Cell cluster migration: Connecting experiments with physical models

In multi-cellular organisms, the migration of cohesive clusters of cells containing many individual cells is a common occurrence. Examples include the migration of cells during processes such as the development of the embryo, wound healing, immune response, and the spread of cancer. The migration process depends not only on the traction forces applied by the cluster on its surroundings, in order to move, but also on the viscoelastic properties of both the surrounding matrix and the migrating cellular cluster. Characterizing the viscoelastic properties of the cluster, its environment and the forces within the cluster, in great detail, is difficult both in-vitro and certainly in-vivo. We review here several examples where theoretical studies using simplified models can be used to gain insights into the basic underlying mechanisms that control the cellular migration patterns.