), Milan, Italy
4 IRCCS San Raffaele Scientific Institute, Unit of Immunogenetics, Leukemia Genomics and Immunobiology, Milan, Italy
5 University of Milan-Bicocca, PhD Program in Neuroscience, Monza (MB), Italy
6 University of Milano-Bicocca, Department of Medicine and Surgery, Monza (MB), Italy
7 University of Padua, Biomedical Sciences Department, Padua, Italy
8 Vita-Salute San Raffaele University, Division of Neuroscience, Milan, Italy
9 , University of Siena, Department of Biotechnology, Chemistry and Pharmacy, Siena, Italy
10 University of Brescia, Department of Molecular and Translational Medicine, Pathology Unit, Brescia, Italy
11 University of Massachusetts Medical School, Advanced MRI Center, Boston, United States of America

Introduction

Positron Emission Tomography (PET) using Translocator Protein (TSPO) ligands has been used to detect neuroinflammatory processes in neurological disorders, including Multiple Sclerosis (MS). Aim of this study was to evaluate neuroinflammation in a mouse MS model (EAE) using TSPO-PET with 18F-VC701 developed in collaboration with University of Siena (1), in combination with high resolution Magnetic Resonance Imaging (MRI).

Methods

Female C57BL/6 mice were immunized on day 0 with the peptide MOG35-55/CFA (200 µg/300 µl s.c. in three sites) and treated on day 0 and 2 with PTX (350 ng/100µl PBS i.v.) to induce EAE. Animals were daily monitored for clinical signs (score: 0-5, increasing severity) and disease progression was evaluated with MRI at 1, 2 and 4 weeks post-induction. Microglia activation was assessed in vivo by 18F-VC701 PET at the time of maximum disease score and validated by radioligand ex vivo distribution and immunohistochemistry at 2 and 4 weeks post-immunization. Regional uptake was expressed as percentage of injected dose per gram of tissue (%ID/g ).

Results/Discussion

In vivo and ex vivo analyses show that 18F-VC701 significantly accumulates within the Central Nervous System (CNS), particularly in the cortex, striatum, hippocampus, cerebellum and cervical spinal cord of EAE compared to control mice, at 2 weeks post-immunization. MRI confirmed the presence of focal brain lesions at 2 weeks post-immunization in both T1-weighted and T2 images. Of note, MRI abnormalities attenuated in later post-immunization phase. Neuropathological analysis confirmed the presence of macrophages/microglial activation in EAE mice, consistent with the in vivo increase of 18F-VC701 uptake.

Conclusions

Increase of 18F-VC701 uptake in brain and spinal cord of EAE mice is strongly associated with the presence of microglia activation in the acute phase of the disease. The combined use of TSPO-PET and MRI provided complementary evidence on the ongoing disease process, thus representing an attractive new tool to investigate neuronal damage and neuroinflammation at preclinical levels, particularly in the perspective of using PET/MRI scanners.

References

  1. Mol Imaging. 2015;14. doi: 10.2310/7290.2015.00007.

Acknowledgement

The research leading to these results has received funding from the European grant agreement n° HEALTH-F2-2011-278850 (INMiND) and from the Italian Ministry of Research (MIUR) with the “Cluster Tecnologico Nazionale Scienze della Vita ALISEI”, C.F. 97703670154.

Keywords: EAE monophasic model, neuroinflammation, TSPO-PET, MRI, Multiple Sclerosis
# 147

Monitoring Neuroinflammation with the TSPO tracer [18F]VC701, after LPS systemic administration in male/female adult and aged mice. (#443)

S. Belloli1, 2, V. Murtaj2, 3, 4, M. Pannese5, C. Monterisi2, 4, V. Masiello2, L. Gianolli2, P. Panina-Bordignon5, 6, R. M. Moresco2, 4, 6

1 CNR, Institute of Molecular Bioimaging and Physiology, Segrate (MI), Italy
2 IRCCS San Raffaele Scientific Institute, Experimental Imaging Center, Milan, Italy
3 University of Milano-Bicocca, PhD Program in Neuroscience, Monza (MB), Italy
4 University of Milan-Bicocca, Department of Medicine and Surgery, Monza (MB), Italy
5 IRCCS San Raffaele Scientific Institute, Division of Genetics and Cell Biology, Milano, Italy
6 Interfaculty Centre for Gender Study, San Raffaele Vita e Salute University, Milano, Italy

Introduction

Neuroinflammation is widely studied in many neurodegenerative diseases, including Alzheimer’s and Parkinson’s disease, in which age play a crucial role. Aging process may be considered the result of environmental and genetic factors. Aim of the study is monitoring of brain inflammation and its modulation by gender and age after systemic administration of LPS. To this end, we evaluated microglia activation by ex vivo biodistribution with the Translocator protein (TSPO) specific radiotracer [18F]VC701 and by inflammatory cytokines expression.

