MECHANICAL LOADING AND BONE

拟议研究的长期目标是阐明机械转导的机制。 骨头。我们目前面向生物工程的项目开发了一种高分辨率的压电式机械 利用培养的成骨细胞加载并评价机械刺激在骨中的作用。结果是 揭示了(A)3D胶原基质的变形可以诱导应变诱导的流体流动；(B)应变诱导的流体 流动，而不是应变本身，主要激活成骨细胞中的应激反应基因；以及(C) 三维胶原基质的结构建立了一种应变诱导的流体流动和分子运输模式。 动物研究中的许多证据支持1000-应变促进骨重塑- 2000株微菌。我们的体外研究和这些动物研究之间的一个不清楚的联系是 骨重建中的应变和流体流动。包括我们目前的研究在内的成骨细胞体外培养使用2D 基质或3D基质很难模拟体内应变诱导的流体流动。这一差异是在 体外和体内的数据使得很难评估应变和液体流动在骨重建和骨修复中的作用 消炎。首先，骨骼中的微观应变可能高于宏观应变。 用应变计。因此，高于1000-2000微应变的局部微观应变可能会驱动流体。 在骨头里流动。其次，骨骼中的腔隙管网络可以放大应变诱导的体液流动。 加载频率依赖的方式。最后，骨间质液可能是由原位应变引起的。 以及较远位置的应变，使得相对较软的骨痂变形导致流体流入 骨干的皮质骨。 本更新方案将采用小鼠尺骨体外实验以及小鼠体内负荷实验来检验上述指标。 对数据分歧的可能解释。具体目标包括：(1)制作一种压电体 体外和体内使用的机械加载器；(2)体外宏观和微观应变的量化 使用电子散斑干涉术以及使用荧光恢复的分子传输 光漂白后；(3)进行骨组织形态计量学评价体外数据；(4)检查 负荷驱动的不良反应与基因表达和酶活性(例如，基质金属蛋白酶)。 机械载荷将在尺骨加载(轴向加载)和肘部加载(横向加载)模式下施加。 这两种模式已被证明通过不同的模式促进骨干的骨重建。 应变分布。成功完成拟议的更新建议将提供基本知识 关于骨内液体流动的诱导，并为制定治疗策略建立研究平台 强骨，防止骨质流失。

The long-term objective of the proposed studies is to elucidate the mechanism of mechanotransduction in bone. Our present bioengineering-oriented project developed a high-resolution piezoelectric mechanical loader and evaluated the role of mechanical stimulation in bone using cultured osteoblasts. The results reveal that (a) deformation of 3D collagen matrix can induce strain-induced fluid flow; (b) strain-induced fluid flow, and not strain itself, predominantly activates the stress-responsive genes in osteoblasts; and (c) architecture of 3D collagen matrix establishes a pattern of strain-induced fluid flow and molecular transport. Many lines of evidence in animal studies support enhancement of bone remodeling with strain of 1000 - 2000 microstrains. An unclear linkage between our in vitro studies and these animal studies is the role of strain and fluid flow in bone remodeling. In vitro osteoblast cultures including our current studies use 2D substrates or 3D matrices that hardly mimic the strain-induced fluid flow in vivo. This difference between in vitro and in vivo data makes it difficult to evaluate the role of strain and fluid flow in bone remodeling and anti-inflammation. First, microscopic strain in bone might be higher than the macroscopic strain measured with strain gauges. A local microscopic strain higher than 1000 - 2000 microstrains may therefore drive fluid flow in bone. Second, the lacunocanalicular network in bone could amplify strain-induced fluid flow in a loading-frequency dependent fashion. Lastly, interstitial fluid flow in bone might be induced by in situ strain as well as strain in a distant location, such that deformation of relatively soft epiphyses induces fluid flow in cortical bone in diaphyses. This renewal proposal will use mouse ulnae ex vivo as well as mouse in vivo loading to examine the above possible explanations for the data divergence. Specific aims include: (1) fabricating a piezoelectric mechanical loader for ex vivo and in vivo use; (2) quantifying ex vivo macroscopic and microscopic strains using electronic speckle pattern interferometry as well as molecular transport using fluorescence recovery after photobleaching; (3) conducting bone histomorphometry to evaluate ex vivo data; and (4) examining load-driven adverse effects with gene expression and enzyme activities (e.g., matrix metalloproteinases). Mechanical loads will be given in the ulna-loading (axial loading) and elbow-loading (lateral loading) modes. These two modes have been shown to enhance bone remodeling in the diaphysis with different patterns of strain distribution. Successful completion of the proposed renewal proposal will provide basic knowledge about induction of fluid flow in bone and establish a research platform for devising therapeutic strategies for strengthening bone and preventing bone loss.