Department of Physics, Northeastern University, Boston, Massachusetts 02115, USA.
Department of Physics, Durham University, Science Laboratories, South Road, Durham DH1 3LE, United Kingdom.
Phys Rev Lett. 2022 Apr 29;128(17):178001. doi: 10.1103/PhysRevLett.128.178001.
Biological processes, from morphogenesis to tumor invasion, spontaneously generate shear stresses inside living tissue. The mechanisms that govern the transmission of mechanical forces in epithelia and the collective response of the tissue to bulk shear deformations remain, however, poorly understood. Using a minimal cell-based computational model, we investigate the constitutive relation of confluent tissues under simple shear deformation. We show that an initially undeformed fluidlike tissue acquires finite rigidity above a critical applied strain. This is akin to the shear-driven rigidity observed in other soft matter systems. Interestingly, shear-driven rigidity can be understood by a critical scaling analysis in the vicinity of the second order critical point that governs the liquid-solid transition of the undeformed system. We further show that a solidlike tissue responds linearly only to small strains and but then switches to a nonlinear response at larger stains, with substantial stiffening. Finally, we propose a mean-field formulation for cells under shear that offers a simple physical explanation of shear-driven rigidity and nonlinear response in a tissue.
从形态发生到肿瘤侵袭，生物过程会在活体组织内自发产生切变应力。然而，目前对于上皮组织中机械力传递的机制以及组织对整体切变变形的集体反应仍知之甚少。我们使用一种基于最小细胞的计算模型，研究了简单切变变形下组织的本构关系。我们发现，初始处于无变形状态的类液组织在受到临界应变以上的应变时会获得有限的刚性。这类似于在其他软物质系统中观察到的剪切驱动刚性。有趣的是，通过在控制无变形系统液-固转变的二阶临界点附近的临界标度分析，可以理解剪切驱动刚性。我们进一步表明，类固态组织仅在小应变下呈线性响应，但随后在较大应变下切换为非线性响应，表现出明显的增强。最后，我们提出了一种用于剪切下细胞的平均场公式，为剪切驱动刚性和组织的非线性响应提供了一个简单的物理解释。
