Nakamura, E.; Horiuchi, S.; Maekawa, K.; Gi, T.; Oguri, N.; Aman, M.; Moriguchi-Goto, S.; Asada, Y.; Yamashita, A.

Background and aims: Neutrophil extracellular traps (NETs), fibrin, and the von Willebrand factor (VWF) are present in acute coronary thrombotic plaques. However, the presence and extent of NETs, fibrin, and VWF in early-to-unstable coronary atherosclerotic lesions remain unclear. This study aims to determine the presence and extent of neutrophils, NETs, fibrin, and VWF formation during human coronary atherogenesis. Methods: Coronary sections from autopsy patients with non-cardiac death (n=5, 37 sections) and ischemic heart diseases (n= 11, 65 sections) were classified by atherosclerosis classification: diffuse intimal thickening, pathological intimal thickening, fibrous cap atheroma, fibrocalcified plaque, thin-cap fibroatheroma, ruptured plaque, and intraplaque hemorrhage. We immunohistochemically assessed the expression of CD66b (neutrophils), citrullinated histone H3 (Cit-H3, a marker of NETs), fibrin, and VWF. Results: Neutrophil and Cit-H3 expression were rarely observed, except in thin-cap fibroatheromas and ruptured plaques. Fibrin deposition was observed in pathological intimal thickening and necrotic cores of atheromas, and it was abundant in thin-cap fibroatheroma and ruptured plaques. VWF deposition was observed in the necrotic core of the atheromas and was abundant in ruptured plaques. In non-ruptured plaques, the immunopositive areas for Cit-H3 and fibrin were larger in hemorrhagic plaques than in non-hemorrhagic plaques. Conclusions: These results suggest that NET formation is rare in stable coronary plaques, and fibrin formation begins in stable lesions and increases with plaque destabilization in the coronary artery. Intraplaque hemorrhage may promote NET formation and fibrin deposition in non-ruptured plaques. The abundance of neutrophilic infiltrates and VWF deposition may be a response to plaque rupture.