1. A Longitudinal PET/MRI Study of Colony-Stimulating Factor 1 Receptor-Mediated Microglia Depletion in Experimental Stroke.
- Author
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Barca C, Kiliaan AJ, Foray C, Wachsmuth L, Hermann S, Faber C, Schäfers M, Wiesmann M, Jacobs AH, and Zinnhardt B
- Subjects
- Animals, Carrier Proteins metabolism, Infarction metabolism, Macrophage Colony-Stimulating Factor metabolism, Magnetic Resonance Imaging methods, Mice, Mice, Inbred C57BL, Positron-Emission Tomography methods, Microglia metabolism, Stroke diagnostic imaging, Stroke drug therapy, Stroke metabolism
- Abstract
Microglia-induced neuroinflammation after stroke contributes to the exacerbation of postischemic damage but also supports neurorestorative events. Longitudinal molecular imaging of microglia-targeted therapies will support the assessment of target engagement, therapy efficacy, and deciphering of the mode of action. We investigated the effects of chronic colony-stimulating factor 1 receptor (CSF-1R) inhibitor-mediated microglia depletion on translocator protein (TSPO)-dependent neuroinflammation and cerebrovascular parameters using PET/MRI. Methods: Forty C57BL/6 mice underwent a 30-min transient occlusion of the middle cerebral artery and were randomly assigned to either a control group or a group treated with CSF-1R inhibitor (PLX5622). Eight mice per group were used for N,N -diethyl-2-(2-(4-(2-
18 F-fluoroethoxy) phenyl)5,7dimethylpyrazolo[1, 5a]pyrimidin-3-yl)acetamide (18 F-DPA-714) (TSPO) PET imaging on days 7, 14, 21, and 30 after ischemia and behavioral tests before and after surgery. An extra group of 8 mice underwent MRI, including T2-weighted (infarct), perfusion-weighted (cerebral blood flow), and diffusion-weighted (water diffusion, cellular density) sequences, on days 1, 3, 7, 14, 21, and 30. Ex vivo analysis (immunoreactivity, gene expression) was performed to characterize the inflammatory environment. Results: We demonstrated that long-term CSF-1R inhibition transiently decreased the TSPO PET signal within the infarct. Residual TSPO activity was partly due to a potentially resistant Iba-1-positive cell populations with low CSF-1R and transmembrane 119 expression. The decrease in selected pro- and antiinflammatory marker expression suggested an apparent global dampening of the neuroinflammatory response. Furthermore, the temporal changes in the MRI parameters highlighted treatment-induced effects on reperfusion and tissue homeostasis, associated with impaired motor function at late stages. Conclusion: Longitudinal TSPO PET/MRI allows the assessment of target engagement and optimization of drug efficiency. PLX5622 has promising immunomodulatory effects, and the optimal therapeutic time window for its application needs to be defined., (© 2022 by the Society of Nuclear Medicine and Molecular Imaging.)- Published
- 2022
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