Theranostics 2018; 8(19):5400-5418. doi:10.7150/thno.25572

Research Paper

Identification of new molecular targets for PET imaging of the microglial anti-inflammatory activation state

Alessandro Villa1✉#, Barbara Klein2,3#, Bieneke Janssen4#, Jordi Pedragosa5, Giovanna Pepe1, Bastian Zinnhardt6, Danielle J. Vugts4, Paolo Gelosa7, Luigi Sironi1,7, Wissam Beaino4, Annelaure Damont8, Frédéric Dollé8, Benoit Jego8, Alexandra Winkeler8, Dieter Ory9, Olof Solin10, Johnny Vercouillie11, Uta Funke4,12, Sandra Laner-Plamberger3,13, Linda V. Blomster14, Palle Christophersen14, Elisabetta Vegeto1, Ludwig Aigner2,3, Andreas Jacobs6, Anna M. Planas5, Adriana Maggi1*, Albert D. Windhorst4*

1. Center of Excellence on Neurodegenerative Diseases and Department of Pharmacological and Biomolecular Sciences, University of Milan, Milan, Italy.
2. Institute of Molecular Regenerative Medicine, Paracelsus Medical University, Salzburg, Austria.
3. Spinal Cord Injury and Tissue Regeneration Center (SCI-TReCS), Paracelsus Medical University, Salzburg, Austria.
4. Department of Radiology & Nuclear Medicine, Amsterdam Neuroscience, VU University Medical Center, Amsterdam, the Netherlands.
5. Institut d'Investigacions Biomèdiques Agustí Pi i Sunyer, Barcelona, Spain.
6. European Institute for Molecular Imaging (EIMI), University of Münster, Münster, Germany.
7. Centro Cardiologico Monzino IRCCS, Milan, Italy.
8. IMIV, Service Hospitalier Frédéric Joliot, CEA, Inserm, Université Paris Sud, CNRS, Université Paris-Saclay, Orsay, France.
9. Laboratory for Radiopharmacy, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven, Leuven, Belgium.
10. Radiopharmaceutical Chemistry Laboratory, Turku PET Centre, University of Turku, Turku, Finland.
11. UMRS Inserm U930 - Université de Tours, Tours France
12. BV Cyclotron VU, Amsterdam, the Netherlands.
13. University Clinic for Blood Group Serology and Transfusion Medicine, Paracelsus Medical University, Salzburg, Austria.
14. Saniona A/S, Ballerup, Denmark
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Abstract

Microglia are potential targets for therapeutic intervention in neurological and neurodegenerative diseases affecting the central nervous system. In order to assess the efficacy of therapies aimed to reduce the tissue damaging activities of microglia and/or to promote the protective potential of these cells, suitable pre-clinical and clinical tools for the in vivo analysis of microglia activities and dynamics are required. The aim of this work was to identify new translational markers of the anti-inflammatory / protective state of microglia for the development of novel PET tracers.

Methods: New translational markers of the anti-inflammatory/protective activation state of microglia were selected by bioinformatic approaches and were in vitro and ex vivo validated by qPCR and immunohistochemistry in rodent and human samples. Once a viable marker was identified, a novel PET tracer was developed. This tracer was subsequently confirmed by autoradiography experiments in murine and human brain tissues.

Results: Here we provide evidence that P2RY12 expression increases in murine and human microglia following exposure to anti-inflammatory stimuli, and that its expression is modulated in the reparative phase of experimental and clinical stroke. We then synthesized a novel carbon-11 labeled tracer targeting P2RY12, showing increased binding in brain sections of mice treated with IL4, and low binding to brain sections of a murine stroke model and of a stroke patient.

Conclusion: This study provides new translational targets for PET tracers for the anti-inflammatory/protective activation state of microglia and shows the potential of a rationale-based approach. It therefore paves the way for the development of novel non-invasive methodologies aimed to monitor the success of therapeutic approaches in various neurological diseases.

Keywords: neuroinflammation, microglia, translational markers, radiochemistry, PET tracers.

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How to cite this article:
Villa A, Klein B, Janssen B, Pedragosa J, Pepe G, Zinnhardt B, Vugts DJ, Gelosa P, Sironi L, Beaino W, Damont A, Dollé F, Jego B, Winkeler A, Ory D, Solin O, Vercouillie J, Funke U, Laner-Plamberger S, Blomster LV, Christophersen P, Vegeto E, Aigner L, Jacobs A, Planas AM, Maggi A, Windhorst AD. Identification of new molecular targets for PET imaging of the microglial anti-inflammatory activation state. Theranostics 2018; 8(19):5400-5418. doi:10.7150/thno.25572. Available from http://www.thno.org/v08p5400.htm