The physical state of embryonic tissues emerges from non-equilibrium, collective interactions among constituent cells. Cellular jamming, rigidity transitions and characteristics of glassy dynamics have all been observed in multicellular systems, but it is unclear how cells control these emergent tissue states and transitions, including tissue fluidization. Combining computational and experimental methods, here we show that tissue fluidization in posterior zebrafish tissues is controlled by the stochastic dynamics of tensions at cell–cell contacts. We develop a computational framework that connects cell behaviour to embryonic tissue dynamics, accounting for the presence of extracellular spaces, complex cell shapes and cortical tension dynamics. We predict that tissues are maximally rigid at the structural transition between confluent and non-confluent states, with actively generated tension fluctuations controlling stress relaxation and tissue fluidization. By directly measuring strain and stress relaxation, as well as the dynamics of cell rearrangements, in elongating posterior zebrafish tissues, we show that tension fluctuations drive active cell rearrangements that fluidize the tissue. These results highlight a key role of non-equilibrium tension dynamics in developmental processes.

胚胎组织的物理状态来自组成细胞之间的非平衡、集体相互作用。在多细胞系统中都观察到了细胞干扰、刚性转变和玻璃动力学特征，但尚不清楚细胞如何控制这些出现的组织状态和转变，包括组织流化。结合计算和实验方法，我们在这里表明斑马鱼后部组织中的组织流化受细胞 - 细胞接触处张力的随机动态控制。我们开发了一个计算框架，将细胞行为与胚胎组织动力学联系起来，解释细胞外空间、复杂细胞形状和皮质张力动力学的存在。我们预测组织在汇合和非汇合状态之间的结构转变时具有最大的刚性，主动产生的张力波动控制应力松弛和组织流化。通过直接测量拉长斑马鱼后部组织中的应变和应力松弛以及细胞重排的动力学，我们表明张力波动会驱动活跃的细胞重排，从而使组织流动。这些结果突出了非平衡张力动力学在发育过程中的关键作用。我们表明，张力波动会驱动活跃的细胞重排，从而使组织流动。这些结果突出了非平衡张力动力学在发育过程中的关键作用。我们表明，张力波动会驱动活跃的细胞重排，从而使组织流动。这些结果突出了非平衡张力动力学在发育过程中的关键作用。