Effects of Stretch and Intercellular Force Transmission on Tensional Homeostasis in Multicellular Clusters

活细胞在外界干扰下维持其内部机械应力的能力对于细胞和组织的正常生理功能以及对各种疾病的保护是必不可少的。这就是所谓的张力动态平衡。张力稳态的破坏是大多数晚期实体癌(癌症)的标志，也是动脉硬化(动脉粥样硬化)和血栓形成(血栓形成)的标志。虽然细胞之间的物理相互作用似乎是张力内稳态的基础，但重要的问题仍然存在。首先，目前尚不清楚细胞间的力传递如何影响张力稳态。其次，对于细胞在最初达到稳定状态后如何应对外界机械环境的变化(如机械拉伸)，人们知之甚少。为了解决这些问题，本项目将提出并应用一个生物力学成像计算平台。使用这项技术可以回答的基本问题将提高对细胞如何对机械环境做出反应的基本理解。生物力学成像方法和软件将分发给任何感兴趣的研究人员，以便在细胞机械生物学和组织工程学社区内广泛传播这项技术。此外，研究生和本科生将在一个高度多学科的环境中接受培训，并将指导高中生进行为期六周的研究体验。生物力学成像计算平台通过同时测量(1)细胞传递到基质的牵引力和(2)外部拉伸产生的细胞内位移来绘制细胞内的应力分布。在这个项目中，研究人员将首先通过使用线粒体作为受托标记来提高生物力学成像技术的能力，以获得更准确的细胞内应力图。改进后的技术将被用来解决两个基本问题。首先，我们将研究外部拉伸对多细胞集群张力动态平衡的影响。这将使用牛主动脉内皮细胞和原代人脐静脉内皮细胞来完成。其次，该系统将被用来解开细胞间应力传递与张力稳态的相关性。这将包括调查细胞-细胞黏附连接的作用以及基板硬度对细胞-细胞与细胞基质之间的力传递的影响。该奖项反映了NSF的法定使命，并已通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The ability of living cells to maintain their internal mechanical stress in response to external disturbances is essential for normal physiological functions of cells and tissues and for a protection against various diseases. This is known as tensional homeostasis. Breakdown of tensional homeostasis is the hallmark of most advanced solid cancers (carcinomas), as well as of stiffening of the arteries (atherosclerosis) and clot formation (thrombosis). While physical interactions between cells appear to be fundamental to tensional homeostasis, important questions remain. First, it is not known how the transmission of forces between cells impacts tensional homeostasis. Second, there is little understanding of how cells respond to external changes in their mechanical environment (e.g., mechanical stretch) after having initially achieved a steady state. In order to address these questions, this project will advance and apply a biomechanical imaging computational platform. The fundamental questions that can be answered using this technique will improve basic understanding of how cells respond to their mechanical environment. The biomechanical imaging methods and software will be distributed to any interested researcher in order to broadly disseminate this technique within the cellular mechanobiology and tissue engineering communities. In addition, graduate students and undergraduate students will be trained in a highly multidisciplinary environment and will mentor high school students for a six-week research experience.The biomechanical imaging computational platform maps intracellular stress distribution through simultaneous measurements of (1) traction forces that are transmitted by cells to the substrate and (2) intracellular displacements generated by externally applied stretch. In this project, the researchers will first improve the ability of the biomechanical imaging technique by using mitochondria as fiduciary markers in order to obtain more accurate maps of intracellular stress. The improved technique will then be used to address two fundamental questions. First, the impact of external stretch on tensional homeostasis of multicellular clusters will be investigated. This will be done using bovine aortic endothelial cells and primary human umbilical vein endothelial cells. Second, the system will be used to unravel the relevance of intercellular stress transmission on tensional homeostasis. This will include the investigation of the role of cell-cell adherens junctions and the impact of substrate stiffness on both cell-cell vs cell-matrix force transmission.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.