Abstract 12449: Identification of Novel Gene Fragments Encoding Ligands Specifically Homing to Experimental Vulnerable Plaque.
Introduction: Vulnerable plaque (VP) development is in part an injury response of the vessel wall, and as such involves complex processes including homing of stem/progenitor cells and cells mediating inflammatory related processes. Although several ligands essential for homing of these cells to VP are known, it is likely many are still undiscovered. The aim of this study is to identify novel molecules binding to VP.
Methods: To accomplish this we a) developed a unique mouse model of atherosclerotic plaque containing many of the phenotypic features characteristic of human VP (lard fed, apoE knockout on a mixed genetic background subjected to chronic stress); b) used a unique phage display library derived from human bone marrow cDNA to fish, in vivo, for proteins preferentially binding to VP.
Results: We isolated 11 different, previously unknown human genes encoding protein ligands recognizing VP. Phage encoding these proteins demonstrated a 6 fold increase in binding to VP compared to normal vessels. The genes were highly and preferentially expressed in human non-lineage committed bone marrow progenitor cells vs non-progenitor cells (>100x). When expressed as fusion proteins with the g10 capsid phage protein, the ligands demonstrated their ability to home to VP in vivo; thus, multispectral analysis showed colocalization of the labeled ligands with VP. Adhesion and migration of progenitor and inflammatory cells through the vascular endothelial cell layer is a critical process in plaque development; we therefore examined the effects of the identified proteins on cell invasion capacity of monocytes. By using ECIS (Electric substrate impedance sensing) we discovered that a subset of proteins block the IL-1β-dependent invasion of monocytes into an endothelial cell (EC) monolayer. Further, other ligands activate ECs, as evidenced by inducing p38 phosphorylation.
Conclusion: We identified novel human genes encoding proteins that a) home to VP in an experimental model, b) influence cell invasion across an EC monolayer, and c) activate EC signaling pathways. We believe further studies of these ligands will improve our understanding of VP pathophysiology and might lead to their use as targeting molecules for imaging and drug development.
- © 2010 by American Heart Association, Inc.