The Compression Network

Contact inhibition — cells stop dividing when they touch their neighbors — is the standard explanation for why tissues stop growing. But the mechanism is local: each cell senses its immediate surroundings. How does a tissue-scale decision emerge from cell-scale sensing?

Daraf, Lavi, Saleem, Sevilla Sanchez, Feldman, and Atia (arXiv:2509.16661) find that epithelial tissues use a self-organized network to arrest proliferation. As the tissue approaches confluence, two interpenetrating networks materialize: islands of mechanically compressed, non-cycling cells percolating through an ocean of tensed, cycling cells. When the compression network percolates — connects from one side of the tissue to the other — proliferation arrests globally.

The mechanism is not contact inhibition in the classical sense. Individual cells don’t stop dividing because their neighbors are touching them. They stop because they find themselves in a connected compression network whose geometry follows a power-law size distribution consistent with preferential attachment. The network is the signal, not the contact.

The structural insight: tissue growth stops at a percolation threshold, not at a density threshold. A tissue at the same cell density but with a different compression network topology would behave differently. The relevant variable is connectivity, not crowding. The tissue doesn’t count its cells — it feels its mechanical network, and stops when that network spans the domain.

Growth arrests not when the room is full, but when the pressure network is connected.