1. ¹INSERM Unit 375, IRCAD, F-67091 Strasbourg, France
2. ²Laboratoire PHASE, CNRS UPR 292, F-67037 Strasbourg, France
3. ³Institute for Health and Consumer Protection, European Commission Joint Research Centre, Ispra I-21020, Italy

Correspondence: Marc Aprahamian, INSERM Unit 375, IRCAD, Hôpitaux Universitaires, BP 426, F-67091 Strasbourg Cedex, France. Fax: (33) 3 88 11 90 99. E-mail: Marc.Aprahamian@ircad.u-strasbg.fr

Received 12 August 2002; Accepted 14 March 2003.

Abstract

Whole-body imaging of green fluorescent protein (GFP) can be used to test the efficiency of gene carriers for in vivo transduction. The aim of the current study was to determine the sensitivity and the accuracy of a GFP imaging procedure by in vivo investigation of GFP-expressing tumor cells. An improved method of whole-body GFP imaging made use of a laser excitation source and band-pass filters matched specifically to GFP and constitutive tissue fluorescence emission bands. Processing of the primary GFP fluorescence images acquired by the CCD camera subtracted background tissue autofluorescence. Our approach achieved 100% sensitivity and specificity for in vivo detection of 10%-transfected BxPc3 pancreatic tumor after subcutaneous grafting or orthotopical implantation in the pancreas of nude mice. It also detected less transfected tumors (i.e., 1 to 5%) but with a loss in sensitivity (50% of cases). The system was employed over a 5-week period to monitor the persistence of GFP expression in 10%-transfected BxPc3 tumors orthotopically implanted in the pancreas of two nude mice, allowing the direct visualization of tumor progression and spread. In facilitating the temporal–spatial follow-up of GFP expression in vivo, the optimized laser-induced fluorescence imaging device can support preclinical investigations of vectors for therapeutic gene transduction through regular, harmless, real-time monitoring of theirin vivo transductional efficacy and persistence.