Rupture-Repair Cycles in Regenerating Hydra Tissues

Destructive mechanical breakdowns and fractures are ubiquitous events in driven physical matter; living tissues, by contrast, can rupture repeatedly while restoring integrity. Here we study rupture-repair interplay in regenerating Hydra tissues, which cycle through osmotic inflation, pressure release by rupture, and resealing. We utilize bright-field imaging of the tissues projected area as a readout of the rupture magnitude before it is arrested. Analyzing these event statistics, we find that the tail of the area-drop distribution is controlled by Ca2+-dependent repair efficiency. When the Ca2+ response is weakened, either by partially blocking gap-junctions mediating the intercellular communication, or by inhibiting stretch-activated Ca2+ channels, the actomyosin force that arrests the rupture process is delayed or reduced. Under these conditions, rare large pressure releases become more likely, and the tail of the distribution crosses over from an exponential behavior, exhibiting a characteristic scale, to a power-law one consistent with a critical-like regime reflecting intermittent rupture propagation. These results identify mechanically evoked Ca2+ activity as a control axis linking repair to rupture statistics in a living tissue. It supports a picture of rupture front advancing by stick-slip-like dynamics as it encounters a heterogeneous mechanical landscape, akin to failure-front propagation in disordered materials.