Collagen pre-strain discontinuity at the bone-Cartilage interface.
Collagen pre-strain discontinuity at the bone-Cartilage interface.
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DOI：
10.1371/journal.pone.0273832
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发表时间：
2022
期刊：
影响因子：
3.7
通讯作者：
中科院分区：
文献类型：
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作者：
骨-软骨单元（BCU）是关节的普遍特征，其是机械分级的，并承受剪切和压缩应变。BCU的变化与骨关节炎（OA）进展有关。在这里，我们报告存在的生理内部应变梯度（预应变）在超微结构尺度的细胞外基质（ECM）成分，特别是胶原纤维的BCU。我们使用X射线散射，探针的原胶原分子在基质原纤维的原纤维水平D-交错轴向周期性的变化，作为微观预应变的措施。我们发现钙化板中的矿化胶原纳米纤维相对于底层骨小梁处于拉伸预应变状态。这种行为与先前接受的概念形成对比，即胶原组织中的纤维预应变（或D-交错）总是随着矿化而减少，通过减少水合作用和相关的膨胀压力。在BCU的钙化部分内，观察到预应变的更精细梯度（超过约50μm增加0.6%）。增加的纤维预应变与先前的研究报告在压缩下的大的组织水平的残余应变有关。这些发现可能具有生物力学适应性意义：更高的内在分子水平弹性/对生理压缩的损伤抵抗力，以及骨-软骨界面重塑过程中分子水平预应变的破坏可能是骨关节炎退行性变的潜在因素。
The bone-cartilage unit (BCU) is a universal feature in diarthrodial joints, which is mechanically-graded and subjected to shear and compressive strains. Changes in the BCU have been linked to osteoarthritis (OA) progression. Here we report existence of a physiological internal strain gradient (pre-strain) across the BCU at the ultrastructural scale of the extracellular matrix (ECM) constituents, specifically the collagen fibril. We use X-ray scattering that probes changes in the axial periodicity of fibril-level D-stagger of tropocollagen molecules in the matrix fibrils, as a measure of microscopic pre-strain. We find that mineralized collagen nanofibrils in the calcified plate are in tensile pre-strain relative to the underlying trabecular bone. This behaviour contrasts with the previously accepted notion that fibrillar pre-strain (or D-stagger) in collagenous tissues always reduces with mineralization, via reduced hydration and associated swelling pressure. Within the calcified part of the BCU, a finer-scale gradient in pre-strain (0.6% increase over ~50μm) is observed. The increased fibrillar pre-strain is linked to prior research reporting large tissue-level residual strains under compression. The findings may have biomechanical adaptative significance: higher in-built molecular level resilience/damage resistance to physiological compression, and disruption of the molecular-level pre-strains during remodelling of the bone-cartilage interface may be potential factors in osteoarthritis-based degeneration.