Identification of dendritic cells in aortic atherosclerotic lesions in rats with diet-induced hypercholesterolaemia.

We have previously identified dendritic cells (DCs) in the intima of human large arteries. These vascular DCs are common in atherosclerotic lesions but their immature forms are also present in normal arterial intima. Pathophysiological studies on vascular DCs are limited because they have only been studied in human specimens obtained at operation or post-mortem. The aim of the current study was to determine whether DCs participate in the development of atherosclerotic lesions in hypercholesterolemic rats. Male Wistar rats were divided into a control (n=13) and experimental cohort (n=48). The experimental animals were fed an atherogenic diet and 1% saline, while the controls were fed standard rat cubes and water. The aortas were obtained from both groups at 10, 20, and 30 weeks following commencement of the diet. An en face immunohistochemical technique, routine section immunohistochemistry, and transmission electron microscopy were used to detect the presence of DCs in the aortas. Examination of the aortas showed that S100+ cells with dendritic cell morphology were present in the aortic intima of hypercholesterolemic rats. The S100+ DCs displayed immunopositivity for OX-62 and MHC Class II antibodies. Within various types of atherosclerotic lesions, these cells were clustered throughout the intima but were especially prominent around arterial branch-points where they co-localized with various cell types, including T-cells and macrophages. Ultrastructural analysis confirmed the presence of cells with characteristics typical of DCs. These features included the presence of a well-developed tubulovesicular system, dendritic processes, and a lack of secondary lysosomes and phagosomes. This study establishes the presence of DCs in the aortic intima of rats with diet-induced atherosclerosis. The presence of DCs in this model of experimental atherogenesis could provide a new approach to investigating the function of DCs and may help clarify the immune-inflammatory mechanisms underlying atherosclerosis.