BONE STEM CELLS, OSTEOBLASTS, & TGF-BETA IN OSTEOPOROSIS

骨质疏松症是一种骨骼疾病，其骨吸收水平 超过骨形成的速度，导致骨量的损失。两者都有 骨形成和骨吸收的局部控制是 成骨细胞，一种也能产生生长因子和细胞因子的细胞 显然是以一种独裁和旁分泌的方式来影响 成骨细胞和破骨细胞。其中最重要的是 药物正在转化生长因子-β(TGF-β)，这是一种已知的蛋白质 刺激细胞增殖、分化和基质合成 在体内具有骨诱导活性。随着年龄的增长， 成骨细胞的生物合成活性下降，我们认为，随之而来的是 维持进一步发展所需的转化生长因子-β水平或有效作用 基质合成与成骨细胞前体增殖成熟。 然而，转化生长因子-β合成下降和/或 转化生长因子-β效应活性降低和成骨细胞减少 前驱体库和进一步的基质合成尚未完全完成 有记录在案。这是本文件中描述的研究的总体目标 应用程序提供此文档。具体来说，我们建议 测试与年龄相关的(II型)骨质疏松症的假设 部分来自内源性合成的下降和/或有效 转化生长因子-β对OPC的自分泌作用导致OPC减少 骨基质蛋白合成的数量和减少。这一假设 将通过追求以下具体目标进行测试：(1)完成 回收细胞中OPC数量和成骨活性的分析 取自幼崽(4个月大)的骨髓和骨膜间， 中年(12月龄)和老年(24月龄)BALBc小鼠。(2) 转化生长因子-β1、β2、β3和 相关骨形态发生蛋白(BMPs)及其分泌水平 Y和o小鼠培养的OPC中的转化生长因子-β蛋白。(3)建立 三者的信使核糖核酸丰度、数目及总结合亲和力 Y和o小鼠培养的OPC中转化生长因子-β受体的类型。 (4)评估转化生长因子-β是否是血管生成的自分泌/旁分泌调节因子。 骨祖细胞和分化中的成骨细胞。为此，OPC 在有或没有转化生长因子的情况下培养动物。 β、抗转化生长因子-β抗体和转化生长因子-β反义寡核苷酸。 (5)确定是否可以增加老年鼠的OPC普查， 可能通过在体内引入外源转化生长因子-β，达到y水平。 总的来说，拟议研究的结果应提供一个 对经常提出的反馈关系的初步直接评估 转化生长因子-β与成骨细胞功能之间的关系 与年龄相关的骨质疏松性骨丢失是这一过程中断的结果。 两性关系。

Osteoporosis is a skeletal disorder in which the level of bone resorption exceeds that of bone formation resulting in a loss of bone mass. Both bone formation and the local control of bone resorption are functions of the osteoblast, a cell that also produces growth factors and cytokines that apparently work in an autocrine and paracrine fashion to influence both osteoblasts and osteoclasts. Among the most important of these agents is transforming growth factor-beta (TGF-beta), a protein known to stimulate cell proliferation, differentiation and matrix synthesis and capable of osteoinductive activity in vivo. With advancing age, osteoblast biosynthetic activity declines and with it, we suggest, the level or effective action of TGF-beta necessary for sustaining further matrix synthesis and osteoblast precursor proliferation and maturation. However, the linkage between a decline in TGF-beta synthesis and/or diminished TGF-beta effector activity and a reduction in the osteoblastic precursor pool and further matrix synthesis has not been fully documented. It is the overall objective of the studies described in this application to provide this documentation. Specifically, we propose to test the hypothesis that age-related (Type II) osteoporosis results, in part, from a decline in the endogenous synthesis and/or effective autocrine action of TGF-beta on OPCs resulting in a diminution in OPC number and a reduction in bone matrix protein synthesis. This hypothesis will be tested by pursuing the following specific aims: (1) completing our analysis of OPC number and osteogenic activity in cells recovered from the bone marrow and periosteal compartments of young (y. 4 month), middle age (m. 12 month) and old (o. 24 month) BALBc mice. (2) determining the steady state mRNA abundance of TGF-beta1,beta2,beta3 and related bone morphogenetic proteins (BMPs), and the secreted levels of TGF-beta protein in OPCs cultured from y and o mice. (3) establishing the mRNA abundance and number and overall binding affinity of the three types of TGF-beta receptor in cultured OPCs derived from y and o mice. (4) assessing whether TGF-beta is an autocrine/paracrine regulator of osteoprogenitor cells and differentiating osteoblasts. To this end, OPCs from o and y animals will be cultured in the presence and absence of TGF- beta, anti-TGF-beta antibodies and TGF-beta antisense oligonucleotides. (5) determining whether the OPC census in old mice can be increased, perhaps to y levels, by introducing exogenous TGF-beta in vivo. Collectively, the results of the proposed studies should provide an initial direct assessment of the often proposed feedback relationship between TGF-beta and osteogenic cell function and of the hypothesis that age-related osteoporotic bone loss is the result of a disruption in this relationship.