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

骨质疏松症是一种骨骼疾病，其中骨吸收水平 超过了骨形成的速度，导致骨量丢失。 两 骨形成和骨吸收的局部控制是 成骨细胞，一种也产生生长因子和细胞因子的细胞 显然是以自分泌和旁分泌的方式影响 成骨细胞和破骨细胞。 其中最重要的 药物是转化生长因子-β（TGF-β），一种已知 刺激细胞增殖、分化和基质合成， 能够在体内具有骨诱导活性。 随着年龄的增长， 成骨细胞生物合成活性下降，我们认为， 水平或有效的行动所需的TGF-β，以维持进一步 基质合成和成骨细胞前体增殖和成熟。 然而，TGF-β合成下降和/或 TGF-β效应活性降低，成骨细胞 前体池和进一步的基质合成还没有完全 记录在案。 这是本文所述研究的总体目标， 申请提供此文档。 具体来说，我们建议 测试年龄相关性（II型）骨质疏松症的结果的假设， 部分，从内源性合成和/或有效的下降 TGF-β对OPC的自分泌作用导致OPC减少 数量和骨基质蛋白合成减少。 这一假设 将通过以下具体目标进行测试：（1）完成 我们分析了回收的细胞中OPC数量和成骨活性， 从年轻人的骨髓和骨膜隔室（y. 4个月）， 中年（M。12个月）和老年人（O。24月龄）BALB c小鼠。 （二） 确定TGF-β 1、β 2、β 3和β 4的稳态mRNA丰度， 相关的骨形态发生蛋白（BMP），和分泌水平的 从y和o小鼠培养的OPCs中的TGF-β蛋白。 (3)建立 mRNA丰度和数量以及这三种蛋白的总体结合亲和力 来源于y和o小鼠的培养OPCs中的TGF-β受体类型。 (4)评估TGF-β是否是一种自分泌/旁分泌调节剂， 骨祖细胞和分化中的成骨细胞。 为此，OPC 来自o和y动物的细胞将在存在和不存在TGF-β 1的情况下培养。 抗TGF-β抗体和TGF-β反义寡核苷酸。 (5)确定是否可以增加老年小鼠中的OPC普查， 通过在体内引入外源性TGF-β，可能达到γ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 TGF-β和成骨细胞功能之间的联系， 与年龄相关的骨质疏松性骨丢失是由于这种破坏， 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.