Sato M, Ohshima N, Nerem R M
Department of Biomedical Engineering, University of Tsukuba, Japan.
J Biomech. 1996 Apr;29(4):461-7. doi: 10.1016/0021-9290(95)00069-0.
The viscoelastic properties of cultured endothelial cells exposed to shear stress were measured by the micropipette technique and analyzed using a standard linear viscoelastic model. Cells from porcine aorta were cultured on glass coverslips. A shear stress of 2 Pa was applied using a parallel-plate flow chamber. After flow exposure, the cells were detached from the coverslips and suspended in culture medium. The micropipette experiment was performed on single cells under an inverted microscope. The desired negative pressure was applied stepwise to the tip of the micropipette by opening a solenoid valve. The deformation process of cells in the micropipette was observed through a TV camera and recorded on a videotape. To obtain the viscoelastic parameters, a half-space model of an endothelial cell was used. The cell was assumed to be a homogeneous and incompressible material, and a standard linear viscoelastic model was employed to account for the viscoelastic response. Cells exposed to shear stress for 6 h became spherical in shape after detachment from the substrate. In the case of a 24 h exposure, about half of the detached cells retained an elongated shape upon detachment, with the others taking on a spherical shape. The elastic constants, as determined based on the model, were approximately two times higher for the elongated cells than for control cells from static culture, no-flow conditions, indicating that the elongated cells became stiffer. Enhanced viscous properties also were observed for the elongated cells. These viscoelastic properties are considered to be closely related to cytoskeletal structure. Spherical cells upon detachment, even those that had been exposed to shear stress for 24 h, did not show such significant changes in viscoelastic mechanical properties.
采用微量移液器技术测量了暴露于剪切应力下的培养内皮细胞的粘弹性特性，并使用标准线性粘弹性模型进行分析。从猪主动脉获取的细胞培养在玻璃盖玻片上。使用平行板流动腔施加2 Pa的剪切应力。流动暴露后，将细胞从盖玻片上分离并悬浮于培养基中。在倒置显微镜下对单个细胞进行微量移液器实验。通过打开电磁阀逐步向微量移液器尖端施加所需的负压。通过电视摄像机观察微量移液器中细胞的变形过程，并记录在录像带上。为了获得粘弹性参数，使用了内皮细胞的半空间模型。假设细胞为均匀且不可压缩的材料，并采用标准线性粘弹性模型来解释粘弹性响应。暴露于剪切应力6小时的细胞从基质上分离后变成球形。在暴露24小时的情况下，约一半分离的细胞在分离时保持伸长形状，其他细胞则呈球形。根据该模型确定的弹性常数，伸长细胞比静态培养、无流动条件下的对照细胞大约高两倍，表明伸长细胞变得更硬。伸长细胞还表现出增强的粘性特性。这些粘弹性特性被认为与细胞骨架结构密切相关。分离时的球形细胞，即使是那些已暴露于剪切应力24小时的细胞，在粘弹性力学性能上也未显示出如此显著的变化。
