Cells at the edges of migrating epithelial sheets pull themselves systematically and cooperatively into empty space regardless of the direction they are moving in, reports a paper published online this week in Nature Materials. The discovery of this basic cell-patterning motif should lead to a deeper understanding of cellular migration during wound healing, tumour invasion and embryonic development, for example.
Epithelial cell monolayers are one-cell-thick sheets that line body cavities or surfaces such as the skin, lungs and blood vessels. Jeffrey Fredberg and colleagues used monolayer stress microscopy to probe the velocities, cellular tractions and intercellular stresses in an epithelial cell sheet advancing towards and past a circular area onto which the cells could not adhere. They found that cells located near the non-adhesive area exerted tractions on the substrate that pulled the sheet towards the unfilled area, independently of whether the cells approached it, migrated tangentially along the edge or receded from it. Although the origin of the mechanism behind this cell-patterning motif is not currently understood, the authors suggest that its effects on the migration of cell sheets are pervasive and should lead to improved designs of tissue scaffolds for regenerative medicine.