Maggiano Isabel S, Maggiano Corey M, Clement John G, Thomas C David L, Carter Yasmin, Cooper David M L
Department of Anatomy and Cell Biology, University of Saskatchewan, Saskatoon, SK, Canada.
Department of Anthropology, University of West Georgia, Carrollton, GA, USA.
J Anat. 2016 May;228(5):719-32. doi: 10.1111/joa.12430. Epub 2016 Jan 7.
This study uses synchrotron radiation-based micro-computed tomography (CT) scans to reconstruct three-dimensional networks of Haversian systems in human cortical bone in order to observe and analyse interconnectivity of Haversian systems and the development of total Haversian networks across different ages. A better knowledge of how Haversian systems interact with each other is essential to improve understanding of remodeling mechanisms and bone maintenance; however, previous methodological approaches (e.g. serial sections) did not reveal enough detail to follow the specific morphology of Haversian branching, for example. Accordingly, the aim of the present study was to identify the morphological diversity of branching patterns and transverse connections, and to understand how they change with age. Two types of branching morphologies were identified: lateral branching, resulting in small osteon branches bifurcating off of larger Haversian canals; and dichotomous branching, the formation of two new osteonal branches from one. The reconstructions in this study also suggest that Haversian systems frequently target previously existing systems as a path for their course, resulting in a cross-sectional morphology frequently referred to as 'type II osteons'. Transverse connections were diverse in their course from linear to oblique to curvy. Quantitative assessment of age-related trends indicates that while in younger human individuals transverse connections were most common, in older individuals more evidence of connections resulting from Haversian systems growing inside previously existing systems was found. Despite these changes in morphological characteristics, a relatively constant degree of overall interconnectivity is maintained throughout life. Altogether, the present study reveals important details about Haversian systems and their relation to each other that can be used towards a better understanding of cortical bone remodeling as well as a more accurate interpretation of morphological variants of osteons in cross-sectional microscopy. Permitting visibility of reversal lines, synchrotron radiation-based micro-CT is a valuable tool for the reconstruction of Haversian systems, and future analyses have the potential to further improve understanding of various important aspects of bone growth, maintenance and health.
本研究使用基于同步辐射的显微计算机断层扫描（CT）来重建人类皮质骨中哈弗斯系统的三维网络，以便观察和分析哈弗斯系统的相互连接性以及不同年龄段哈弗斯网络的发育情况。更好地了解哈弗斯系统之间的相互作用对于增进对重塑机制和骨骼维持的理解至关重要；然而，例如之前的方法（如连续切片）并未揭示足够的细节来追踪哈弗斯分支的具体形态。因此，本研究的目的是确定分支模式和横向连接的形态多样性，并了解它们如何随年龄变化。识别出了两种类型的分支形态：侧向分支，即从小的骨单位分支从较大的哈弗斯管分叉而出；以及二叉分支，即从一个形成两个新的骨单位分支。本研究中的重建还表明，哈弗斯系统经常以先前存在的系统为路径，导致横截面形态常被称为“II型骨单位”。横向连接的走向多样，从线性到倾斜再到弯曲。对与年龄相关趋势的定量评估表明，在较年轻的个体中横向连接最为常见，而在较年长的个体中，发现更多由哈弗斯系统在先前存在的系统内生长而产生的连接证据。尽管形态特征存在这些变化，但一生中整体相互连接程度相对保持恒定。总之，本研究揭示了关于哈弗斯系统及其相互关系的重要细节，可用于更好地理解皮质骨重塑以及更准确地解释横截面显微镜下骨单位的形态变异。基于同步辐射的显微CT能够显示反转线，是重建哈弗斯系统的宝贵工具，未来的分析有可能进一步增进对骨骼生长、维持和健康等各个重要方面的理解。
