Induction of atherosclerotic plaque rupture in apolipoprotein E-/- mice after adenovirus-mediated transfer of p53

Background-The presence of the tumor-suppressor gene p53 in advanced atherosclerotic plaques and the sensitivity to p53-induced cell death of smooth muscle cells isolated from these plaques have fueled speculation about the role of p53 in lesion destabilization and plaque rupture. In this study. we describe a strategy to promote (thrombotic) rupture of preexisting atherosclerotic lesions using p53-induced lesion remodeling. Methods and Results-Carotid atherogenesis was initiated in apolipoprotein E knockout mice by placement of a perivascular silastic collar. The resulting plaques were incubated transluminally with recombinant adenovirus carrying either a p53 or beta-galactosidase (lacZ) transgene. p53 transfection was restricted to the smooth muscle cell-rich cap of the plaque and led to an increase in cap cell apoptosis I day after transfer. p53 overexpression resulted in a marked decrease in the cellular and extracellular content of the cap, reflected by a markedly reduced cap/intima ratio (0.21+/-0.04 versus 0.46+/-0.03. P<0.001). The latter is a characteristic feature of plaque vulnerability to rupture, and whereas spontaneous rupture of p53-treated lesions was rare. it was found in 40% of cases after treatment with the vasopressor compound phenylephrine (P=0.003). Conclusions-We have demonstrated a potential role of p53-induced remodeling in atherosclerotic plaque destabilization. Being the first example of inducible rupture at a predefined location, this model offers a unique opportunity to delineate the processes that precede rupture and to evaluate plaque-stabilizing therapies.