Department of Materials, Imperial College London, UK; Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, USA.
Department of Physical Therapy, College of Staten Island, USA.
Bone. 2018 May;110:107-114. doi: 10.1016/j.bone.2018.01.024. Epub 2018 Feb 2.
Enzymatic collagen cross-linking has been shown to play an important role in the macroscopic elastic and plastic deformation of bone across ages. However, its direct contribution to collagen fibril deformation is unknown. The aim of this study is to determine how covalent intermolecular connections from enzymatic collagen cross-links contribute to collagen fibril elastic and plastic deformation of adults and children's bone matrix. We used ex vivo data previously obtained from biochemical analysis of children and adults bone samples (n = 14; n = 8, respectively) to create 22 sample-specific computational models of cross-linked collagen fibrils. By simulating a tensile test for each fibril, we computed the modulus of elasticity (E), ultimate tensile and yield stress (σ and σ), and elastic, plastic and total work (W, W and W) for each collagen fibril. We present a novel difference between children and adult bone in the deformation of the collagen phase and suggest a link between collagen fibril scale and macroscale for elastic behavior in children bone under the influence of immature enzymatic cross-links. We show a parametric linear correlation between W and immature enzymatic collagen cross-links at the collagen fibril scale in the children population that is similar to the one we found at the macroscale in our previous study. Finally, we suggest the key role of covalent intermolecular connections to stiffness parameters (e.g. elastic modulus and W) in children's collagen fibril and to toughness parameters in adult's collagen fibril, respectively.
酶交联胶原在骨骼的宏观弹性和塑性变形中起着重要作用。然而，其对胶原纤维变形的直接贡献尚不清楚。本研究旨在确定酶交联胶原的共价分子间连接如何影响成人和儿童骨基质中胶原纤维的弹性和塑性变形。我们使用先前从儿童和成人骨骼样本的生化分析中获得的离体数据（n=14；n=8，分别），为 22 个交联胶原纤维的特定样本创建了计算模型。通过模拟每个纤维的拉伸试验，我们计算了每个胶原纤维的弹性模量（E）、极限拉伸和屈服应力（σ和σ）以及弹性、塑性和总功（W、W和 W）。我们提出了儿童和成人骨骼在胶原相变形方面的新差异，并提出了在不成熟酶交联的影响下，儿童骨骼中胶原纤维尺度与宏观尺度之间的弹性行为之间的联系。我们在儿童人群中显示了胶原纤维尺度上 W 与不成熟酶胶原交联之间的参数线性相关性，这与我们在之前的研究中在宏观尺度上发现的相关性相似。最后，我们建议共价分子间连接对儿童胶原纤维的刚度参数（如弹性模量和 W）以及对成年胶原纤维的韧性参数具有关键作用。
