Molecular imaging of stretch-induced tissue factor expression in carotid arteries with intravascular ultrasound

RATIONALE AND OBJECTIVES. Molecular imaging with targeted contrast agents e nables tissues to be distinguished by detecting specific cell-surface recep tors, In the present study, a ligand-targeted acoustic nanoparticle system Is used to identify angioplasty-induced expression of tissue factor by smoo th muscle cells within carotid arteries. METHODS. Pig carotid arteries were overstretched with balloon catheters, tr eated with tissue factor-targeted or a control nanoparticle system, and ima ged with intravascular ultrasound before and after treatment. RESULTS. Tissue factor-targeted emulsions bound and increased the echogenic ity and gray-scale levels of overstretched smooth muscle cells within the t unica media, versus no change in contralateral control arteries. Expression of stretch-induced tissue factor in carotid artery media was confirmed by immunohistochemistry, CONCLUSIONS. The potential for abnormal thrombogenicity of balloon-injured arteries, as reflected by smooth muscle expression of tissue factor, was im aged using a novel, targeted, nanoparticulate ultrasonic contrast agent.