title: A PET brain reporter gene system based on type 2 cannabinoid receptors.
abstract: PET of gene expression in the brain may greatly facilitate neuroscience research and potential clinical implementation of gene or cell therapy of central nervous system diseases. To date, no adequate PET reporter system is available for the central nervous system because available tracers either do not cross the intact blood-brain barrier or have high background signals. Here we report the first, to our knowledge, PET reporter system for imaging gene expression in the intact brain.
  
  
  METHODS
  We selected the human type 2 cannabinoid receptor (hCB(2)) as a reporter because of its low basal expression in the brain. An inactive mutant (D80N) was chosen so as not to interfere with signal transduction. As a reporter probe we used the (11)C-labeled CB(2) ligand, (11)C-GW405833, which readily crosses the blood-brain barrier. Dual-modality imaging lentiviral and adeno-associated viral vectors encoding both hCB(2)(D80N) and firefly luciferase or enhanced green fluorescent protein were engineered and validated in cell culture. Next, hCB(2)(D80N) was locoregionally overexpressed in rat striatum by stereotactic injection of lentiviral and adeno-associated viral vectors.
  
  
  RESULTS
  Kinetic PET revealed specific and reversible CB(2) binding of (11)C-GW405833 in the transduced rat striatum. hCB(2) and firefly luciferase expression was followed until 9 mo and showed similar kinetics. Both hCB(2) expression and enhanced green fluorescent protein expression were confirmed by immunohistochemistry.
  
  
  CONCLUSIONS
  Dual-modality imaging viral vectors encoding hCB(2)(D80N) were engineered, and the reporter system was validated in different animal species. The results support the potential future clinical use of CB(2) as a PET reporter in the intact brain.
authors.affiliation: Division of Nuclear Medicine, University Hospital and K.U. Leuven, Leuven, Belgium.
authors.forename: Caroline
authors.initials: C
authors.lastname: Vandeputte
authors.forename: Nele
authors.initials: N
authors.lastname: Evens
authors.forename: Jaan
authors.initials: J
authors.lastname: Toelen
authors.forename: Christophe M
authors.initials: CM
authors.lastname: Deroose
authors.forename: Barbara
authors.initials: B
authors.lastname: Bosier
authors.forename: Abdelilah
authors.initials: A
authors.lastname: Ibrahimi
authors.forename: Anke
authors.initials: A
authors.lastname: Van der Perren
authors.forename: Rik
authors.initials: R
authors.lastname: Gijsbers
authors.forename: Peter
authors.initials: P
authors.lastname: Janssen
authors.forename: Didier M
authors.initials: DM
authors.lastname: Lambert
authors.forename: Alfons
authors.initials: A
authors.lastname: Verbruggen
authors.forename: Zeger
authors.initials: Z
authors.lastname: Debyser
authors.forename: Guy
authors.initials: G
authors.lastname: Bormans
authors.forename: Veerle
authors.initials: V
authors.lastname: Baekelandt
authors.forename: Koen
authors.initials: K
authors.lastname: Van Laere
mesh_terms: D000818:Animals; D001921:Brain / Q000000981:diagnostic imaging* / Q000378:metabolism*; D002250:Carbon Radioisotopes; D000229:Dependovirus / Q000235:genetics; D017930:Genes, Reporter / Q000235:genetics*; D005818:Genetic Engineering / Q000379:methods*; D005822:Genetic Vectors / Q000235:genetics; D057809:HEK293 Cells; D006801:Humans; D007211:Indoles / Q000138:chemical synthesis / Q000737:chemistry / Q000493:pharmacokinetics; D008297:Male; D051379:Mice; D009025:Morpholines / Q000138:chemical synthesis / Q000737:chemistry / Q000493:pharmacokinetics; D049268:Positron-Emission Tomography / Q000379:methods*; D011854:Radiochemistry; D051381:Rats; D043885:Receptor, Cannabinoid, CB2 / Q000235:genetics*; D015203:Reproducibility of Results; D013045:Species Specificity
chemical_list: C463040:1-(2,3-dichlorobenzoyl)-5-methoxy-2-methyl-(2-(mopholin-4-yl)ethyl)-1H-indole; D002250:Carbon Radioisotopes; D007211:Indoles; D009025:Morpholines; D043885:Receptor, Cannabinoid, CB2