Methods

[18F]VC701 biodistribution was measured at 6 hours after systemic injection of LPS/vehicle in adult (2-3 months old) and aged (17-19 months old) C57BL/6 male and female mice. Two hours after the i.v. injection of 173±31 µCi of the tracer, animals were sacrificed and specific brain regions (cortex, hippocampus and cerebellum) collected for gamma counting and RT-PCR analysis of different markers of inflammation.

Results/Discussion

Basal [18F]VC701 uptake in cortex and hippocampus of young females resulted significantly lower than that of young males (gender difference). Peripheral challenge with LPS induced a significant increase of [18F]VC701 uptake in cortex and cerebellum of aged male mice (p<0.05 vs ctrl). No significant increase of tracer uptake was observed in aged female mice compared to age-matched controls. In addition, LPS didn’t induce radioligand uptake increase in young animals, considering both males and females. Measurements of cytokines transcripts showed higher IL-1β and TNF-α mRNAs expression in both male and female aged mice treated with LPS compared to corresponding young animals. Interestingly, aged male mice showed a greater IL-1β mRNAs expression compared to aged female mice, while no gender difference was observed for TNF-α expression. LPS induce striatal decrease of TREM-2 expression in adult male mice and a decrease of the messanger in all the areas examined in aged males and females.

Conclusions

The results of this study confirmed an exaggerated response of the aged brain to a peripheral inflammatory challenge that could be detected in vivo by PET imaging with TSPO ligands as [18F]VC701 and post mortem by RT-PCR. This analysis showed also a different response to brain insult between males and females, confirming the sex differences observed in some human neurodegenerative disorders as AD.

Acknowledgement

The research leading to these results has received funding from the European grant agreement n° HEALTH-F2-2011-278850 (INMiND) and from the Italian Ministry of Research (MIUR) with the “Cluster Tecnologico Nazionale Scienze della Vita ALISEI”, C.F. 97703670154.

Keywords: Inflammation, aging, LPS, PET imaging, gender analysis
# 148

Dedicated volumetric analysis of the spatiotemporal interaction of activated microglia and MMPs in ischemic stroke (#525)

C. Barca1, C. Foray1, S. Hermann1, M. Schäfers1, 2, A. H. Jacobs1, 2, B. Zinnhardt1, 2

1 Westfälische Wilhelms University Münster, European Institute for Molecular Imaging (EIMI), Münster, North Rhine-Westphalia, Germany
2 Universitätsklinikum Münster, Department of Nuclear Medicine, Münster, North Rhine-Westphalia, Germany

Introduction

In vivo positron emission tomography (PET) using [18F]DPA-714 and [18F]BR-351 allows non-invasive assessment of the spatiotemporal expression of the translocator protein (TSPO)1 and matrix metalloproteinases (MMPs)2 respectively. Our work showed MMPs preceded microglial activation ([18F]DPA-714)3. However, the overall spatial relation of both imaging biomarkers remains to be elucidated.

Therefore, we aimed (i) to assess the temporal distribution of [18F]DPA-714 and [18F]BR-351 and (ii) to investigate their spatial interaction in a tMCAO mouse model using a dedicated volumetric analysis.

Methods

As described by Zinnhardt et al. (2015), a total of n=28 C57BL/6 mice underwent combined PET-CT and subsequent MR imaging for both [18F]DPA-714 and [18F]BR-351 to assess microglia activation and MMP activity 24-48 hours (n=8), 7 ± 1 days (n=7), 14 ± 1 days (n=6) and 21 ± 1 days (n=7) after a 30 min tMCAo. In the current work, the same dataset was analyzed using an improved volumetric approach: an ipsilesional hemisphere atlas based VOI was applied to PET-CT co-registered imaging data and thresholded by the mean uptake + 2.5*standard deviation (sd) of contralateral striatum. Mean lesion-to-contralateral (L/C) ratios, percentages of overlap and exclusive tracer uptake areas were determined. The relation of both tracer volumes to the lesion extent depicted by T2w MRI is been investigated.

