Photopolymérisation de microstructures 3D pour le contrôle de l'architecture et des communications multicellulaires – 3DPHOTOPOL

Most methods in modern cell biology are implicitly based on the assumption that the behavior of a cell is predominantly determined by its individual biochemical and genetic properties. Moreover, complex processes such as tumorigenesis, are studied by methods that make it quite difficult if not impossible to take into account the diversity of the participating cells and their mutual interactions. Nevertheless, it is now widely acknowledged that cellular diversity and microenvironmental effects are key determinants for the emergence of collective processes such as the homeostasis of healthy tissues or their destabilization during dysplasia or tumor growth and metastatic escape. In the prokaryotic world as well, several collective phenomena have been observed, such as quorum sensing between bacteria or the formation of bacterial biofilms. In all these collective phenomena, each individual cell seems to obey external signals that guide its individual behavior. Conversely, many observations indicate that altered collective behaviors in a complex microenvironment, e.g. the loss of tissue homeostasis, are key steps in the process of cancer development, leading to pathological types of organization : benign or malignant solid tumor, metastatic foci. Nevertheless, we do not know of any quantitative model to quantitatively study collective aspects of tumorigenesis by controling each participating individual cell and the microenvironment. How project here is to construct 3D microstructures to organize an ensemble of cells –first as a 2D lattice– and control the interactions between them, by providing each individual with a geometrically, mechanicaly and chemicaly defined position template. We will study in a quantitative and reproducible fashion, how collective properties emerge either spontaneously or as a response to local perturbations : tissue stability, dysplasic destabilization, tumor growth, mesenchymal transition and metastatic escape. We will also study the local and collective conditions for the nucleation and growth of bacterial biofilms. 3D microstructures will be fabricated by two-photon induced photopolymerization, and the unique features of that method will be very useful for the present project : 1/ microstructure can be made with virtually no constraint on the geometry, provided it can be described with submicroscopic voxel –typically 0.2x0.2x0.7 μm3–, 2/ a broad range of materials can be used – hydrogels and resins-, offering a wide range of chemical derivatizations and elasticity, 3/ microstructures can be constructed sequentially using different chemistries and Young moduli. Since elasticity can be controlled, the envisaged microstructures will also be used to assess intercellular forces by measuring microstructure strains. The two participating teams focus on chemistry and microbiology on the one hand, and cell biology and non-linear imaging and optics on the other hand. Therefore, the collaboration is very important to develop the microfabrication methodology between optics and chemistry, but two distinct biological models and questions will be then studied with our microstructures : 1/ construction of a controlled lattice of epithelial cells to study the stability of the unperturbed cell lattice, and the emergence of the order-disorder transition during the induction of a dysplasic-like behavior or the stimulation of an epithelium-mesenchyme transition, 2/ fabrication of various templates to study the condition for the nucleation and growth of biofilms. Microstrutures compatible with cell culture should be more generally useful as "3D multicellular chips" for cell biology, pharmacology, and tissue engineering at the single-cell level. For those reasons, we want to set-up a two-photon photopolymerization microfabrication station ; we also ask for a technical support salary, because that equipment will be open to collaborations.