Extracellular traps in lipid-rich lesions of carotid atherosclerotic plaques: Implications for lipoprotein retention and lesion progression

Purpose To investigate the presence and location of extracellular traps (ETs) in atherosclerotic plaques and to determine whether they are spatially associated with inflammatory cells and the lipid core. Materials and Methods Human carotid atherosclerotic plaques were collected from seven patients after surgical endarterectomy. Sequential tissue sections were stained with hematoxylin-eosin or subjected to immunohistochemistry to detect ETs, neutrophils and macrophages or apolipoprotein B (ApoB). To demonstrate the specificity of the antibody used to detect ETs, the adjacent tissue section was pretreated with deoxyribonuclease-1 (DNase-1) before immunostaining for ETs. Results All seven carotid plaques demonstrated advanced atherosclerotic lesions. Extensive ET and ApoB immunostaining was detected predominantly within the acellular lipid core. Along the edges of the lipid core, confocal microscopy revealed areas suggestive of active release of ETs from MPO-positive cells. Pretreatment of tissue sections with DNase-1 abolished ET signal in the extracellular matrix, but not the signal within the cells along the margins of the core. Conclusions The localization of ETs to the lipid core suggests a possible binding site for lipoproteins, which may further promote lesion progression and inflammation.