Growth Factor Based on Enhancement of Bone Repair

骨折和骨缺损的愈合涉及细胞和生长因子之间的复杂相互作用。 目前，重组BMP 2，一种有效的骨形成诱导剂，被批准用于许多骨形成疾病。 骨科应用，但它可能会产生严重的副作用，可能与高剂量有关 采用将BMP 2与其他骨形成调节剂结合可以提高其在骨形成中的功效和效力。 骨科应用。我们的初步数据表明，血小板衍生生长因子可以阻断骨形态发生蛋白2在骨膜中的作用 祖细胞和阻止BMP 2诱导的骨生成。血小板源性生长因子（PDGF）及其受体在 骨折愈合，然而，PDGF在愈合过程中的体内作用，以及它如何与BMP 2信号相互作用， 没有很好的定义。 我们的假设是PDGF是骨愈合过程中BMP 2信号传导的关键调节因子。我们提出了三 目的：在目的1中，我们将定义PDGF调节BMP 2信号传导的机制。PDGF的作用 将在Smad磷酸化水平上评估BMP 2诱导的Smad信号传导，荧光素酶报告基因 活性和下游基因的表达。我们将评估 下游信号传导途径参与PDGF对BMP信号传导的抑制。体内研究将 在目标2和目标3中进行。我们将利用骨折和骨缺损模型。在目标2中， 评价使用体内条件性缺失破坏内源性PDGFRβ信号传导的影响 approach.我们建议靶向缺失间充质祖细胞、软骨细胞和成骨细胞 使用谱系特异性诱导型Cre转基因模型在骨折愈合过程中的谱系。条件的影响 PDGFRβ信号在骨折愈合中的激活将通过组织特异性表达PDGFRβ受体来实现。 PDGFRβ激酶结构域的组成型活性形式。在目标3中，我们将评估BMP 2/PDGF的功效。 局部联合治疗。此外，我们还将评估PDGFR抑制剂在 在不同的愈合阶段全身性地施用，从而允许精确控制剂量和时间。组合 将用单独不诱导缺损桥接的BMP 2剂量测试治疗。 我们的项目将提供更好地了解PDGF和BMP 2在骨生成过程中的相互作用 和骨骼愈合。通过调节PDGF和BMP 2信号传导增加成骨修复的潜力 在体内骨缺损愈合过程中，将概述这种治疗方法未来临床评价的可能性。

The healing of fractures and bone defects involves complex interactions between cells and growth factors. Currently, recombinant BMP2, a potent inducer of bone formation, is approved for use in a number of orthopedic applications, however it can generate serious side effects likely associated with the high doses used. Combining BMP2 with other modulators of bone formation could improve its efficacy and potency in orthopedic applications. Our preliminary data indicate that PDGF blocks the effects of BMP2 in periosteal progenitor cells and prevents BMP2 induced osteogenesis. PDGF and its receptors are abundant during fracture healing, however the in vivo role of PDGF during healing, and how it interacts with BMP2 signaling, is not well defined. Our hypothesis is that PDGF is a critical regulator of BMP2 signaling during bone healing. We propose three aims: In aim 1 we will define the mechanisms by which PDGF regulates BMP2 signaling. The effects of PDGF on BMP2-induced Smad signaling will be evaluated at the level of Smad phosphorylation, luciferase reporter activity and downstream gene expression in periosteal progenitor cells in vitro. We will evaluate which downstream signaling pathways are involved in the inhibition of BMP signaling by PDGF. In vivo studies will be conducted in Aim 2 and Aim 3. We will utilize models of bone fracture and bone defects. In Aim 2 we will evaluate the effects of disrupting endogenous PDGFRβ signaling using an in vivo conditional deletion approach. We propose to target deletion to mesenchymal progenitor cells, chondrocytes and osteoblast lineages during fracture healing using lineage specific inducible Cre transgenic models. Effects of conditional activation of PDGFRβ signaling on fracture healing will be achieved by tissue specific expression of a constitutively active form of the PDGFRβ kinase domain. In Aim 3 we will evaluate the efficacy of BMP2/PDGF combination treatment delivered locally. In addition, we will evaluate the effects of a PDGFR inhibitor delivered systemically at different stages of healing allowing for precise control of dosage and timing. Combination treatments will be tested with a dose of BMP2 that alone does not induce bridging of the defect. Our project will provide better understanding on the interactions of the PDGF and BMP2 during osteogenesis and bone healing. The potential for an increase in osteogenic repair by modulating PDGF and BMP2 signaling during bone defect healing in vivo will outline the possibility of future clinical evaluation of this treatment.