MICROBUBBLES TARGETED TO INTERCELLULAR-ADHESION MOLECULE-1 BIND TO ACTIVATED CORONARY-ARTERY ENDOTHELIAL-CELLS

Background-Preclinical atherosclerosis is associated with increased en dothelial cell (EC) expression of leukocyte adhesion molecules (LAMs), which mediate monocyte adhesion during atherogenesis. Identification of cell-surface LAMs may uniquely allow assessment of endothelial func tion, but there are no in vivo methods for detecting LAMs,. We tested a new microbubble designed to bind to and allow specific ultrasound de tection of intercellular adhesion molecule-1 (ICAM-1). Methods and Res ults-A perfluorobutane gas-filled lipid-derived microsphere with monoc lonal antibody to ICAM-1 covalently bound to the bubble shell was synt hesized. Bubbles with either nonspecific IgG or no protein on the shel l were synthesized as controls. Coverslips of cultured human coronary artery ECs were placed in a parallel-plate perfusion chamber and expos ed to 1 of the 3 microbubble species, followed by perfusion with cultu re medium. Experiments were performed with either normal or interleuki n-1 beta-activated ECs overexpressing ICAM-1, and bubble adherence was quantified with epifluorescent videomicroscopy. There was limited adh erence of control bubbles to normal or activated ECs, whereas a 40-fol d increase in adhesion occurred when anti-ICAM-1-conjugated bubbles we re exposed to activated ECs compared with normal ECs (8.1+/-3.5 versus 0.21+/-0.09 bubbles per cell, respectively, P<0.001). Although dimini shed, this difference persisted even after perfusion at higher wall sh ear rates. Conclusions-A gas-filled microbubble with anti-ICAM-1 antib ody on its shell specifically binds to activated ECs overexpressing IC AM-1. Diagnostic ultrasound in conjunction with targeted contrast agen ts has the unique potential to characterize cell phenotype in vivo.