  Recent work on particle-based models of tissues has suggested that any finite
rate of cell division and cell death is sufficient to fluidize an epithelial
tissue. At the same time, experimental evidence has indicated the existence of
glassy dynamics in some epithelial layers despite continued cell cycling. To
address this discrepancy, we quantify the role of cell birth and death on
glassy states in confluent tissues using simulations of an active vertex model
that includes cell motility, cell division, and cell death. Our simulation data
is consistent with a simple ansatz in which the rate of cell-life cycling and
the rate of relaxation of the tissue in the absence of cell cycling contribute
independently and additively to the overall rate of cell motion. Specifically,
we find that a glass-like regime with caging behavior indicated by subdiffusive
cell displacements can be achieved in systems with sufficiently low rates of
cell cycling.
