163 - Two-Photon Excited Fluorescence (TPEF) may be useful to delimit macrophage subsets based on their metabolic activity and cellular responses in atherosclerotic plaques (ID 1378)
Abstract
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.
Methods
To address this question, different in vitro models of FMs were phenotypically and optically characterized, in comparison with M1 and M2 cells, representative of the extremes of macrophage polarization (inflammatory and immunoregulatory, respectively).
Results
Our results showed that (1) FMs present an intermediate phenotype expressing low level of both “M1” and “M2” markers, (2) as hypothesized, M1 and M2 models presented significantly distinct optical properties and (3) the more pathophysiological FM model induced by oxidized LDL + CE showed significantly distinguishable optical ratio from both M1 and M2 cells and also from unstimulated MPs (M0).
Conclusions
To conclude, TPEF imaging may be useful to detect vulnerable area where cells drastically change their metabolic activity and functional responses. Metabolism pathways responsible for these properties are being explored.
