Wong Stephanie, Guo Wei-Hui, Wang Yu-Li
Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15219.
Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15219
Proc Natl Acad Sci U S A. 2014 Dec 2;111(48):17176-81. doi: 10.1073/pnas.1412285111. Epub 2014 Nov 17.
Rigidity sensing and durotaxis are thought to be important elements in wound healing, tissue formation, and cancer treatment. It has been challenging, however, to study the underlying mechanism due to difficulties in capturing cells during the transient response to a rigidity interface. We have addressed this problem by developing a model experimental system that confines cells to a micropatterned area with a rigidity border. The system consists of a rigid domain of one large adhesive island, adjacent to a soft domain of small adhesive islands grafted on a nonadhesive soft gel. This configuration allowed us to test rigidity sensing away from the cell body during probing and spreading. NIH 3T3 cells responded to the micropatterned rigidity border similarly to cells at a conventional rigidity border, by showing a strong preference for staying on the rigid side. Furthermore, cells used filopodia extensions to probe substrate rigidity at a distance in front of the leading edge and regulated their responses based on the strain of the intervening substrate. Soft substrates inhibited focal adhesion maturation and promoted cell retraction, whereas rigid substrates allowed stable adhesions and cell spreading. Myosin II was required for not only the generation of probing forces but also the retraction in response to soft substrates. We suggest that a myosin II-driven, filopodia-based probing mechanism ahead of the leading edge allows cells to migrate efficiently, by sensing physical characteristics before moving over a substrate to avoid backtracking.
硬度感知和趋硬性被认为是伤口愈合、组织形成和癌症治疗中的重要因素。然而，由于在捕捉细胞对硬度界面的瞬态反应过程中存在困难，研究其潜在机制一直具有挑战性。我们通过开发一种模型实验系统解决了这个问题，该系统将细胞限制在具有硬度边界的微图案区域内。该系统由一个大的粘附岛的刚性区域组成，与接枝在非粘附性软凝胶上的小粘附岛的软区域相邻。这种配置使我们能够在探测和铺展过程中测试远离细胞体的硬度感知。NIH 3T3细胞对微图案化的硬度边界的反应与传统硬度边界处的细胞相似，表现出强烈倾向于停留在刚性一侧。此外，细胞利用丝状伪足延伸在前沿前方一定距离处探测底物硬度，并根据中间底物的应变调节其反应。软底物抑制粘着斑成熟并促进细胞回缩，而硬底物允许稳定的粘附和细胞铺展。肌球蛋白II不仅是产生探测力所必需的，也是对软底物作出回缩反应所必需的。我们认为，前沿前方由肌球蛋白II驱动的基于丝状伪足的探测机制使细胞能够通过在移动到底物上之前感知物理特性来有效迁移，从而避免回溯。
