Radiotracer characterization of coronary artery lesions

Activated alphavbeta3 integrin targeting in injury-induced vascular remodeling

There is currently no imaging modality to track the remodeling process, a common feature of a broad spectrum of vasculopathies, in vivo. alphavbeta3 Integrin is up-regulated in proliferating vascular cells. RP748, a novel peptidomimetic tracer, binds specifically to the activated alphavbeta3 conformer and exhibits favorable binding characteristics for in vivo imaging. In a model of injury-induced vascular remodeling in apoE null mice, RP748 localization to the injured carotid arteries parallels vascular cell proliferation, providing an opportunity to image the remodeling process in vivo.

Vascular targeting: recent advances and therapeutic perspectives

The ability to deliver therapeutics site—specifically in vivo—remains a major challenge for the treatment of malignant, inflammatory, cardiovascular, and degenerative diseases. The need to target agents safely, efficiently, and selectively has become increasingly evident because of progress in vascular targeting. The vascular endothelium is a central target for intervention, given its multiple roles in the physiology (in health) and pathophysiology (in disease) and its direct accessibility to circulating ligands. In cancer, the expression of specific molecules on the surface of vascular endothelial and perivascular cells might enable direct therapeutic targeting. The use of in vivo phage display has significantly contributed to the identification of such targets, which have been successfully used for directed vascular targeting in preclinical animal models. Several animal studies have been performed by using fused molecules between tumor endothelium-directed molecules and immunomodulatory, procoagulant, or cytotoxic molecules. In addition to delivery of therapeutic agents, vascular targeted gene therapies based on both ligand-directed delivery of gene vectors to tumor endothelium and transcriptional targeting have also emerged. In this review, we discuss ligand-directed vascular targeting strategies with an emphasis on recent developments related to phage-display-based screenings.

Seeing Within

Molecular imaging is a rapidly evolving discipline with the goal of developing tools to display and quantify molecular and cellular targets in vivo. The heart of this field is based on the rational design and screening of targeted and activatable imaging reporter agents to sense fundamental processes of biology. Parallel advances in small animal imaging systems and in agent synthesis have allowed molecular imaging applications to extend into the in vivo arena. These advances have permitted, for example, in vivo sensing of inflammation, apoptosis, cell trafficking, and gene expression. In this review, we first review core principles of molecular imaging with an emphasis on smart, activatable agent technology. We then discuss applications of state-of-the-art molecular probes to interrogate important aspects of cardiovascular biology, with a focus on atherosclerosis, thrombosis, and heart failure. In the ensuing years, we anticipate that fundamental aspects of cardiovascular biology will be detectable in vivo, and that promising molecular imaging agents will be translated into the clinical arena to guide diagnosis and therapy of human cardiovascular illness.

Molecular imaging in nuclear cardiology

State-of-the-art techniques have been used to measure key aspects of cardiovascular pathophysiology from the birth of radionuclide cardiovascular imaging. However, during the last 30 years, there have been few innovative imaging advances to further our understanding of the complex physiologic processes. Molecular imaging now offers an array of tools to develop advanced diagnostic approaches and therapies for patients with coronary artery disease and heart failure. For example, the enhanced understanding of the pathophysiology of atheroma makes it possible to identify vulnerable plaque based on its metabolic signature or the presence of excessive apoptosis. Because the metabolic and apoptotic signals are large, it is likely that even small lesions will be visible. Of the many approaches that are being developed, 2 tracers appear most likely to be tested in the near future: (1) [18F]-fluorodeoxyglucose, to determine macrophage metabolism; and (2) radiolabeled annexin, to measure apoptosis of the inflammatory cells. Using existing techniques such as perfusion imaging, appropriate patients can be selected for treatment with novel therapies, such as stem cell transplantation or vascular gene therapy. Using positron tomography in place of single photon imaging adds the capability for the measurement of absolute perfusion and perfusion reserve to the information on regional perfusion. Flow reserve detects global decreases in perfusion and refines the determination of lesion severity available from perfusion imaging.