London Centre for Nanotechnology, University College London, London WC1E 6BT, United Kingdom.
Laboratoire de Biologie Cellulaire et Moléculaire du Controle de la Prolifération, Centre de Biologie Intégrative, CNRS, Université Toulouse III Paul Sabatier, Université de Toulouse, 31062 Toulouse, France.
Proc Natl Acad Sci U S A. 2020 Apr 28;117(17):9377-9383. doi: 10.1073/pnas.1917838117. Epub 2020 Apr 13.
Epithelial monolayers are two-dimensional cell sheets which compartmentalize the body and organs of multicellular organisms. Their morphogenesis during development or pathology results from patterned endogenous and exogenous forces and their interplay with tissue mechanical properties. In particular, bending of epithelia is thought to result from active torques generated by the polarization of myosin motors along their apicobasal axis. However, the contribution of these out-of-plane forces to morphogenesis remains challenging to evaluate because of the lack of direct mechanical measurement. Here we use epithelial curling to characterize the out-of-plane mechanics of epithelial monolayers. We find that curls of high curvature form spontaneously at the free edge of epithelial monolayers devoid of substrate in vivo and in vitro. Curling originates from an enrichment of myosin in the basal domain that generates an active spontaneous curvature. By measuring the force necessary to flatten curls, we can then estimate the active torques and the bending modulus of the tissue. Finally, we show that the extent of curling is controlled by the interplay between in-plane and out-of-plane stresses in the monolayer. Such mechanical coupling emphasizes a possible role for in-plane stresses in shaping epithelia during morphogenesis.
上皮细胞单层是二维的细胞层，将多细胞生物的身体和器官分隔开。它们在发育或病理过程中的形态发生是由有组织的内源性和外源性力以及它们与组织力学特性的相互作用所导致的。特别是，上皮细胞的弯曲被认为是由沿着其顶底轴极化的肌球蛋白马达产生的主动扭矩引起的。然而，由于缺乏直接的机械测量，这些面外力对形态发生的贡献仍然难以评估。在这里，我们使用上皮细胞卷曲来描述上皮细胞单层的面外力学。我们发现，在没有体内和体外基质的情况下，上皮细胞单层的自由边缘会自发形成高曲率的卷曲。卷曲起源于基底部肌球蛋白的富集，它产生了一个主动的自发曲率。通过测量使卷曲变平所需的力，我们可以估算出组织的主动扭矩和弯曲模量。最后，我们表明卷曲的程度受到单层中面内和面外应力相互作用的控制。这种机械耦合强调了面内应力在形态发生过程中塑造上皮细胞的可能作用。
