Epithelium consists of closely packed cells that make up the inside or outside lining of body's surfaces. We study the growth of an epithelium in a confined geometry. Using microfabrication techniques, we developed a surface treatment protocol allowing tissue confinement inside an adhesive area over a few weeks. The technique achieves a micrometer resolution and any geometry of the adhesive area is feasible. In our study, the size is such that cells behave collectively. We analyse the growth of epithelium with Madine Derby Canine (MDCK) cells in circular adhesive regions. Migration and densification of the tissue are studied with PIV (Particle Image Velocimetry) and others image analysis techniques. We characterize velocity field and observe large amplitude oscillations of the velocity, whose period match the hypothesis of stress wave propagating through the epithelium. We also characterize the appearance of a tridimensionnal rim of cells at the periphery of the epithelium, similar to the first step of tubulogenesis. In two other experiments, using opposite geometry, we study how the epithelium can cover an anti-adhesive region. We show the covering requires a supracellular actomyosine cable, and the cable tension balanced by a surface tension defines a critical size beyond which the anti-adhesive region cannot be covered by the epithelium
Growth and densification of an epithelium in confined geometry