Osteocyte differentiation & MCP-3 chemoattractant in mechanical stress responses

成骨细胞是骨细胞的前体细胞。一个特定的遗传程序和基因表达谱是这个分化过程的基础，成熟的骨细胞，但该程序的详细组成部分是未知的。我们已经开始定义一个基因表达模式的子集，代表成骨细胞的状态，因为它向骨细胞周围的类骨质积极矿化。使用成骨细胞和骨细胞模型组成的两个细胞系，2 T3，成骨细胞样细胞，和MLO-Y 4，骨细胞样细胞，我们已经定义了一个子集的基因，是低的成骨细胞，并成为高表达的骨细胞模型。此外，已经鉴定了骨细胞中对流体流动做出响应的基因子集。编码单核细胞趋化蛋白MCP-3的一个基因在骨细胞中比成骨细胞高13至19倍，成为骨细胞并鉴定对骨细胞功能重要的基因。短期目标是确定MCP-3在骨细胞功能中的作用。我们的假设是MCP-3是成骨细胞分化为骨细胞的标志物，也是破骨细胞前体向骨募集的关键分子。在这个提议中，我们将解决1）MCP-3在骨细胞功能中的作用和2）在体外和体内机械应变下MCP-3基因表达的调节。为了实现这些目标，将使用MPO-Y 4细胞系、原代骨细胞、原代成骨细胞和在培养物中形成含有骨细胞样细胞的矿化结节的2 T3细胞系。在这些模型中，将测试增加流体流动的幅度和频率对MCP-3产生、基因表达模式和功能的影响。两种啮齿动物体内机械应变模型，牙齿移动模型和尺骨疲劳负荷模型将用于访问和验证体外模型中发现的基因表达变化。我们还将使用MCP受体无效等位基因的转基因小鼠，CCR 2小鼠将在破骨细胞前体募集方面存在缺陷。这些研究的结果将极大地扩展我们关于骨细胞功能重要基因的数据库，也将有助于深入了解破骨细胞向骨微骨折部位募集的机制。

Osteoblasts are the precursors to osteocytes. A specific genetic program and gene expression profile underlies this differentiation process to a mature osteocyte, but the detailed components of that program are unknown. We have begun to define a subset of gene expression patterns that represent the state of the osteoblast as it progresses towards an osteocyte surrounded by osteoid that is actively mineralizing. Using osteoblast and osteocyte models composed of two cell lines, 2T3, an osteoblast-like cell, and MLO-Y4, an osteocyte-like cell, we have defined a subset of genes that are low in osteoblasts and become highly expressed in the osteocytes model. Additionally, a subset of genes in the osteocyte that respond to fluid flow have been identified Additionally, a subset of genes in the osteocyte that respond to fluid flow have been identified. One genes that encodes for Monocyte Chemoattractant Protein, MCP-3, is 13 TO 19 fold higher in osteocytes compared to osteoblast becomes an osteocyte and identify genes important for osteocyte function. The short- term goal is to determine the role of MCP-3 in osteocyte function. Our hypothesis is that MCP-3 is a marker for differentiation of osteoblasts into osteocytes and a critical molecule in recruitment of osteoclast precursors to bone. In this proposal we will address 1) the role of MCP-3 in osteocyte function and 2) the regulation of MCP-3 gene expression under mechanical strain both in vitro and in vivo. To accomplish these goals, the MPO-Y4 cell line, primary osteocytes, primary osteoblasts and the 2T3 cell line that forms mineralized nodules containing osteocyte-like cells in culture will be used. Increasing magnitude and frequency of fluid flow will be tested for effect on MCP-3 production, gene expression patterns and function in these models. Two rodent in vivo models of mechanical strain, the tooth movement model and ulnae-fatigue loading model will be used to access and validate gene expression changes found in the in vitro models. We will also use transgenic mice with a null allele of the MCP receptor, CCR2 mice will have defects in osteoclast precursor recruitment. Results from these studies will dramatically expand our database on genes important for osteocyte function and should also lead to insights into the mechanism of osteoclast recruitment to sties of bone microfracture.