Modeling of microstructural kinematics during simple elongation of central nervous system tissue
Modeling of microstructural kinematics during simple elongation of central nervous system tissue
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DOI：
10.1115/1.1632627
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发表时间：
2003-12-01
影响因子：
1.7
通讯作者：
Meaney, DF
中科院分区：
文献类型：
--
作者：
Bain, AC;Shreiber, DI;Meaney, DF
中枢神经系统（CNS）白质中轴突和神经胶质细胞的损伤几乎是创伤性脑损伤的普遍特征，但尚不清楚组织机械变形如何转移到中枢神经系统的细胞成分。定义细胞变形与所应用的组织变形场的关系，既可以突出显示有机械损伤风险的细胞群，又可以定义特定细胞群中将表现出损伤的细胞比例。在这项研究中，开发了基于微观结构的中枢神经系统白质模型，并针对简单伸长下测量到的中枢神经系统组织微观结构的变化进行了测试。结果表明，未拉伸的视神经中的轴突明显呈波浪状或起伏状，其中测量的轴突路径长度大于轴突的端到端距离。平均波动参数（定义为真实轴突长度除以端到端长度）为 1.13。在拉伸的神经中，平均轴突波动随着所施加的拉伸比 (lambda) 的增加而减少，平均波动值在 lambda = 1.06 时降至 1.06，在 lambda = 1.12 时降至 1.04，在 lambda = 1.25 时降至 1.02。描述轴突与周围神经胶质细胞逐渐耦合或束缚的模型最适合实验数据。这些建模工作表明，经历变形的轴突和神经胶质细胞群的比例随着施加的伸长而增加，这与轴突和神经胶质细胞损伤在白质损伤水平较高时增加的观察结果一致。最终，这些结果可以与创伤性脑损伤的计算模拟结合使用，以帮助确定中枢神经系统白质中的细胞结构对机械损伤的相对风险。
Damage to axons and glial cells in the central nervous system (CNS) white matter is a nearly universal feature of traumatic brain injury, yet it is not clear how the tissue mechanical deformations are transferred to the cellular components of the CNS. Defining how cellular deformations relate to the applied tissue deformation field can both highlight cellular populations at risk for mechanical injury, and define the fraction of cells in a specific population that will exhibit damage. In this investigation, microstructurally based models of CNS white matter were developed and tested against measured transformations of the CNS tissue microstructure under simple elongation. Results show that axons in the unstretched optic nerves were significantly wavy or undulated, where the measured axonal path length was greater than the end-to-end distance of the axon. The average undulation parameter-defined as the true axonal length divided by the end-to-end length-was 1.13. In stretched nerves, mean axonal undulations decreased with increasing applied stretch ratio (lambda)-the mean undulation values decreased to 1.06 at lambda = 1.06, 1.04 at lambda =1.12, and 1.02 at lambda =1.25. A model describing the gradual coupling, or tethering, of the axons to the surrounding glial cells best fit the experimental data. These modeling efforts indicate the fraction of the axonal and glial populations experiencing deformation increases with applied elongation, consistent with the observation that both axonal and glial cell injury increases at higher levels of white matter injury. Ultimately, these results can be used in conjunction with computational simulations of traumatic brain injury to aid in establishing the relative risk of cellular structures in the CNS white matter to mechanical injury.