Results/Discussion

[18F]BR-351 uptake significantly increase as early as day 7 (ANOVA, L/C: 2.08±0.18, p=0.043) while [18F]DPA-714 uptake peaked at day 14 (ANOVA; L/C: 2.17 ± 0.41; p=0.011) (Fig. 1). Volumetric data analysis showed [18F]BR-351 total voxel numbers (paired t-test, 190 ± 164, p<0.001) to be smaller than for [18F]DPA-714 (488 ± 288) in the ipsilesional hemisphere, indicative of a more extended microglial activation compared to MMPs (Fig. 2). 

Tracer volumes showed a constant overlap of 14.0 ± 14.2% over time (ANOVA, p=0.255). 82.4 ± 16.1 % of the total [18F]DPA-714 volumes were exclusive and non-overlapping with [18F]BR-351, whereas 50.5 ± 33.6% [18F]BR-351 volumes were exclusive for [18F]BR-351. This indicates both mechanisms to be partly independent. Published in vitro data 4,5,6 already suggested partly differential expressions but this has never been tracked by in vivo PET imaging.

Conclusions

The improved volumetric approach allows dedicated analysis of spatial dynamics of MMPs and microglia activation in ischemic lesion. Our results indicated a primary MMPs activation independent of microglia while later expression may be sustained by activated microglia in specific overlapping regions of the damaged tissue.

References

1 Chen MK, Guilarte TR. Translocator protein 18 kDa (TSPO): molecular sensor of brain injury and repair. Pharmacol Ther 2008; 118:1-17.

2 Wagner S, Faust A, Breyholz HJ, Schober O, Schafers M, Kopka K. The MMP inhibitor (R)-2-(N-benzyl-4-(2-[18F]fluoroethoxylphenylsulphonamido)-N-hydroxy-3-methylbuta namide: Improved precursor synthesis and fully automated radiosynthesis. Appl Radiat Isot 2011; 69: 862-868.

3 Zinnhardt B, Viel T, Wachsmuth L, et al. Multimodal imaging reveals temporal and spatial microglia and matrix metalloproteinase activity after experimental stroke. J Cereb Blood Flow Metab. 2015; 35:1711–1721.

4 Romanic AM, White RF, Arleth AJ, Ohlstein EH, Barone FC. Matrix metalloproteinase expression increases after cerebral focal ischemia in rats: inhibition of matrix metalloproteinase-9 reduces infarct size. Stroke 1998; 29: 1020-1030.

5 Magnoni S, Baker A, George SJ, Duncan WC, Kerr LE, McCulloch J, Horsburgh K (2004) Differential alterations in the expression and activity of matrix metalloproteinases 2 and 9 after transient cerebral ischemia in mice. Neurobiol Dis 17:188–97

6 Rivera S, Ogier C, Jourquin J, Timsit S, Szklarczyk AW, Miller K, Gearing AJ, Kaczmarek L, Khrestchatisky M (2002) Gelatinase B and TIMP-1 are regulated in a celland time-dependent manner in association with neuronal death and glial reactivity after global forebrain ischemia. Eur J Neurosci 15:19–32

Figure 1. Quantification of PET imaging data.
[18F]BR-351 peak uptake ratio (light gray) was observed at day 7 and still elevated at day 21 after tMCAO (*p<0.05). [18F]DPA-714 uptake ratio (black) peaked at day 14, with a slight decrease at day 21 (*p<0.05).
Figure 2. Volumetric analysis of tracers uptake over time

(A) [18F]DPA-714 signal (black) after thresholding showed larger number of voxels compared to [18F]BR-351 (light gray), except at 24-48H (*p<0.05, ***p<0.001). (B) Representative images of spatiotemporal distribution of both [18F]DPA-714 (yellow) and [18F]BR-351 (red) tracers in the lesioned area at different time points in different mice (24-48 h, 7, 14 and 21 days) after tMCAo.

