Role of TNFalpha in Osteoclast-Mediated Bone Loss

描述(申请人提供)：慢性炎症引起的骨丢失 发生于破骨细胞性骨吸收增加，主要由 增加局部促炎细胞因子的产生。肿瘤坏死因子α是一种主要的 炎症介质，并直接和间接参与了 破骨细胞的产生。目前，尽管抗肿瘤坏死因子药物代表着一种 主要的治疗进展，这些药物的疗效在某种程度上受到 事实上，许多从这些药物中获得显著缓解的RA患者 继续遭受渐进性关节侵蚀。在这项提案中，我们计划 进一步研究肿瘤坏死因子α对破骨细胞介导的骨丢失和Will的影响 检验以下假设：1)肿瘤坏死因子α通过以下途径促进破骨细胞生成 启动祖细胞分化为破骨细胞谱系，从而 增加前驱体池；2)RANK信令对于 肿瘤坏死因子α在体内诱导破骨细胞分化；3)肿瘤坏死因子α维持成熟 破骨细胞通过Src依赖和等级独立的机制存活 从而促进了增强的再吸收。为了检验假设1，我们将使用 人肿瘤坏死因子-TG转基因小鼠检测肿瘤坏死因子α对破骨细胞的影响 前体数量、肿瘤坏死因子α介导的启动持续时间和 抗肿瘤坏死因子治疗在这个引爆。为了检验假设2，我们将使用三个 活体模型：a)我们将产生并分析hTNF-TG/RANK-/-小鼠以 确定慢性肿瘤坏死因子α的过度表达是否可以弥补 RANK信号；b)将RANK-/-小鼠的骨髓细胞转移到致死性 C)用RANK：Fc处理hTNF-Tg小鼠，并检测 因为有破骨细胞的存在。为了检验假设3，我们将阻止 不同途径和破骨细胞对Src家族激酶活性的影响 从src-/-小鼠观察肿瘤坏死因子α和肿瘤坏死因子受体拮抗剂对其功能的影响 生死存亡。将产生hTNF-TG/src-/-小鼠，并给予RANK：Fc至 确定对破骨细胞耗竭的影响。这些研究将提供 关于肿瘤坏死因子α诱导的机制的明确的体内证据 破骨细胞性骨吸收，并提供临床前数据，可能有助于 开发针对腐蚀性疾病的治疗干预措施。

DESCRIPTION (provided by applicant): Chronic inflammation-mediated bone loss occurs due to increased osteoclastic bone resorption, mediated largely by the increased local production of pro-inflammatory cytokines. TNFalpha is a major inflammation mediator and is both directly and indirectly involved in the production of osteoclasts. At present, although the anti-TNF drugs represent a major therapeutic advance, the efficacy of these agents is somewhat clouded by the fact that many RA patients who receive significant relief from these drugs continue to suffer progressive joint erosion. In this proposal, we plan to further investigate TNFalpha effects on osteoclast-mediated bone loss and will test the following hypotheses: 1) TNFalpha promotes osteoclastogenesis by priming the differentiation of progenitors into the osteoclast lineage, thus increasing the precursor pool; 2) RANK signaling is essential for TNFalpha-induced osteoclastogenesis in vivo; and 3) TNFalpha sustains mature osteoclast survival through a Src-dependent and RANK-independent mechanism, thus promoting enhanced resorption. To examine hypothesis 1, we will use hTNF-Tg transgenic mice to determine the effects of TNFalpha on osteoclast precursor numbers, the duration of TNFalpha-mediated priming and the effect of anti-TNF therapy on this priming. To test hypothesis 2, we will use three in vivo models: a) we will generate and analyze hTNF-Tg/RANK-/- mice to determine if chronic TNFalpha over-expression can compensate for the absence of RANK signaling; b) transfer bone marrow cells from RANK-/- mice to lethally irradiated hTNF-Tg mice; and c) treat hTNF-Tg mice with RANK:Fc and examine them for the presence of osteoclasts. To examine hypothesis 3, we will block the activity of Src family kinases by various approaches and use osteoclasts from src-/- mice to evaluate the effects of TNFalpha and TNF blockade on their survival. hTNF-Tg/src-/- mice will be generated and treated with RANK:Fc to determine the effect on osteoclast depletion. These studies will provide definitive in vivo evidence as to the mechanism of TNFalpha-induced osteoclastic bone resorption and also provide pre-clinical data that may help develop a therapeutic intervention for erosive diseases.