« Growth of epithelial tissues in three-dimensional confined geometries » par Mme Laura Alaimo

Promoteur de thèse: Prof.Sylvain Gabriele

Résumé de la dissertation :

The migration of epithelial tissues in confined microenvironment is essential for the development of tube-like structures, in the metastatic process or during wound-healing. However, most of the prior studies investigating the role of physical cues on collective cell migration employed two-dimensional (2D) flat culture systems that do not replicate out-of-plane spatial confinements encountered in complex physiological environments. To address this issue, we studied in the first part of this thesis the coordinated migration of epithelial cell sheets in microchannels of varying widths (from 100 to 300 µm) to reproduce in vitro a controlled three-dimensional (3D) microenvironments. We observed that the cell density decreases from the rear to the front of the tissue, whereas the mean cell area conversely increases, independently of the channel dimension. Our findings show that the migration velocity increases with the channel widening but drops significantly with time. Interestingly, we demonstrate that the jamming transition from a solid-like to a fluid-like state is not controlled by the cell density but rather by the strengthening of cell-cell adhesions. In the second part of this thesis, we studied the self-healing process under a vertical compression, as observed in many pathological situations. Indeed, uncontrolled growth in a confined space generates mechanical compressive stress, but little is known about how such stress affects epithelial migration. To tackle this problem, we used a pillar stencil approach to create well-defined circular gaps of different diameters (from 100 to 300 µm) within an epithelial cell monolayer. Upon pillar removal, cells migrated collectively to close the gap. We applied a constant vertical force using pistons of specified weight in contact with the epithelial monolayer. We quantified the decrease of gap area and cell perimeter over time and showed the different regimes depending on the vertical pressure. Altogether, our findings provide insights into the emerging migratory modes for epithelial migration and growth under 3D spatial confinement, which are reminiscent of the in vivo scenario.