Studies of Osteoclast Lineage in Health and Diseases

尽管我们对调节OC功能的分子信号了解很多，但我们对此知之甚少 OC从祖细胞发展而来的血统和机制。此应用程序的目标是更好地 明确OC祖细胞(OCP)的成熟和运输及其在健康中调节这一过程的机制 因此，我们可以确定潜在的药物靶点，以开发出治疗骨骼疾病的卓越疗法。这个 中心假设是：1)在动态平衡期间，骨髓驻留细胞是主要的OCP来源， 而在炎症或骨折修复期间，循环细胞成为OCP的重要来源。 2)OCP向成骨细胞迁移、植入和成熟的调控机制不同 在健康和疾病状态之间。为了检验这些假设，我们提出了以下目标： 1.定义CX3CR1 OCP在动态平衡期间OC发育中的作用，并确定 调节其归巢、植入和成熟为OC的机制： 1A)在不同年龄的CX3CR1-CreERT2-Ai14小鼠身上进行时间进程研究，以检测标记的OC 形成动力学。我们还将监测标记的OCP在骨髓、血液和脾中的动力学。 1b)趋化因子受体CX3CR1在OCP上表达，以前曾被认为影响 OCP的归巢、植入和成熟。我们将确定它在OCP谱系发展和 体内稳态条件下的转运(当骨髓源性细胞作为OCP来源占优势时) 用CX3CR1-CreERT2-Ai14小鼠产生CX3CR1基因缺失。 2.观察OCP在骨炎症和骨折修复过程中的循环归巢情况。 这些研究将检验两种疾病模型，在这两种模型中，我们以前证明了循环OCP是 被招募植入骨中：TNFa诱导的骨炎症和修复骨折。 2)研究肿瘤坏死因子α诱导的炎症性骨模型(WT Parabion将肿瘤坏死因子α注射到其头盖骨； 另一种是CX3CR1-EGFP；陷阱-td番茄小鼠)，并确定循环标记的比率 炎症部位的细胞形成OC，然后消失。 2B)研究共生骨折模型(一个WT Parabion接受股骨骨折；另一个Parabion是 CX3CR1-EGFP；陷阱-td番茄小鼠)，并确定循环中的标记细胞回到 修复骨痂，形成OC，消失。 2C)测定成骨、成骨和植入骨内循环OCP的表型和动力学 通过注射来自CX3CR1-EGFP的选定群体的OCP，TNFa诱导炎症或骨折修复； Trap-td番茄小鼠，并监测标记的OC在骨骼中的出现和消失的比率。 2D)确定CX3CR1缺失对OCP循环到家、植入和 成熟的骨与肿瘤坏死因子引起的炎症或骨折修复使用异种异种和过继移植。

Although, we know much about the molecular signals that regulate OC function, we know relatively little about the lineage and mechanisms that OC use to develop from progenitors. The goal of this application is to better define OC progenitor (OCP) maturation and trafficking and the mechanisms regulating this process in health and disease so that we can identify potential drug targets to develop superior therapies for bone diseases. The central hypotheses are: 1) During homeostasis marrow-resident cells are the principal OCP source, while during inflammation or fracture repair, circulating cells become a significant source of OCP. 2) The mechanisms regulating OCP migration, engraftment and maturation to OC in bone differ between healthy and disease states. To test these hypotheses, we propose the following aims: 1. Define the role that CX3CR1+ OCP have in OC development during homeostasis and identify mechanisms regulating their homing, engraftment and maturation to OC: 1A) Perform time course studies in CX3CR1-CreERT2-Ai14 mice at various ages to examine labeled OC formation kinetics. We will also monitor the kinetics of labeled OCP in the bone marrow, blood and spleen. 1B) The chemokine receptor CX3CR1 is expressed on OCP and has previously been implicated to influence OCP homing, engraftment and maturation. We will determine its role in OCP lineage development and trafficking in vivo under homeostatic conditions (when marrow-derived cells predominate as the OCP source) using CX3CR1-CreERT2-Ai14 mice to generate Cx3cr1 gene deletions. 2. Examine OCP homing from the circulation during bone inflammation and fracture repair. These studies will examine two disease models in which we previously demonstrated that circulating OCP are recruited to engraft in bone: TNFa-induced bone inflammation and a repairing fracture. 2A) Study a TNFa-induced inflammatory bone model (a WT parabiont has TNFα injected over its calvaria; the other parabiont is a CX3CR1-EGFP; TRAP-tdTomato mouse) and determine the rate that circulating labeled cells home to the inflammatory site, form OC and disappear. 2B) Study a parabiosis fracture model (a WT parabiont receives a femur fracture; the other parabiont is a CX3CR1-EGFP; TRAP-tdTomato mouse) and determine the rate that circulating labeled cells home to the repairing callus, form OC and disappear. 2C) Determine the phenotype and kinetics of circulating OCP that home, mature and engraft in bone with TNFa-induced inflammation or fracture repair by injecting selected populations of OCP from CX3CR1-EGFP; TRAP-tdTomato mice and monitoring the rates that labeled OC appear and disappear in bone. 2D) Determine the effect that deletion of Cx3cr1 has on the ability of circulating OCP to home, engraft and mature in bone with TNFa-induced inflammation or a fracture repair using parabiosis and adoptive transfer.