Development of a non-invasive optical imaging method for tracking vascular gene expression

Gene therapy is an exciting frontier in modern medicine. To date, no imaging modalities are available for monitoring vascular gene therapy. Green fluorescent protein (GFP) has become an increasingly common marker for gene therapy. We have developed an optical imaging method to track vascular gene expression by detecting fluorescence emitted from GFP or red fluorescent protein (RFP) in arterial walls following gene transfer. We surgically transferred GFP- and RFP-vectors into the femoral and carotid arteries of three New Zealand white rabbits. Excitation light was transmitted through a fiber-optic ring-light (Nevoscope) and GFP and RFP fluorescence was detected by a charge coupled device (CCD) camera. Direct contact images of the target arteries demonstrated that this method was capable of both discriminating between normal and transferred arterial tissues and mapping fluorescent protein localization. Subsequent measurements by confocal microscopy showed statistically significant differences in average fluorescent signal intensity between the control and transferred tissues. This result was corroborated by immunohistochemical staining. These preliminary results are encouraging evidence that the optical imaging method can be developed further to be performed non-invasively and in vivo in a clinical setting.