  Morphogenesis, tissue regeneration and cancer invasion involve transitions in
tissue morphology. These transitions, caused by collective cell migration
(CCM), have been interpreted as active wetting/de-wetting transitions. This
phenomenon is considered on model system such as wetting of cell aggregate on
rigid substrate which includes cell aggregate movement and
isotropic/anisotropic spreading of cell monolayer around the aggregate
depending on the substrate rigidity and aggregate size. This model system
accounts for the transition between 3D epithelial aggregate and 2D cell
monolayer as a product of: (1) tissue surface tension, (2) surface tension of
substrate matrix, (3) cell-matrix interfacial tension, (4) interfacial tension
gradient, (5) viscoelasticity caused by CCM, and (6) viscoelasticity of
substrate matrix. These physical parameters depend on the cell contractility
and state of cell-cell and cell matrix adhesion contacts, as well as, the
stretching/compression of cellular systems caused by CCM. Despite extensive
research devoted to study cell wetting, we still do not understand interplay
among these physical parameters which induces oscillatory trend of cell
rearrangement. This review focuses on these physical parameters in governing
the cell rearrangement in the context of epithelial aggregate
wetting.de-wetting, and on the modelling approaches aimed at reproducing and
understanding these biological systems. In this context, we do not only review
previously-published bio-physics models for cell rearrangement caused by CCM,
but also propose new extensions of those models in order to point out the
interplay between cell-matrix interfacial tension and epithelial
viscoelasticity and the role of the interfacial tension gradient in cell
spreading.
