Coupling osteoinductive factors to graft materials to promote osteoregeneration

描述（由申请人提供）：由于自体骨移植的局限性，同种异体骨、异种骨和异体材料通常用于骨移植手术。然而，这些材料缺乏骨诱导性。这项研究的目的是将骨诱导因子结合到这些替代移植源的表面，以增强骨缺损部位的骨再生。我们的研究小组正在利用一种独特的方法，包括将钙结合氨基酸结构域七谷氨酸（E7）添加到来自BMP 2的骨诱导肽中。临床前研究表明，在皮下（异位）和下颌骨缺损模型中，与E7修饰的BMP 2肽（E7-BMP 2 pep）结合的移植物材料比未涂覆的材料刺激了更大的新骨合成。重要的是，骨形成与用全长rBMP 2包被的移植物诱导的骨形成相当，并且在某些情况下更大，并且在E7-BMP 2 pep组中没有注意到副作用。相反，植入rBMP 2的动物出现慢性炎症和白内障。我们假设E7-BMP 2 pep是一种有效、安全且易于翻译的试剂，可用于增强各种骨移植材料的性能，包括同种异体移植物、异种移植物和同种异体移植物。本提案有两个主要目标：（1）全面分析宿主对E7-BMP 2 pep的反应，以推进翻译研究（目的1）;（2）阐明BMP 2模拟肽激活骨祖细胞的机制，更广泛的目标是鉴定具有最大骨诱导潜力的BMP 2衍生物。目标1：宿主对E7-BMP 2 pep偶联移植物材料的反应下颌骨缺损模型将用于评估E7-BMP 2 pep偶联材料对免疫和异物反应、纤维化、血管生成、新形成骨的数量和质量以及植入物整合的影响。还将监测肽和rBMP 2远离植入部位的扩散。我们假设E7-BMP 2 pep将保持紧密定位在缺损内，促进快速有效的骨愈合。目标2：利用细胞培养和颅骨器官培养系统，将阐明E7修饰的BMP 2模拟肽调节干/祖细胞的机制。此外，将开发具有激活突变的BMP 2肽变体，并且在互补研究中，将E7结构域工程化到全长rBMP 2上以改善与载体的偶联。将评价这些BMP变体的受体结合活性以及细胞信号传导和成骨细胞生成的诱导。将通过下颌骨种植体研究证实变体的骨诱导性增强。目的2的广泛目标是鉴定用于E7定向偶联至移植材料的理想BMP 2货物分子。

DESCRIPTION (provided by applicant): Due to limitations associated with autografted bone, allograft, xenograft and alloplast materials are commonly used for bone grafting procedures. However these materials lack osteoinductivity. The proposed research aims to couple osteoinductive factors to the surface of these alternative graft sources in order to enhance osteoregeneration in sites of bone deficiency. Our group is utilizing a unique approach involving the addition of a calcium-binding amino acid domain, heptaglutamate (E7), to an osteoinductive peptide derived from BMP2. Preclinical studies show that graft materials coupled with the E7-modified BMP2 peptide (E7-BMP2pep) stimulated significantly greater new bone synthesis than uncoated materials in both a subcutaneous (ectopic) and mandibular defect model. Importantly, bone formation was comparable to, and in some cases greater than, that induced by graft coated with full-length rBMP2, and no side effects were noted for the E7-BMP2pep group. In contrast, animals implanted with rBMP2 developed chronic inflammation and cataracts. We hypothesize that the E7-BMP2pep is an effective, safe, and readily translatable agent that can be used to enhance the performance of a wide array of bone grafting materials including allograft, xenograft and alloplast. There are two major objectives of this proposal: (1) to comprehensively analyze host response to the E7- BMP2pep in order to advance the research toward translation (Aim 1); and (2) to elucidate the mechanism by which BMP2 mimetic peptides activate osteoprogenitor cells, with the broader goal of identifying a BMP2 derivative with maximal osteoinductive potential. AIM 1: Host response to E7-BMP2pep-coupled graft materials A mandibular defect model will be used to assess the effects of E7-BMP2pep coupled materials on immune and foreign body response, fibrosis, angiogenesis, quantity and quality of newly-formed bone, and implant integration. Dissemination of the peptides and rBMP2 away from the implant site will also be monitored. We hypothesize that E7-BMP2pep will remain tightly localized within the defect, promoting rapid and effective bone healing. AIM 2: Molecular characterization and engineering of BMP2 mimetics to enhance osteoinductive potential Using cell culture and calvarial organ culture systems, the mechanisms by which E7-modified BMP2 mimetic peptides regulate stem/progenitor cells will be elucidated. Additionally, BMP2 peptide variants with activating mutations will be developed, and in complementary studies, an E7 domain will be engineered onto full-length rBMP2 to improve coupling to carriers. These BMP variants will be evaluated for receptor binding activity and induction of cell signaling and osteoblastogenesis. Enhanced osteoinductivity of the variants will be confirmed by mandibular implant studies. The broad goal of Aim 2 is to identify the ideal BMP2 cargo molecule for E7- directed coupling to graft materials.