College of Engineering and Informatics, National University of Ireland Galway, Ireland; Nanoscale Function Group, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Ireland.
College of Engineering and Informatics, National University of Ireland Galway, Ireland.
Acta Biomater. 2015 Nov;27:236-250. doi: 10.1016/j.actbio.2015.09.006. Epub 2015 Sep 7.
A novel series of experiments are performed on single cells using a bespoke AFM system where the response of cells to dynamic loading at physiologically relevant frequencies is uncovered. Measured forces for the untreated cells are dramatically different to cytochalasin-D (cyto-D) treated cells, indicating that the contractile actin cytoskeleton plays a critical role in the response of cells to dynamic loading. Following a change in applied strain magnitude, while maintaining a constant applied strain rate, the compression force for contractile cells recovers to 88.9±7.8% of the steady state force. In contrast, cyto-D cell compression forces recover to only 38.0±6.7% of the steady state force. Additionally, untreated cells exhibit strongly negative (pulling) forces during unloading half-cycles when the probe is retracted. In comparison, negligible pulling forces are measured for cyto-D cells during probe retraction. The current study demonstrates that active contractile forces, generated by actin-myosin cross-bridge cycling, dominate the response of single cells to dynamic loading. Such active force generation is shown to be independent of applied strain magnitude. Passive forces generated by the applied deformation are shown to be of secondary importance, exhibiting a high dependence on applied strain magnitude, in contrast to the active forces in untreated cells.
A novel series of experiments are performed on single cells using a bespoke AFM system where the response of cells to dynamic loading at physiologically relevant frequencies is uncovered. Contractile cells, which contain the active force generation machinery of the actin cytoskeleton, are shown to be insensitive to applied strain magnitude, exhibiting high resistance to dynamic compression and stretching. Such trends are not observed for cells in which the actin cytoskeleton has been chemically disrupted. These biomechanical insights have not been previously reported. This detailed characterisation of single cell active and passive stress during dynamic loading has important implications for tissue engineering strategies, where applied deformation has been reported to significantly affect cell mechanotransduction and matrix synthesis.
使用定制的原子力显微镜系统对单个细胞进行了一系列新颖的实验，揭示了细胞对生理相关频率下动态加载的反应。未经处理的细胞的测量力与细胞松弛素-D（细胞-D）处理的细胞有很大的不同，这表明收缩性肌动蛋白细胞骨架在细胞对动态加载的反应中起着关键作用。在改变施加应变幅度的同时，保持恒定的施加应变速率，收缩细胞的压缩力恢复到稳态力的 88.9±7.8%。相比之下，细胞-D 细胞的压缩力仅恢复到稳态力的 38.0±6.7%。此外，在探针缩回时，未经处理的细胞在卸载半周期期间表现出强烈的负（拉）力。相比之下，在探针缩回期间，对细胞-D 细胞测量到可忽略不计的拉力。本研究表明，由肌动球蛋白交联循环产生的主动收缩力主导了单个细胞对动态加载的反应。这种主动力产生被证明与施加的应变幅度无关。由施加的变形产生的被动力被证明是次要的，与未经处理的细胞中的主动力相比，它们对施加的应变幅度高度依赖。
使用定制的原子力显微镜系统对单个细胞进行了一系列新颖的实验，揭示了细胞对生理相关频率下动态加载的反应。含有肌动蛋白细胞骨架的主动力产生机制的收缩细胞对施加的应变幅度不敏感，表现出对动态压缩和拉伸的高抵抗力。对于其中肌动蛋白细胞骨架已被化学破坏的细胞，未观察到这种趋势。这些生物力学见解以前没有报道过。在动态加载过程中单细胞主动和被动应力的这种详细特征对于组织工程策略具有重要意义，据报道，施加的变形会显著影响细胞的机械转导和基质合成。
