Imaging transgene expression in live animals

Monitoring the expression of therapeutic genes in targeted tissues in disea se models is important to assessing the effectiveness of systems of gene th erapy delivery. We applied a new light-detection cooled charged-coupled dev ice (CCCD) camera for continuous in vivo assessment of commonly used gene t herapy delivery systems (such as ex vivo manipulated cells, viral vectors, and naked DNA), without the need to kill animals. We examined a variety of criteria related to real-time monitoring of luciferase (luc) gene expressio n in tissues including bone, muscle, salivary glands, dermis, liver, perito neum, testis, teeth, prostate, and bladder in living mice and rats. These c riteria included determination of the efficiency of infection/transfection of various viral and nonviral delivery systems, promoter specificity, and v isualization of luciferase activity, and of the ability of luciferin to rea ch various organs. The exposure time for detection of luc activity by the C CCD camera is relatively short (approximately 2 minutes) compared with the intensified CCD camera photon-counting method (approximately 15 minutes). H ere we transduce a variety of vectors (such as viruses, transfected cells, and naked DNA) by various delivery methods, including electroporation, syst emic injection of viruses, and tail-vein, high-velocity-high-volume adminis tration of DNA plasmids. The location, intensity, and duration of luc expre ssion in different organs were determined. The distribution of luciferin is most probably not a barrier for the detection of in vivo luciferase activi ty. We showed that the CCCD photon detection system is a simple, reproducib le, and applicable method that enables the continuous monitoring of a gene delivery system in living animals.