Effects of fluid shear stress duration on the mechanical properties of HeLa cells using atomic force microscopy

Abstract

Cellular mechanical properties play a critical role in physiological and pathological processes, with fluid shear stress being a key determinant. Despite its importance, the impact of fluid shear stress on the mechanical characteristics of HeLa cells and its role in the mechanism of tumor metastasis remain poorly understood. This study aims to investigate the effects of varying durations of fluid shear stress on the mechanical properties of HeLa cells, thereby elucidating the mechanical interactions between the fluid flow environment and cancer cells during tumor metastasis. We established an in vitro fluid shear stress cell experimental system and analyzed the flow field characteristics within a parallel plate flow chamber using computational fluid dynamics software. Atomic force microscopy was used to measure the mechanical properties of HeLa cells at different time points under a fluid shear stress of 10 dyn/cm², a value representative of physiological conditions. computational fluid dynamics analysis confirmed the stability of laminar flow and the uniformity of shear stress within the parallel plate flow chamber. The experimental results revealed that with increasing fluid shear stress exposure duration, HeLa cells exhibited a fusiform shape, with a reduction in cell height and a significant decrease in cell Young's modulus. By integrating atomic force microscopy with the in vitro fluid shear stress cell experimental system, this study demonstrates the substantial influence of fluid shear stress on the mechanical properties of HeLa cells. This provides novel insights into the behavior of cancer cells within the in vivo flow environment. Our findings enhance the understanding of cellular mechanical property regulation and offer valuable insights for biomedicine engineering research.

Fig 1. Computational Fluid Dynamics results for a parallel plate flow chamber based on FLUENT.

(a) Global finite element mesh division of flow field. (b) Local finite element mesh. (c) Global flow field pressure distribution nephogram. (d) Z = 0 characteristic surface pressure distribution nephogram.(e) Flow field velocity vector distribution nephogram.(f) Flow field velocity distribution nephogram.(g-j) Fluid shear stress nephogram for four working conditions (5、10、15 and 20dyn/cm²).

Fig 2. AFM probe is controlled to perform indentation assay on a Hela cell to record force curves for measuring cellular Young ‘s modulus.

Fig 3. The experimental technology combining a fluid shear stress experimental system with Atomic Force Microscopy (AFM).

(a) Schematic diagram of a fluid shear stress experimental system. (b) Assembly diagram of a parallel-plate flow chamber. (c) Experimental Apparatus of Fluid Shear Stress System. (d) Parallel Plate Flow Chamber. (e) Atomic Force Microscopy (AFM). (f) AFM probe is controlled to measure single living Hela cells under the guidance of optical microscope.

Fig 4. Comparative Analysis of Hela Cells Cultured under Static Conditions and Exposed to Fluid Shear Stress.

(a) Optical microscopy images comparing the effect of fluid shear stress duration on cell morphology. (b) Atomic Force Microscopy (AFM) height maps of cells under different fluid shear stress durations. (c) Cell height curve under different fluid shear stress over time.

Fig 5. Measuring results of Hela cells subjected to different durations of fluid shear stress by Atomic Force Microscopy (AFM)

(a) AFM topography of Hela cell. (b) Corresponding deflection images of the margin of Hela cell. (c) Young’s Modulus Graph obtained by Atomic Force Microscopy (AFM).

Fig 6. Measuring the Young’s modulus of Hela cells subjected to different durations of fluid shear stress by Atomic Force Microscopy (AFM).