MOLECULAR MECHANISMS OF GALLIUM ON BONE FORMATION

骨形成减少是骨形成障碍的重要组成部分。 导致II型骨质疏松症的病理生理学，并最终导致髋关节 骨折 更全面地了解细胞和分子 控制骨形成的事件将导致新的治疗方法 骨质疏松症的治疗方法 硝酸镓是美国食品药品管理局的新产品- 经批准的药物，已证实对治疗骨紊乱有效 新陈代谢. 最近的研究表明，硝酸镓可以 转录调节两种骨基质蛋白的表达， 骨Gla蛋白（BGP或骨钙素）和（I）型胶原， 它模仿自然生长因子， 预期有利于新骨形成。 我们建议在 细胞和分子水平的作用机制镓对 骨形成 本提案的具体目标是： 表征硝酸镓对成骨培养物的影响， 正常大鼠颅骨细胞。 原代成骨细胞， 可重复的发育序列将暴露于镓， 膜内骨化的不同阶段，以检查镓 对细胞增殖、分化和基因表达的影响 2)描绘BGP上的DNA序列（响应元件）， 作为镓作用靶标的（I）型胶原基因 硝酸盐 BGP的一系列5 '-侧翼缺失和（I）型 胶原蛋白基因启动子区域已经稳定和瞬时地 将分析转染到骨细胞培养物中的镓 目的3）鉴定I型胶原蛋白中的序列 基因负责转录反应硝酸镓在 转基因小鼠模型，以研究镓对 在完整动物中各自的启动子区。 I型胶原基因 对镓的反应性将在暴露于正常的 发展线索和组织相互作用;目的4），以确定 与硝酸镓相互作用的转录因子 BGP和I型胶原基因上的调节元件， 转录调控这些基因。 这些研究的结果 将提供深入了解分子事件，这是关键的新的 以及硝酸镓如何调节这些事件。

Decreased bone formation is an important component of the pathophysiology that leads to Type II osteoporosis and, ultimately, hip fractures. A more complete understanding of the cellular and molecular events which control bone formation will lead to new therapeutic approaches for osteoporosis. Gallium nitrate is a new U.S.F.D.A.- approved drug with proven efficacy for the treatment of disordered bone metabolism. Recent studies show that gallium nitrate can transcriptionally regulate the expression of two bone matrix proteins, bone Gla protein (BGP or osteocalcin) and type (I) collagen, in a manner that mimics naturally occurring growth factors and that would be expected to favor new bone formation. We propose to study at the cellular and molecular levels the mechanism(s) of action of gallium on bone formation. The specific objectives of this proposal are: AIM 1) to characterize the effects of gallium nitrate on osteogenic cultures of normal rat calvarial cells. Primary osteogenic cells which undergo a reproducible developmental sequence will be exposed to gallium at different stages of intramembranous ossification to examine gallium effects on cell proliferation, differentiation and gene expression; AIM 2) to delineate the DNA sequence(s) (response elements) on the BGP and type (I) collagen genes which are the target(s) of action of gallium nitrate. A series of 5'-flanking deletions of the BGP and type (I) collagen gene promoter regions that have been stably and transiently transfected into bone cell cultures will be analyzed for gallium responsiveness; AIM 3) to identify sequences in the type (I) collagen gene responsible for the transcriptional response to gallium nitrate in transgenic mouse models in order to study gallium effects on the respective promoter regions in intact animals. Type (I) collagen gene responsiveness to gallium will be examined in cells exposed to normal developmental cues and tissue interactions; AIM 4) to identify the transcription factor(s) which interact with the gallium nitrate regulatory element(s) on the BGP and type (I) collagen genes to transcriptionally regulate these genes. The results of these studies will provide insight into molecular events which are critical for new bone formation, and how gallium nitrate modulates these events.