Role of the Intrinsic Coagulation Pathway in Atherogenesis Assessed in Hemophilic Apolipoprotein E Knockout Mice

Abstract

Objective-The contribution of thrombosis and coagulation in atherogenesis is largely unknown. We investigated the contribution of the coagulation intrinsic factor VIII (FVIII)-dependent pathway in atherogenesis. Methods and Results-Apolipoprotein E and FVIII double-deficient mice (E°/FVIII°) were generated. Aortic root lesions were analyzed in 14-week-old and 22-week-old female mice maintained for 8 or 16 weeks, respectively, on a normal chow diet or a hypercholesterolemic diet. Conclusion-Despite a higher plasma total cholesterol concentration compared with E°mice, E°/FVIII°mice developed dramatically less early-stage atherosclerotic lesions. Whereas early lesions in E°mice contained abundant fibrin(ogen) deposits on which few platelets adhered, lesions in E°/FVIII°were almost devoid of fibrin(ogen), and no platelets could be detected. Key Words: atherosclerosis Ⅲ hemophilia Ⅲ mouse Ⅲ knockout C omplications of atherosclerosis are the main causes of death in industrialized countries. The current paradigm establishes procoagulant state and thrombosis to be the major reason for complications. Consequently, it has been assumed that thrombosis and coagulation would also be involved in lesion formation. For instance, it is known that platelet activation and adhesion occur during the very first steps of the disease, 1 and the presence of the coagulation factor VIII (FVIII) has been reported in the vicinity of macrophages and smooth muscle cells in human atherectomy specimens. 2 Yet, the contribution of coagulation and thrombosis in atherogenesis remains largely unknown. Apolipoprotein E knockout (E°) mice are a reference model for experimental atherosclerosis. 3,4 As a result of their severe hypercholesterolemia, which can be aggravated by a hypercholesterolemic diet, these mice develop all stages of disease, from early fatty lesions through to mature fibrofatty plaques. 5 The present study was aimed at determining the influence of the intrinsic coagulation pathway in atherogenesis by analyzing lesion development in E°mice deficient for the FVIII. We found that the absence of this coagulation factor has a strong impact on the early stage of lesion formation. Materials and Methods Generation of E°/FVIII°MiceE°/FVIII°double-deficient mice were generated by crossing E°and FVIII°single knockout mice. FVIII°mice were provided kindly by Dr Kazazian 6,7 (University of Pennsylvania, Philadelphia). E°, FVIII°, and E°/FVIII°F2 offspring were used to establish the 3 genotype colonies. The genotyping was performed by polymerase chain reaction on DNA extracted from mouse tails. Experimental ProtocolsFive-to 6-week-old E°/FVIII°, control E°, and FVIII°female mice were placed on a normal chow diet (ND) or a hypercholesterolemic 0.15% cholesterol Western diet (WD) for 8 or 16 weeks (respectively, the "8-week protocol" and the "16-week protocol"). Weights were measured at death. All experiments were approved by our institutional ethical committee. Plasma MeasurementsCitrated blood collected at death was centrifuged at 4°C for 5 minut...

Atherosclerosis in Mice Is Not Affected by a Reduction in Tissue Factor Expression

“…33 However, a recent study demonstrated a reduction of lesion size in FVIII-deficient apoE Ϫ/Ϫ mice after 8 weeks on an atherogenic diet and, to a lesser extent, at 16 weeks. 34 These studies suggest that the role of coagulation in the development of atherosclerotic lesions is complex and may play a more prominent role in early lesion development in mice.…”

How I treat patients with inherited bleeding disorders who need anticoagulant therapy

“…5 Although epidemiologic data clearly demonstrate that CVD occurs in inherited bleeding disorders, studies on the protective effect of hemophilia and VWD against the development of atherosclerosis have generated conflicting data. Studies using animal models have shown both protection 6 and lack of protection 7,8 on the development of atherosclerosis. Earlier human studies using arterial intimal medial thickness (IMT) as a surrogate for atherosclerosis are similarly conflicting, with some suggesting a protective effect and others failing to demonstrate protection.…”

Cardiovascular risk in patients with hemophilia

“…Apolipoprotein E knockout (apoE 2/2 ) mice that have accelerated atherosclerosis, developed less early-stage atherosclerotic lesions when they were also factor VIII-deficient. 24 On the other hand, in mice with a low-density lipoprotein receptor null mutation, another accelerated atherosclerosis model, the protective effect of factor VIII deficiency was not observed. 25 In humans, several earlier studies analyzed the presence of subclinical atherosclerosis by measuring the carotid and femoral intima media thickness (IMT) in patients with hemophilia or von Willebrand disease.…”