Cytochemical Characterization for Macrophages Engulf Cholesterol Crystals and Myeloperoxidase in Neutrophil Extracellular Traps (NETs) Sampled From Disrupted Aortic Plaques

This study aimed to develop simple and cytochemical detection methods for identifying macrophages that engulf cholesterol crystals (CCs) and for visualizing the granule enzyme myeloperoxidase (MPO) in putative neutrophil extracellular traps (NETs). Specimens were collected from blood-derived debris using filter paper and non-obstructive general angioscopy (NOGA), and analyzed using various staining techniques. Cytochemical staining methods included supra-vital Sternheimer staining, nonspecific esterase staining, and immunocytochemistry, which effectively detected macrophages actively phagocytosing CCs. MPO was visualized using the diaminobenzidine (DAB) method, which demonstrated MPO-positive NETs adhering to fibrin cores, as well as released and dispersed MPO granules. The diameter of MPO-positive granules ranged from 0.1668 to 0.6502 µm. These findings suggest that simple, rapid, and accessible cytochemical techniques are useful for elucidating the pathophysiology of atherosclerotic lesions, particularly in the context of innate immune responses.