[Principles of spatial organization of cellular sheets]

The principles of the spatial organisation of epithelial sheets are described, and a new approach to studying their histoarchitecture is proposed. The approach is based on the concept of modular structure of tissues and consists in constructing a family of topological and geometrical models of tissue structure and their experimental verification. Theoretical evidence was obtained that at least 11 topological variants of cell mosaic patterns can be realized in simple epithelia but not one as has been suggested so far. Nine variants of epithelial mosaics predicted have been found experimentally in various animals, and the discovery of the other two is expected in the future. New thus far unknown properties of tissues such as translation symmetry and stoichiometry of the composition were described. By using this approach, it is possible to predict and find new variants of topology of multirow and multilayer epithelia and prognose their changes during normal and pathological morphogenesis.