Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada.
J Biomech. 2009 Dec 11;42(16):2768-73. doi: 10.1016/j.jbiomech.2009.07.035. Epub 2009 Sep 17.
The viscoelastic properties of cells are important in predicting cell deformation under mechanical loading and may reflect cell phenotype or pathological transition. Previous studies have demonstrated that viscoelastic parameters estimated by finite element (FE) analyses of micropipette aspiration (MA) data differ from those estimated by the analytical half-space model. However, it is unclear whether these differences are statistically significant, as previous studies have been based on average cell properties or parametric analyses that do not reflect the inherent experimental and biological variability of real experimental data. To determine whether cell material parameters estimated by the half-space model are significantly different from those predicted by the FE method, we implemented an inverse FE method to estimate the viscoelastic parameters of a population of primary porcine aortic valve interstitial cells tested by MA. We found that inherent differences between the analytical and inverse FE estimation methods resulted in statistically significant differences in individual cell properties. However, in cases with small pipette to cell radius ratios and short loading periods, model-dependent differences were masked by experimental and cell-to-cell variability. Analytical models that account for finite cell-size and loading rate further relaxed the experimental conditions for which accurate cell material parameter estimates could be obtained. These data provide practical guidelines for analysis of MA data that account for the wide range of conditions encountered in typical experiments.
细胞的黏弹性特性在预测细胞在机械载荷下的变形中非常重要，并且可能反映细胞表型或病理转化。先前的研究已经证明，通过微管吸吮（MA）数据分析的有限元（FE）分析估算的黏弹性参数与通过分析半空间模型估算的参数不同。然而，目前尚不清楚这些差异是否具有统计学意义，因为之前的研究基于平均细胞特性或参数分析，这些分析不能反映真实实验数据的固有实验和生物学变异性。为了确定通过半空间模型估算的细胞材料参数是否与 FE 方法预测的参数有显著差异，我们实施了反向 FE 方法来估算通过 MA 测试的一组原代猪主动脉瓣膜间质细胞的黏弹性参数。我们发现，分析和反向 FE 估计方法之间的固有差异导致个体细胞特性存在统计学上的显著差异。然而，在小管与细胞半径比小且加载时间短的情况下，由实验和细胞间变异性掩盖了模型依赖性差异。考虑到有限的细胞尺寸和加载速率的分析模型进一步放宽了可以获得准确细胞材料参数估计的实验条件。这些数据为分析 MA 数据提供了实用指南，这些数据考虑了在典型实验中遇到的广泛条件。
