Osteoclast-Osteocyte Interaction's in Paget's Disease

项目概要/摘要： 佩吉特病（PD）通常在>50岁的患者中被诊断，并且以局灶性骨为特征 由于快速的新骨形成，从最初的溶解性阶段进展到混合性溶骨-成骨阶段的病变（PDL） 阵PD患者很少出现诊断时存在的PDL以外的新PDL。主蜂窝 PD中的异常存在于破骨细胞（OCL）中。然而，负责高度集中的机制 PDL的性质，为什么PD在老年患者中被诊断，特别是在携带基因突变的患者中 与PD相关，以及PD中驱动旺盛再吸收/形成的机制尚不清楚。我们展示 来自70% PD患者的OCL表达麻疹病毒核衣壳蛋白（MVNP）， 用靶向OCL的MVNP（MVNP小鼠）产生PDL和PD特征性的异常OCL。MVNP- 表达OCL和来自PD患者的OCL对RANKL高度反应并表达高IL-6水平， 其在OCL中诱导高水平的IGF 1（OCL-IGF 1）以促进MVNP小鼠中的成骨细胞（OB）分化。 重要的是，来自PD患者而非正常供体的OCL也表达增加的IL-6和IGF 1。我们证实 OCL-IGF 1在体内PD和正常骨重建中的作用，通过产生具有靶向IGF 1的WT和MVNP小鼠。 OCL中Igf 1的缺失。我们发现，MVNP小鼠，而不是缺乏OCL-Igf 1的MVNP小鼠发展PDL。 因此，PD中高OCL-IGF 1水平可能是诱导PDL所必需的。然而，这些结果并不能解释为什么 PDL发生在老年患者或动物模型中，并在局部长期存在。这些观察结果 最容易解释的是长寿骨细胞群的随机变化，最有可能是骨细胞 （OCys）。在这个建议中，我们将测试假设：pagetic OCL的前体，这是超反应， RANKL，定位于含有衰老、病变前OCys的特定骨骼部位， 局部RANKL升高。随着PD-OCL数量的增加，它们过度分泌足够的IL-6和IGF-1， 减少Sost/sclerostin，增加Wnts表达，阻断OCy分化，并直接作用于OB， 促进新骨形成。在初步研究中，我们发现PD中的OCys（PD-OCys）表达较低， 水平的OCy成熟标志物，并显示显著减少的树突状过程。此外，百分比 MVNP小鼠中邻近PDL的硬化蛋白+ OCys的量显著低于不具有PDLs的MVNP小鼠。 PDLs或WT小鼠，IGF 1抑制OCys中硬化蛋白的表达。重要的是，相似的形态学 OCys在PD患者的骨样品中发生变化，但在正常供体中没有。这些结果表明 OCys可能是PD发病机制的关键因素。为了进一步验证这一假设，我们将：目标1。 描述OCL-IGF 1在PD和PD-OCys中的作用，确定相关的分子机制，并测试是否 增加的OCL-IGF 1足以诱导PDL和PD-OCys。目标二。确定衰老OCys的作用 在PDL和PD的位置、发展、进展和持续性中。我们将评估是否延长 PD-OCL暴露于正常OCys，或在老年小鼠中较短时间暴露于OCys足以使PDL发育。

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.