Tissue Fracture in Development and Disease

维持和产生机械力是哺乳动物组织生理的正常组成部分：肠上皮在肠道蠕动时被拉伸，肺泡在呼吸时变形，皮肤表皮层为外部环境提供机械屏障。即使是最简单的组织，其机械完整性和力传递对其正常功能也至关重要。这在病变状态下尤其明显，细胞骨架或细胞间粘附蛋白的点突变导致机械故障，如起泡、开裂和出血。尽管具有重要的基础意义，但我们对简单组织的机械失效模式没有基本的了解，也没有对不同成分如何结合形成持久组织的分子理解。这主要是由于缺乏适当的实验工具和体内组织固有的复杂性。该研究项目将结合机械工程和分子生物学的实验工具，了解简单上皮组织在高机械负荷下是如何断裂的，以及组织耐久性的关键分子决定因素。我开发了一种新的系统来表征简单上皮组织的机械特性。该系统将进一步发展，用于同时测量组织水平的机械力和单层断裂成像。裂缝可以在亚毫秒的时间尺度上发生，这对于传统的显微镜来说太快了。将使用高速摄像机以每秒数百帧的速度捕捉故障模式，并使用快速数据采集系统记录组织力的变化。这将允许表征裂纹前缘，因为它通过组织在控制机械力下传播。一种新的组织断裂力学描述将被开发出来，并将在不同的分子条件下进行比较。不同的细胞骨架网络对单层耐久性的贡献将采用“自上而下”的方法进行研究。裂缝的传播（速度，力，形状）将在使用遗传和药物抑制组合干扰不同细胞骨架成分的组织中进行测量。这些数据将为这些细胞骨架网络如何协同产生能够承受机械负荷的耐用组织提供新的见解。跨学科的工作将允许从机械和分子的角度对组织的机械失效和断裂有一个基本的了解。考虑到组织机械完整性对成人组织和发育正常生理的普遍意义，以及上皮组织有趣的基本材料特性，这些结果将引起工程师、临床医生和发育生物学家的兴趣。

Sustaining and generating mechanical forces is a normal part of physiology for mammalian tissue: Intestinal epithelia are stretched during peristaltic movements in the gut, lung alveoli deform during breathing and skin epidermal layers provide a mechanical barrier to the external environment. Mechanical integrity and force transmission in even the simplest tissues is critical to their proper function. This is particularly apparent in diseased states where point mutations to cytoskeletal or intercellular adhesion proteins result in mechanical failures such as blistering, cracking and hemorrhaging. Despite the fundamental significance, we do not have a fundamental understanding of the modes through which simple tissues mechanically fail, or a molecular understanding of how different components combine to create durable tissues. This is primarily due to the lack of appropriate experimental tools and the inherent complexity of in vivo tissues. This research program will combine experimental tools from mechanical engineering and molecular biology to understand how simple epithelial tissues fracture under high mechanical loads and the key molecular determinants of tissue durability. I have developed a novel system to characterize the mechanical properties of simple epithelial tissues. This system will be further developed for the simultaneous measurement of tissue-level mechanical forces and imaging of monolayer fracture. Fractures can occur on the sub-millisecond timescale, which is too rapid for conventional microscopy. A high-speed camera will be used to capture the mode of failure at a rate of hundreds of frames per second and a rapid DAQ system to record the changes in tissue forces. This will allow for the characterization of the crack front as it propagates through the tissue under controlled mechanical forces. A novel mechanical description of tissue fracture will be developed that will be compared across different molecular conditions. The contribution of different cytoskeletal networks to monolayer durability will be investigated by taking a `top down' approach. The propagation of cracks (speed, force, shape) will be measured in tissues where different cytoskeletal components have been perturbed using a combination of genetic and pharmacological inhibition. This data will provide new insights into how these cytoskeletal networks synergistically generate durable tissues capable of sustaining mechanical loads. Working across disciplines will allow for a fundamental understanding of how tissues mechanically fail and fracture from both a mechanical and molecular perspective. Given the general significance of tissue mechanical integrity for normal physiology in both adult tissue and development and the interesting fundamental material properties of epithelial tissue, the outcomes will be of interest to engineers, clinicians and developmental biologists alike.