Kavli Affiliate: Mark J. Bowick
| First 5 Authors: Yiwen Tang, Siyuan Chen, Mark J. Bowick, Dapeng Bi,
| Summary:
Biological tissues transform between solid-like and liquid-like states in
many fundamental physiological events. Recent experimental observations further
suggest that in two-dimensional epithelial tissues these solid-liquid
transformations can happen via intermediate states akin to the intermediate
hexatic phases observed in equilibrium two-dimensional melting. The hexatic
phase is characterized by quasi-long-range (power-law) orientational order but
no translational order, thus endowing some structure to an otherwise
structureless fluid. While it has been shown that hexatic order in tissue
models can be induced by motility and thermal fluctuations, the role of cell
division and apoptosis (birth and death) has remained poorly understood,
despite its fundamental biological role. Here we study the effect of cell
division and apoptosis on global hexatic order within the framework of the
self-propelled Voronoi model of tissue. Although cell division naively destroys
order and active motility facilitates deformations, we show that their combined
action drives a liquid-hexatic-liquid transformation as the motility increases.
The hexatic phase is accessed by the delicate balance of dislocation defect
generation from cell division and the active binding of
disclination-antidisclination pairs from motility. We formulate a mean-field
model to elucidate this competition between cell division and motility and the
consequent development of hexatic order.
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