Optical imaging of cardiac reporter gene expression in living rats.
BACKGROUND
Studies of cardiac gene transfer rely on postmortem analysis using histologic staining or enzyme assays. Noninvasive imaging of the temporal and spatial characteristics of cardiac gene expression in the same subject offers significant advantages.


RESULTS
Rats underwent direct myocardial injection via left thoracotomy with adenovirus-expressing firefly luciferase (Ad-CMV-Fluc; n=30). The reporter substrate D-luciferin was injected intraperitoneally. Serial images were acquired by use of a cooled charged couple detector (CCD) camera. Results are expressed as relative light unit per minute (RLU/min). Rats transduced with 1x10(9) plaque-forming units show decremental cardiac luciferase activity over time: 152 070+/-21 170 (day 2), 195 806+/-62 630 (day 5), 7250+/-2941 (day 8), and 2040+/-971 RLU/min (day 14). To assess the detection sensitivity, serially diluted titers of Ad-CMV-Fluc were injected: 1x10(9) (195 393+/-14 896), 1x10(8) (33 777+/-18 179), 1x10(7) (417+/-91), 1x10(6) (185+/-64), 1x10(5) (53+/-1), and control (54+/-1) (P<0.05 for 1x10(9), 1x10(8), and 1x10(7) plaque-forming units versus control adenovirus-expressing mutant thymidine kinase [Ad-CMV-HSV1-sr39tk]; n=3). Finally, rats were euthanized, and in vitro luciferase activity correlated with in vivo CCD signals (r2=0.92).


CONCLUSIONS
This study demonstrates for the first time the feasibility of imaging the location, magnitude, and time course of cardiac reporter gene expression in living rats. Cardiac gene therapy studies could be aided with wider application of this approach.
Wu
Joseph C
JC
Crump Institute for Molecular Imaging and Department of Medicine, Division of Cardiology, UCLA School of Medicine, Los Angeles, Calif, USA.
Inubushi
Masayuki
M
Sundaresan
Gobalakrishnan
G
Schelbert
Heinrich R
HR
Gambhir
Sanjiv S
SS
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D003952:Diagnostic Imaging / Q000295:instrumentation / Q000379:methods*; D004333:Drug Administration Routes; D005240:Feasibility Studies; D049454:Firefly Luciferin / Q000008:administration & dosage; D015870:Gene Expression / Q000502:physiology*; D017930:Genes, Reporter / Q000502:physiology*; D005822:Genetic Vectors / Q000008:administration & dosage / Q000235:genetics / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D008156:Luciferases / Q000008:administration & dosage / Q000235:genetics / Q000378:metabolism; D008163:Luminescent Measurements; D009206:Myocardium / Q000378:metabolism*; D055095:Optics and Photonics; D051381:Rats; D017207:Rats, Sprague-Dawley; D012044:Regression Analysis; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014161:Transduction, Genetic
D049454:Firefly Luciferin; D008156:Luciferases