Aim: Experimental autoimmune encephalomyelitis (EAE), an animal model of Multiple Sclerosis, provides a powerful tool to investigate in vivo neuroinflammation with micro-PET and new translocator protein (18 kDa) (TSPO) radioligands. Here we have evaluated the feasibility of imaging cerebral glial activation in a mouse model of relapsing-remitting (RR) EAE using PET and [18F]DPA-714. Methods: SJL/J females mice 6 weeks old were immunized subcutaneously with PLP139-151 peptide in complete Freund's adjuvant. Pertussis toxin was injected intraperitoneally (the same day of immunization and 1 day later). Naive females SJL/J mice and mice injected with saline-complete Freund's adjuvant were used as controls. PET-CT (GE Explore Vista, PET spatial resolution=1.6 mm) studies were performed under general anesthesia (Isoflurane 2% Oxygen, 2 L/min) in 8 EAE mice in the acute phase (12 -16 days after immunization) at different clinical stages (score range:1-4) and in 6 controls. Images were acquired in dynamic 3D mode over 30 minutes starting 20 minutes after tail vein injection of 5-10 MBq (SRA:200-800 GBq/?mol). ROIs were manually defined based on CT images on the cerebellum, brainstem, olfactory bulb and the frontal cortex using PMOD software. Cerebellar, brainstem and olfactory bulb uptakes were normalized to those of the frontal cortex. Statistical analysis was performed using Student's t-test and Pearson correlation. Hematoxylin-eosin stain was used to assess the presence of inflammatory infiltrates during the acute phase in the brain, cerebellum and spinal cord Results: In the EAE mice, [18F]DPA-714 uptake was significantly increased (p<0.02) in the cerebellum (1.885±0.340), brainstem (1.972±0.292) and OB (1.535±0.122) compared to controls (cerebellum: 1.409±0.295; brainstem=1.586±0.162; OB=1.205±0.235). Increased [18F]DPA-714 uptake in the cerebellum and brainstem but not in the OB was associated with increased clinical scores (p<0.05). Conclusions: These preliminary results suggest that increased cerebral [18F]DPA-714 uptake can be measured with microPET in a mouse model of RR-EAE in regions known to be the site of increased TSPO expression and/or glial activation. The increase of [18F]DPA-714 binding seems to be related to the degree of clinical severity. Future studies are required to characterize by immunohistochemistry the cellular correlates of increased radiotracer uptake in specific brain regions. Aknowledgement The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement n° HEALTH-F2-2011-278850 (INMiND).
PET imaging of brain TSPO expression in a mouse model of Experimental Autoimmune Encephalomyelitis using [18F]DPA-714
A Zannetti;CVicidomini;S Gargiulo;M Gramanzini;
2014
Abstract
Aim: Experimental autoimmune encephalomyelitis (EAE), an animal model of Multiple Sclerosis, provides a powerful tool to investigate in vivo neuroinflammation with micro-PET and new translocator protein (18 kDa) (TSPO) radioligands. Here we have evaluated the feasibility of imaging cerebral glial activation in a mouse model of relapsing-remitting (RR) EAE using PET and [18F]DPA-714. Methods: SJL/J females mice 6 weeks old were immunized subcutaneously with PLP139-151 peptide in complete Freund's adjuvant. Pertussis toxin was injected intraperitoneally (the same day of immunization and 1 day later). Naive females SJL/J mice and mice injected with saline-complete Freund's adjuvant were used as controls. PET-CT (GE Explore Vista, PET spatial resolution=1.6 mm) studies were performed under general anesthesia (Isoflurane 2% Oxygen, 2 L/min) in 8 EAE mice in the acute phase (12 -16 days after immunization) at different clinical stages (score range:1-4) and in 6 controls. Images were acquired in dynamic 3D mode over 30 minutes starting 20 minutes after tail vein injection of 5-10 MBq (SRA:200-800 GBq/?mol). ROIs were manually defined based on CT images on the cerebellum, brainstem, olfactory bulb and the frontal cortex using PMOD software. Cerebellar, brainstem and olfactory bulb uptakes were normalized to those of the frontal cortex. Statistical analysis was performed using Student's t-test and Pearson correlation. Hematoxylin-eosin stain was used to assess the presence of inflammatory infiltrates during the acute phase in the brain, cerebellum and spinal cord Results: In the EAE mice, [18F]DPA-714 uptake was significantly increased (p<0.02) in the cerebellum (1.885±0.340), brainstem (1.972±0.292) and OB (1.535±0.122) compared to controls (cerebellum: 1.409±0.295; brainstem=1.586±0.162; OB=1.205±0.235). Increased [18F]DPA-714 uptake in the cerebellum and brainstem but not in the OB was associated with increased clinical scores (p<0.05). Conclusions: These preliminary results suggest that increased cerebral [18F]DPA-714 uptake can be measured with microPET in a mouse model of RR-EAE in regions known to be the site of increased TSPO expression and/or glial activation. The increase of [18F]DPA-714 binding seems to be related to the degree of clinical severity. Future studies are required to characterize by immunohistochemistry the cellular correlates of increased radiotracer uptake in specific brain regions. Aknowledgement The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement n° HEALTH-F2-2011-278850 (INMiND).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
