Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, USA.
Department of Bioengineering, University of Pennsylvania, Philadelphia, PA 19104-6321, USA.
J R Soc Interface. 2017 Oct;14(135). doi: 10.1098/rsif.2017.0326.
Excessive deformation of nerve fibres (axons) in the spinal facet capsular ligaments (FCLs) can be a cause of pain. The axons are embedded in the fibrous extracellular matrix (ECM) of FCLs, so understanding how local fibre organization and micromechanics modulate their mechanical behaviour is essential. We constructed a computational discrete-fibre model of an axon embedded in a collagen fibre network attached to the axon by distinct fibre-axon connections. This model was used to relate the axonal deformation to the fibre alignment and collagen volume concentration of the surrounding network during transverse, axial and shear deformations. Our results showed that fibre alignment affects axonal deformation only during transverse and axial loading, but higher collagen volume concentration results in larger overall axonal strains for all loading cases. Furthermore, axial loading leads to the largest stretch of axonal microtubules and induces the largest forces on axon's surface in most cases. Comparison between this model and a multiscale continuum model for a representative case showed that although both models predicted similar averaged axonal strains, strain was more heterogeneous in the discrete-fibre model.
神经纤维（轴突）在脊柱小关节囊韧带（FCL）中过度变形可能是疼痛的一个原因。轴突嵌入 FCL 的纤维细胞外基质（ECM）中，因此了解局部纤维组织和微力学如何调节它们的机械行为至关重要。我们构建了一个嵌入在胶原纤维网络中的轴突的计算离散纤维模型，该模型通过不同的纤维-轴突连接附着在轴突上。该模型用于在横向、轴向和剪切变形过程中，将轴突的变形与周围网络的纤维排列和胶原体积浓度联系起来。我们的结果表明，纤维排列仅在横向和轴向加载时影响轴突的变形，但较高的胶原体积浓度会导致所有加载情况下的总轴突应变更大。此外，轴向加载会导致轴突微管的最大拉伸，并在大多数情况下在轴突表面上产生最大的力。对这个模型和一个代表性案例的多尺度连续体模型进行比较表明，尽管这两个模型都预测了相似的平均轴突应变，但离散纤维模型中的应变更加不均匀。
