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首页> 外文期刊>Journal of orthopaedic research >Dysregulated TGF- signaling alters bone microstructure in a mouse model of Loeys-Dietz syndrome
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Dysregulated TGF- signaling alters bone microstructure in a mouse model of Loeys-Dietz syndrome

机译:TGF-信号通路失调改变了Loeys-Dietz综合征小鼠模型的骨微结构

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Loeys-Dietz syndrome (LDS) is a connective tissue disorder characterized by vascular and skeletal abnormalities resembling Marfan syndrome, including a predisposition for pathologic fracture. LDS is caused by heterozygous mutations in the genes encoding transforming growth factor- (TGF-) type 1 and type 2 receptors. In this study, we characterized the skeletal phenotype of mice carrying a mutation in the TGF- type 2 receptor associated with severe LDS in humans. Cortical bone in LDS mice showed significantly reduced tissue area, bone area, and cortical thickness with increased eccentricity. However, no significant differences in trabecular bone volume were observed. Dynamic histomorphometry performed in calcein-labeled mice showed decreased mineral apposition rates in cortical and trabecular bone with normal numbers of osteoblasts and osteoclasts. Mechanical testing of femurs by three-point bending revealed reduced femoral strength and fracture resistance. In vitro, osteoblasts from LDS mice demonstrated increased mineralization with enhanced expression of osteoblast differentiation markers compared with control cells. These changes were associated with impaired TGF-1-induced Smad2 and Erk1/2 phosphorylation and upregulated TGF-1 ligand mRNA expression, compatible with G357W as a loss-of-function mutation in the TGF- type 2 receptor. Paradoxically, phosphorylated Smad2/3 in cortical osteocytes measured by immunohistochemistry was increased relative to controls, possibly suggesting the cross-activation of TGF--related receptors. The skeletal phenotype observed in the LDS mouse closely resembles the principal structural features of bone in humans with LDS and establishes this mouse as a valid in vivo model for further investigation of TGF- receptor signaling in bone. (c) 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:1447-1454, 2015.
机译:Loeys-Dietz综合征(LDS)是一种结缔组织疾病,其特征是类似于Marfan综合征的血管和骨骼异常,包括病理性骨折的易感性。 LDS是由编码转化生长因子-(TGF-)1型和2型受体的基因中的杂合突变引起的。在这项研究中,我们表征了携带与人类严重LDS相关的TGF-2型受体突变的小鼠的骨骼表型。 LDS小鼠的皮质骨显示组织面积,骨面积和皮质厚度显着减少,且离心率增加。但是,没有观察到小梁骨体积的显着差异。在钙黄绿素标记的小鼠中进行的动态组织形态计量学显示,成骨细胞和破骨细胞数量正常时,皮质和小梁骨中的矿物质沉积率降低。通过三点弯曲对股骨进行机械测试,发现股骨强度和抗骨折性降低。在体外,与对照细胞相比,来自LDS小鼠的成骨细胞显示出矿化增加,成骨细胞分化标记物表达增强。这些变化与TGF-1诱导的Smad2和Erk1 / 2磷酸化受损以及TGF-1配体mRNA表达上调有关,与G357W相容,作为TGF-2型受体功能丧失的突变。矛盾的是,通过免疫组织化学法测定的皮质骨细胞中的磷酸化Smad2 / 3相对于对照有所增加,这可能暗示了TGF相关受体的交叉激活。在LDS小鼠中观察到的骨骼表型与具有LDS的人的骨骼的主要结构特征非常相似,并将该小鼠确立为进一步研究骨骼中TGF-受体信号传导的有效体内模型。 (c)2015骨科研究学会。由Wiley Periodicals,Inc.出版,J Orthop Res 33:1447-1454,2015。

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