Studies of the Fate of the Osteoclast

描述（由申请人提供）：骨质流失与多种疾病有关，在这些疾病中，促炎细胞因子的产生增加通过增加破骨细胞的形成、激活和存活来促进骨质流失。大多数已发表的数据表明，这些作用主要是通过基质细胞产生M-CSF和RANKL间接介导的，它们与破骨细胞上的受体结合，激活c-Fos/AP-1、NFkappaB和NFAT2，这三者的表达都是破骨细胞形成所必需的。然而，破骨细胞表达越来越多的药物受体，包括促炎细胞因子，这表明细胞因子对破骨细胞的直接和间接影响可能共同诱导骨质流失。我们的首要假设是，在疾病状态下，破骨细胞数量可能受到细胞因子对破骨细胞谱系细胞的直接作用的调节，这可能导致这些细胞内的自我延续，上调周期，并随后导致骨质流失。然而，确切的机制和所涉及的信号分子仍有待充分阐明。我们计划利用NFkappaB dKO、TNF转基因和野生型小鼠，研究细胞因子对破骨细胞及其前体的直接影响，并确定c-Fos/AP-1、NFkappaB和NFAT2信号在这一过程中的作用。我们提出以下具体目标：充分表征细胞因子和逆转录病毒将c-Fos/AP-1基因转移到wt和NFkB dKO脾细胞的作用，并确定当c-Fos表达时是否有其他破骨细胞刺激因子直接诱导破骨细胞形成；2. 确定c-Fos和细胞因子的逆转录病毒转移直接诱导破骨细胞形成的机制，并研究NFkB在这一过程中的作用；3. 在细胞因子介导的骨病模型中，细胞因子和c-Fos/AP-1的表达是否在破骨细胞及其前体中上调。这些研究将更好地定义关键信号通路的作用，并促进我们对直接调节破骨细胞形成和存活的机制的理解。最终，它们将导致特定治疗剂的发展，以预防和治疗与破骨细胞活性增加相关的常见骨病。

DESCRIPTION (provided by applicant): Bone loss is associated with a variety of conditions in which increased production of pro-inflammatory cytokines promotes bone loss by increasing osteoclast formation, activation and survival. Most published data indicate that these effects are mediated mainly indirectly through stromal cell production of M-CSF and RANKL, which bind to their receptors on osteoclasts and activate c-Fos/AP-1, NFkappaB, and NFAT2, expression of each of which is required for osteoclast formation. However, osteoclasts express receptors for a growing list of agents, including pro-inflammatory cytokines, suggesting that direct and indirect effects of cytokines on osteoclasts could combine to induce bone loss. Our over-riding hypothesis is that in disease states, osteoclast numbers may be regulated by direct effects of cytokines on cells in the osteoclast lineage that can lead to self perpetuating, up-regulatory cycles within these cells and subsequently to bone loss. However, the precise mechanisms and the signaling molecules involved remain to be fully elucidated. We plan to investigate the direct effects of cytokines on osteoclasts and their precursors and to determine the roles of c-Fos/AP-1, NFkappaB and NFAT2 signaling in this process using NFkappaB dKO, TNF transgenic and wild-type mice. We propose the following Specific Aims: 1. To fully characterize the effects of cytokines and retroviral transfer of c-Fos/AP-1 genes to wt and NFkB dKO splenocytes and to determine if other osteoclast stimulating factors induce osteoclast formation directly when c-Fos is expressed; 2. To determine the mechanisms whereby retroviral transfer of c-Fos and cytokines induce osteoclast formation directly and to examine the role of NFkB in this process; 3. To examine if cytokine and c-Fos/AP-1 expression are up-regulated in osteoclasts and their precursors in models of cytokine-mediated bone disease. These studies will better define the roles of key signaling pathways and advance our understanding of the mechanisms that directly regulate osteoclast formation and survival. Ultimately they should lead to the development of specific therapeutic agents to prevent and treat common bone diseases associated with increased osteoclast activity.