Keywords: microglia, matrix metalloproteases, positron emission tomography, stroke
# 149

Dedicated volumetric analysis of the spatiotemporal interaction of activated microglia and experimental glioma during therapy (#544)

C. Foray1, 4, S. Valtorta7, 8, 9, C. Barca1, 4, M. Schäfers1, 5, 6, R. M. Moresco7, 8, 9, A. H. Jacobs1, 3, 4, B. Zinnhardt1, 2, 4

1 European Institute for Molecular Imaging - EIMI, Münster, Germany
2 Imaging Neuroinflammation in Neurodegenerative Diseases (INMIND) EU FP7 consortium, Münster, Germany
3 Department of Geriatrics, Johanniter Hospital, Evangelische Kliniken, Bonn, Germany
4 PET Imaging in Drug Design and Development (PET3D), Münster, Germany
5 Cells in Motion (CiM) Cluster of Excellence, Münster, Germany
6 University Hospital Muenster, Department of Nuclear Medicine, Münster, Germany
7 Tecnomed Foundation and Medicine and Surgery Department, University of Milan-Bicocca, Milan, Italy
8 Experimental Imaging Center, IRCCS San Raffaele Scientific Institute, Milan, Italy
9 SYSBIO.IT, Centre of Systems Biology, Milan, Italy

Introduction

Gliomas are the most aggressive malignant brain tumors in adults. Despite treatment options such as surgery and chemotherapy patients have a poor prognosis. The translocator protein TSPO, marker of glioma cells and associated microglial activation, is considered to be a key factor of tumor invasion and malignancy. In this study non-invasive MRI/PET imaging of TSPO by [18F]DPA-714 and tumor growth ([18F]FET) was performed to validate TSPO as diagnostic imaging biomarker in gliomas and to monitor the suitability of the combination of biomarkers in temozolomide (TMZ)-mediated treatment response.

Methods

N=12 female NMRI nude mice underwent MRI and PET/CT scans after intra-striatal implantation of 2x10^5 Gli36ΔEGFR-LITG glioma cells. 10 days p.i. mice were treated with 50 mg/kg of TMZ intraperitoneally in DMSO for 5 days. The control group was injected with vehicle only. All mice were subjected to PET imaging at d0 (basal levels) and at d6 (after treatment) with [18F]DPA-714 (TSPO; 20 MBq; 60 min p.i.) and [18F]FET (amino acid transport; 10 MBq, 20 min p.i.). PET/CT and MR images were co-registered using the skull contour and MRI brain volume of the mice. Tumor-to-background uptake ratios (T/B) were calculated by dividing the mean radiotracer uptake by the mean radiotracer uptake in the contralateral hemisphere. After the last scan, brains were harvested for histological analysis.

Results/Discussion

In DMSO treated animals the T/B ratio (Tmean/Bmean 0.37±0.05; p<0.01) for [18F]FET and the [18F]FET-derived tumor volume (0.025±0.005 cm³/ml; p< 0.001) were significantly increased at day 6. TMZ treatment significantly reduced the [18F]FET T/B ratio (Tmean/Bmean 0.229±0.07; p<0.01) as well as the tumor volume comparing day 0 and 6 (0.02±0.005; p<0.01)(Fig. 1).

The volumetric analysis of unique tracers uptake areas indicated an increase in [18F]FET between day 0 and day 6 in DMSO treated group whereas in TMZ treated mice the signal is reduced. TMZ treatment significantly decreased unique [18F]FET areas comparing DMSO and TMZ groups at day 6 (35.2±7.1; p<0.01; Fig. 2 A).

Unique [18F]DPA-714 areas were significantly reduced in DMSO treated mice (12.1±7,7; p<0.05), whereas a significant increase was observed over time in TMZ treated mice (31.1±11; p<0.05).

The increase in [18F]DPA-714 signal is more pronounced between DMSO and TMZ treated groups at day 6 (41.5±2.2; p<0.001; Fig. 2 B).

Conclusions

The combination of [18F]FET and [18F]DPA-714 imaging biomarkers with MRI allows for the imaging of glioma growth and glioma-associated inflammation. TMZ-induced therapy effects can be detected non-invasively with [18F]FET, represented by the decrease of tumor growth. In the case of [18F]DPA-714, therapeutic effects may partially  be masked by TMZ-induced microgliosis.

