  Interfacial instability is highly relevant to many important biological
processes. A key example arises in wound healing experiments, which observe
that an epithelial layer with an initially straight edge does not heal
uniformly. We consider the phenomenon in the context of active fluids.
Improving upon the approximation used in J. Zimmermann, M. Basan and H. Levine,
Euro. Phys. J.: Special Topics 223, 1259 (2014), we perform a linear stability
analysis on a two dimensional incompressible hydrodynamic model of an active
fluid with an open interface. We categorise the stability of the model and find
that for experimentally relevant parameters, fingering stability is always
absent in this minimal model. Our results point to the crucial importance of
density variation in the fingering instability in tissue regeneration.
