Ocean and Mechanical Engineering, Florida Atlantic University, 777 Glades Rd., Boca Raton, Florida, USA.
Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, Massachusetts, USA.
Lab Chip. 2021 Sep 14;21(18):3458-3470. doi: 10.1039/d1lc00598g.
Red blood cells (RBCs) are subjected to recurrent changes in shear stress and oxygen tension during blood circulation. The cyclic shear stress has been identified as an important factor that alone can weaken cell mechanical deformability. The effects of cyclic hypoxia on cellular biomechanics have yet to be fully investigated. As the oxygen affinity of hemoglobin plays a key role in the biological function and mechanical performance of RBCs, the repeated transitions of hemoglobin between its R (high oxygen tension) and T (low oxygen tension) states may impact their mechanical behavior. The present study focuses on developing a novel microfluidic-based assay for characterization of the effects of cyclic hypoxia on cell biomechanics. The capability of this assay is demonstrated by a longitudinal study of individual RBCs in health and sickle cell disease subjected to cyclic hypoxia conditions of various durations and levels of low oxygen tension. The viscoelastic properties of cell membranes are extracted from tensile stretching and relaxation processes of RBCs induced by the electrodeformation technique. Results demonstrate that cyclic hypoxia alone can significantly reduce cell deformability, similar to the fatigue damage accumulated through cyclic mechanical loading. RBCs affected by sickle cell disease are less deformable (significantly higher membrane shear modulus and viscosity) than normal RBCs. The fatigue resistance of sickle RBCs to the cyclic hypoxia challenge is significantly inferior to that of normal RBCs, and this trend is more significant in mature erythrocytes of sickle cells. When the oxygen affinity of sickle hemoglobin is enhanced by anti-sickling drug treatment of 5-hydroxymethyl-2-furfural (5-HMF), sickle RBCs show ameliorated resistance to fatigue damage induced by cyclic hypoxia. These results indicate an important biophysical mechanism underlying RBC senescence in which the cyclic hypoxia challenge alone can lead to mechanical degradation of the RBC membrane. We envision that the application of this assay can be further extended to RBCs in other blood diseases and other cell types.
红细胞（RBCs）在血液循环过程中反复受到剪切应力和氧张力的变化。循环剪切应力已被确定为单独削弱细胞机械变形能力的重要因素。循环低氧对细胞生物力学的影响尚未得到充分研究。由于血红蛋白的氧亲和力在 RBC 的生物学功能和机械性能中起着关键作用，血红蛋白在其 R（高氧张力）和 T（低氧张力）状态之间的反复转变可能会影响其机械行为。本研究专注于开发一种新的基于微流控的测定方法，用于研究循环低氧对细胞生物力学的影响。通过对处于不同持续时间和低氧张力水平的循环低氧条件下的健康和镰状细胞病个体 RBC 的纵向研究，证明了该测定方法的能力。通过电极变形技术诱导的 RBC 拉伸和松弛过程，从细胞膜的粘弹性特性中提取出来。结果表明，单独的循环低氧就能显著降低细胞的变形能力，类似于通过循环机械加载积累的疲劳损伤。受镰状细胞病影响的 RBC 比正常 RBC 的变形能力更低（膜剪切模量和粘度明显更高）。镰状 RBC 对循环低氧挑战的抗疲劳能力明显低于正常 RBC，在镰状细胞的成熟红细胞中这种趋势更为明显。当镰状血红蛋白的氧亲和力通过 5-羟甲基-2-糠醛（5-HMF）的抗镰状药物治疗增强时，镰状 RBC 对循环低氧诱导的疲劳损伤的抵抗力得到改善。这些结果表明，在 RBC 衰老的重要生物物理机制中，单独的循环低氧挑战就可以导致 RBC 膜的机械降解。我们设想，该测定方法的应用可以进一步扩展到其他血液疾病和其他细胞类型的 RBC 中。
