Pesen Tuna, Akgun Bora, Unlu Mehmet Burcin
Department of Physics, Boğaziçi University, 34342, Beşiktaş, İstanbul, Türkiye.
Center for Life Sciences and Technologies, Boğaziçi University, 34342, Beşiktaş, İstanbul, Türkiye.
Sci Rep. 2025 Mar 17;15(1):9060. doi: 10.1038/s41598-025-93288-8.
Mechanical features of cells play a crucial role in many biological processes such as crawling, proliferation, spreading, stretching, contracting, division, and programmed cell death. The loss of cell viscoelasticity underlines different types of diseases such as cancer, sickle cell, malaria, and diabetes mellitus. To understand the loss of viscoelasticity, mechanical responses of various kinds of cells to stress or strain are under investigation. Especially red blood cells (RBCs) or erythrocytes are one of the simple structured cells such that the effects of stress or strain could be easily assessed. With their viscoelastic nature, they can deform by preserving cell integrity when passing through blood vessels that are smaller than their size. In this study, we investigated the mechanical response of RBCs under repetitive stretching-relaxation cycles and examined some of the universal cytoskeleton laws at the single cell level over the whole body. For this, the individual RBCs were exposed to repetitive biaxial stretch-relaxation cycles of 5 s duration by optical tweezers to assess their mechanical response. According to the findings, the cells became stiffer with each stretch and became completely undeformable after a certain number of stretch-relaxation cycles. We observed that with the increasing number of stretching cycles, cell stiffness changed as a sign of weak power law, implying cell rheology is scale-free and decay times were increased, showing the transition from fast to slow regime. In addition, the appearance of the cells became non-uniform with darker areas in some parts and highly elongated shape in the most extreme cases.
细胞的力学特性在许多生物过程中起着至关重要的作用，如爬行、增殖、铺展、拉伸、收缩、分裂和程序性细胞死亡。细胞粘弹性的丧失是多种疾病的基础，如癌症、镰状细胞病、疟疾和糖尿病。为了理解粘弹性的丧失，正在研究各种细胞对应力或应变的力学响应。特别是红细胞是结构简单的细胞之一，因此应力或应变的影响很容易评估。由于其粘弹性，它们在通过比自身尺寸小的血管时可以在保持细胞完整性的情况下发生变形。在本研究中，我们研究了红细胞在重复拉伸-松弛循环下的力学响应，并在单细胞水平上研究了全身的一些普遍的细胞骨架规律。为此，通过光镊对单个红细胞施加持续5秒的重复双轴拉伸-松弛循环，以评估其力学响应。根据研究结果，细胞在每次拉伸后都会变得更硬，并且在一定数量的拉伸-松弛循环后变得完全不可变形。我们观察到，随着拉伸循环次数的增加，细胞硬度呈弱幂律变化，这意味着细胞流变学是无标度的，衰减时间增加，表明从快速状态向缓慢状态的转变。此外，细胞的外观变得不均匀，某些部分出现较暗区域，在最极端的情况下呈高度拉长的形状。
