Imaging Pulmonary Gene Expression with Positron Emission Tomography

• Published in: American journal of respiratory and critical care medicine 2003-05, Vol.167 (9), p.1257-1263
• Main Authors: Richard, Jean-Cristophe, Zhou, Zhaohui, Ponde, Datta E, Dence, Carmen S, Factor, Philip, Reynolds, Paul N, Luker, Gary D, Sharma, Vijay, Ferkol, Tom, Piwnica-Worms, David, Schuster, Daniel P
• Format: Article
• Language: English
• Subjects: Adenoviruses; Analysis of Variance; Animals; Biological and medical sciences; Cystic fibrosis; Cytomegalovirus; Edema; Enzyme-Linked Immunosorbent Assay; Fluorodeoxyglucose F18; Gene expression; Gene Expression - genetics; Gene therapy; Gene Transfer Techniques; Genes, Reporter - genetics; Genetic Therapy - methods; Guanine - analogs & derivatives; Heat shock proteins; Herpes viruses; Herpesvirus 1, Human - enzymology; Herpesvirus 1, Human - genetics; Investigative techniques, diagnostic techniques (general aspects); Kinases; Least-Squares Analysis; Lung - pathology; Lung Diseases - pathology; Lung Diseases - therapy; Lungs; Medical sciences; Methods; Models, Animal; Radionuclide investigations; Radiopharmaceuticals; Rats; Rats, Sprague-Dawley; Respiratory system; Thymidine Kinase - genetics; Time Factors; Tomography; Tomography, Emission-Computed - methods; Tomography, Emission-Computed - standards; Transgenes - genetics; Treatment Outcome
• ISSN: 1073-449X; 1535-4970
• DOI: 10.1164/rccm.200210-1217OC

We evaluated positron emission tomographic imaging of pulmonary transgene expression, using an enhanced mutant herpes simplex virus-1 thymidine kinase as the reporter gene, in the lungs of normal rats. Sixteen rats were studied 3 days after an intratracheal administration of 5 x 10(9) to 1 x 10(11) viral particles of a replication-incompetent adenovirus containing a fusion gene of the mutant kinase and green fluorescent protein. Three rats infected with adenovirus containing no insert (null vector) served as control subjects. Images were obtained 1 hour after an intravenous injection of 9-(4-[18F]-fluoro-3-hydroxymethylbutyl)guanine, an imaging substrate for the viral kinase. After euthanasia, tissue radioactivity was determined in a gamma counter, and thymidine kinase activity and green fluorescent protein levels were measured in lung tissue samples. Imaging and gamma counting radioactivity measurements were strongly and linearly correlated (r2 = 0.96, p < 0.001). Imaging detected thymidine kinase expression above background (null vector) in 15 of 16 rats, even at low viral doses that produced little to no measurable green fluorescent protein expression. Lung 9-(4-[18F]-fluoro-3-hydroxymethylbutyl)guanine uptake (as assessed by imaging) correlated with in vitro assays of both kinase activity (r(2) = 0.48, p < 0.001) and fluorescent protein (r(2) = 0.46, p < 0.001). We conclude that positron emission tomographic imaging is a sensitive and quantitative method for detecting pulmonary reporter gene expression noninvasively.