Metzger Thomas A, Shudick Jonelle M, Seekell Raymond, Zhu Yingxi, Niebur Glen L
Tissue Mechanics Laboratory, Bioengineering Graduate Program, University of Notre Dame, Notre Dame, IN, USA.
Dept. of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN, USA.
J Mech Behav Biomed Mater. 2014 Dec;40:307-313. doi: 10.1016/j.jmbbm.2014.09.008. Epub 2014 Sep 16.
The progression of several diseases, such as osteoporosis and diabetes, are associated with changes in marrow composition and physiology. As these diseases are affected by aging and activity, the biomechanical properties and mechanobiology of marrow may play a role in their progression. Bone marrow is comprised primarily of cells, and provides a niche for several mechanosensitive cell lineages. The mechanical signals imparted to the cells depend on their interaction with one another, the extracellular matrix, and the intercellular fluid. At a macroscopic scale, these interactions manifest as viscosity in marrow. Marrow viscosity has been measured in human and bovine bone. However, a large range of storage, retrieval, and measurement techniques has resulted in inconsistent data. To provide physiologically relevant data, marrow samples from young adult pigs were harvested and tested within less than 8h of slaughter. The viscosity was over 100Pas at a shear rate of 1s(-1), and decreased with shear rate according to a power law. However, the marrow did not exhibit a measurable yield stress as some complex fluids do. The viscosity of samples that had been frozen and thawed prior to testing was lower by an order of magnitude. The difference in properties was associated with a loss of integrity of the marrow adipocyte membranes. Previous reports of bone marrow viscosity have shown inconsistent results, which may be due to different storage and handling prior to testing. The higher viscosity compared to previous reports would impact poroelastic models of bone, and suggests that the stress on marrow cells during whole bone loading may be higher than previously believed.
骨质疏松症和糖尿病等多种疾病的进展与骨髓成分和生理功能的变化有关。由于这些疾病受衰老和活动的影响，骨髓的生物力学特性和力学生物学可能在其进展中起作用。骨髓主要由细胞组成，并为几种机械敏感细胞谱系提供微环境。施加给细胞的机械信号取决于它们彼此之间、细胞外基质和细胞间液的相互作用。在宏观尺度上，这些相互作用表现为骨髓的粘性。已经在人和牛的骨骼中测量了骨髓粘性。然而，大量的储存、提取和测量技术导致了不一致的数据。为了提供生理相关数据，从年轻成年猪身上采集骨髓样本，并在屠宰后不到8小时内进行测试。在剪切速率为1s(-1)时，粘度超过100Pas，并根据幂律随剪切速率降低。然而，骨髓并没有像一些复杂流体那样表现出可测量的屈服应力。测试前经过冷冻和解冻的样本粘度降低了一个数量级。性质上的差异与骨髓脂肪细胞膜完整性的丧失有关。先前关于骨髓粘性的报告显示结果不一致，这可能是由于测试前不同的储存和处理方式。与先前报告相比更高的粘度会影响骨的多孔弹性模型，并表明全骨加载过程中骨髓细胞上的应力可能比先前认为的更高。
