PDF(Pubmed)
Abstract：
Despite the dominant role of bone mass in osteoporotic fractures, aging bone tissue properties must be thoroughly understood to improve osteoporosis management. In this context, collagen content and integrity are considered important factors, although limited research has been conducted on the tensile behavior of demineralized compact bone in relation to its porosity and elastic properties in the native mineralized state. Therefore, this study aims (i) at examining the age-dependency of mineralized bone and collagen micromechanical properties; (ii) to test whether, and if so to which extent, collagen properties contribute to mineralized bone mechanical properties. Two cylindrical cortical bone samples from fresh frozen human anatomic donor material were extracted from 80 proximal diaphyseal sections from a cohort of 24 female and 19 male donors (57 to 96 years at death). One sample per section was tested in uniaxial tension under hydrated conditions. First, the native sample was tested elastically (0.25 % strain), and after demineralization, up to failure. Morphology and composition of the second specimen was assessed using micro-computed tomography, Raman spectroscopy, and gravimetric methods. Simple and multiple linear regression were employed to relate morphological, compositional, and mechanical variables with age and sex. Macro-tensile properties revealed that only elastic modulus of native samples was age dependent whereas apparent elastic modulus was sex dependent (p < 0.01). Compositional and morphological analysis detected a weak but significant age and sex dependency of relative mineral weight (r = -0.24, p < 0.05) and collagen disorder ratio (I∼1670/I∼1640, r = 0.25, p < 0.05) and a strong sex dependency of bone volume fraction while generally showing consistent results in mineral content assessment. Young\'s modulus of demineralized bone was significantly related to tissue mineral density and Young\'s modulus of native bone. The results indicate that mechanical properties of the organic phase, that include collagen and non-collagenous proteins, are independent of donor age. The observed reduction in relative mineral weight and corresponding overall stiffer response of the collagen network may be caused by a reduced number of mineral-collagen connections and a lack of extrafibrillar and intrafibrillar mineralization that induces a loss of waviness and a collagen fiber pre-stretch.
摘要：
尽管骨量在骨质疏松性骨折中起主导作用，必须彻底了解老化的骨组织特性，以改善骨质疏松症的管理。在这种情况下，胶原蛋白含量和完整性被认为是重要因素，尽管对去矿质致密骨在天然矿化状态下的孔隙率和弹性特性的拉伸行为进行了有限的研究。因此,这项研究的目的是（一）检查年龄依赖性的矿化骨和胶原微机械特性；（二）测试是否，如果是的话，在多大程度上，胶原特性有助于矿化骨的机械性能。从24名女性和19名男性供体（死亡时57至96岁）的80个近端骨干切片中提取了来自新鲜冷冻的人类解剖供体材料的两个圆柱形皮质骨样品。在水合条件下在单轴拉伸下测试每个部分一个样品。首先,对天然样品进行弹性测试(0.25%应变)，去矿化后,直到失败。使用显微计算机断层扫描评估第二个标本的形态和组成，拉曼光谱,和重量分析法。采用简单和多元线性回归来关联形态学，组成,以及年龄和性别的机械变量。宏观拉伸性能表明，只有天然样品的弹性模量与年龄有关，而表观弹性模量与性别有关（p<0.01）。成分和形态学分析检测到相对矿物质重量（r=-0.24，p<0.05）和胶原障碍比率（I〜1670/I〜1640，r=0.25，p<0.05）的年龄和性别依赖性较弱，但在矿物质含量评估中表现出强烈的性别依赖性。脱钙骨的杨氏模量与组织矿物质密度和天然骨的杨氏模量显着相关。结果表明,有机相的力学性能,包括胶原蛋白和非胶原蛋白，与捐赠者年龄无关。观察到的相对矿物质重量的减少和胶原蛋白网络的相应的总体更硬响应可能是由于矿物质-胶原蛋白连接的数量减少以及缺乏纤维外和纤维内矿化而引起的，这导致波度和胶原纤维预拉伸的损失。
