COLONY STIMULATING FACTOR 1--REGULATION AND ROLE IN BONE

描述：（改编自研究者摘要）成骨细胞， 除了形成骨外，还在骨吸收中起中心作用。 虽然成骨细胞介导骨坏死的确切机制 骨吸收尚不清楚，一个广泛持有的假设是， 成骨细胞对骨吸收剂的反应， 激活破骨细胞或其前体。 虽然这些的性质 细胞因子是未知的，一个潜在的候选者是集落刺激 因子-1（CSF-1）。 有大量的体内和体外证据表明 CSF-1对细胞增殖和 破骨细胞祖细胞的分化：（1）CSF-1缺乏， 体内引起op/op小鼠的骨硬化症;（2）CSF-1刺激 体外破骨细胞形成和骨吸收;（3）CSF-1是体外破骨细胞形成和骨吸收的主要机制。 成骨细胞分泌的主要集落刺激活性 甲状旁腺激素（PTH）。 尽管有越来越多的证据表明 成骨细胞衍生的CSF-1在破骨细胞发育中的作用， 已知关于成骨细胞中CSF-1基因表达的调节， 或CSF-1的同种型，其由 成骨细胞 此外，CSF-1在脑缺血中的确切生理作用也被证实。 对正常的骨重建知之甚少。 申请人最近证明肿瘤坏死因子 (TNF)和PTH增加CSF-1基因表达和蛋白释放， 成骨细胞通过转录机制。 他们计划继续这些 通过表征顺式作用元件观察，PTH和TNF 诱导CSF-1基因表达，并检测潜在转录 因素介导这种反应，使用删除的组合 分析和核蛋白-DNA结合研究。 他们还 通过流式细胞术和反向PCR分析证实， 成骨细胞表达CSF-1的细胞表面形式的转录RNA， 其通过TNF治疗而增加。 因此，他们将扩大这一点， 通过检查相对表达、调节和 CSF-1的可溶性和细胞表面形式的生物学意义。 对于这些研究，他们将表征mRNA和蛋白质种类 CSF-1的合成、加工和释放， TNF处理的成骨细胞，并将检查可溶性和 细胞表面形式的CSF-1对破骨细胞形成的影响。 最后，他们会 研究CSF-1在体内骨重建中的作用， 分析具有CSF-1的靶向过表达的转基因小鼠， 成骨细胞 总之，这些研究应该阐明CSF-1的 调节和作用的骨，并可能提高对基本的理解， 骨吸收机制。

DESCRIPTION: (Adapted From Investigator's Abstract) The osteoblast, in addition to forming bone, plays a central role in bone resorption. Although the precise mechanism by which osteoblasts mediate osteoclastic bone resorption is unclear, one widely held hypothesis is that in response to bone resorbing agents, osteoblasts secrete cytokines which activate osteoclasts or their precursors. While the nature of these cytokines is unknown, one potential candidate is colony stimulating factor-1 (CSF-1). There is substantial in vivo and in vitro evidence that CSF-1 is critically important for both the proliferation and differentiation of osteoclast progenitors: (1) deficiency of CSF-1 in vivo causes osteopetrosis in the op/op mouse; (2) CSF-1 stimulates osteoclast formation and bone resorption in vitro; and (3) CSF-1 is the principal colony stimulating activity secreted by osteoblasts in response to parathyroid hormone (PTH). Although there is mounting evidence for osteoblast-derived CSF-1's role in osteoclast development, little is known regarding the regulation of CSF-1 gene expression in osteoblasts, or the isoforms of CSF-1 which are synthesized and secreted by osteoblasts. In addition, the precise physiologic role of CSF-1 in normal bone remodeling is poorly understood. The applicants have recently demonstrated that tumor necrosis factor (TNF) and PTH increase CSF-1 gene expression and protein release in osteoblasts by a transcriptional mechanism. They plan to pursue these observations by characterizing cis acting elements by which PTH and TNF induce CSF-1 gene expression, and examining potential transcription factors mediating this response, using a combination of deletional analysis and nuclear protein-DNA binding studies. They have also demonstrated by flow cytometry and by PCR analysis of reverse- transcribed RNA that osteoblasts express a cell surface form of CSF-1, which is increased by TNF treatment. They will, therefore, extend this observation by examining the relative expression, regulation and biological significance of the soluble and cell surface forms of CSF-1. For these studies they will characterize the mRNA and protein species of CSF-1 which are synthesized, processed and released by untreated and TNF-treated osteoblasts, and will examine the effects of the soluble and cell-surface forms of CSF-1 on osteoclast formation. Finally, they will examine the role of CSF-1 in bone remodeling in vivo by developing and analyzing a transgenic mouse with targeted over-expression of CSF-1 in osteoblasts. Taken together, these studies should elucidate CSF-1's regulation and role in bone and may improve the understanding of basic mechanisms of bone resorption.