Surface tension determines tissue shape and growth kinetics
The growth of tissue is an essential process controlling morphogenesis and regeneration of organs [1]. In general tissue forming cells are interactive and motile [2], which can give rise to emergent physical properties such as viscous fluid behaviour as has been shown for epithelial monolayers during embryogenesis [3, 4], and for cell-agglomerates [5] with a measurable surface tension [6]. However, the mechanical integrity of tissues is provided by extracellular matrices (ECM) that turn tissues into solids with well-defined elastic properties [7]. Paradoxically, it has been shown by in-vitro experiments that even osteoid-like tissue with large amounts of ECM grows according to rules reminiscent of fluid behavior [8, 9]. Motivated by this conundrum, we show here quantitatively, by constraining growing tissues to surfaces of con ...