<p class="MsoNormal">Mechanical stimulation is an essential factor in the interaction between cell and extracellular matrix. Previous studies have shown cyclic mechanical stimulation could lead to subsequent biomechanical effect and biological effect on cells. In this study, we presented a confocal-based cell-specific finite element(FE) model to investigate the effect of cyclic compression on single viscoelastic myoblast. The FE model consisted of the cytoplasm and the nucleus. The nucleus and cytoplasm were both assumed as viscoelastic materials. Instantaneous relaxation moduli and equilibrium moduli of the cytoplasm were assumed as 5.0 kPa and 2.6 kPa, respectively. Instantaneous relaxation moduli and equilibrium moduli of the nucleus were assumed as 9.8 kPa and 5.1 kPa, respectively. The relaxation time constants of cytoplasm and nucleus were both assumed as 0.3 s. The Possion’s ratio of the cytoplasm and nucleus was 0.37 and 0.3, respectively. Both the nucleus and cytoplasm were modeled using C3D10 elements. Tie constraint was attached to the outer surface of nucleus and the inner face of the cytoplasm. The bottom of the cell was fixed in six degrees of freedom. Sinusoidal compression was evenly applied to the nodes on the top surface of the myoblast. A compressive stress of 500 ± 500 Pa at 0 Hz(static loading of 500 Pa),0.25 Hz,0.5 Hz,0.75 Hz,1 Hz,5 Hz,10 Hz were applied on the apical surface of the myoblast. A parametric analysis was conducted to further investigate the effect of compression amplitude, the relaxation time on the tensile strain of cell membrane. The cyclic compression was selected as 500 ± 100 Pa，500 ± 200 Pa，500 ± 300 Pa，500 ± 400 Pa. The relaxation time was selected as 0.18s,1.32s and 13s.</p><p class="MsoNormal">The average tensile strain on the surface of cell showed classic creep behavior. The mean value of ratio between the integral of average tensile strain in all elements on the cell membrane over a period of time to the time duration was calculated and defined as MAS index. In long term (after 4s), there is no difference in MAS index under cyclic loading compared to that under static loading. In short term (0-4s), the decrease of MAS index under cyclic loading compared to the static loading was 3.57% (0.25 Hz), 3.09% (0.5 Hz), 2.69% (0.75 Hz), 1.89% (1 Hz), 0.41% (5 Hz), 0.20% (10Hz). Assuming the cell would damage when a certain percentage of membrane elements were strained beyond a tensile strain threshold, 5% was selected as damage threshold and the result showed cyclic compressive loading would decrease the percentage of damaged elements compared to static loading. When the tensile damage threshold was 5%, the percentage of damaged membrane decrease under cyclic loading compared to the static loading was 10.98% (0.25 Hz), 8.63% (0.5 Hz), 7.45% (0.75 Hz), 6.27% (1 Hz), 1.18% (5 Hz), 0.39% (10 Hz). The differences of both the MAS index and the percentage of damaged elements under cyclic loading and static loading were the largest at 0.25 Hz. Parametric analysis showed the relaxation time and the compression amplitude would influence the cell viscoelastic responses. The difference between MAS index under cyclic loading and the static loading was largest at 1 Hz (relaxation time=0.18s), 0.25 Hz (relaxation time=0.3s), 0.1Hz (relaxation time=1.32s), 0.02 Hz (relaxation time=13s). The percentage difference between MAS index under cyclic loading and static loading was increasing as the ratio of cyclic compression amplitude and static compression magnitude increased while the percentage of damaged elements showed little percentage difference. These results may provide support for the application of cyclic compressive stimulation in prevention of cell damage under prolonged loading, and the selection of optimal compression frequency, amplitude under cyclic stimulation in such application.</p>

Finite Element Analysis of Single Viscoelastic Myoblast Under Cyclic Compression

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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