VCAM-1 siRNA reduces neointimal formation after surgical mechanical injury of the rat carotid artery

Objective

Restenosis is one of several complications following carotid endarterectomy (CEA). The pathogenesis of restenosis may be related to postsurgery inflammation and leukocyte recruitment mediated by cellular adhesion molecules. In this study, we examine the role of vascular cell adhesion molecule-1 (VCAM-1) in carotid neointimal hyperplasia following carotid surgical mechanical de-endothelialization (CSMDE) in a rat model of CEA.

Methods

The inhibition of siRNA on VCAM-1 protein expression was determined by using the methods of immunostaining and Western blot. Ultrasound imaging and morphometric analysis were applied to measure the degree of CSMDE-induced carotid artery neointimal hyperplasia of rats.

Results

We found that a lentivirus-based construct expressing a small interfering RNA (siRNA) against VCAM-1 could effectively (P < .05, n = 10 per group) reduce VCAM-1 protein expression in the carotid arteries of rats undergoing CSMDE (CSMDE+RNAi: 135.0 ± 27.6%) when compared that of CSMDE with scrambled siRNA (CSMDE+CON: 182.7 ± 36.4%). Doppler ultrasonography revealed that CSMDE+RNAi was accompanied by a significant reduction in the extent of stenosis demonstrated by increased blood velocity (665.85 ± 48.37 mm/s) and linear diameter (0.59 ± 0.77 mm) compared to CSMDE+CON (46.72 ± 28.67 mm/s with undetectable linear diameter, P < .05, n = 10 per group). In addition, morphometric analysis of hematoxylin and eosin (HE)-stained sections indicated that the intima (innermost layer of media at lesion site)/media area ratio (I/M) was significantly increased (P < .05, n = 10 per group) both in the CSMDE (3.99 ± 0.65) and CSMDE+CON (4.33 ± 0.59) groups compared with the SHAM group (0.35 ± 0.13). However, CSMDE+RNAi resulted in a significant (P < .05, n = 10 per group) decrease in the I/M ratio (1.79 ± 0.43) compared to CSMDE+CON, whereas there were no significant differences in the total arterial area and medial areas among the groups.

Conclusion

These results suggest that perivascular events mediated by VCAM-1 are likely to play an important role in the pathogenesis of carotid artery neointimal hyperplasia in rats after CSMDE.

Clinical Relevance

Carotid endarterectomy (CEA) is an effective treatment for carotid artery atherosclerotic disease, but there can be complications such as the development of intimal hyperplasia. Post-CEA restenosis is a multifactorial process initiated by vessel injury and inflammatory reactions. The results of this study support the notion that perivascular events mediated by vascular cell adhesion molecule-1 (VCAM-1) are likely to play an important role in the pathogenesis of neointimal hyperplasia in rats following carotid surgical mechanical de-endothelialization, and VCAM-1 siRNA may be used by local delivery during CEA operation to reduce restenosis.