[论文解读] Computational Modeling of the Effects of Inflammatory Response and Granulation Tissue Properties on Human Bone Fracture Healing

Mohammad S. Ghiasi, Jason E. Chen+3 more|arXiv (Cornell University)|Aug 13, 2018

Bone fractures and treatments参考文献 48被引用 5

一句话总结

本研究开发了一种基于有限元的计算模型，以探究早期阶段的生物和机械因素——特别是间充质干细胞（MSC）迁移、肉芽组织刚度、骨痂厚度和骨端间隙大小——对人类骨骨折愈合的影响。结果表明，MSC迁移速度越快、肉芽组织越坚硬、骨痂越厚、间隙越小，愈合效果越好，但均存在一个饱和阈值，超过该阈值后进一步改善不再显著。研究识别出初始组织特性在某一最优范围内时可实现最高效的愈合，与一期和二期骨愈合概念一致。

ABSTRACT

Bone healing process includes four phases: inflammatory response, soft callus formation, hard callus development, and remodeling. Mechanobiological models have been used to investigate the role of various mechanical and biological factors on the bone healing. However, the initial phase of healing, which includes the inflammatory response, the granulation tissue formation and the initial callus formation during the first few days post-fracture, are generally neglected in such studies. In this study, we developed a finite-element-based model to simulate different levels of diffusion coefficient for mesenchymal stem cell (MSC) migration, Young's modulus of granulation tissue, callus thickness and interfragmentary gap size to understand the modulatory effects of these initial phase parameters on bone healing. The results showed that faster MSC migration, stiffer granulation tissue, thicker callus and smaller interfragmentary gap enhanced healing to some extent. After a certain threshold, a state of saturation was reached for MSC migration rate, granulation tissue stiffness and callus thickness. Therefore, a parametric study was performed to verify that the callus formed at the initial phase, in agreement with experimental observations, has an ideal range of geometry and material properties to have the most efficient healing time. Findings from this paper quantified the effects of the healing initial phase on healing outcome to better understand the biological and mechanobiological mechanisms and their utilization in the design and optimization of treatment strategies. Simulation outcomes also demonstrated that for fractures, where bone segments are in close proximity, callus development is not required. This finding is consistent with the concepts of primary and secondary bone healing.

研究动机与目标

• 探究在机械生物学模型中常被忽视的早期炎症反应和肉芽组织动力学对骨骨折愈合的影响。
• 量化关键参数——MSC迁移速率、肉芽组织弹性模量、骨痂厚度和骨端间隙——对愈合结果的调节作用。
• 识别出初始骨痂中机械与生物学特性最优化的范围，以最大化愈合效率。
• 将模型与实验观察结果进行验证，并区分一期与二期骨愈合机制。

提出的方法

• 开发了一种基于有限元的计算模型，用于模拟骨愈合初期（炎症反应、肉芽组织形成和早期骨痂发育）的过程。
• 模型将间充质干细胞（MSC）迁移的扩散系数、肉芽组织的弹性模量、骨痂厚度和骨端间隙大小作为可调节参数引入。
• 开展了参数化研究，独立评估各参数变化对愈合进程和结果的影响。
• 模型模拟了机械与生物学反馈回路，整合了细胞迁移与组织成熟随时间的变化。
• 将模拟结果与一期和二期骨愈合的已知生物学原理进行验证。
• 进行了饱和阈值分析，以确定参数值进一步增加不再提升愈合效率的临界点。

实验结果

研究问题

• RQ1 间充质干细胞（MSC）迁移速率在多大程度上影响早期骨愈合的效率？
• RQ2 肉芽组织刚度（弹性模量）对骨痂形成和愈合进程有何影响？
• RQ3 骨痂厚度和骨端间隙大小在多大程度上调节愈合时间和结果？
• RQ4 是否存在一个初始组织特性的最优范围，可在达到饱和点前最大化愈合效率？
• RQ5 该模型是否能基于初始机械条件支持区分一期与二期骨愈合？

主要发现

• 更快的间充质干细胞（MSC）迁移速率可提升愈合效率，但仅在达到饱和阈值前有效，超过后不再有进一步改善。
• 肉芽组织刚度增加（更高的弹性模量）可改善愈合结果，但仅在一定范围内有效，超过后收益趋于平稳。
• 更厚的骨痂形成可加快愈合，但仅在最优范围内有效；超过该范围后无额外益处。
• 更小的骨端间隙显著提升了愈合效率，支持稳定骨折中的一期骨愈合概念。
• 模型表明，对于骨端紧密贴合的骨折，骨痂发育并非必需，与一期愈合机制一致。
• 识别出初始骨痂在几何形状与材料特性方面存在一个最优化范围，可最有效地缩短愈合时间。