Mechanisms of altered extracellular matrix signaling in Osteogenesis Imperfecta

成骨不全中细胞外基质信号传导改变的机制

• 批准号: 8914966
• 负责人: STEFANIE L ALEXANDER
• 金额: $ 4.05万
• 依托单位: BAYLOR COLLEGE OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-05 至 2017-08-04
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8914966
• 关键词: Affect; Binding; Biochemical; Biological Availability; Biology; Biomechanics; Bone Development; Bone Marrow; Bone Tissue; Calorimetry; Cell Culture System; Cell Transplants; Collagen; Collagen Type I; Craniofacial Abnormalities; Data; Deformity; Dentin Dysplasia; Disease; Extracellular Matrix; Fracture; Genetic; Goals; Health; Homeostasis; Human; Immature Bone; Knock-out; Knockout Mice; Lead; Leucine; Link; Modeling; Molecular; Mus; Mutant Strains Mice; Mutation; Osteoblasts; Osteogenesis Imperfecta; Osteoporosis; Paper; Pathogenesis; Patients; Phenotype; Post-Translational Protein Processing; Property; Proteoglycan; Reporting; Research; Role; Sampling; Signal Pathway; Signal Transduction; Signaling Molecule; Stromal Cells; Structural Protein; Structure; Surface Plasmon Resonance; Testing; Tissues; Titrations; Transforming Growth Factor beta; asporin; base; biglycan; bone; bone mass; cell behavior; decorin; evaluation/testing; fetal; mouse model; new therapeutic target; novel; overexpression; protein complex; therapeutic target; tomography

DESCRIPTION (provided by applicant): Osteogenesis imperfecta (OI) is a debilitating genetic osteodysplasia that results in low bone mass, bone deformity, and bone fractures. Despite extensive research, the molecular pathogenesis behind OI is still poorly understood. Most cases of OI are caused by mutations in the structural protein type I collagen (dominant OI) or in protein complexes that post-translationally modify type I collagen (recessive OI); both types of mutations often lead to biochemical overmodification. Type I collagen, while important for structural integrity of bone is also essential for extracellular matrix (ECM) cell signaling. It extensively interacts with ECM components that regulate bioavailability of signaling molecules, thereby affecting tissue-specific cell behavior. We have demonstrated that excessive activation of the transforming growth factor-beta (TGFβ) signaling pathway is pathogenic in mouse models of dominant (Col1α2tm1.1Mcbr) and recessive (Crtap-/-) OI. However, the mechanism by which altered collagen structure or post-translational modification leads to altered signaling in OI is unclear. Small leucine-rich proteoglycans (SLRPs) are important regulators of matrix signaling that also bind type I collagen and could establish a link between structural proteins and signaling. Currently, the SLRPs decorin (Dcn), biglycan (Bgn), and asporin (Aspn) are the only matrix components known to bind both type I collagen and TGFβ. Their importance in bone is demonstrated by the phenotype in their absence. The Bgn- knockout mouse has an osteoporosis phenotype with altered sequestration and signaling of TGFβ in bone. Only one paper has studied the bone from Dcn-/- mice, but Dcn-knockdown osteoblast cells transplanted into mice generate immature, highly mineralized bone reminiscent of bone from OI patients. Decorin and biglycan from human OI bone samples are produced and secreted in a fetal-like form suggesting a connection between OI and changes in SLRPs. We hypothesize that changes in type I collagen in OI disturb binding to the SLRPs decorin, biglycan, and asporin, which in turn alters TGFβ availability in the matrix. We aim to test this hypothesis by comparing the biochemical interaction of SLRPs with type I collagen from wildtype, dominant OI, or recessive OI mice and determining the effects of SLRPs on TGFβ bioavailability and signaling in OI. Our preliminary data implies that decorin binds less to type I collagen from Crtap-/- mutant mice than wildtype mice. Based on this data and the phenotype of Dcn-knockout osteoblasts, the third aim of this project is to characterize the bone phenotype of the Dcn-/- mouse to assess the phenotypic overlap with OI bone. This research is important for establishing common mechanisms of disease, which may provide potential therapeutic targets for patients with dominant or recessive OI.

描述（由申请人提供）：成骨不全症（OI）是一种使人衰弱的遗传性骨发育不良，会导致骨量低、骨畸形和骨折。尽管进行了广泛的研究，但成骨不全背后的分子发病机制仍然知之甚少。大多数 OI 病例是由结构蛋白 I 型胶原蛋白（显性 OI）或蛋白质突变引起的 翻译后修饰 I 型胶原蛋白的复合物（隐性 OI）；这两种类型的突变通常都会导致生化过度修饰。 I 型胶原蛋白虽然对骨骼结构完整性很重要，但对于细胞外基质 (ECM) 细胞信号传导也至关重要。它与调节信号分子生物利用度的 ECM 成分广泛相互作用，从而影响组织特异性细胞行为。我们已经证明，转化生长因子-β (TGFβ) 信号通路的过度激活在显性 (Col1α2tm1.1Mcbr) 和隐性 (Crtap-/-) OI 小鼠模型中具有致病性。然而，胶原蛋白结构改变或翻译后修饰导致 OI 信号改变的机制尚不清楚。富含亮氨酸的小蛋白多糖 (SLRP) 是基质信号传导的重要调节剂，也能结合 I 型胶原蛋白，并可以在结构蛋白和信号传导之间建立联系。目前，SLRP 核心蛋白聚糖 (Dcn)、双糖链蛋白聚糖 (Bgn) 和阿孢菌素 (Aspn) 是唯一已知可结合 I 型胶原和 TGFβ 的基质成分。它们在骨骼中的重要性可以通过它们不存在时的表型来证明。 Bgn 敲除小鼠具有骨质疏松表型，骨中 TGFβ 的隔离和信号传导发生改变。只有一篇论文研究了 DCN-/- 小鼠的骨骼，但移植到小鼠体内的 DCN 敲低成骨细胞会产生不成熟、高度矿化的骨骼，让人想起 OI 患者的骨骼。人类 OI 骨样本中的核心蛋白聚糖和双糖链蛋白以类似胎儿的形式产生和分泌，表明 OI 与 SLRP 变化之间存在联系。我们假设 OI 中 I 型胶原蛋白的变化会干扰与 SLRP 核心蛋白聚糖、双糖链蛋白聚糖和阿孢菌素的结合，从而改变基质中 TGFβ 的可用性。我们的目的是通过比较 SLRP 与来自野生型、显性 OI 或隐性 OI 小鼠的 I 型胶原蛋白的生化相互作用，并确定 SLRP 对 OI 中 TGFβ 生物利用度和信号传导的影响来检验这一假设。我们的初步数据表明，与野生型小鼠相比，核心蛋白聚糖与 Crtap-/- 突变小鼠的 I 型胶原蛋白的结合较少。基于这些数据和 DCN 敲除成骨细胞的表型，该项目的第三个目标是表征 Dcn-/- 小鼠的骨表型，以评估与 OI 骨的表型重叠。这项研究对于建立常见的疾病机制非常重要，可能为显性或隐性 OI 患者提供潜在的治疗靶点。