Osteoclast-Osteocyte Interaction's in Paget's Disease

项目摘要/摘要： Paget病(PD)通常诊断于50岁的患者，以局灶性骨骼为特征。 病变(PDL)，由于快速的新骨形成，从最初的溶骨阶段进展到骨溶解-成骨细胞混合期 队形。帕金森病患者很少出现新的PDL，而不是出现新的PDL。主要的细胞 帕金森病的异常存在于破骨细胞(OCL)。然而，导致高度聚焦的机制 PDLS的性质，为什么在老年患者中诊断为PD，特别是在携带基因突变的患者中 与帕金森病有关，以及帕金森病患者旺盛的吸收/形成的机制尚不清楚。我们展示了 70%PD患者的OCL表达麻疹病毒核衣壳蛋白(MVNP)，转基因小鼠 以OCLs为靶点的MVNP(MVNP小鼠)可发展为PDLS和具有PD特征的OCLs异常。MVNP- 表达OCL和PD患者的OCL对RANKL具有高反应性，并表达高水平的IL-6， 在OCL中诱导高水平的IGF1(OCL-IGF1)促进MVNP小鼠成骨细胞(OB)的分化。 重要的是，来自PD患者而非正常供者的OCL也表达增加的IL-6和IGF1。我们确认了 OCL-IGF1‘S在WT和MVNP小鼠体内帕金森病和正常骨重建中的作用 OCL中Igf1基因的缺失。我们发现MVNP小鼠而不是缺乏OCL-Igf1的MVNP小鼠发生了PDLS。 因此，帕金森病患者可能需要高水平的OCL-IGF1来诱发PDLS。然而，这些结果并不能解释为什么 PDLS发生在老年患者或动物模型中，并在局部持续较长时间。这些观察结果是 最容易用长寿的骨细胞群中的随机变化来解释，很可能是骨细胞 (OCys)。在这项提议中，我们将检验假设：Pagtic OCL前体，它是高反应的 RANKL，是含有衰老的、皮损前病变的OCys的特定骨骼部位的家园，这些OCys产生或诱导 当地增加的RANKL。随着PD-OCL数量的增加，它们会过度分泌足够的IL-6和IGF-1来 降低sOST/skerostin，增加WNTS表达，阻断OCY分化，直接作用于OB 促进新骨形成。在初步研究中，我们发现PD(PD-OCys)中OCys的表达水平较低 OCY成熟标志物的水平，并显示树突状突起明显减少。此外，该百分比 与无PDLS的MVNP小鼠相比，MVNP小鼠PDLS附近的skerostin+OCys的表达显著降低 PDLS或WT小鼠，IGF1抑制OCys中skerostin的表达。重要的是，相似的形态 帕金森病患者的骨骼样本中的OCys发生了变化，但不是正常的捐赠者。这些结果表明 OCys可能是帕金森病发病的关键因素。为了进一步检验这一假设，我们将：目标1。 鉴定OCL-IGF1‘在PD和PD-OCys中的S效应，确定涉及的分子机制，并检验是否 OCL-IGF1升高足以诱发PDLS和PD-OCys。目的2.确定衰老的OCys的作用 在PDLS和PD的定位、发展、进展和持续方面。我们将评估是否会延长 PD-OCL暴露于正常的OCys，或较短的OCys暴露在老年小鼠中，足以导致PDLS的发生。

Project Summary/Abstract: Paget’s Disease (PD) is usually diagnosed in patients >50 years of age, and is characterized by focal bone lesions (PDLs) that progress from an initial lytic to a mixed osteolytic-osteoblastic phase, due to rapid new bone formation. PD patients rarely develop new PDLs beyond those present at diagnosis. The primary cellular abnormality in PD resides in the osteoclast (OCL). However, the mechanisms responsible for the highly focal nature of PDLs, why PD is diagnosed in elderly patients, especially in patients harboring genetic mutations linked to PD, and the mechanisms driving the exuberant resorption/formation in PD, are unclear. We showed that OCLs from 70% of PD patients express measles virus nucleocapsid protein (MVNP), and transgenic mice with MVNP targeted to OCLs (MVNP mice) develop PDLs and the abnormal OCLs characteristic of PD. MVNP- expressing OCLs and OCLs from PD patients are hyper-responsive to RANKL and express high IL-6 levels, which induce high levels of IGF1 in OCLs (OCL-IGF1) to promote osteoblast (OB) differentiation in MVNP mice. Importantly, OCLs from PD patients but not normal donors also express increased IL-6 and IGF1. We confirmed OCL-IGF1’s role in PD and normal bone remodeling in vivo by generating WT and MVNP mice with targeted deletion of Igf1 in OCLs. We found that MVNP mice but not MVNP mice lacking OCL-Igf1 developed PDLs. Thus, high OCL-IGF1 levels in PD may be required to induce PDLs. However, these results do not explain why PDLs occur in aging patients or animal models and persist locally for long periods. These observations are most readily explained by stochastic changes in a long-lived bone cell population, most likely osteocytes (OCys). In this proposal we will test the Hypothesis: that pagetic OCL precursors, which are hyper-responsive to RANKL, home to specific skeletal sites containing senescent, pre-lesional OCys that produce or induce locally increased RANKL. As PD-OCLs numbers increase, they hyper-secrete sufficient IL-6 and IGF-1 to decrease Sost/sclerostin, increase expression of Wnts, block OCy differentiation and act directly on OB to enhance new bone formation. In preliminary studies, we found that OCys in PD (PD-OCys) express lower levels of OCy maturation markers, and display markedly reduced dendritic processes. Further, the percentage of sclerostin+ OCys adjacent to PDLs in MVNP mice was significantly lower compared to MVNP mice without PDLs or WT mice, and that IGF1 suppressed sclerostin expression in OCys. Importantly, similar morphologic changes occurred in OCys in bone samples of a PD patient, but not a normal donor. These results suggest that OCys may be key contributors to the pathogenesis of PD. To further test this hypothesis, we will: Aim 1. Characterize OCL-IGF1’s effects in PD and PD-OCys, identify the molecular mechanisms involved, and test if increased OCL-IGF1 is sufficient to induce PDLs and PD-OCys. Aim 2. Determine the role of senescent OCys in the location, development, progression and persistence of PDLs and PD. We will assess if prolonged exposure of PD-OCLs to normal OCys, or shorter exposure to OCys in older mice suffices for PDLs to develop.