ED Sciences de la Vie et de la Santé
From Cell to Nano-Object: Biological Signatures and Imaging Strategies for Foam Macrophages in Atherosclerosis
by Amina Sarah HENNI MANSOUR (Centre de Résonnance Magnétique des Systèmes Biologiques)
The defense will take place at 10h00 - RMSB- salle de conférence Centre de Résonance Magnétique des Systèmes Biologiques, UMR5536 CNRS, 2 Rue Dr Hoffmann Martinot, 33000 Bordeaux.
in front of the jury composed of
- Florence OTTONES - Maîtresse de conférences - Université de Bordeaux - Directeur de these
- François CANONNE-HERGAUX - Chargé de recherche - Inserm U1188 – DéTROI - Rapporteur
- Émilie SECRET - Chargée de recherche - PHENIX UMR 8234 - Rapporteur
- MERCHED AKSAM - Professeur des universités - BRIC - Inserm U1312 - Examinateur
- Thomas CHARLES - Professeur des universités - UMR 1231 INSERM/Université de Bourgogne UFR Sciences de la Vie, de la Terre et de l'Environnement (SVTE) - Examinateur
- Nicolas LARMONIER - Professeur des universités - CNRS UMR 5164 / UF Biologie - Université de Bordeaux - Examinateur
Atherosclerosis is a chronic inflammatory disease whose clinical complications depend more on plaque composition and biological activity than on the degree of stenosis alone. Macrophages play a central role in this process, yet their phenotypic, metabolic, and functional heterogeneity complicates their detection and targeting. This thesis investigated foam macrophages as dynamic targets through two complementary approaches developed within the ANR-funded MEAP and NanoBioID projects, respectively: the use of endogenous optical signatures of macrophages and the biological evaluation of magnetic iron oxide nanoflowers designed to target foam macrophages. Human monocyte-derived macrophages were polarized or converted into foam cells through exposure to oxidized or acetylated low-density lipoproteins. Multiparametric characterization combining flow cytometry, cytokine measurements, metabolic flux analysis, oxidative stress assessment, and two-photon excited fluorescence (TPEF) imaging showed that the Mox and Mac models represent distinct states that extend beyond the simplified M1/M2 paradigm. Mox50 macrophages displayed impaired mitochondrial respiration, greater reliance on glycolysis, increased reactive oxygen species (ROS), and lysosomal accumulation of ceroids. In these cells, fluorescence detected within the FAD spectral window increased despite reduced respiration. Its decrease following α-tocopherol treatment and its association with ceroids led us to define it as a “FAD-like” signal, indicative of oxidative and lysosomal overload rather than enhanced oxidative phosphorylation. A preliminary investigation of aortas from Apoe⁻/⁻ mice supported the feasibility of label-free detection of regions associated with dysfunctional macrophages. Within the NanoBioID project, the interactions between several nanoflower (NF) formulations and macrophages were assessed in vitro. Oleic acid (OA) functionalization markedly increased cellular association and uptake compared with the reference PEGylated formulation. The findings suggested the involvement of CD36 or other lipid-recognition pathways, without establishing an exclusive mechanism. The formation of a protein corona in human serum strongly reduced uptake, demonstrating that the acquired biological identity of NFs determines their interactions with cells. Overall, the formulations showed good metabolic compatibility under the conditions tested, although they were not biologically inert. Finally, the absence of significant cholesterol efflux did not support, at this stage, the theranostic functionality of ApoA1-bearing formulations. Overall, this thesis highlights the interplay between two evolving identities: that of the macrophage, shaped by its lipid and inflammatory environment, and that of the nano-object, remodelled by the protein corona. It proposes an integrated approach in which multiphoton imaging provides a local readout of macrophage dysfunction, whereas magnetic nanoflowers could enable broader plaque detection by magnetic resonance imaging. These findings open new avenues for multiparametric biological imaging of high-risk plaques.