Role of TNFalpha in Osteoclast-Mediated Bone Loss

描述（由申请人提供）：慢性炎症介导的骨丢失 由于骨吸收增加而发生，主要由 促炎细胞因子的局部产生增加。TNF α是一种主要的 炎症介质，并直接和间接参与 破骨细胞的产生。目前，虽然抗TNF药物代表了 虽然这些药物是一项重大的治疗进展，但其疗效受到以下因素的影响 事实上，许多从这些药物中获得显着缓解的RA患者 继续遭受关节侵蚀。在这份提案中，我们计划 进一步研究TNF α对破骨细胞介导的骨丢失的作用， 检验以下假设：1）TNF α通过以下途径促进破骨细胞生成： 引发祖细胞分化成破骨细胞谱系，从而 增加前体库; 2）RANK信号传导对于 TNF α诱导的体内破骨细胞生成;和3）TNF α维持成熟的 破骨细胞通过Src依赖性和RANK非依赖性机制存活， 从而促进增强的再吸收。为了检验假设1，我们将使用 hTNF-Tg转基因小鼠，以确定TNF α对破骨细胞的影响 前体数、TNF α介导的启动持续时间以及 抗肿瘤坏死因子治疗。为了检验假设2，我们将使用三个 体内模型：a）我们将产生并分析hTNF-Tg/RANK-/-小鼠， 确定慢性TNF α过度表达是否可以弥补缺乏 RANK信号传导; B）将来自RANK-/-小鼠的骨髓细胞转移至致死性 辐照的hTNF-Tg小鼠;和c）用RANK：Fc处理hTNF-Tg小鼠，并检查 他们的存在是因为破骨细胞。为了检验假设3，我们将 通过各种方法和使用破骨细胞研究Src家族激酶的活性 以评估TNF α和TNF阻断对src-/-小鼠 生存将生成hTNF-Tg/src-/-小鼠，并用RANK：Fc处理， 确定对破骨细胞消耗的影响。这些研究将提供 关于TNF α诱导的细胞凋亡机制的确定性体内证据 骨吸收，并提供临床前数据，可能有助于 为侵蚀性疾病制定治疗干预措施。

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.