Abstract 12503: Binding Characteristics of Microparticles Targeted to E-Selectin versus VCAM-1 Under Conditions of Shear Stress: Implications for the Rational Design of Targeted Imaging Agents
Background: Endothelial E-Selectin and VCAM-1 are targets for molecular imaging of inflammation and atherosclerosis, but approaches targeting each molecule have rarely been compared. Obtaining sufficient binding of contrast agent at sites of inflammation under flow conditions is challenging. We tested the hypothesis that choice of target affects binding of imaging microparticles under shear stress.
Methods and Results: Binding of antibody-conjugated microparticles of iron oxide (Ab-MPIO) to basal and stimulated (10ng/mL TNF-α; 8 hours) human umbilical vein endothelial cells was evaluated under shear stress in a parallel-plate flow chamber. At 1 dyne, TNF-α stimulation caused significantly greater binding of E-Selectin-MPIO (mean 18 SEM ±1 versus 0.2 ±0) and VCAM-1-MPIO (26 ±2 versus 0.6 ±0) per field of view compared to basal conditions (P<0.001 for both comparisons). When shear stress was increased to 5 dyne, binding of microparticles to both E-Selectin and VCAM-1 was reduced; however, E-Selectin-MPIO binding was 7-fold greater than VCAM-1-MPIO binding to stimulated cells (7 ±1 versus 1 ±0; P<0.001). Quantitative flow cytometry confirmed no E-Selectin or VCAM-1 expression under basal conditions and demonstrated that on stimulated cells the relative abundance of E-Selectin exceeded that of VCAM-1 by approximately 2.7-fold (Figure).
Conclusions: We have shown that (1) at 1 dyne both E-Selectin-MPIO and VCAM-1-MPIO can distinguish inflamed endothelium, (2) at shear stress approaching arterial conditions E-Selectin-MPIO demonstrate a 7-fold increase in binding efficiency compared with VCAM-1-MPIO and (3) the dynamic range of E-Selectin expression is greater than that of VCAM−1. In summary, E-Selectin may be a more attractive target than VCAM-1 for molecular imaging of atherosclerosis, where target-ligand binding must take place under shear stress.
- © 2010 by American Heart Association, Inc.