title: Positron emission tomography imaging of cardiac reporter gene expression in living rats.
abstract: BACKGROUND
  Imaging reporter gene expression is useful for noninvasive monitoring of gene therapy. In this study, we imaged cardiac reporter gene expression in living rats using micro positron emission tomography (microPET).
  
  
  RESULTS
  Rats (n=10) underwent intramyocardial injection with 1x10(9) pfu of adenovirus carrying cytomegalovirus promoter-driving herpes simplex virus type 1 mutant thymidine kinase (Ad-CMV-HSV1-sr39tk) as PET reporter gene. Control rats (n=4) received 1x10(9) pfu of adenovirus carrying cytomegalovirus promoter-driving firefly luciferase (Ad-CMV-Fluc). On days 2 to 4, microPET images were obtained after a tail vein injection of nitrogen-13 ammonia ([13N]-NH3) as myocardial perfusion tracer, followed by 9-(4-[18F]-fluoro-3 hydroxymethylbutyl) guanine ([18F]-FHBG) to assess HSV1-sr39tk expression. After imaging, hearts were removed for ex vivo [18F] gamma counting and thymidine kinase enzyme assay. Results show homogenous myocardial distribution of [13N]-NH3 on all microPET images. Rats injected with Ad-CMV-HSV1-sr39tk have significant [18F]-FHBG uptake in the anterolateral wall compared with background signal in controls. Gamma counting shows 20.0+/-4.4-fold increase of radioactivity, whereas enzyme assay shows 22.1+/-6.1-fold increase of thymidine kinase activity in Ad-CMV-HSV1-sr39tk injected rats (P<0.05).
  
  
  CONCLUSIONS
  Successful imaging of cardiac HSV1-sr39tk expression was performed in living rats with microPET. The presence of [18F]-FHBG uptake is confirmed by gamma counting and the presence of HSV1-sr39TK protein by thymidine kinase enzyme assay. Cardiac reporter gene imaging by PET may eventually be applied toward human gene therapy studies.
authors.affiliation: Crump Institute for Molecular Imaging, UCLA School of Medicine, Los Angeles, Calif 90095-1770, USA.
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Wu
authors.forename: Masayuki
authors.initials: M
authors.lastname: Inubushi
authors.forename: Gobalakrishnan
authors.initials: G
authors.lastname: Sundaresan
authors.forename: Heinrich R
authors.initials: HR
authors.lastname: Schelbert
authors.forename: Sanjiv S
authors.initials: SS
authors.lastname: Gambhir
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D002318:Cardiovascular Diseases / Q000628:therapy; D005240:Feasibility Studies; D005462:Fluorine Radioisotopes; D005720:Gamma Rays; D015870:Gene Expression; D017930:Genes, Reporter; D015316:Genetic Therapy; D005822:Genetic Vectors; D006147:Guanine / Q000031:analogs & derivatives*; D006321:Heart / Q000000981:diagnostic imaging*; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013937:Thymidine Kinase / Q000235:genetics / Q000378:metabolism; D014055:Tomography, Emission-Computed / Q000379:methods*
chemical_list: C113308:9-(4-fluoro-3-hydroxymethylbutyl)guanine; D005462:Fluorine Radioisotopes; D006147:Guanine; D013937:Thymidine Kinase