Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15219, USA.
Lab Chip. 2011 Oct 21;11(20):3538-44. doi: 10.1039/c1lc20504h. Epub 2011 Sep 7.
The biophysical machinery that permits a cell to sense substrate rigidity is poorly understood. Rigidity sensing of adherent cells likely involves traction forces applied through focal adhesions and measurement of resulting deformation. However, it is unclear if this measurement takes place underneath single focal adhesions, over local clusters of focal adhesions, or across the length of the entire cell. To address this question, we developed a composite, chip-based material containing many arrays of 6.5 μm × 6.5 μm rigid adhesive islands, with an edge-edge distance of 8 μm, grafted onto the surface of a non-adhesive polyacrylamide hydrogel. This material is thus rigid within single islands while long-range rigidity is determined by the hydrogel. On soft gels, most NIH 3T3 cells spread only across two islands in a given dimension forming small stress fibers and focal adhesions. On stiff gels, cell spreading, stress fibers, and focal adhesions were indistinguishable from those on regular culture surfaces. We conclude that rigidity sensing is dictated by material compliance across the cell length and that responses to rigidity may be inhibited at any point when large substrate strain is encountered during spreading. Our finding may serve as a guideline for the design of biomaterials for tissue engineering.
细胞感知基质刚性的生物物理机制尚不清楚。黏附细胞的刚性感知可能涉及通过黏着斑施加的牵引力以及对产生的变形的测量。然而，尚不清楚这种测量是在单个黏着斑下进行的，还是在局部黏着斑簇上进行的，或者是在整个细胞长度上进行的。为了解决这个问题，我们开发了一种基于芯片的复合材料，其中包含许多 6.5 μm×6.5 μm 的刚性黏附岛阵列，边缘到边缘的距离为 8 μm，接枝到非黏附性聚丙烯酰胺水凝胶的表面。因此，在单个岛屿内，这种材料是刚性的，而长程刚性则由水凝胶决定。在软凝胶上，大多数 NIH 3T3 细胞仅在给定尺寸的两个岛屿上展开，形成小的应力纤维和黏着斑。在硬凝胶上，细胞铺展、应力纤维和黏着斑与常规培养表面上的那些无法区分。我们得出结论，刚性感知由整个细胞长度上的材料顺应性决定，并且在铺展过程中遇到大的基底应变时，任何位置的刚性响应都可能受到抑制。我们的发现可能为组织工程生物材料的设计提供指导。
