A mechanism-based theory of cellular and tissue plasticity

Plastic deformation in cells and tissues has been found to play crucial roles in collectie cell migration, cancer metastasis, and morphogenesis. Howeer, the fundamental question of how plasticity is initiated in indiidual cells and then propagates within the tissue remains elusie. Here, we deelop a mechanism-based theory of cellular and tissue plasticity that accounts for all key processes inoled, including the actiation and deelopment of actie contraction at different scales as well as the formation of endocytic esicles on cell junctions and show that this theory achiees quantitatie agreement with all existing experiments. Specifically, it reeals that, in response to optical or mechanical stimuli, the myosin contraction and thermal fluctuation-assisted formation and pinching of endocytic esicles could lead to permanent shortening of cell junctions and that such plastic constriction can stretch neighboring cells and trigger their actie contraction through mechanochemical feedbacks and eentually their plastic deformations as well. Our theory predicts that endocytic esicles with a size around 1 to 2 mu m will most likely be formed and a higher irreersible shortening of cell junctions could be achieed if a long stimulation is split into multiple short ones, all in quantitatie agreement with experiments. Our analysis also shows that constriction of cells in tissue can undergo elastic/unratcheted to plastic/ratcheted transition as the magnitude and duration of actie contraction increases, ultimately resulting in the propagation of plastic deformation waes within the monolayer with a constant speed which again is consistent with experimental obserations.