Quantitative analysis of [18F]FET and [18F]DPA-714 T/B uptake ratios and tumor volume

Fig.1 A) Quantitative analysis of changes in [18F]FET and [18F]DPA-714 T/B uptake ratio after 6 days from the beginning of the therapy with DMSO (vehicle) and 50 mg/kg TMZ . B) Quantitative analysis of the changes in tumor volume (cm3/ml) after 6 days of therapy with TMZ. Differences between the treated (TMZ) and control (DMSO) groups were tested for significance using t-Test.

Volumetric analysis of unique tracers uptake areas
Fig.2 Quantitative analysis of changes in [18F]FET and [18F]DPA-714 tracers uptake volumes in DMSO and TMZ treated groups. Differences were tested for significance using t-Test. Data are represented as mean±SD.
Keywords: positron emission tomography, glioma, TSPO, FET
# 150

In vivo imaging of α7 nicotinic receptors as a novel method to monitor neuroinflammation after cerebral ischemia (#245)

L. Colás1, M. Domercq2, P. Ramos-Cabrer1, V. Gómez-Vallejo1, A. Palma2, D. Padro1, S. Plaza-García1, K. R. Pulagam1, M. Higuchi3, C. Matute2, J. Llop1, A. Martin1

1 CICbiomaGUNE, San Sebastián, Spain
2 Achucarro-University of the Basque Country, Leioa, Spain
3 QST-NIRS, Chiba, Japan

Introduction

In vivo positron emission tomography (PET) imaging of nicotinic acetylcholine receptors (nAChRs) is a promising tool for the imaging evaluation of neurologic and neurodegenerative diseases. However, the role of α7 nAChRs after brain diseases such as cerebral ischemia and its involvement in inflammatory reaction is still largely unknown.

Methods

In vivo and ex vivo evaluation of α7 nAChRs expression after transient middle cerebral artery occlusion (MCAO) was carried out using PET imaging with [11C]NS14492 and immunohistochemistry (IHC). Pharmacological activation of α7 receptors was evaluated with magnetic resonance imaging (MRI), [18F]DPA-714 PET, IHC, real time polymerase chain reaction (qPCR) and neurofunctional studies.

Results/Discussion

In the ischemic territory, [11C]NS14492 signal and IHC showed an expression increase of α7 receptors in microglia and astrocytes after cerebral ischemia. The role played by α7 receptors on neuroinflammation was supported by the decrease of [18F]DPA-714 binding in ischemic rats treated with the α7 agonist PHA 568487 at day 7 after MCAO. Moreover, compared to non-treated MCAO rats, PHA-treated ischemic rats showed a significant reduction of the cerebral infarct volumes and an improvement of the neurologic outcome. PHA treatment significantly reduced the expression of cellular adhesion molecules in MCAO rats and in endothelial cells after in vitro ischemia. Despite that, the activation of α7 nAChR had no influence to the blood brain barrier (BBB) permeability measured by MRI.

Conclusions

Taken together, these results suggest that the nicotinic α7 nAChRs play a key role in the inflammatory reaction and the leukocyte recruitment following cerebral ischemia in rats.

Keywords: [11C]NS14492; [18F]DPA-714; PET; cerebral ischemia; MRI; neuroinflammation
# 151

Mouse models of Tauopathy exhibit significant decline in Fludeoxyglucose (18FDG) metabolism using micro-positron emission tomography (µPET) and computed tomography (µCT) imaging (#468)

S. L. Mendoza1, E. M. Blessing1, Y. Lin1, R. Bartlett1, E. Sigurdsson1, Y. Wadghiri1

1 NYU School Of Medicine, New York, New York, United States of America

Introduction

18FDG PET/CT is an integral part of the clinical diagnosis of Alzheimer’s disease (AD) in which hypometabolism is observed in several brain regions [1-3]. Genetically engineered mice modelling AD have been critical in better understanding this devastating disease. While 18FDG-PET has been used to study amyloid-β models[4], there has been little research investigating Tau pathology. In this study, we aimed to examine whole brain 18FDG-PET metabolism in two mouse models of Tauopathy known to exhibit age-dependent Tau pathology and compare them to wildtype age–matched controls.

