Vimentin promotes collective cell migration through collagen networks via increased matrix remodeling and spheroid fluidity

Intermediate filaments (IF) are diverse and cell-type specific. The IF protein vimentin, expressed in mesenchymal cells and different cancer cells, is functionally associated with cell migration through fibrous tissues. Vimentin increases cell elongation needed for migration, yet also acts as a cytoskeletal cage that hinders cells squeezing through small spaces. To determine how vimentin facilitates cell migration through the extracellular matrix (ECM) and around neighboring cells in tissues, we examine the collective invasion of cell spheroids embedded in collagen networks. Unlike single-cell migration in collagen networks, the collective invasion of cells through the collagen network is increased by vimentin for both mouse embryonic fibroblasts (MEF) and co-cultures of MEF with MDA-MB-231 breast cancer cells. Using multiple experimental systems, we show that vimentin increases spheroid contractility and that vimentin-mediated collective cell expansion depends on matrix metalloproteinases (MMP), which degrade collagen networks. In addition, through advanced imaging and a computational 3D cell vertex model, we find that vimentin enhances the elongation of cells in spheroids embedded in collagen, indicating increased spheroid fluidity and active collagen contraction. Altogether, these results reveal new insights on vimentin's effects in enhancing collective cell migration in 3D matrix environments through collagen remodeling and tissue fluidity.