  Pulsatory activity patterns, driven by mechanochemical feedback, are
prevalent in many biological systems. Here we present a theoretical framework
to elucidate the mechanical origin and regulation of pulsatile activity
patterns within multicellular tissues. We show that a simple mechanical
feedback at the level of individual cells - activation of contractility upon
stretch and subsequent inactivation upon turnover of active elements - is
sufficient to explain the emergence of quiescent states, long-range wave
propagation, and traveling activity pulse at the tissue-level. We find that the
transition between a propagating pulse and a wave is driven by the competition
between timescales associated with cellular mechanical response and geometrical
disorder in the tissue. This sheds light on the fundamental role of cell
packing geometry on tissue excitability and spatial propagation of activity
patterns.

Biological Physics;Soft Condensed Matter;Tissues and Organs