  Using a three-dimensional active vertex model, we numerically study the
shapes of strained unsupported epithelial monolayers subject to active
junctional noise due to stochastic binding and unbinding of myosin. We find
that while uniaxial, biaxial, and isotropic in-plane compressive strains do
lead to the formation of longitudinal, herringbone-pattern, and labyrinthine
folds, respectively, the villus morphology characteristic of, e.g., the small
intestine appears only if junctional tension fluctuations are strong enough to
fluidize the tissue. Moreover, the fluidized epithelium features villi even in
absence of compressive strain provided that the apico-basal differential
tension is large enough. We analyze several details of the different epithelial
forms including the role of strain rate and the modulation of tissue thickness
across folds. Our results show that nontrivial morphologies can form even in
unsupported, non-patterned epithelia.
