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点加载条件下细胞皮层刚化与微丝骨架重组
Alternative TitleMechanical point loading induced cortex stiffening and actin reorganization
胡锦荣
Thesis Advisor吕守芹
2019
Degree Grantor中国科学院大学
Place of Conferral北京
Subtype硕士
Degree Discipline一般力学与力学基础
Keyword原位力学性质扫描 单细胞 骨架重组
Abstract

细胞一直处于各种不同的力学微环境中,受到不同类型的力学刺激,如流体剪切、机械压力和机械拉伸等。对于不同的力学环境刺激,细胞会有不同的响应。作为细胞抵抗外界力学刺激的结构单元,细胞骨架在细胞感知和响应不同的力学微环境方面十分关键,因而细胞骨架如何对各种各样的力学刺激进行响应一直受到研究者重视。细胞骨架在不同力学刺激下的响应与细胞的力学性质是高度关联的。尽管很多研究利用磁镊、光镊、原子力显微镜、微针和微管吸吮等生物力学手段,揭示不同细胞在各种加载条件下的响应以及加载前后力学性质的变化,但多数的研究仍然基于群体细胞平均化的结果,而在力学加载前后,对单细胞骨架重组导致的细胞力学性质变化的原位测量仍然研究不足。基于此,本文1)首先利用原子力显微镜的表面力学性质扫描功能,原位地扫描了在探针点加载前后单细胞表面力学性质的变化。结果表明,在点加载后,细胞表面刚度(此处即皮层骨架刚度)将会上升,并且这种上升是骨架收缩能力依赖的。之后,2)本文提出基于有限单元法的连续介质细胞模型,阐明在点加载后,皮层骨架刚度上升能对细胞核起到结构上的保护功能。3)考虑到骨架力学性质变化(本文中即皮层骨架刚化)与其结构重组密不可分,本文紧接着使用柱形原子力探针考察点加载细胞时微丝骨架重组行为。实验发现,加载力越大、加载时长越长,骨架重组行为越明显。同时,用微针压载活染骨架的细胞,也能观测到微丝骨架对点加载的快速响应动力学行为(< 10秒)。本工作提出了一种在力学加载前后,原位扫描细胞表面力学性质的方法,并辅以活细胞骨架荧光检测,进一步深化了骨架对外界物理力学刺激响应的认识。

Other Abstract

Cells always situate in different mechanical milieus,apposing to diverse mechanical stimuli, such as shear stress, mechanical compression, stretch, etc. Cells response to different mechanical stimuli differently. As the main structural elements for cells to resist physical interference, cytoskeleton is crucial on pathways for cells to sense and response to different mechanical microenvironments, thus, how cytoskeleton responses to diverse mechanical stimuli have attracted much attention. Cytoskeleton responses under different mechanical loadings are highly coupled with mechanical properties of the cells. Though many works had shed light on cellular responses upon specific loadings and changes of cellular mechanical properties before and after mechanical loadings using biomechanical approaches like magnetic and optical tweezers, AFM, microneedle, micropipette aspiration, etc., most of the works are bulk studies and average effects from cell population are analyzed, it in situ change of mechanical properties stemming from cytoskeleton reorganization of a single cell under mechanical loading remains unclear. This paper utilized quantitative mechanical mapping AFM to probe surface mechanical property variations before and after mechanical point loadings it in situ. After point loading, cell surface stiffness elevated (here namely cortex stiffening) and elevation of that kind was actomyosin contractility dependent. In this work, a continuum cell model based on finite element method (FEM) was then proposed, elucidating cortex stiffening after point loading as structural protection to the nucleus. Considering alterations of cytoskeletal mechanics (as cortex stiffening in this work) is highly contingent on its structural reorganization,  flat-ended AFM probes were used to further probed cytoskeleton reorganization and found that the larger the loading force and the longer the loading duration was, the more apparent cytoskeleton reorganization was. Meanwhile, microneedle point loading upon actin-stained live cells revealed fast cytoskeleton reorganization dynamics (< 10 s). This work proposed an approach to probe cell surface mechanical properties before and after mechanical loadings, and furthered our knowledge to cytoskeleton responses to physical and mechanical stimuli from outside by supplementing with live cell actin fluorescence imaging.

Language中文
Document Type学位论文
Identifierhttp://dspace.imech.ac.cn/handle/311007/78583
Collection国家微重力实验室
Recommended Citation
GB/T 7714
胡锦荣. 点加载条件下细胞皮层刚化与微丝骨架重组[D]. 北京. 中国科学院大学,2019.
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