Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan; Center for Measurement Standards, Industrial Technology Research Institute, No. 321, Sec. 2, Kuangfu Rd., Hsinchu 30011, Taiwan.
Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.
Biomaterials. 2021 Jul;274:120861. doi: 10.1016/j.biomaterials.2021.120861. Epub 2021 Apr 30.
Recent progress in mechanobiology sheds light on the regulation of cellular phenotypes by dissipative property of matrices, i.e., viscosity, fluidity, and stress relaxation, in addition to extensively studied elasticity. However, most researches have focused on bulk mechanics, despite cells in 2D culture can only interact with matrix interface directly. Here, we studied the impact of interfacial viscosity as well as elasticity of substrates on the early stage of adhesion behaviors of epithelial cells through new material design and mechanical characterization. The materials are copolymers of ε-caprolactone and d,l-lactide photocrosslinked by benzophenone. The substrate viscoelasticity changes depending on the polymer molecular weight and irradiation time. The interfacial elasticity and relaxation were determined by atomic force microscopy with modes of nanoindentation and tip-dwelling, respectively. MDCK cells changed morphologically, ranging from loose beaded assembly to more compact spheroids and eventual spread monolayer clusters, in response to the interfacial viscoelasticity change. Such morphological changes were mainly determined by substrate interfacial relaxation, rather than interfacial elasticity. Single-cell tracking identified biphasic motility with the minimum speed at intermediate relaxation time (~350 ms), where cells showed transitional morphologies between epithelial and mesenchymal traits. In that relaxation level, partially deformed cells moved around to coalesce with surrounding cells, eventually assembling into compact cellular aggregates. These results highlight, unlike the conventional hanging-drop technique, an appropriate level of interfacial relaxation is critical for efficient cell aggregate maturation on adhesive viscoelastic matrices. This work not only elucidates that the interfacial relaxation as the essential mechanical parameter for epithelial cell adhesion and migration, but also gives useful tips for creating physiologically relevant drug screening platform.
最近的机械生物学进展揭示了细胞表型的调控不仅受到基质弹性（如粘度、流动性和应力松弛）的影响，还受到广泛研究的基质耗散特性（如粘度、流动性和应力松弛）的影响。然而，尽管 2D 培养的细胞只能直接与基质界面相互作用，但大多数研究都集中在体力学上。在这里，我们通过新材料设计和力学特性研究，研究了界面粘度和基底弹性对上皮细胞早期黏附行为的影响。这些材料是ε-己内酯和 d,l-丙交酯的共聚物，通过苯甲酮光交联。基底的粘弹性取决于聚合物的分子量和辐照时间。界面弹性和松弛通过原子力显微镜的纳米压痕和尖端停留模式来确定。MDCK 细胞的形态发生变化，从松散的珠状聚集到更紧密的球体，最终发展为单层细胞簇，这是对界面粘弹性变化的响应。这种形态变化主要取决于基底界面松弛，而不是界面弹性。单细胞跟踪确定了具有中间松弛时间（~350ms）的最小速度的双相运动，其中细胞表现出上皮和间充质特征之间的过渡形态。在该松弛水平下，部分变形的细胞四处移动以与周围细胞融合，最终聚集形成紧密的细胞聚集体。这些结果表明，与传统的悬滴技术不同，适当的界面松弛水平对于在粘性弹性基质上有效成熟细胞聚集体是至关重要的。这项工作不仅阐明了界面松弛是上皮细胞黏附和迁移的基本力学参数，而且为创建生理相关的药物筛选平台提供了有用的提示。
