Molecular Imaging of Platelet–Endothelial Interactions and Endothelial von Willebrand Factor in Early and Mid-Stage Atherosclerosis

Abstract

Background Non-thrombotic platelet-endothelial interactions may contribute to atherosclerotic plaque development, although in vivo studies examining mechanism without platelet pre-activation are lacking. Using in vivo molecular imaging at various stages of atherosclerosis, we quantified platelet-endothelial interactions and evaluated the contribution of major adhesion pathways. Methods and Results Mice deficient for the LDL-receptor and Apobec-1 were studied as an age-dependent model of atherosclerosis at 10, 20, 30, and 40 wks of age, which provided progressive increase in stage from very early fatty streak (10 wks) to large complex plaques without rupture (40 wks). Platelet-targeted contrast ultrasound molecular imaging of the thoracic aorta performed with microbubbles targeted to GPIbα demonstrated selective signal enhancement as early as 10 weeks of age. This signal increased progressively with age (almost 8-fold increase from 10 to 40 weeks, ANOVA p<0.001). Specificity for platelet targeting was confirmed by the reduction in platelet-targeted signal commensurate with the decrease in platelet count after immunodepletion with anti-GPIb or anti-CD41 antibody. Inhibition of P-selectin in 20 and 40 wk atherosclerotic mice resulted in a small (15-30%) reduction in platelet signal. Molecular imaging with microbubbles targeted to the A1 domain of von Willebrand factor (VWF) demonstrated selective signal enhancement at all time points which did not significantly increase with age. Treatment of 20 and 40 week mice with recombinant ADAMTS13 eliminated platelet and VWF molecular imaging signal. Conclusions Platelet-endothelial interactions occur in early atherosclerosis. These interactions are in part due to endothelial VWF large multimers which can be reversed with exogenous ADAMTS13.

Effects of anti‐β2GPI antibodies on VWF release from human umbilical vein endothelial cells and ADAMTS13 activity

“…on endothelial cells in response to anti-β2GPI IgG. Although the presence of VWF-platelet strings has been noted upon exposure of endothelial cells to agonists such as PMA, histamine, some pro inflammatory cytokines, 35 and have been visualized in vivo, 36 the role of VWF-platelet string formation in APS needs further evaluation. 37 We also only investigated the formation at one shear rate, 5 dynes/ cm 2 and it is possible that a phenotype of increased VWF plateletstring formation would be revealed at higher or lower shear rates.…”

Intracellular delivery and ultrasonic activation of folate receptor-targeted phase-change contrast agents in breast cancer cells in vitro

“…Microbubble contrast agents have been investigated for ultrasound imaging of atherosclerosis [11], tumor angiogenesis [12], and other applications of intravascular tumor imaging [5, 7, 13]. Gas-filled microbubbles (MBs) provide high imaging contrast relative to tissue, yet they are restricted to the vasculature by their size (typically 1 – 10 microns).…”

Sentinel Lymph Node Characterization with a Dual-Targeted Molecular Ultrasound Contrast Agent

“…The aim of this study was to improve accuracy of SLN characterization using CEUS after intravenous injection of dual-targeted microbubbles allowing detection of angiogenesis and inflammation within the SLNs. In several studies, targeted contrast agents have been successfully applied for the detection of neovasculature [35-37] and inflammation [38, 39] as well as other purposes [40, 41]. Nonetheless, the application of targeted microbubbles to lymph nodes has been rather limited [42, 43].…”