Department of Chemical and Materials Engineering, The University of Auckland, Auckland, New Zealand.
J Anat. 2010 Mar;216(3):310-9. doi: 10.1111/j.1469-7580.2009.01197.x.
Although age- and degeneration-related changes in the morphology and biochemistry of the annulus fibrosus have been extensively reported, studies of tensile strength changes show only a weak correlation with maturity. Given that the disc is a tissue system in which significant levels of deformation occur with normal physiological loading, there may be structure-related properties that provide a better indicator of the influence of ageing on its function. This study is a morphological investigation of lamellar interfibre cohesivity with respect to maturity. Anterior segments of ovine lumbar discs in two age groups were cut at one of two section angles to generate intralamellar and interlamellar slices. These slices of hydrated annular tissue were subjected separately to microtensile and swelling forces, and examined using differential interference contrast microscopy. There were distinct differences in microstructural responses to transverse extension between the immature and mature intralamellar slices. The immature tissue exhibited a diffuse expansion of the array to form a fine fibrous net. In contrast, the mature tissue displayed a discontinuous expansion with the development of clefts and localized fibre buckling. A difference was also observed in the free-swelling response; the immature slices remained planar, whereas the cropped lamellar fibres in the mature slices exhibited a folded, buckled morphology. Morphological evidence from these experiments infers differences in fibre cohesivity between the immature and mature tissues, consistent with biochemical and histological studies. More extreme levels of deformation in the mature tissue could result in discontinuous opening of the fibrous arrays, which might have the potential to lead to cleft formation. These clefts may, in turn, provide micropaths through which nuclear material could extrude. Importantly, with many animal studies carried out on immature discs, the results here suggest that some caution is required with respect to extrapolating annular behaviour beyond this age group.
尽管已有大量研究报道了纤维环的形态和生物化学随年龄和退变而发生的变化，但关于拉伸强度变化的研究仅显示出与成熟度的微弱相关性。鉴于椎间盘是一种在正常生理负荷下会发生显著变形的组织系统，可能存在与结构相关的特性，可以更好地指示年龄对其功能的影响。本研究旨在探讨纤维环板层内纤维黏附性与成熟度的关系。将两个年龄组绵羊腰椎间盘的前节沿两个节段角度之一切割，以生成板层内和板层间切片。将这些水合的环状组织切片分别承受微拉伸力和膨胀力，并使用相差微分干涉对比显微镜进行检查。在不成熟和成熟的板层内切片中，横向拉伸的微观结构反应存在明显差异。不成熟的组织表现为纤维排列的弥散扩张，形成精细的纤维网。相比之下，成熟组织显示出不连续的扩张，出现裂隙和局部纤维弯曲。在自由膨胀反应中也观察到差异；不成熟的切片保持平面，而成熟切片中的裁剪板层纤维呈现折叠、弯曲的形态。这些实验的形态学证据推断不成熟和成熟组织之间的纤维黏附性存在差异，这与生化和组织学研究一致。成熟组织中更极端的变形水平可能导致纤维排列的不连续打开，这可能导致裂隙形成。这些裂隙反过来又可能为核物质挤出提供微孔路径。重要的是，由于许多动物研究都是在不成熟的椎间盘上进行的，因此这里的结果表明，在这个年龄组之外推断环形行为时需要谨慎。
