Accelerated Atherosclerosis and Calcification in Vein Grafts

Abstract

Abstract-Vein grafts fail due to development of intimal hyperplasia and accelerated atherosclerosis. Many murine genetic models in which genes are overexpressed, deleted, or mutated have been introduced recently. Therefore, mouse models are very well suited to dissect the relative contribution of different genes in the development of accelerated atherosclerosis. In the present study, we evaluated whether accelerated atherosclerosis in human vein grafts could be mimicked in hypercholesterolemic APOE*3 Leiden transgenic mice. Venous bypass grafting was performed in the carotid artery in APOE*3 Leiden mice fed either a standard chow diet or a high cholesterol-rich diet for 4 weeks. At several time points (0 hour to 28 days), mice were euthanized and the morphology of the vein grafts was analyzed. In normocholesterolemic mice, vein graft thickening up to 10-fold original thickness, predominantly consisting of ␣-smooth muscle cell actin-positive cells, was observed after 28 days. In hypercholesterolemic mice, accelerated atherosclerosis with accumulation of lipid-loaded foam cells was observed within 7 days after surgery. This accelerated atherosclerosis progressed in time and resulted in significant increase in vein graft thickening up to 50 times original thickness with foam cell-rich lesions and calcification within 28 days after surgery.

Inhibition of Complement Component C3 Reduces Vein Graft Atherosclerosis in Apolipoprotein E3–Leiden Transgenic Mice

“…16 When performed in hypercholesterolemic mice, vein graft thickening occurs with signs of accelerated atherosclerosis. 13 The morphology of the observed lesions strongly resembles that seen in human vein grafts, underscoring the relevance of this model. Because the complement cascade is an important part of the innate immune system and is also involved in initiation of adaptive immune responses, it may be one of the mediators of inflammatory processes in remodeling vein grafts.…”

“…Although the apolipoprotein E3-Leiden mice used in this study suffered relatively mild hypercholesterolemia (serum cholesterol 8 to 10 mmol/L), cholesterol levels still exceed serum levels seen in most of the patients. As previous reports have shown, severe hypercholesterolemia might induce increased vascular inflammatory reactions 13,31 and consequently atherosclerotic lesion formation. Furthermore, because of anatomic variations between humans and mice, it can be assumed that after engraftment, as a result of the 10-fold increase in blood pressure, more extensive graft distension and subsequent vascular damage and SMC apoptosis are occurring in murine vein grafts (only a few cell layers thick) compared with the human counterpart.…”

“…13 In the Crry-Ig-treated group, thickened vein grafts had a significantly higher relative SMC content than the control group (control, 33Ϯ5%; Crry-Ig, 47Ϯ3%; Pϭ0.04). The amount of collagen deposition, however, did not significantly differ between both groups (control, 33Ϯ4%; Crry-Ig, 29Ϯ2%; Pϭ0.5).…”

“…This mouse model highly resembles graft morphology in patients regarding leukocyte adhesion and influx, foam cell accumulation, calcification in the vessel wall, and development of a thin fibrous cap. 13 Not only was expression of several complement factors, on both RNA and protein levels, in the thickened vein graft shown, but it was also demonstrated that treatment with Crry-Ig, which inhibits C3 activation, resulted in a significant decrease of intimal hyperplasia and accelerated atherosclerosis in murine vein grafts. In the present study, we show that activation of complement cascade plays a pivotal role in the development of vein graft thickening.…”

Quaking, an RNA-Binding Protein, Is a Critical Regulator of Vascular Smooth Muscle Cell Phenotype

“…24 Immunohistochemical analysis and quantitation of femoral arteries was performed as described previously. 25 Incorporation of 5-bromo-2-deoxyuridine (BrdU) into DNA as a marker of DNA synthesis was studied by intraperitoneal BrdU injection (100 mg/kg) 72, 48, and 24 hours before euthanasia. QKI was detected using a rabbit polyclonal antihuman QKI antibody (N20; Santa Cruz Biotechnology, CA).…”