The role of connective Tissue Growth Factor on BMP9-Induced Osteogenesis

描述（由申请人提供）：成骨细胞分化和骨形成是正常骨骼发育和修复/骨折愈合所必需的精心策划的级联事件。本申请的目的是表征结缔组织生长因子 (CTGF) 对成骨细胞分化和骨形成的作用，最终目标是使用 BMP-9 及其下游靶标（例如 CTGF）作为患者的骨再生剂。 CTGF 是一种分泌蛋白，具有四个不同的模块（结构域），与几种细胞外基质蛋白具有结构同源性。每个模块可以具有一个或多个不同的功能。我们发现，在骨形态发生蛋白（BMP）诱导的成骨细胞分化途径的早期，CTGF 表达持续上调。几种 BMP，尤其是 BMP9，已被证明是成骨细胞分化和骨形成的有效刺激剂。有趣的是，CTGF 表达的时间调节可能对于 BMP 诱导的成骨细胞分化至关重要。为了进一步了解调节间充质干细胞成骨谱系特异性分化和骨形成的分子事件，我们提出了一系列假设驱动的实验，这些实验将确定 CTGF 在这一精心策划的过程中的作用。具体来说，我们将确定：（1）CTGF的特定模块和CTGF的时间表达是否调节BMP9诱导的体外成骨细胞分化； (2)在异位骨形成动物模型中，CTGF是否调节BMP9诱导的骨形成； (3)通过RNA干扰(RNAi)介导的敲低暂时控制CTGF沉默是否调节BMP9诱导的体外成骨细胞分化和体内异位骨形成。从这些实验中获得的知识将扩大我们对 BMP 和 CTGF 在间充质干细胞成骨分化和骨形成中的作用的理解。 BMP 及其下游靶点（如 CTGF）在许多骨科疾病中具有广泛的临床应用，例如增强顽固性骨折愈合或促进患者骨再生。 外行声明：在正常发育和骨愈合中，有一个精心策划的过程，刺激前体细胞成为骨形成细胞，并最终形成骨。该提案研究了一个重要因素（结缔组织生长因子）在这一复杂的骨形成过程中的功能，其目标是将其应用于患者的骨折愈合和骨再生。

DESCRIPTION (provided by applicant): Osteoblastic differentiation and bone formation is a well orchestrated cascade of events that is necessary for normal bone development and repair/fracture healing. The objective of this application is to characterize the role of Connective Tissue Growth Factor (CTGF) on osteoblastic differentiation and bone formation, with the ultimate goal of using BMP-9 and its downstream targets (e.g. CTGF), as bone regeneration agents in patients. CTGF is a secreted protein which has four distinct modules (domains) that share structural homology to several extracellular matrix proteins. Each module may have one or more distinct functions. We have found that CTGF expression is consistently upregulated early in the pathway of Bone Morphogenetic Protein (BMP)-induced osteoblastic differentiation. Several BMPs, especially BMP9, have been shown to be potent stimulators of osteoblastic differentiation and bone formation. Interestingly, temporal regulation of CTGF expression may be essential for BMP-induced osteoblastic differentiation. In order to further understand the molecular events regulating osteogenic lineage-specific differentiation of mesenchymal stem cell and bone formation, we propose a series of hypothesis-driven experiments that will determine the role of CTGF in this well-orchestrated process. Specifically, we will determine: (1) whether specific modules of CTGF and temporal expression of CTGF regulate BMP9-induced osteoblastic differentiation in vitro; (2) if CTGF regulates BMP9-induced bone formation in a heterotopic bone formation animal model; and (3) whether temporally controlled CTGF silencing by RNA interference (RNAi)-mediated knockdown modulates BMP9-induced osteoblastic differentiation in vitro, and heterotopic bone formation in vivo. Knowledge gained from these sets of experiments will expand our understanding of the role of BMPs and CTGF on osteogenic differentiation of mesenchymal stem cells and bone formation. Both BMPs and their downstream targets, like CTGF, can have a broad range of clinical applications in a number of orthopaedic conditions, such as enhancing recalcitrant fracture healing or promoting bone regeneration in patients. LAY STATEMENT: In normal development and bone healing, there is a well-orchestrated process of stimulating precursor cells to become bone-forming cells, and the eventual formation of bone. This proposal examines the function of an important factor (Connective Tissue Growth Factor) in this complex process of bone formation, with the goal of its application in fracture healing and bone regeneration in patients.