Contrast enhanced ultrasound molecular imaging of platelets in the inflammatory procession of atherosclerosis

Objective To assess the role of activated platelets in the inflammatory procession of atherosclerosis(AS) by ultrasound molecular imaging. Methods Sixty ApoE-/- mice were fed with high fat diet to establish AS model as experimental group, and 40 C57BL/6J mice were fed with normal diet as control group. Biotin-avidin bridging method was used to construct platelet-targeted microbubbles with recombinant vWF-A1 domain (Mb-A1), microbubbles carrying monoclonal antibodies to VCAM-1 (Mb-VCAM1) and microbubbles carrying IgG monoclonal antibody (Mb-ctrl). In vitro and in vivo experiments were carried out to evaluate the ability of Mb-A1 to target platelets on vascular endothelial surface. Contrast enhanced ultrasound molecular imaging of proximal ascending aorta was performed with Mb-A1, Mb-VCAM1 and Mb-ctrl. The expression and distribution of platelets and monocytes/macrophages on the endothelium of ascending aorta of AS mice were observed and analyzed by immunofluorescence staining. Results ①A large number of Mb-A1 adhering to the surface of activated platelets coated in Petri dishes were observed under fluoresce. ②After platelet immune-depletion in 30-week AS mice, the signal intensity of Mb-A1 decreased significantly in ascending aorta, while that of Mb-ctrl has no obvious change(P<0.05). ③In ApoE-/- mice, signals from platelet targeted microbubbles increased from 8 to 32 weeks of age in ApoE-/- mice, which coincided with the increase of signals from VCAM-1 targeted microbubbles(P<0.05). ④Activated platelets on the endothelial surface of ascending aorta increased progressively with age from 8 weeks, and partly overlapped with the distribution of monocytes/macrophages. Conclusions Platelets contribute to the initiation and progression of atherosclerosis as an inflammatory mediator through the interaction with vascular endothelium. Key words: Contrast enhanced ultrasound; Targeted microbubble; Atherosclerosis; Inflammation; Platelet