Introduction

Over the last decade, atomic force microscopy (AFM) has played an important role in understanding nanomechanical properties of various cancer cell lines. This study is focused on Lewis lung carcinoma cell tumours as 3D multicellular spheroid (MS). Not much is know about the mechanical properties of the cells and the surrounding extracellular matrix (ECM) in rapidly growing tumours.

Methods

Depth-dependent indentation measurements were conducted with the AFM. Force-vs.-indentation curves were used to create stiffness profiles as a function of depth. Here studies were focused on the outer most layer, i.e., proliferation zone of the spheroid.

Results

Both surface and sub-surface stiffness profiles of MS were created. This study revealed three nanomechanical topographies, Type A-high modulus due to collagen fibers, Type B-high stiffness at cell membrane and ECM interface and Type C-increased modulus due to cell lying deep inside matrix at a depth of 1.35 μm. Both Type and Type-B topographies result from collagen-based structures in ECM.

Conclusion

This study has first time revealed mechanical constitution of an MS. Depth-dependent indentation studies have the revealed role of various molecular and cellular components responsible for providing mechanical stability to MS. Nanomechanical heterogeneities revealed in this investigation can shed new light in developing correct dosage regime for collagenase treatment of tumours and designing better controlled artificial extracellular matrix systems for replicating tissue growth in-vitro.

中文翻译：

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多细胞球体中细胞外基质和细胞的纳米力学分析。

介绍

在过去十年中，原子力显微镜 (AFM) 在了解各种癌细胞系的纳米力学特性方面发挥了重要作用。这项研究的重点是刘易斯肺癌细胞肿瘤作为 3D 多细胞球体 (MS)。对于快速生长的肿瘤中细胞和周围细胞外基质 (ECM) 的机械特性知之甚少。

方法

使用 AFM 进行与深度相关的压痕测量。力与压痕曲线用于创建作为深度函数的刚度曲线。这里的研究集中在最外层，即球体的增殖区。

结果

创建了 MS 的表面和次表面刚度分布。该研究揭示了三种纳米力学形貌，A 型 - 由胶原纤维引起的高模量，B 型 - 细胞膜和 ECM 界面处的高刚度，以及 C 型 - 由于细胞位于基质内部深处 1.35  μm的深度而增加的模量。类型和 B 型拓扑结构都是由 ECM 中基于胶原蛋白的结构产生的。

结论

这项研究首次揭示了 MS 的机械结构。深度依赖性压痕研究揭示了负责为 MS 提供机械稳定性的各种分子和细胞成分的作用。该研究中揭示的纳米力学异质性可以为开发用于肿瘤胶原酶治疗的正确剂量方案和设计更好控制的人工细胞外基质系统以复制体外组织生长提供新的启示。