Experimental study of USPIO-enhanced MRI in the detection of atherosclerotic plaque and the intervention of atorvastatin

Abstract

Ultrasmall superparamagnetic iron oxide (USPIO) can identify atherosclerotic vulnerable plaque and atorvastatin can stabilize vulnerable plaque by inhibiting the inflammatory response. Using balloon injury in rabbit abdominal aortic endothelial cells and p53 gene transfecting the local plaque, we established an atherosclerotic vulnerable plaque model. In the treatment group, animals were treated with atorvastatin for 8 weeks. At the end of week 16, the animals in each group underwent medication trigger. USPIO-enhanced MRI was utilized to detect vulnerable plaque formation and the transformation of stable plaque in the treatment group. Pathological and serological studies were conducted in animal sera and tissues. The images from the USPIO-enhanced MRI, and the vulnerable plaque showed low signal, especially on T2*-weighted sequences (T2*WI). Plaque signal strength reached a negative enhancement peak at 96 h. Compared with the other groups, lipids, cell adhesion molecule-1 and vascular cell adhesion molecule-1 levels were significantly lower (P<0.05) in the treatment group. In conclusion, USPIO-enhanced MRI can identify vulnerable plaque formation by deposition in macrophages, while atorvastatin is able to inhibit the progression of atherosclerosis and promote plaque transformation to the stable form.

Keywords: atherosclerotic plaque; cell adhesion molecule-1; superparamagnetic iron oxide.

Figure 1.

The intensity change of plaque signals in 3 groups after USPIO particle enhancement. USPIO, ultrasmall superparamagnetic iron oxide.

Figure 2.

Comparison of SNR. Comparison of the SNR change before its enhancement at 96 h after enhancement, the negative enhancement of plaque signals in group B peaked. By contrast, the changes in groups A and C showed no statistical difference, indicating that the nature and composition of plaques did not change significantly. SNR, signal-to-noise ratio.

Figure 3.

(A) Group B significantly reduced lumen, the lumen uniform group C.

Figure 4.

Group B, substantial foam cell proliferation. The collagen proliferation was not obvious in the 3 groups.

Figure 5.

(A) The control group (×100) showed no particle deposition or (C) (×100) visible macrophage USPIO particle deposition, and was (B) the same at high magnification (×200). USPIO, ultrasmall superparamagnetic iron oxide.

Figure 6.

Electron microscopy. (A) Increased lysosomes, (B) foam cell proliferation with visible lipid droplets. (C) Iron particle deposition inside macrophages.