Positron emission tomography reporter gene imaging in the myocardium: for monitoring of angiogenic gene therapy in ischemic heart disease

Cardiac angiogenic gene therapy has emerged as a novel treatment approach for patients with intractable ischemic heart disease, aiming at facilitating neovascularization to augment blood flow in the ischemic myocardium by introducing genes encoding for angiogenic factors. While several clinical trials for cardiac angiogenic gene therapy are currently in progress, there remains a discrepancy between impressive preclinical results and their limited clinical findings. On the other hand, positron emission tomography (PET) reporter gene imaging has been developed to monitor expression of transgenes in vivo. PET reporter genes encode for proteins that retain complementary positron-emitting tracers (PET reporter probes), and theoretically any therapeutic gene can be linked and coexpressed with an appropriate PET reporter gene. Consequently, PET reporter gene imaging with a PET reporter probe affords external determination of the location, magnitude, and duration of expression of therapeutic genes noninvasively. Since PET imaging can be performed in various species ranging from mice to humans, in vivo cardiac PET reporter gene imaging could play a critical role in identifying the "missing link" as a powerful translational research tool. In this article, we discuss the role of PET reporter gene imaging in basic and clinical research on cardiac angiogenic gene therapy.