We Share Science

Video abstract for the article 'Morphological instabilities of stratified epithelia: a mechanical instability in tumour formation' by Thomas Risler and Markus Basan (Thomas Risler and Markus Basan 2013 New J. Phys. 15 065011). Read the full article in New Journal http://iopscience.iop.org/1367-2630/15/6/065011. From Focus on the Physics of Cancer GENERAL SCIENTIFIC SUMMARY Introduction and background. Most tumours originate from epithelia, which are the tissues that line the surface of the body as well as its cavities and tubes. Epithelia can either consist of a single layer of cells or be multi-layered when they serve protective functions. They rest upon a basement membrane separating them from a supporting connective tissue, from which nutrients, oxygen and metabolites diffuse. Epithelia are under constant cell renewal, and in healthy multi-layered epithelia, cell division takes place exclusively in a region close to the basement membrane. The interface between the epithelium and the connective tissue is rarely flat, but presents different degrees of undulation. These undulations are typically more pronounced in pre-malignant and malignant tissues, where more layers of dividing cells are present. Main results. On long timescales, cellular rearrangements at the microscopic scale lead to a fluid-like behaviour of the tissue. Treating the epithelium as a viscous medium with source and sink terms representing cell division and cell death, we find a novel hydrodynamic instability at finite wavelength, which could be responsible for these undulations. The tissue properties that favour this instability match known characteristics of cancerous tissues. Metabolites diffusing from the connective tissue enhance the instability via a mechanism reminiscent of the Mullins--Sekerka instability from single-diffusion processes of crystal growth. Wider implications. Invasive protrusions of cancerous tissues may originate from the same driving force, prior to the emergence of proper motile phenotypes. One may therefore speculate that a physical mechanism such as the instability proposed here could initiate the emergence of invasive phenotypes.