Methods

Animals: Two Tau models (htau/PS1[5] and JNPL3[6]) and C57Bl/6 wildtype serving as control were split into two age groups for comparison between early and advanced stages of the pathology (see summary table in Figure 1.A). µPET Imaging: All mice were examined under isoflurane (1.0-3.0% in air) on a Siemens Inveon scanner after fasting for at least 8 hours. Subjects imaging while maintained under a heating pad set to 38oC. The scan consisted of a 60 minute µPET acquisition following the injection of 18FDG (300-400 µCi dose diluted into a 200µL volume of physiological saline) via the femoral artery using a infusion pump (rate: 60 µL/min, PHD2000, Harvard Apparatus). A 100-µm µCT scan was systematically acquired after each µPET to assess the attenuation correction for the 18FDG datasets.

Results/Discussion

Time activity curves were obtained from a region of interest placed over the entire brain of the µPET datasets. The Inveon research workplace (IRW) was used to measure the average standard uptake value (SUV) within the steadiest time window and corresponding to the interval between 25 minutes and 35 minutes. Figure 1.B illustrates the comparison of the mean SUV of 18FDG uptake between JNPL3 mice (SUV=1.75, n=6), Htau mice (SUV=1.46, n=6) and WT controls (SUV=1.66, n=5). There was no significant difference observed between these three groups at the young age. In contrast, Figure 1.C show that WT mouse group exhibited an 18FDG uptake (SUV =1.98, n=10) that was significantly greater than both Tau models, JNPL3 mice (SUV=1.69, n=16, p<0.010, t-test) and Htau mice (SUV=1.53, n=9, p<0.010, t-test).  Figure 2 shows a color-coded overlay of the 18FDG uptake within the µCT anatomical context illustrated in three orientations corresponding to A) WT, B) HTau and C) JNPL3 groups.

Conclusions

The two mouse models Htau/PS1 and JNPL3 at the early stage of the Tau pathology didn’t exhibit any significant difference in SUV uptake of 18FDG using PET between both groups or when compared with the age-matched WT control. However, at an advanced stage of the pathology, the SUV uptake in the whole brain of the older wild type mice was significantly higher than the Tau mouse models.

References

1.De Leon MJ, Convit A, Wolf OT, et al. Prediction of cognitive decline in normal elderly subjects with 2-[F-18]fluoro-2-deoxy-Dglucose/positron-emission tomography (FDG/PET). Proc Natl AcadSci USA 2001;98:10966–71

2.Silverman DHS, Small GW, Chang CY, et al. Positron emission tomography in evaluation of dementia—Regional brain metabolism and long-term outcome. JAMA 2001;286:2120–27

3.Fan Ding1, Jia Yao1, Jamaica R. Rettberg2, Shuhua Chen1, et al. Early Decline in Glucose Transport and Metabolism Precedes Shift to Ketogenic System in Female Aging and Alzheimer’s Mouse Brain: Implication for Bioenergetic Intervention. PloS one, 2013

4. Lewis J, McGowan E, Rockwood J, Melrose H, Nacharaju P, Van Slegtenhorst M, Gwinn-Hardy K, Paul Murphy M, Baker M, Yu X, Duff K, Hardy J, Corral A, Lin WL, Yen SH, Dickson DW, Davies P, Hutton M. Neurofibrillary tangles, amyotrophy and progressive motor disturbance in mice expressing mutant (P301L) tau protein. Nat Genet. 2000 Aug;25(4):402-5. PubMed.

5. Allal Boutajangout, David Quartermain and Einar M. Sigurdsson. Immunotherapy Targeting Pathological Tau Prevents Cognitive Decline in a New Tangle Mouse Model. Journal of Neuroscience 8 December 2010, 30 (49) 16559-16566

Acknowledgement

This work was partially funded by an NIH/NIA R01 NIH AG032611 and AG020197 to EMS. It was performed at the Preclinical imaging core; a shared resource partially supported by the NYUCI Center Support Grant, “NIH/NCI 5P30CA016087”, the NIBIB Biomedical Technology Resource Center (NIH P41 EB017183) and by NIH grant UL1 TR00038 from the National Center for Advancing Translational Sciences (NCATS).

