Department of Chemical and Materials Engineering, University of Auckland, Auckland, New Zealand.
J Anat. 2012 Jul;221(1):39-46. doi: 10.1111/j.1469-7580.2012.01507.x. Epub 2012 Apr 26.
The intervertebral disc nucleus has traditionally been viewed as a largely unstructured amorphous gel having little obvious integration with the cartilaginous endplates (CEPs). However, recent work by the present authors has provided clear evidence of structural cohesion across the nucleus-endplate junction via a distinctive microanatomical feature termed insertion nodes. The aim of this study was to explore the nature of these insertion nodes at the fibrillar level. Specially prepared vertebra-nucleus-vertebra composite samples from ovine lumbar motion segments were extended axially and chemically fixed in this stretched state, and then decalcified. Sections taken from the samples were prepared for examination by scanning electron microscopy. A close morphological correlation was obtained between previously published optical microscopic images of the nodes and those seen using low magnification SEM. Progressively high magnifications provided insight into the fibrillar-level modes of structural integration across the nucleus-endplate junction. The closely packed fibrils of the CEP were largely parallel to the vertebral endplate and formed a dense, multi-layer substrate within which the nodal fibrils appeared to be anchored. Our idealised structural model proposes a mechanism by which this integration is achieved. The nodal fibrils, in curving into the CEP, are locked in place within its close-packed layers of transversely aligned fibrils, and probably at multiple levels. Secondly, there appears to be a subtle interweaving of the strongly aligned nodal fibrils with the multi-directional endplate fibrils. It is suggested that this structural integration provides the nucleus with a form of tethered mobility that supports physiological functions quite distinct from the primary strength requirements of the disc.
椎间盘核传统上被认为是一种结构松散的无定形凝胶，与软骨终板（CEP）几乎没有明显的整合。然而，本研究小组最近的工作通过一种称为插入节点的独特微观解剖特征，提供了核-终板交界处结构内聚的明确证据。本研究的目的是在纤维水平上探索这些插入节点的性质。从绵羊腰椎运动节段的椎间体-核-椎间体复合样本中特别制备样本，使其轴向延伸并在拉伸状态下化学固定，然后脱钙。从样本中取出的切片用于扫描电子显微镜检查。在以前发表的节点光学显微镜图像和使用低倍扫描电镜观察到的图像之间获得了密切的形态相关性。逐渐提高放大倍数可以深入了解核-终板交界处的纤维水平结构整合模式。CEP 的紧密堆积纤维与椎体终板基本平行，并在其中形成一个密集的多层基质，节点纤维似乎固定在其中。我们的理想结构模型提出了一种实现这种整合的机制。节点纤维在弯曲进入 CEP 时，被锁定在其紧密堆积的横向排列纤维层内，并且可能在多个层面上。其次，似乎存在节点纤维与多向终板纤维的微妙交织。有人认为，这种结构整合为核提供了一种受约束的活动性，这种活动性支持与椎间盘的主要强度要求截然不同的生理功能。
