Two-photon excited fluorescence (TPEF) may be useful to delimit macrophage subsets based on their metabolic activity and cellular responses in atherosclerotic plaques

Background and Aims: Atherosclerosis is characterized by the formation of lipid plaques at arterial walls. Blood-derived macrophages induce inflammation leading to plaque destabilization and rupture responsible for cardiovascular events. Plaque vulnerability was attributed to (1) a large lipid core containing necrotic “foamy” macrophages (FMs), (2) a thin fibrous cap, and potentially (3) an imbalance between inflammatory versus immunoregulatory macrophages. Recently these functional status were shown to rely on differential use of energetic metabolism (glycolysis for the former and mitochondrial respiratory chain for the latter) which may lead to different levels of autofluorescent cofactors. We hypothesized that high-resolution two-photon excited fluorescence (TPEF) imaging of NADH and FAD cofactors may be useful to follow metabolic activity and cellular responses of the macrophages present in atherosclerotic plaques.