Cell divisions suppress dynamical correlations in solid tissues

TL;DR

This study uses a two-dimensional elastoplastic model to show that cell divisions in tissues suppress large-scale rearrangements and avalanches, maintaining marginal stability but reducing long-range dynamical correlations.

Contribution

It demonstrates that cell divisions act as active plastic events that suppress system-spanning avalanches, contrasting with passive amorphous solids, and explains this through energy balance considerations.

Findings

Cell divisions fluidize tissue below passive yield stress.

They suppress system-spanning avalanches of cell rearrangements.

Avalanche suppression is due to energy injected by cell divisions.

Abstract

Developing tissues often maintain mechanical coherence while continuously remodeling through cellular processes such as cell divisions and rearrangements. In this way, they are an example of amorphous solids. In passive amorphous solids, local rearrangements can trigger one another through long-ranged elastic interactions, leading to system-spanning avalanches near yielding. Whether similar collective dynamics should be expected in living tissues is unclear, because cell divisions generate stress and remodeling events independently of local mechanical stability. Here, we address this question using a two-dimensional elastoplastic model in which cell divisions are treated as active plastic events. We find that while cell divisions fluidize the tissue below the passive yield stress, but preserve the marginal stability in the quasistatic limit. However, they also strongly suppress the system-spanning avalanches of cell rearrangements, in constrast with the expected behavior in passive amorphous solids. Finally, we show that the avalanche supression originates from the energy balance in the system. Namely, the energy injected by cell divisions allows for shear flow below the yield stress, but also provides a finite budget for rearrangements. These results suggest that proliferating tissues display the structural hallmarks of marginal amorphous solids while exhibiting much shorter-ranged correlations in dynamics, compared to passive amorphous solids.