A Simple Method of Plaque Rupture Induction in Apolipoprotein E–Deficient Mice

Abstract

Objective-The development of a murine model of atherosclerotic plaque rupture. Methods and Results-The left common carotid arteries of male apolipoprotein E (apoE)-deficient mice (9 weeks old) were ligated just proximal to their bifurcations. After 4 weeks on a standard diet, the mice received polyethylene cuff placement just proximal to the ligated site, and the animals were then processed for morphological studies at specific time points. Ligation of the carotid artery in apoE-deficient mice for 4 weeks induced marked intimal hyperplasia, which is a lipid-and collagen-rich lesion that contains a number of macrophages, T lymphocytes, and smooth muscle cells. Subsequently, the cuff placement evoked intraplaque hemorrhage and plaque rupture with fibrin(ogen)-positive luminal thrombus in this region accompanying a decrease in collagen content as well as an increase in apoptotic cells in the intima within a few days after cuff placement. Conclusions-We demonstrated the murine model of human plaque rupture, which is simple, fast, and highly efficient.This model would help us not only to understand the mechanism of human plaque rupture but also to assess various already-known and as-yet-unknown agents in the future. Key Words: animal model Ⅲ plaque rupture Ⅲ thrombus Ⅲ apoptosis Ⅲ collagen I t is widely believed that rupture of a vulnerable atherosclerotic plaque leads to acute coronary events and stroke. The vulnerable plaque is generally composed of an atrophic fibrous cap, a lipid-rich necrotic core, the accumulation of inflammatory cells, 1,2 and imbalance between extracellular matrix synthesis and degradation resulting in decreased extracellular matrix protein content and increased proteinases, including matrix metalloproteinases (MMPs). 3-5 However, the exact mechanisms involved in the plaque rupture remain unknown. See page 1191Pathological animal models are valuable in the research on human diseases and their therapy. Mice are appropriate laboratory animals because of their small size, which makes them easy to manage and feed, and their superior potential for reproduction. Furthermore, recent methods of analysis and alterations of genes have enlarged their potential as model animals.The apolipoprotein E (apoE)-deficient mouse has become established as a model of hypercholesterolemia and atherosclerotic lesion development. 6,7 Although several plaque rupture models using the apoE-deficient mouse have been proposed, in most of the models, plaque rupture has been seen less frequently even, in old mice after prolonged feeding with very high-cholesterol diets. 8,9 More recently, Johnson et al reported that after 8 weeks of fat feeding of apoE-deficient mice, 62% of animals exhibited acute plaque rupture, which is defined as a visible breach in the cap with intraplaque hemorrhage, in the brachiocephalic artery. 10 In addition, in most of the models, there is no convincing evidence of the formation of platelet and fibrin-rich occlusive thrombus at the site of presumed rupture, 8 -10 which is characteristic of the h...

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“…Compared to rodents, human plaques show more complex lesions and specifically more calcification. Experimental characterization of plaque instability is challenging as mouse models for atherosclerotic plaque rupture are scarcely available [44][45][46] and not well characterized [47].…”

Vulnerable Plaque in a Swine Model of Carotid Atherosclerosis

“…Plaque ruptures have been observed in mouse models of atherosclerosis, which were created to simulate coronary artery diseases. 4,6 Because distal embolism is not a main mechanism of acute coronary syndrome, this phenomenon has never been reported in these models.…”

“…[1][2][3] Various mouse models of plaque rupture have been created in Apolipoprotein E or low-attenuation lipoprotein-receptor knockout mice, but whether they represent the same type of plaque rupture is still debated. [4][5][6][7] The advantages of the mouse model include the low cost and the availability of a transgenic technique to dissect the relevant pathologic processes. The size of the vessel and hemodynamic factors are, however, very different from those in humans, making it difficult to generalize the results to patients.…”

Increased Carotid Artery Lesion Inflammation Upon Treatment With the CD137 Agonistic Antibody 2A

“…Surgery was performed as previously described. 17 In brief, the right carotid artery was partially ligated during general isoflurane anesthesia. Mice received 0.1 mg/kg buprenorfin subcutaneously before wakening and recovery.…”

“…After 4 weeks, a conical polyethene cuff (Promolding B.V., The Netherlands) was surgically placed around the ligated vessel proximal to the ligation to provoke atherothrombosis. 17 Four days after cuff placement mice were euthanized and plaques were assessed (see below). One person performed vascular clinical events in individuals with risk factors of cardiovascular disease.…”