跟腱止点在复载时重建其矿化前沿，但保留卸载的纳米级印记
The Achilles tendon enthesis rebuilds its mineralization front on reloading but retains a nanoscale imprint of unloading
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中文总结 AI 辅助
研究发现小鼠跟腱止点复载时可重建矿化前沿，但会保留卸载的纳米级印记，揭示其为机械调控的梯度界面，机械历史会印记于纳米结构。
中文摘要 AI 辅助
止点是一种梯度纤维软骨界面，负责在肌腱与骨骼间传递载荷，但其矿化前沿稳定的纳米级机制仍不明确。本研究结合多模态二维/三维X射线成像与非线性光学显微镜，绘制小鼠跟腱止点在卸载和复载状态下的结构、晶体及细胞外基质分布。卸载会降低与潮线相关的双光子荧光（2PF）峰，伴随矿化扩散至此前未矿化的纤维软骨区域；该卸载相关矿化表现为表观微晶尺寸增大、c轴晶格参数扩大、晶体织构降低及胶原有序梯度减弱，与矿化环境改变一致。复载时，2PF峰恢复，但在距原始边界约20μm处形成新的潮线，产生矿化镶嵌图中具有持久纳米级印记的区域。这些发现表明，止点是机械调控的梯度界面，基质介导的边界控制约束矿化形成，且机械历史会以印记形式保留在纳米结构中。
英文摘要
The enthesis is a graded fibrocartilaginous interface that transfers load between tendon and bone, yet the nanoscale mechanisms stabilizing its mineralization front remain unclear. Here, we combine multimodal 2D/3D X-ray imaging with nonlinear optical microscopy to map structural, crystalline and extracellular matrix organization across the murine Achilles tendon enthesis under unloading and reloading. Unloading reduces the tidemark-associated two-photon fluorescence (2PF) peak and is accompanied by diffuse mineralization into previously unmineralized fibrocartilage. This unloading-associated mineral exhibits increased apparent crystallite size, an enlarged c-axis lattice parameter, reduced crystalline texture and a diminished collagen order gradient, consistent with an altered mineralization environment. Upon reloading, the 2PF peak recovers, but a new tidemark forms ~20 um from the original boundary, creating a zone with a persistent nanoscale imprint in the mineral tessellation. These findings establish the enthesis as a mechanically governed graded interface in which matrix-mediated boundary control constrains mineral formation and in which a record of mechanical history is imprinted into the nanostructure.
