The effect of sustained compression on oxygen metabolic transport in the intervertebral disc decreases with degenerative changes.
The effect of sustained compression on oxygen metabolic transport in the intervertebral disc decreases with degenerative changes.
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DOI：
10.1371/journal.pcbi.1002112
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发表时间：
2011-08
影响因子：
4.3
通讯作者：
Lacroix D
中科院分区：
文献类型：
--
作者：
Malandrino A;Noailly J;Lacroix D
间盘代谢运输对脊柱功能至关重要，并为细胞提供组织维持所需的营养。椎间盘退行性改变改变了组织力学，但机械负荷和椎间盘运输之间的相互作用仍然是一个悬而未决的问题。将人体椎间盘的孔力学有限元模型与氧气和乳酸传输模型相耦合。通过包括应变相关的扩散和平流，将变形和流体流动与运输预测联系起来。这两个溶质运输模型也耦合到细胞新陈代谢。用这种方法，在每日负荷-恢复压缩下，对健康椎间盘中代谢和机械运输耦合的相关性进行了评估。对盘状高度、胞体密度和材料退化变化进行了参数模拟，研究了它们对计算的溶质浓度的影响。在考虑短周期循环压缩的情况下，还研究了载荷频率和幅值对健康腰椎间盘的影响。结果表明，当较大的体积变化改变扩散距离和扩散系数时，外部载荷会影响圆盘内氧和乳酸的区域分布，特别是在模拟健康圆盘特性时。在持续压缩和循环压缩下，平流都可以忽略不计。模拟退变，机械变化抑制了对运输的机械效应，而椎间盘高度、液体含量、核压力和总体细胞密度降低显著影响了运输预测。对于健康的腰椎间盘，养分浓度模式主要取决于持续压缩和恢复的时间。细胞密度对代谢转运的相关影响表明，细胞数量的紊乱可能是通过改变代谢平衡而导致椎间盘退变的。结果还表明，健康的椎间盘特性对代谢运输有积极的影响。因此，与维持组织功能组合物相关的这种关系将把盘功能与盘营养联系起来。下腰痛在工业化国家是一种非常常见的病理，通常是由于姿势不好造成的。它也与椎间盘老化高度相关。椎间盘的老化是一个正常的过程，其特征是其结构和功能发生了一系列变化。将正常衰老转化为退化性疾病的事件仍不清楚。并发症，如有限的营养和可能减少的椎间盘细胞随着年龄的增长，使问题错综复杂，多因素。使用包括营养成分和机械成分的数值模型，我们发现了两种不同的情况，当观察外部负荷对与视盘新陈代谢相关的两种重要细胞溶质：氧和乳酸的影响时。当压缩健康的椎间盘时，机械载荷的影响比退化的椎间盘更大，并且促进了溶质浓度的波动。此外，细胞密度的改变似乎是椎间盘退变过程中的基础，其与其他退行性改变的因果关系应进一步调查。机械和细胞模式对维持健康状态的重要性为椎间盘再生医学领域提供了新的见解。
Intervertebral disc metabolic transport is essential to the functional spine and provides the cells with the nutrients necessary to tissue maintenance. Disc degenerative changes alter the tissue mechanics, but interactions between mechanical loading and disc transport are still an open issue. A poromechanical finite element model of the human disc was coupled with oxygen and lactate transport models. Deformations and fluid flow were linked to transport predictions by including strain-dependent diffusion and advection. The two solute transport models were also coupled to account for cell metabolism. With this approach, the relevance of metabolic and mechano-transport couplings were assessed in the healthy disc under loading-recovery daily compression. Disc height, cell density and material degenerative changes were parametrically simulated to study their influence on the calculated solute concentrations. The effects of load frequency and amplitude were also studied in the healthy disc by considering short periods of cyclic compression. Results indicate that external loads influence the oxygen and lactate regional distributions within the disc when large volume changes modify diffusion distances and diffusivities, especially when healthy disc properties are simulated. Advection was negligible under both sustained and cyclic compression. Simulating degeneration, mechanical changes inhibited the mechanical effect on transport while disc height, fluid content, nucleus pressure and overall cell density reductions affected significantly transport predictions. For the healthy disc, nutrient concentration patterns depended mostly on the time of sustained compression and recovery. The relevant effect of cell density on the metabolic transport indicates the disturbance of cell number as a possible onset for disc degeneration via alteration of the metabolic balance. Results also suggest that healthy disc properties have a positive effect of loading on metabolic transport. Such relation, relevant to the maintenance of the tissue functional composition, would therefore link disc function with disc nutrition. Low back pain is a very common pathology in industrialized countries, often due to bad posture. It is also highly related to intervertebral disc aging. Aging of the disc is a normal process characterized by series of changes in its structure and function. The events that convert normal aging into degenerative disease is still not clear. Complications such as limited nutrition and possible reduction of disc cells with age make the issue intricate and multi-factorial. Using a numerical model that includes both nutritional and mechanical components, we found two different situations when looking at the effect of external loadings on two important cell solutes related with disc metabolism: oxygen and lactate. The effect of mechanical loading was greater when compressing a healthy disc than a degenerated one and promoted fluctuations of solutes concentrations. Also, changes in cell density seem fundamental in the process of disc degeneration and its causality with other degenerative changes should be further investigated. The importance of both mechanical and cellular patterns to maintain a healthy condition provides new insights to the field of disc regenerative medicine.
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