Intraplaque injection of Ad5-CMV.p53 aggravates local inflammation and leads to plaque instability in rabbits.

This study aims to develop a new animal model of vulnerable plaques and investigate the potential mechanisms of exogenous p53-induced plaque instability. Forty rabbits underwent aortic balloon injury, were fed a 1% cholesterol diet for 10 weeks and then normal chow for 6 weeks. Rabbits were divided into Ad5-CMV.p53-treated group (n = 16), Ad5-CMV.lac Z-treated group (n = 16) and blank control group (n = 8). Under the guidance of intravascular ultrasound, a 50-microl suspension of adenovirus containing p53 or lac Z was injected into the largest plaque of the first two groups, respectively, and these rabbits received pharmacological triggering 2 weeks later. In 76.9% of rabbits with p53 transfection, plaque rupture was found, which was significantly (P < 0.05) higher than that in the Ad5-CMV.lac Z-treated plaques (23.1%), or blank controls plaques (0%). Increased apoptotic cells, and subsequently, decreased vascular smooth muscle cells and collagen content, enhanced intima macrophage accumulation, increased C-reactive protein (CRP) and matrix metalloproteinases staining and high serum levels of high sensitive CRP (hs-CRP) and monocyte chemoattractant protein-1 (MCP-1) were observed in Ad5-CMV.p53-treated rabbits. However, a binary logistic regression model revealed that hs-CRP concentration rather than apoptosis rate played an independent role in plaque rupture with an odds ratio as 1.314 (95% CI: 1.041-1.657, P = 0.021), and there were high positive correlations between inflammatory biomarkers (hs-CRP or MCP-1) and apoptosis (R(2) = 0.761, and R(2) = 0.557, respectively, both P < 0.01). Intraplaque injection of p53 gene provides a safe and effective method for inducing plaque vulnerability in rabbits. The destabilizing effect of p53 overexpression is mediated mainly through apoptosis-enhanced inflammation rather than cell apoptosis itself.