Fig. 2.

Mechanical control of compaction. A – Schematic of a minimal tissue from low (left) to high (right) compaction. The degree of compaction is given by the angles of contact θ (magenta), which results from the ratio of tension within the tissue γ_cc (green) and between the outside of the tissue and its surrounding γ_cm (red). Therefore, the compaction parameter α = γ_cc/2γ_cm = cos(θ/2), as given by the Young–Dupré equation, reflects both the degree of compaction and the balance of tensions in the tissue. Compaction corresponds to a decrease of the compaction parameter α. B – Compaction occurs when the tension γ_cm increases (top right) and/or the tension γ_cc decreases (bottom right). Contractility controls both γ_cm and γ_cc. Adhesion may theoretically control γ_cc directly, but its signaling to decrease contractility at cell–cell contacts constitutes the primary influence of adhesion to tissue compaction.