Atherosclerosis progression and monocyte emigration from plaque.

Evaluation of: Llodrá J, Angeli V, Liu J, Trogan E, Fisher AE, Randolph GJ: Emigration of monocyte-derived cells from atherosclerotic lesions characterizes regressive, but not progressive, plaques. Proc. Natl Acad. Sci. 101(32), 11779-11784 (2004). Monocyte/macrophages are the most abundant immune cells in atherosclerotic lesions, in which they have a pivotal role. The present study sought to determine how dyslipidemia affects the fate of monocytes recruited to the plaque. The researchers used an in vitro model of a vessel wall to demonstrate that platelet-activating factor and lysophosphatidic acid, two key mediators of atherosclerosis, impair the ability of monocytes to emigrate from the cultured vessel wall. Furthermore, an in vivo model of aortic arch transplantation demonstrated reduced emigration of monocyte-derived cells into the plaque-draining lymph node under conditions of atherosclerotic lesion progression. Thus, progression of atherosclerosis is characterized by reduced emigration of monocyte-derived cells in addition to new monocyte recruitment into the vessel wall. Interestingly, these sequestered cells bear features reminiscent of dendritic cells, which may locally exacerbate inflammatory reactions.