Noninvasive radionuclide imaging of cardiac gene therapy: progress and potential

Over the past decade, several clinical trials have evaluated the efficacy of cardiac-specific gene therapy. Despite encouraging results in basic research and preclinical studies, most of the recent large, randomized, placebo-controlled cardiac gene therapy trials have failed to provide convincing evidence of improvements in clinical outcomes. Because many of these problems are due to the lack of appropriate monitoring techniques, there is a critical need to develop noninvasive imaging techniques that can verify vector delivery and gene expression in target and nontarget tissues. The field of molecular imaging of cardiac gene expression is rapidly advancing because it offers distinct advantages over conventional methods, including the ability to noninvasively measure the location, time course, and magnitude of gene expression. We aim to give readers a clear understanding of how molecular imaging can enable noninvasive tracking of cardiac gene transfer and expression. We discuss limitations of current methods for analyzing gene transfer and describe how reporter gene imaging works.