Abstract：
We report on the 3D ultrastructure of the mineralized petrous bone of mature pig using focused ion beam - scanning electron microscopy (FIB-SEM). We divide the petrous bone into two zones based on the degree of mineralization; one zone close to the otic chamber has higher mineral density than the second zone further away from the otic chamber. The hypermineralization of the petrous bone results in the collagen D-banding being poorly revealed in the lower mineral density zone (LMD), and absent in the high mineral density zone (HMD). We therefore could not use D-banding to decipher the 3D structure of the collagen assembly. Instead we exploited the anisotropy option in the Dragonfly image processing software to visualize the less mineralized collagen fibrils and/or nanopores that surround the more mineralized zones known as tesselles. This approach therefore indirectly tracks the orientations of the collagen fibrils in the matrix itself. We show that the HMD bone has a structure similar to that of woven bone, and the LMD is composed of lamellar bone with a plywood-like structural motif. This agrees with the fact that the bone close to the otic chamber is fetal bone and is not remodeled. The lamellar structure of the bone further away from the otic chamber is consistent with modeling/remodeling. The absence of the less mineralized collagen fibrils and nanopores resulting from the confluence of the mineral tesselles may contribute to shielding DNA during diagenesis. We show that anisotropy evaluation of the less mineralized collagen fibrils could be a useful tool to analyze bone ultrastructures and in particular the directionality of collagen fibril bundles that make up the bone matrix.
摘要：
我们使用聚焦离子束-扫描电子显微镜（FIB-SEM）报告了成熟猪矿化岩骨的3D超微结构。我们根据矿化程度将岩骨分为两个区域；靠近耳腔的一个区域比远离耳腔的第二个区域具有更高的矿物质密度。岩骨的过度矿化导致胶原蛋白D带在较低的矿物质密度区（LMD）中显示不佳，并且在高矿物密度区（HMD）中不存在。因此,我们不能使用D-显带来破译胶原组装体的3D结构。相反，我们利用了Dragonfly图像处理软件中的各向异性选项，以可视化矿化程度较低的胶原纤维和/或纳米孔，这些胶原纤维和/或纳米孔围绕着更多的矿化区域。因此,该方法间接地跟踪基质本身中的胶原纤维的取向。我们证明HMD骨骼具有类似于编织骨骼的结构，LMD由具有胶合板状结构基序的板层骨组成。这与接近耳腔的骨是胎儿骨并且不被重塑的事实一致。远离耳腔的骨的层状结构与建模/重塑一致。由于矿物镶嵌物的汇合而导致的较少矿化的胶原纤维和纳米孔的缺乏可能有助于在成岩过程中屏蔽DNA。我们表明，对矿化程度较低的胶原纤维的各向异性评估可能是分析骨超微结构，特别是构成骨基质的胶原纤维束的方向性的有用工具。