Figure 1
Figure 2
# 152

Validation of the Poly I: C model of schizophrenia in females: in vivo neuroimaging studies (#419)

H. Rojas1, M. Casquero-Veiga1, M. Desco Menéndez3, 1, 4, M. L. Soto-Montenegro1, 2

1 Instituto de Investigación Sanitaria Gregorio Marañón, Laboratorio de Imagen Médica, Unidad de Medicina y Cirugía Experimental, Madrid, Spain
2 CIBER de Salud Mental (CIBERSAM), Madrid, Spain
3 Universidad Carlos III de Madrid, Departamento de Bioingeniería e Ingeniería Aeroespacial, Leganés, Spain
4 Centro Nacional de Investigaciones Cardiovasculares (CNIC), Madrid, Spain

Introduction

Maternal immune activation is considered an enviromental factor which increases the risk of suffering from schizophrenia in the offspring. Recently, we have characterized the maternal immune stimulation (MIS) animal model of schizophrenia in males and demonstrated that MIS affects metabolic brain activity, neurotransmission and sensorimotor gating, in a maturation-dependent manner. The aim of this work is to validate the MIS model in females by positron emission tomography with [18F]-deoxyglucose (FDG-PET), and structural magnetic resonance imaging studies (MR).

Methods

In GD15, PolyI:C (Poly) or saline (Sal) were injected to pregnant Wistar rats. Female offspring (10 saline and 10 Poly) were imaged in a preclinical PET/CT scanner at two temporal points (adolescence and adulthood). FDG (~ 1 mCi) was administered through tail vein and, after a 45 min of uptake period, animals were scanned for 45 min. Images were reconstructed using a 2D-OSEM. Differences in uptake between groups were assessed with Statistical Parametric Mapping software (SPM12). MR images were acquired at adulthood and 7 regions of interest were studied (whole brain, dorsal and ventral hippocampus, prefrontal cortex, caudate-putamen, pituitary and ventricles). MR data was analyzed by a 2 way-ANOVA analysis.

Results/Discussion

At adolescence, Poly I:C offspring showed increased uptake in the cerebellum and inferior colliculus  (K=778, p<0.001, T=4.91) and reduced uptake in the retrosplenial (K=117, p=0.001, T= 3.82) and perirhinal cortex (K=145, p=0.007, T=2.71) compared to saline offspring. At adulthood, PolyI:C offspring showed increased metabolism in the olfactory bulb (K=237, p=0.003, T=3.18) and reduced metabolism in the thalamus and dorsal hippocampus (K=364, p=0.004, T=2.69) compared to saline offspring. No significant brain volume changes were found in the ROI analysis although a tendency was found in the hippocampus and the pituitary gland.

 

Conclusions

The metabolic and volumetric changes found in the MIS animals are not associated with the changes found in the MIS model in males and schizophrenic patients. Taking into account that schizophrenia onset in women occurs later than in men, it would be interesting to extend this study to other stages of adult development. Therefore, our results suggest that the MIS model in females might not be appropriate for the study of threrapeutic preventive strategies in schizophrenia.

References

Paxinos G, Watson C. The Rat Brain in Stereotaxic Coordinates. 1998.

Acknowledgement

This work was supported by supported by the Ministry of Economy and Competitiveness ISCIII-FIS grants (PI14/00860, PI17/01766, CPII/00005), co-financed by ERDF (FEDER) Funds from the European Commission, “A way of making Europe”,  Delegación del Gobierno para el Plan Nacional sobre Drogas, Comunidad de Madrid (BRADE-CMS2013/ICE-2958) and Fundación Alicia Koplowitz (FAK 16/01).

Figure 1. - Brain metabolic changes in the MIS female offspring.
Colored PET overlays on MR reference indicate increased [18F]FDG uptake (hot colors) or decreased (cold colors) in the Poly I:C offspring compared to saline offspring, in adolescence (Left) and adulthood (Right). Stereotaxic space of Paxinos & Watson (1998). The color bars represent the T values corresponding to lower and higher FDG uptake.
Keywords: schizophrenia, maternal immune stimulation (MIS), Poly I:C acid, females, positron emission tomography (PET), magnetic resonance imaging (MRI)
# 153

Characterisation of microstructural alterations in a weight drop mTBI rat model: a longitudinal diffusion MRI and histological analysis (#100)

K. Braeckman1, B. Descamps1, L. Pieters3, K. Caeyenberghs2, C. Vanhove1

1 Ghent University, Infinity lab/Medical Imaging and Signal Processing Group, Gent, Belgium
2 Australian Catholic University, The Centre of Disability and Development Research, Melbourne, Australia
3 Ghent University, Department of Basic Medical Sciences, Gent, Belgium

Introduction

Traumatic brain injury (TBI) is the leading cause of acquired disability in young adults, often caused by traffic accidents or sport injuries1. Mild TBI (mTBI) is the most common type of TBI. While conventional scans (CT or anatomical MRI) cannot image the diffuse and subtle injury in mTBI, the patients can have chronic cognitive defects even years after their injury. Due to the lack of specificity of DTI metrics for histological features2, the aim of this study is to characterise microstructural changes with advanced diffusion MRI analysis and link the findings to the histological analysis.

