Expansive Arterial Remodeling Is Associated With Increased Neointimal Macrophage Foam Cell Content The Murine Model of Macrophage-Rich Carotid Artery Lesions

Background— Recent observations associate plaque instability with expansive arterial remodeling, suggesting a common driving mechanism. Methods and Results— To demonstrate that macrophages, a characteristic of vulnerable plaques, also assist in expansive remodeling, we compared carotid artery remodeling due to formation of experimental macrophage-rich and macrophage-poor lesions in the flow cessation model in hypercholesterolemic apolipoprotein E knockout (ApoE KO) and wild type (WT) mice. After ligation, macrophages started to rapidly accumulate in ApoE KO but not in WT carotid artery lesions. Macrophage-rich ApoE KO intimal lesions grew fast, typically occluding within 14 days, despite a tripling of the vessel area. Outward remodeling of macrophage-rich ApoE KO arteries positively correlated with macrophage area (r2=0.600, P<0.001). To investigate potential mechanisms of macrophage-enabled expansive remodeling, we compared levels of matrix metalloproteinases in homogenates of macrophage-rich and macroph...