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Crossfibrillar mineral tessellation in normal and Hyp mouse bone as revealed by 3D FIB-SEM microscopy.
Journal of Structural Biology ( IF 3 ) Pub Date : 2020-08-14 , DOI: 10.1016/j.jsb.2020.107603
Daniel J Buss 1 , Natalie Reznikov 2 , Marc D McKee 3
Affiliation  

In bone, structural components such as mineral extend across length scales to provide essential biomechanical functions. Using X-ray micro-computed tomography (µCT), and focused ion beam scanning electron microscopy (FIB-SEM) in serial-surface-view mode, together with 3D reconstruction, entire mouse skeletons and small bone tissue volumes were examined in normal wildtype (WT) and mutant Hyp mice (an animal model for X-linked hypophosphatemia/XLH, a disease with severe hypomineralization of bone). 3D thickness maps of the skeletons showed pronounced irregular thickening and abnormalities of many skeletal elements in Hyp mice compared to WT mice. At the micro- and nanoscale, near the mineralization front in WT tibial bone volumes, mineralization foci grow as expanding prolate ellipsoids (tesselles) to abut and pack against one another to form a congruent and contiguous mineral tessellation pattern within collagen bundles that contributes to lamellar periodicity. In the osteomalacic Hyp mouse bone, mineralization foci form and begin initial ellipsoid growth within normally organized collagen assembly, but their growth trajectory aborts. Mineralization-inhibiting events in XLH/Hyp (low circulating serum phosphate, and increased matrix osteopontin) combine to result in decreased mineral ellipsoid tessellation – a defective mineral-packing organization that leaves discrete mineral volumes isolated in the extracellular matrix such that ellipsoid packing/tessellation is not achieved. Such a severely altered mineralization pattern invariably leads to abnormal compliance, other aberrant biomechanical properties, and altered remodeling of bone, all of which indubitably lead to macroscopic bone deformities and anomalous mechanical performance in XLH/Hyp. Also, we show the relationship of osteocytes and their cell processes to this mineralization pattern.



中文翻译:

3D FIB-SEM 显微镜显示正常和 Hyp 小鼠骨骼中的交叉纤维矿物镶嵌。

在骨骼中,矿物质等结构成分跨越长度尺度,以提供基本的生物力学功能。使用 X 射线微型计算机断层扫描 (µCT) 和聚焦离子束扫描电子显微镜 (FIB-SEM) 在串行表面视图模式下,连同 3D 重建,在正常野生型中检查整个小鼠骨骼和小骨组织体积(WT) 和突变Hyp小鼠(X 连锁低磷血症/XLH 的动物模型,一种严重的骨矿化不足的疾病)。骨骼的 3D 厚度图显示Hyp中许多骨骼元素明显不规则增厚和异常小鼠与 WT 小鼠相比。在微米和纳米尺度上,在 WT 胫骨体积的矿化前沿附近,矿化灶随着扩大的长椭圆体(细长椭圆体)而生长,相互邻接和堆积,从而在胶原束内形成一致且连续的矿物质镶嵌图案,有助于形成板层周期性。在骨软化Hyp小鼠骨骼中,矿化灶形成并在正常组织的胶原蛋白组装中开始初始椭圆体生长,但它们的生长轨迹中止。XLH/ Hyp中的矿化抑制事件(低循环血清磷酸盐和增加的基质骨桥蛋白)结合导致矿物质椭圆体镶嵌减少 - 一种有缺陷的矿物质填充组织,使离散的矿物质体积隔离在细胞外基质中,从而无法实现椭圆体填充/镶嵌。这种严重改变的矿化模式总是导致异常顺应性、其他异常的生物力学特性和改变的骨重塑,所有这些都无疑会导致 XLH/ Hyp的宏观骨畸形和异常的机械性能。此外,我们还展示了骨细胞及其细胞过程与这种矿化模式的关系。

更新日期:2020-09-18
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