Methods

10 female Wistar rats sustained mTBI utilizing a weight drop model3, the other 10 received a sham injury. MRI data were acquired on a 7T MRI-scanner (Bruker) before, 1 day, 1 week and 3 months after injury. T2-weighted images were acquired for anatomical reference. Multi-shell diffusion data were acquired (b=800, 1500 and 2000 s/mm2; 32, 46 and 64 directions). The diffusion kurtosis tensor was estimated in corrected DWI images4,5 and maps for the diffusion, kurtosis and white matter metrics were calculated6,7. A VOI analysis was performed in the hippocampus, cingulum, cortex and corpus callosum. Rats were sacrificed and perfused with 4% PFA 1 day (n=3), 1 week (n=4) and 3 months (n=12) after impact. Sections of the brain were stained with anti-SYN, Luxol Fast Blue, anti-GFAP and anti-NF. 

Results/Discussion

RK showed a significant decrease after 1 day and 1 week post injury in the corpus callosum, cingulum and hippocampus only in the TBI group. In the cortex, there was a significant decrease in AK after 1 week. Also, the AWF was significantly decreased in all 4 ROIs one week after impact, only in the TBI group (Fig 1). The decrease in kurtosis could indicate a loss of organisation in the microstructure. Furthermore, the general decrease in AWF suggests axonal damage. Unfortunately, no differences between the 2 groups were found for those metrics on any timepoint. Histological analysis revealed a near significant increase in NF in the cingulum and GFAP in the cortex 1 day post injury (p=0.064 and p=0.064)(Fig 2). Indeed, in the cortex there was a near significant increase in GFAP expression 1 day post impact which is associated with inflammation. The increase in NF expression in the cingulum demonstrates a higher amount of dephosphorylated neurofilament, possibly leading to compaction.

Conclusions

Longitudinal changes in DKI and white matter metrics can be used to investigate the recovery process in the brain after a mild TBI. The RK and AWF showed a significant decrease only in the TBI group, 1 week after impact. This can be explained by a compromise in tissue microstructure accompanied by inflammation, such that axons cannot function properly.

References

  1. Thurman. The Epidemiology of Traumatic Brain Injury in Children and Youths: A Review of Research Since 1990. J Child Neurol. 2016; 31(1):20-27.
  2. Jones, et al. White matter integrity, fiber count, and other fallacies: The do's and don'ts of diffusion MRI. NeuroImage. 2013; 73:239-254.
  3. Marmarou, et al. A new model of diffuse brain injury in rats Part I: Pathophysiology and biomechanics. J Neurosurg. 1994; 80:291-300.
  4. Leemans, et al. ExploreDTI: a graphical toolbox for processing, analyzing, and visualizing diffusion MR data. Proceedings 17th Scientific Meeting, International Society for Magnetic Resonance in Medicine; 2009.
  5. Veraart, et al. Weighted linear least squares estimation of diffusion MRI parameters: strengths, limitations, and pitfalls. NeuroImage. 2013; 81:335-346.
  6. Veraart, et al. More Accurate Estimation of Diffusion Tensor Parameters Using Diffusion Kurtosis Imaging. MRM. 2011; 65:138-145.
  7. Fieremans, et al. White matter characterization with diffusional kurtosis imaging, NeuroImage, 2011; 58(1):177-188.
Fig 1
Change in axonal water fraction (AWF) from baseline in the corpus callosum, hippocampus, cingulum and cortex for the TBI and sham group. *p<0.05 compared to baseline. §p<0.05 compared to 1 day. #p<0.05 compared to 1 week.
Fig 2
Staining area of anti-neurofilament (NF) in the cingulum (A) and anti-glial fibrillary acidic protein (GFAP) in the cortex (B) one day post impact.
Keywords: TBI, DTI, DKI, histology, mTBI, MRI, diffusion