Microfluidic Approaches to Study Mechanotransduction in Cell Division and Migration

施加在细胞上的物理力驱动表型变化，并在发育形态发生、正常生理功能和病理条件下定义组织和组织模式。机械转导是指细胞将机械输入转化为生物反应的过程。血管系统为研究机械转导提供了理想的模型，因为细胞持续暴露于外部物理力，包括血流施加的剪切应力和血压引起的切向应力。血管平滑肌细胞（VSMCs）通常存在于被细胞外基质包围的三维介质中。然而，在内皮脱落和暴露于血小板衍生生长因子B （PDGF-B）等生长因子后，VSMCs经历了从收缩到合成的表型转换，它们增殖并从介质迁移到内膜。因此，细胞的微环境发生了巨大的变化：VSMCs在通过内部弹性板的紧窗迁移时受到压缩和变形，一旦到达内膜表面，它们就暴露在流动血液的剪切应力下。调控VSMC迁移和增殖的生化信号已被研究多年。然而，这些物理力对损伤后VSMCs的影响尚不清楚，我们试图了解细胞如何将机械转导信号与细胞骨架的变化结合起来，从而影响迁移和增殖的行为决定。该基金的重点是研究暴露于流体剪切和压缩应力下的vsmc的机械转导机制，使用微流体装置模拟体内微环境。*******基本原理和假设：细胞骨架在迁移VSMCs的机械转导中起着重要作用：它承受施加在细胞上的物理力的冲击，是表型开关的目标，并控制胞内细胞器的位置，以完成增殖和迁移所需的极性。我假设VSMCs中细胞骨架组织的改变是由于细胞迁移到内膜时所暴露的两种不同的物理力：血流对内膜表面细胞施加的剪切力。2. 压缩力，使细胞和细胞核变形，因为它挤压通过内部弹性板的小窗口，将内层和内层分开。******

Physical forces exerted on cells drive changes in phenotype and define organization and tissue patterning during developmental morphogenesis, normal physiologic function, and under pathologic conditions. The term mechanotransduction refers to the process by which cells transduce mechanical inputs into biological responses. The vascular system provides an ideal model to study mechanotransduction, because cells are continuously exposed to external physical forces including shear stress imposed by blood flow, and tangential stress due to blood pressure. Vascular smooth muscle cells (VSMCs) normally reside within the media in a 3D environment surrounded by extracellular matrix. However after endothelial denudation and with exposure to growth factors like platelet derived growth factor B (PDGF-B) VSMCs undergo a phenotypic switch from contractile to synthetic, and they proliferate and migrate from the media to the intimal layer. As a result the microenvironment of the cell changes dramatically: VSMCs undergo compression and deformation as they migrate through tight fenestrae in the internal elastic lamina, and once on the intimal surface, they are exposed to shear stress from flowing blood. The biochemical signals regulating VSMC migration and proliferation have been studied for many years. However the effects of these physical forces on VSMCs after injury are not well understood, and we seek to understand how cells integrate mechanotransduction signals with changes in the cytoskeleton to influence behavioural decisions to migrate and proliferate. The focus of this grant is to investigate mechanisms of mechanotransduction in VSMCs exposed to fluid shear and compressive stresses using microfluidic devices to mimic the in vivo microenvironment.*******Rationale and Hypotheses: The cytoskeleton plays an important role in mechanotransduction in migrating VSMCs: it bears the brunt of physical forces imposed upon the cell, is the target of the phenotypic switch, and governs the position of intracellular organelles to accomplish polarity required for proliferation and migration. I hypothesize that alterations in the cytoskeletal organization in VSMCs are due to two distinct physical forces to which the cells are exposed as they migrate into the intimal layer: 1. Shear force exerted by blood flow on cells at the intimal surface. 2. Compressive force which deforms the cell and nucleus as it squeezes through small fenestrae in the internal elastic lamina separating the medial and the intimal layers.******