Fang Ming, Holl Mark M Banaszak
Department of Chemistry, University of Michigan , Ann Arbor, MI, USA.
Bonekey Rep. 2013 Aug 21;2:394. doi: 10.1038/bonekey.2013.128.
Although the axial D-periodic spacing is a well-recognized nanomorphological feature of type I collagen fibrils, the existence of a distribution of values has been largely overlooked since its discovery seven decades ago. Studies based on single fibril measurements occasionally noted variation in D-spacing values, but accredited it with no biological significance. Recent quantitative characterizations supported that a 10-nm collagen D-spacing distribution is intrinsic to collagen fibrils in various tissues as well as in vitro self-assembly of reconstituted collagen. In addition, the distribution is altered in Osteogenesis Imperfecta and long-term estrogen deprivation. Bone collagen is organized into lamellar sheets of bundles at the micro-scale, and D-spacings within a bundle of a lamella are mostly identical, whereas variations among different bundles contribute to the full-scale distribution. This seems to be a very general phenomenon for the protein as the same type of D-spacing/bundle organization is observed for dermal and tendon collagen. More research investigation of collagen nanomorphology in connection to bone biology is required to fully understand these new observations. Here we review the data demonstrating the existence of a D-spacing distribution, the impact of disease on the distribution and possible explanations for the origin of D-spacing variations based on various collagen fibrillogenesis models.
尽管轴向D周期间距是I型胶原纤维公认的纳米形态特征，但自七十年前发现以来，其值分布的存在在很大程度上被忽视了。基于单根纤维测量的研究偶尔会注意到D间距值的变化，但认为其没有生物学意义。最近的定量表征支持，10纳米的胶原D间距分布是各种组织中胶原纤维以及重组胶原体外自组装所固有的。此外，在成骨不全症和长期雌激素缺乏的情况下，这种分布会发生改变。骨胶原在微观尺度上被组织成束状的层板，一个层板束内的D间距大多相同，而不同束之间的变化则构成了整个尺度的分布。对于这种蛋白质来说，这似乎是一个非常普遍的现象，因为在真皮和肌腱胶原中也观察到了相同类型的D间距/束状组织。需要更多关于胶原纳米形态与骨生物学关系的研究调查，以充分理解这些新发现。在这里，我们回顾了证明D间距分布存在的数据、疾病对该分布的影响以及基于各种胶原纤维形成模型对D间距变化起源的可能解释。
