Thèses

Jeudi 19 Juin 2025 à 14h00.

From Single Cells to Tissue: a Multi-Scale Characterization of Growing Tumor Models Under Mechanical Confinement

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Directeur de thèse / thesis director :
Sylvain MONNIER & Charlotte RIVIÈRE

Membres du jury / jury members :
Mme. Audrey Ferrand - Directrice de Recherche, Inserm Toulouse
M. Pierre Nassoy - Directeur de Recherche, CNRS Bordeaux
Mme. Sham Tlili - Chargée de Recherche, CNRS Marseille
Mme. Catherine Barentin - Professeure, Université Lyon 1
Mme. Charlotte Rivière - Professeure, Université Lyon 1
M. Sylvain Monnier - Maître de Conférences, Université Lyon 1
M. Morgan Delarue - Chargé de Recherche, CNRS Toulouse

Résumé / Abstract :
Understanding how mechanics influence cellular fate remains a major challenge. In both development and tumor progression, cells exhibit spatial heterogeneity: their fates such as proliferation, migration, or apoptosis are tightly linked to their local, including both biochemical and physical, environment. For instance, in a tumor, cells at the periph- ery proliferate more than those in the center. In vivo, tumor growth frequently occurs in confined environments leading to the emergence of mechanical stresses, i.e. solid stress, which can in turn affect cell fate, tumor organization, and treatment response. Similarly, biochemical gradients of oxygen or nutrients shape tissue architecture and heterogene- ity. While the impact of physical properties like stiffness and volume is increasingly understood in 2D cultures, dissecting their roles in 3D tissues remains challenging due to imaging limitations and the entanglement with biochemical cues. Standard 3D models, such as tumor spheroids, reproduce these gradients but fail to isolate their individual contributions. New strategies are thus needed to uncouple and probe these factors in controlled systems, to better understand how tissue mechanics and biochemical cues to- gether regulate cellular behavior. To fill that gap, I have designed an original microsystem to obtain tissues of limited thickness, up to 70μm, by confinement. In this set-up, the maximum distance between any cell and the nutrient source is reduced to 35μm. Hence, the chemical gradients are minimized while confinement imposes mechanical stress. By uncoupling mechanical and chemical gradients, we can uniquely decipher the roles of me- chanical stress on cell properties (shape, size, growth, etc.) and extracellular transport, which lead to the emergence of heterogeneous organization. Indeed, the limited thickness of the sample overcomes imaging limitations and enables us to assess physical properties such as nuclear volume and cell density without fixation artifacts. This has required the development of tailored image analysis tools to quantify local parameters in dense living tissues. With this work, I show how mechanical stress builds up in confined tissue, leading to smaller cells and a slowdown of proliferation.

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