  In dense biological tissues, cell types performing different roles remain
segregated by maintaining sharp interfaces. To better understand the mechanisms
for such sharp compartmentalization, we study the effect of an imposed
heterotypic tension at the interface between two distinct cell types in a fully
3D model for confluent tissues. We find that cells rapidly sort and
self-organize to generate a tissue-scale interface between cell types, and
cells adjacent to this interface exhibit signature geometric features including
nematic-like ordering, bimodal facet areas, and registration, or alignment, of
cell centers on either side of the two-tissue interface. The magnitude of these
features scales directly with the magnitude of imposed tension, suggesting that
biologists can estimate the magnitude of tissue surface tension between two
tissue types simply by segmenting a 3D tissue. To uncover the underlying
physical mechanisms driving these geometric features, we develop two minimal,
ordered models using two different underlying lattices that identify an
energetic competition between bulk cell shapes and tissue interface area. When
the interface area dominates, changes to neighbor topology are costly and occur
less frequently, which generates the observed geometric features.
