A novel experimental tool to investigate the mechanics of cell monolayers at tissue, cellular, and subcellular scales

人体的许多空洞和自由表面(如肠道、肺、血管)都有一层一细胞厚的细胞层(单层)。对于这样的单层来说，暴露在机械应力下是正常的生理部分：肺泡在呼吸过程中变形，肠上皮抵抗肠道的蠕动运动，血管内皮细胞暴露在血流中的脉动流体剪应力下。当突变或病原体影响细胞骨架(细胞骨架)或细胞间连接导致组织脆弱性增加(如大疱性表皮、葡萄球菌起泡)时，单层的机械功能在疾病中尤其明显。尽管有明确的生理关联，但目前对细胞单层的机制知之甚少。这些单层内的细胞通过细胞间连接紧密相连：紧密连接形成障碍，限制溶质的通过，而黏附连接和桥粒将组成细胞的细胞骨架整合成一个机械连续体。到目前为止，细胞力学的研究主要集中在分离的细胞上，现在对它们的机械性能以及正常生理和疾病的基本生物学已经有了很大了解。对于单分子层的机制以及它如何与组织的细胞成分及其细胞骨架的机械性能相关的知识相对较少。这主要是由于缺乏特定的实验技术来评估组织的内在机械性能，同时监测细胞和亚细胞的运动。我们的目标是开发一种新的工具来拉伸培养的细胞单层，这些细胞单层是机械地与任何底物隔离的。在组织变形过程中，施加的机械张力将被直接测量，并将同时在亚细胞、细胞和组织长度尺度上对单层进行成像，以便作为施加的力的函数，可以准确地监测亚细胞组件的结构、细胞的形状及其最终的重组。这一新仪器的研究将使我们能够理解单个细胞的结构及其相互之间的排列如何参与设定整个组织的机械性能。因此，我们将能够理解构成细胞骨架或细胞间连接的蛋白质的病理变化如何对组织力学产生灾难性的后果。

Many of the cavities and free surfaces of the human body (e.g. gut, lungs, blood vessels) are lined by a layer of cells one-cell thick (a monolayer). Exposure to mechanical stresses is a normal part of physiology for such monolayers: lung alveoli deform during respiration, intestinal epithelia resist peristaltic movements in the gut, and endothelia are exposed to pulsatile fluid shear stresses in blood flow. The mechanical function of monolayers is particularly apparent in disease when mutations or pathogens affecting the cell skeleton (cytoskeleton) or intercellular junctions result in increased fragility of tissues (e.g. epidermis bullosa, staphylococcus blistering). Despite clear physiological relevance, little is presently known about the mechanics of cell monolayers.Cells within these monolayers are tightly connected to one another by intercellular junctions: tight junctions form barriers restricting the passage of solutes whilst adherens junctions and desmosomes integrate the cytoskeletons of constituent cells into a mechanical continuum. To date, research in cell mechanics has primarily focused on isolated cells and much is now known about their mechanical properties as well as the underlying biology in normal physiology and disease. Comparatively little is known about the mechanics of monolayers and how it relates to the mechanical properties of the tissue's cellular constituents and their cytoskeleton. This is primarily due to the lack of specific experimental techniques to assess the intrinsic mechanical properties of tissues while monitoring cellular and subcellular traits.We aim to develop a novel tool to stretch cultured cell monolayers that are mechanically isolated from any substrate. During tissue deformation, the applied mechanical tension will be directly measured and monolayers will simultaneously be imaged at subcellular, cellular and tissue length scales, such that the architecture of the sub-cellular components, the shape of the cells and their eventual reorganisation can be accurately monitored as a function of the imposed force. The studies enabled by this novel instrument will allow us to understand how the structure of individual cells and their arrangement relative to one another participate in setting the mechanical properties of whole tissues. As a consequence, we will be able to understand how pathological changes in the proteins that form part of the cytoskeleton or the intercellular junctions can have catastrophic consequences for tissue mechanics.