Viscoelastically tunable substrates elucidate the interface-relaxation-dependent adhesion and assembly behaviors of epithelial cells
Viscoelastically tunable substrates elucidate the interface-relaxation-dependent adhesion and assembly behaviors of epithelial cells
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DOI：
10.1016/j.biomaterials.2021.120861
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发表时间：
2021-05-12
期刊：
影响因子：
14
通讯作者：
Nakanishi, Jun
中科院分区：
文献类型：
--
作者：
Chang, Alice Chinghsuan;Uto, Koichro;Nakanishi, Jun
力学生物学的最新进展揭示了基质的耗散特性对细胞表型的调节，即基质的粘度、流动性和应力松弛，以及广泛研究的弹性。然而，尽管二维培养中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方面。在这里，我们通过新材料的设计和力学表征，研究了基质的界面粘度和弹性对上皮细胞早期黏附行为的影响。材料为二苯甲酮光交联己内酯和D，L-丙交酯的共聚物。基质的粘弹性随聚合物的相对分子质量和辐照时间的变化而变化。用原子力显微镜分别测定了纳米压痕和尖端压痕模式下的界面弹性和松弛。随着界面粘弹性的变化，MDCK细胞在形态上发生了变化，从疏松的珠状组装到更紧密的球状和最终展开的单层簇。这种形态变化主要是由基质的界面松弛决定的，而不是由界面弹性决定的。单细胞追踪发现，在中间松弛时间(类似于350ms)，双相运动的速度最小，此时细胞显示出介于上皮和间充质特征之间的过渡形态。在松弛水平，部分变形的细胞四处移动，与周围的细胞结合，最终聚集成致密的细胞聚集体。这些结果强调，与传统的悬滴技术不同，适当程度的界面松弛对于粘性粘弹性基质上高效的细胞聚集体成熟至关重要。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，而且为建立与生理相关的药物筛选平台提供了有用的提示。
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 epsilon-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 tipdwelling, 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 (similar to 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.