Continuum modeling of non-conservative fluid membrane for simulating long-term cell dynamics
Continuum modeling of non-conservative fluid membrane for simulating long-term cell dynamics
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DOI：
10.1140/epje/s10189-022-00223-0
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发表时间：
2022-08
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影响因子：
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通讯作者：
Satoru Okuda;Katsuhiko Sato;T. Hiraiwa
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作者：
Satoru Okuda;Katsuhiko Sato;T. Hiraiwa
活细胞通过它们在三维（3D）空间中的力生成而主动变形和移动。这些3D细胞动力学发生在长期时间范围内，从几十分钟到几天不等。在这样的时间尺度上，由于内吞作用和胞吐作用引起的细胞膜成分的周转不能被忽略，即，表面膜动态变形而没有质量守恒。虽然膜周转是必不可少的大变形的细胞，还没有计算框架来模拟长期的细胞动力学与非保守的流体膜。在本文中，我们提出了一个计算框架，用于模拟细胞膜在三维空间中的长期动力学。为此，在所提出的框架中，细胞表面膜被视为粘性流体膜，没有质量守恒。采用三角形网格对细胞形状进行离散，用有效能量和耗散函数表示细胞的动力学行为。通过引入一种改进的动态网格重划分方法，对膜运动引起的网格变形进行了动态优化。为了验证所提出的框架，进行了数值模拟，显示出的膜流是在物理上一致的方式再现，并重新网格化方法的人为影响是可以忽略不计的。为了进一步证明所提出的框架的适用性，数值模拟了由类似于马兰戈尼效应的机制诱导的细胞迁移，即，由电池主动产生的极化表面张力。所观察到的细胞行为与现有的解析解一致，表明所提出的计算框架可以定量地再现具有膜周转的长期活性细胞动力学。基于对细胞膜动力学的简单描述，该框架为分析各种细胞的成形和运动提供了有用的基础。图形摘要
Living cells actively deform and move by their force generations in three-dimensional (3D) space. These 3D cell dynamics occur over a long-term time scale, ranging from tens of minutes to days. On such a time scale, turnover of cell membrane constituents due to endocytosis and exocytosis cannot be ignored, i.e., the surface membrane dynamically deforms without mass conservation. Although membrane turnover is essential for large deformation of cells, there is no computational framework yet to simulate long-term cell dynamics with a non-conservative fluidic membrane. In this paper, we proposed a computational framework for simulating the long-term dynamics of a cell membrane in 3D space. For this purpose, in the proposed framework, the cell surface membrane is treated as a viscous fluid membrane without mass conservation. Cell shape is discretized by a triangular mesh, and its dynamics are expressed by effective energy and dissipation function. The mesh structure, distorted by membrane motion, is dynamically optimized by introducing a modified dynamic remeshing method. To validate the proposed framework, numerical simulations were performed, showing that the membrane flow is reproduced in a physically consistent manner and that the artificial effects of the remeshing method were negligible. To further demonstrate the applicability of the proposed framework, numerical simulations of cell migration induced by a mechanism similar to the Marangoni effect, i.e., the polarized surface tension actively generated by the cell, were performed. The observed cell behaviors agreed with existing analytical solutions, indicating that the proposed computational framework can quantitatively reproduce long-term active cell dynamics with membrane turnover. Based on the simple description of cell membrane dynamics, this framework provides a useful basis for analyzing various cell shaping and movement.Graphical abstract