Xu Han, Donegan Stephanie, Dreher Jordan M, Stark Alicia J, Canović Elizabeth P, Stamenović Dimitrije, Smith Michael L
Department of Biomedical Engineering, Boston University, 44 Cummington Mall, Boston, MA 02215, United States.
Department of Biomedical Engineering, Boston University, 44 Cummington Mall, Boston, MA 02215, United States; Department of Mechanical Engineering, Boston University, 110 Cummington Mall, Boston, Massachusetts 02215, United States.
Acta Biomater. 2020 Sep 1;113:372-379. doi: 10.1016/j.actbio.2020.06.043. Epub 2020 Jul 5.
Tensional homeostasis is widely recognized to exist at the length scales of organs and tissues, but the cellular length scale mechanism for tension regulation is not known. In this study, we explored whether tensional homeostasis emerges from the behavior of the individual focal adhesion (FA), which is the subcellular structure that transmits cell stress to the surrounding extracellular matrix. Past studies have suggested that cell contractility builds up until a certain displacement is achieved, and we thus hypothesized that tensional homeostasis may require a threshold level of substrate displacement. Micropattern traction microscopy was used to study a wide range of FA traction forces generated by bovine vascular smooth muscle cells and bovine aortic endothelial cells cultured on substrates of stiffness of 3.6, 6.7, 13.6, and 30 kPa. The most striking feature of FA dynamics observed here is that the substrate displacement resulting from FA traction forces is a unifying feature that determines FA tensional stability. Beyond approximately 1 μm of substrate displacement, FAs, regardless of cell type or substrate stiffness, exhibit a precipitous drop in temporal fluctuations of traction forces. These findings lead us to the conclusion that traction force dynamics collectively determine whether cells or cell ensembles develop tensional homeostasis, and this insight is necessary to fully understand how matrix stiffness impacts cellular behavior in healthy conditions and, more important, in pathological conditions such as cancer or vascular aging, where environmental stiffness is altered. STATEMENT OF SIGNIFICANCE: Tensional homeostasis is widely recognized to exist at the length scales of organs and tissues, but the cellular length scale mechanism for tension regulation is not known. In this study, we explored whether tensional homeostasis emerges from the behavior of the individual focal adhesion (FA), which is the subcellular structure that transmits cell stress to the extracellular matrix. We utilized micropattern traction microscopy to measure time-lapses of FA forces in vascular smooth muscle cells and in endothelial cells. We discovered that the magnitude of the substrate displacement determines whether the FA has low temporal variability of traction forces. This finding is significant since it is the first known feature of tensional homeostasis that is broadly unifying across a range of environmental conditions and cell types.
张力稳态在器官和组织的长度尺度上广泛存在，这一点已得到广泛认可，但张力调节的细胞长度尺度机制尚不清楚。在本研究中，我们探究了张力稳态是否源自单个粘着斑（FA）的行为，粘着斑是将细胞应力传递至周围细胞外基质的亚细胞结构。以往研究表明，细胞收缩性会不断增强，直至达到一定的位移，因此我们推测张力稳态可能需要底物位移达到阈值水平。微图案牵引显微镜用于研究在刚度为3.6、6.7、13.6和30 kPa的底物上培养的牛血管平滑肌细胞和牛主动脉内皮细胞产生的广泛范围的粘着斑牵引力。此处观察到的粘着斑动力学最显著的特征是，由粘着斑牵引力引起的底物位移是决定粘着斑张力稳定性的统一特征。超过约1μm的底物位移后，无论细胞类型或底物刚度如何，粘着斑的牵引力时间波动都会急剧下降。这些发现使我们得出结论，牵引力动力学共同决定细胞或细胞集合体是否形成张力稳态，而这一见解对于全面理解基质刚度如何在健康状态下，更重要的是在诸如癌症或血管老化等病理状态下影响细胞行为是必要的，在这些病理状态下环境刚度会发生改变。意义声明：张力稳态在器官和组织的长度尺度上广泛存在，这一点已得到广泛认可，但张力调节的细胞长度尺度机制尚不清楚。在本研究中，我们探究了张力稳态是否源自单个粘着斑（FA）的行为，粘着斑是将细胞应力传递至细胞外基质的亚细胞结构。我们利用微图案牵引显微镜测量血管平滑肌细胞和内皮细胞中粘着斑力的时间推移。我们发现底物位移的大小决定了粘着斑的牵引力是否具有较低的时间变异性。这一发现具有重要意义，因为它是张力稳态的首个已知特征，在一系列环境条件和细胞类型中具有广泛的统一性。
