Neutrophil polarisation

中性粒细胞是免疫系统的主要细胞，负责检测和预防细菌感染，以及驱动炎症。中性粒细胞在血流中自由循环，并且当穿过发炎区域时附着血管壁，穿过内皮（跨内皮迁移），并且通过结缔组织迁移到感染部位（趋化性）。在暴露于化学引诱物之前，中性粒细胞是球形的，并且它们的肌动蛋白细胞骨架（细胞形状的主要调节者）形成外周壳。在刺激下，它们变得细长，具有在化学梯度的方向上延伸的富含F-肌动蛋白的板状伪足并开始移动。参与检测和转导的化学吸引信号的信号级联反应正逐渐得到更好的理解，然而，令人惊讶的是，很少有人知道肌动蛋白动力学或皮质力学极化和迁移。迄今为止，中性粒细胞运动的研究集中在2-D基板上的运动。从生理学上讲，中性粒细胞在其有效寿命的大部分时间里都在密闭环境中迁移。对三维运动的现象学描述表明，它通过与平面运动不同的机制运作。尽管其生理上的重要性，运动在3-D已在很大程度上被忽视，由于更大的技术困难，在实验上检查它。我们建议从生物物理学的角度研究中性粒细胞在3-D环境中的极化和运动，重点是细胞骨架的动态和机械力在发挥作用。了解这些现象将推进我们对封闭环境中细胞迁移的认识，这是一个与抗菌和炎症过程特别相关的领域。为了回答这些问题，我们将建立一个多学科的科学家团队，将使用微流体，显微镜，显微操作和分子细胞生物学技术的组合。

Neutrophils are the primary cells of the immune system responsible for detecting and preventing bacterial infections, as well as driving inflammation. Neutrophils circulate freely in the bloodstream, and when passing through an inflamed region attach the blood vessel wall, traverse the endothelium (transendothelial migration), and migrate through the connective tissue to the site of infection (chemotaxis). Prior to chemoattractant exposure, neutrophils are spherical and their actin cytoskeleton, the main regulator of cell shape, forms a peripheral shell. Upon stimulation, they become elongated with an F-actin rich lamellipodium that extends in the direction of the chemical gradient and start moving. The signalling cascade involved in the detection and transduction of chemoattractive signals is becoming progressively better understood; however, surprisingly little is known about actin dynamics or cortex mechanics during polarisation and migration. Studies of neutrophil locomotion to date have concentrated on movement on 2-D substrates. Physiologically, neutrophils spend most of their useful lifetime migrating in confined environments. Phenomenological descriptions of locomotion in 3-D suggest that it operates via different mechanisms than movement on flat surfaces. Despite its physiological importance, locomotion in 3-D has been largely ignored due to greater technical difficulties in examining it experimentally. We propose to examine neutrophil polarisation and locomotion in 3-D environments from a biophysical perspective focusing on the dynamics of the cytoskeleton and the mechanical forces at play. Understanding these phenomena will advance our knowledge of cell migration in confined environments, an area of particular relevance to antibacterial and inflammatory processes. To answer these questions, we will build a multidisciplinary team of scientists that will use a combination of microfluidic, microscopy, micromanipulation, and molecular cell biology techniques.