Development of In Vivo Imaging Tools for Investigating Astrocyte Activation in Epileptogenesis
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Insights into the dynamic changes in molecular processes occurring in the brain during epileptogenesis can substantially improve our understanding of their pathogenetic relevance. In this context, neuroinflammation is a potential mechanism of epileptogenesis which has recently been investigated in animal models by MRI or PET molecular imaging. Here, we developed an alternative and complementary molecular imaging strategy by designing a serotype 8 recombinant adeno-associated virus (AAV8) harboring promoter fragments of the GFAP or IL-1β promoter and a luciferase reporter gene. Mice were injected intrahippocampally with rAAV8 and treated with intracortical kainic acid to induce status epilepticus (SE) and hence epileptogenesis. In vivo bioluminescence imaging combined with immunohistochemistry revealed a significant activation of the GFAP promoter 24 h and 3 days after kainate-induced SE. For IL-1β, we identified the promoter region required for studying cell-specific induction of the promoter in longitudinal studies. We conclude that the GFAP promoter fragment represents a useful tool for monitoring the in vivo activation of astrocytes with an inflammatory phenotype during epileptogenesis, or under other pathophysiological conditions.
KeywordsIn vivo imaging IL-1β GFAP Epilepsy Adeno-associated viral vectors
We thank Prof. P. Auron for his suggestions on the IL-1β promoter cloning; Y. Wang for assisting with in vivo bioluminescence studies; A.Oprisoreanu for assistance with the virus production; L.Dammer and S.Opitz for technical assistance.
Compliance with Ethical Standards
All experimental procedures were conducted in conformity with institutional guidelines that are in compliance with national (D.L. n.26, G.U. March 4, 2014) and international guidelines and laws (EEC Council Directive 86/609, OJ L 358, 1, December 12, 1987, Guide for the Care and Use of Laboratory Animals, U.S. National Research Council, 1996), and were reviewed and approved by the intramural ethical committee and the University of Bonn Medical Center Animal Care Committee.
The studies were approved by the University of Bonn Medical Center Animal Care Committee and Mario Negri Institute for Pharmacological Research Animal Care Committee.
Conflict of Interest
The authors declare that they have no conflict of interest.
This study was supported by the European Union’s Seventh Framework Programme (FP7/2007–2013) under grant agreement no. 602102 (EPITARGET), the Deutsche Forschungsgemeinschaft (SFB 1089) and Fondazione Italiana per la Ricerca sull’Epilessia (AICE-FIRE). The funding bodies did not participate in the design of the study, data collection and analysis, or preparation of the manuscript.
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