Noninvasive photoacoustic computed tomography/ultrasound imaging to identify high-risk atherosclerotic plaques

Purpose Noninvasive detection of high-risk plaques is still challenging. In this study, we aimed to noninvasively assess αvβ3-integrin expression using a customed photoacoustic (PA) computed tomography (PACT)/ultrasound (US) system in atherosclerotic lesions of varying degrees of severity and to explore its potential value for detecting high-risk plaques. Methods We constructed αvβ3-integrin-targeted ultrasmall gold nanorods (AuNRs) with cyclo Arg-Gly-Asp (cRGD) and tested their properties. Employing C57BL/6 J (wild-type, WT) mice and apolipoprotein E gene knockout (ApoE −/− ) mice fed either a chow diet or a high-fat/high-cholesterol diet (HFHCD), we established varying degrees of lesion severity. In vivo PACT/US imaging was performed to assess αvβ3-integrin expression in the 4 groups by cRGD-AuNRs. Further histopathologic examination was conducted to evaluate the plaque vulnerability indicators. Results The data showed that cRGD-AuNRs exhibited excellent photothermal conversion capacity, stability, targeting ability, and biocompatibility. The immunohistochemical results indicated that αvβ3-integrin was upregulated with increasing aggravation of the lesions. In vivo PACT/US imaging showed good consistency with αvβ3-integrin expression. Notably, ApoE −/− mice fed a HFHCD showed an abrupt PA intensity increase compared with the other groups. The histopathologic examination verified that the atherosclerotic plaques of ApoE −/− mice fed the HFHCD developed unstable phenotypes. Correlation analysis showed that PA intensity was mainly related to inflammation and angiogenesis among all of the indicators. Conclusion Our data indicated that αvβ3-integrin is an effective indicator of plaque instability, and noninvasive PACT/US molecular imaging assessment of αvβ3-integrin holds promise in detecting high-risk plaques.