Cell-cell adhesion holds tissues together. The intuition is simple: stronger adhesion means more cohesion, which means less movement. Glue cells together more tightly and the tissue should become more rigid, less fluid, harder for cells to rearrange. This is the standard picture in tissue mechanics, and it is half right.
Nguyen, Bera, Notbohm, and Bi (arXiv:2603.04170, March 2026) show that adhesion has two physically distinct components that act in opposite directions on tissue fluidity.
The first component is energetic — the static cost of maintaining a junction between two cells. Stronger energetic adhesion changes the equilibrium shape of cells, making them more elongated. Elongated cells have lower energy barriers to neighbor exchange — the T1 transition in which two cells swap neighbors by briefly forming a four-cell vertex. Energetically, stronger adhesion promotes fluidity by reshaping cells into configurations that rearrange more easily.
The second component is dissipative — the viscous resistance that a junction exerts when it is being remodeled. When two cells slide past each other, the adhesive bonds at the junction must break and reform. This takes time and dissipates energy. Stronger dissipative adhesion increases the friction during rearrangement, slowing neighbor exchanges. Dissipatively, stronger adhesion suppresses fluidity by resisting the motion that the energetic component facilitates.
The same molecule — a cadherin spanning the junction between two cells — contributes to both components simultaneously. Its binding energy sets the energetic contribution. Its unbinding and rebinding kinetics set the dissipative contribution. Whether increasing adhesion makes a tissue more fluid or more rigid depends on which component dominates at the relevant timescale. Fast perturbations feel the dissipation; slow perturbations feel the energetics.
The double-edged nature explains contradictory experimental findings. Some studies report that reducing adhesion causes tissues to jam. Others report that reducing adhesion causes them to flow. Both are correct — for different tissues, different timescales, and different ratios of energetic to dissipative adhesion. The contradiction was not in the experiments. It was in treating adhesion as a single quantity when it is two.
Nguyen, Bera, Notbohm, and Bi, "Cell-Cell Adhesion as a Double-Edged Sword in Tissue Fluidity," arXiv:2603.04170 (March 2026).