MOLECULAR MECHANISMS OF GALLIUM ON BONE FORMATION

骨形成减少是骨质疏松症的重要组成部分 导致II型骨质疏松症并最终导致髋关节的病理生理学 骨折。对细胞和分子有更全面的了解 控制骨形成的事件将导致新的治疗方法 治疗骨质疏松症的方法。硝酸镓是一种新的美国食品和药物管理局- 已批准有效的治疗骨质疏松症的药物 新陈代谢。最近的研究表明，硝酸镓可以 转录调控两种骨基质蛋白的表达， 骨GLA蛋白(BGP或骨钙素)和(I)型胶原在某种程度上 模拟自然产生的生长因子，这将是 预计会有利于新骨的形成。我们建议去大学学习 细胞和分子水平镓的作用机制(S) 骨形成。这项建议的具体目标是：目标1) 硝酸镓对成骨细胞培养的影响 正常大鼠颅骨细胞。原代成骨细胞经历了 可复制的发育序列将暴露在镓 膜内不同阶段骨化检查镓 对细胞增殖、分化和基因表达的影响 2)描绘骨钙素上的DNA序列(S)(反应元件)，以及 镓作用靶点(S)的I型胶原基因 硝酸盐。BGP和类型(I)的一系列5‘-侧翼缺失 胶原蛋白基因启动子区域一直稳定和瞬时 将被转移到骨细胞培养中的镓进行分析 响应性；目的3)鉴定(I)型胶原中的序列 硝酸镓的转录反应相关基因 转基因小鼠模型，以研究镓对小鼠的影响 在完整动物中各自的启动子区域。(I)型胶原基因 暴露在正常环境中的细胞对镓的反应性将被检测 发育线索和组织相互作用；目的)识别 与硝酸镓相互作用的转录因子(S) 调节元件(S)对骨钙素和(I)型胶原基因的影响 对这些基因进行转录调控。这些研究的结果 将提供对分子事件的洞察，这些事件对新的 骨形成，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.