Airway Smooth Muscle Cell Orientation Control by Contractile Torque

描述（由申请人提供）：众所周知，粘附细胞会根据基底的机械不均匀性（包括基底拉伸和材料各向异性）改变其方向。虽然已知细胞使用它们的收缩机制来机械感知这些不均匀性，但不知道来自底物和细胞内收缩力的机械信号如何协同控制细胞定向。目前的范式认为，来自底物的机械不均匀性是一系列生物化学和重塑事件的先决条件，这些事件将细胞控制到一个新的位置。我们最近的理论研究表明，细胞对底物不均匀性的重新定向和转向可能受到机械机制的控制甚至调节。这使我们提出了以下新颖的、机械的、可测试的工作假设：为了响应基底的机械不均匀性，细胞骨架收缩应力通过一种简单的物理机制——即收缩扭矩——指示细胞的方向，从而将细胞引向新的方向。因此，本研究的主要目的是研究收缩扭矩与细胞重新定向之间的关系。为了实现这一点，我们需要新的实验工具来测量收缩扭矩。因此，我们提出两个目标：1。利用细胞映射流变测量技术测量细胞在非均匀、静态和动态基底拉伸时的收缩力矩。2. 设计具有可变材料各向异性的衬底，以测量在衬底诱导材料各向异性时电池重定向时的收缩扭矩。虽然所提出的工作是任何贴壁细胞的基础，但在这里，我们将注意力限制在气道平滑肌（ASM）细胞的收缩性、机械传感和在基质上的定位问题上。这些问题对于气道力学是至关重要的，因为在适当的情况下，ASM细胞对气道的收缩是正常气道狭窄的关键。如果成功，这项研究将促进我们对机械微环境决定ASM细胞在其自然栖息地的组织和收缩性的机制的理解。

DESCRIPTION (provided by applicant): It is well established that adherent cells change their orientation in response to mechanical non- uniformities of the substrate, including substrate stretching and material anisotropy. While it is known that cells use their contractile machinery to mechanosense these nonuniformities, it is not known how mechanical signals from the substrate and intracellular contractile forces cooperate to govern cell orientation. The current paradigm holds that mechanical nonuniformities from the substrate are a precondition for a cascade of biochemical and remodeling events that govern cell to a new position. Our recent theoretical study suggests that reorientation and steering of the cell in response to substrate nonuniformities may be governed and even regulated by mechanical mechanisms. This led us to the following novel, mechanistic, and testable working hypothesis: In response to mechanical nonuniformities of the substrate, the cytoskeletal contractile stress dictates orientation of the cell via a simple physical mechanism - namely the contractile torque - that steers the cell towards a new orientation. The main goal of this study is therefore to investigate the relationship between the contractile torque and cell reorientation. To accomplish this, we need new experimental tools for measuring the contractile torque. Thus, we propose two aims: 1. To measure the contractile torque during cell reorientation in response to nonuniform, static and dynamic, substrate stretching using the cell mapping rheometry technique. 2. To design a substrate with alterable material isotropy in order to measure the contractile torque during cell reorientation in response to induced material anisotropy of the substrate. Although the proposed work is fundamental to any adherent cells, here we limit attention to the questions of airway smooth muscle (ASM) cell contractility, mechanosensing and positioning on the substrate. These questions are crucial to airway mechanics because, if appropriate, constriction of airways by ASM cells is the key to normal airway narrowing. If successful, this investigation will advance our understanding of the mechanisms by which the mechanical microenvironment dictates organization and contractility of ASM cells in their natural habitat. PUBLIC HEALTH RELEVANCE: A growing body of evidence indicates that the microenvironment of the airways may contribute to the development of pulmonary diseases, such as hypersensitivity to allergy and asthma, by altering structure and spatial organization of airway smooth muscle cells. The present study will investigate the physical mechanisms by which airway smooth muscle cells sense mechanical changes in their microenvironment and respond by altering their orientation and alignment. If successful, this study will establish physical principles that govern airway smooth muscle cell spatial organization and identify potential targets for therapeutic intervention in the future.