Engineering Bone Formation in Multi-Functional Nanocomposite Scaffolds

CBET-0756394 Jabbari在骨再生的自然过程中，细胞外基质保护再生区域免受软组织塌陷的影响，并向迁移细胞提供多种信号，以指导迁移、基质降解和侵袭以及形态发生的级联反应。工程支架应通过提供临时结构支撑来模拟骨细胞外基质的复杂性，与细胞迁移同时降解以增加新基质形成的自由体积，并提供细胞粘附和增殖的位点。假设与具有多个共价连接的活性结构域的功能化肽交联的复合支架可以协调多种再生功能，模拟导致骨形态发生的天然信号级联。考虑到这一假设，本项目的目的是确定具有多个生物活性域的肽的影响，所述多个生物活性域包括结合磷灰石纳米颗粒的域、基质金属蛋白酶（MMP）可降解域和整合素结合的RGD域，分别对临时结构支持、与细胞迁移同时的基质降解以及细胞粘附和增殖。多结构域肽将水凝胶相共价连接到无机纳米磷灰石相以形成多功能复合支架。提出了三项任务来证明概念验证：首先，将使用分子模型来预测纳米复合材料的粘弹响应，并找到磷灰石纳米颗粒、多功能磷灰石结合肽和基质金属蛋白酶的有效浓度范围可降解肽交联剂。第二，将在体外用骨髓基质（BMS）细胞确定复合支架调节细胞迁移至支架降解的能力。第三，纳米复合材料基质对骨生成/血管生成和矿化基质产生的影响将通过在体外接种BMS细胞和通过植入大鼠颅骨缺损模型体内来确定。这项工作的更广泛的影响在于将这些想法应用于骨骼组织再生以外的领域，如牙齿修复，骨关节炎和软骨再生，退行性椎间盘疾病的治疗，心脏瓣膜的置换，靶向肽模拟药物递送系统，以及开发用于祖细胞同时分化为多个谱系的基质。一个广泛的教育组成部分是这个项目的一部分，其中研究生和本科生将受益于整体研究方法，它集成了材料科学与工程，生物化学，分子和细胞生物学，骨科设计支架组织再生。作为推广计划的一部分，每年夏天都会选择一名高中生参加与组织工程相关的研究。

CBET-0756394JabbariIn the natural process of bone regeneration, the extracellular matrix protects the regenerating region from soft tissue collapse and provides multiple signals to the migrating cells to guide the cascade of migration, matrix degradation and invasion, and morphogenesis. An engineered scaffold should mimic the complexity of the bone extracellular matrix by providing temporary structural support, degrade concurrent with cell migration to increase free volume for new matrix formation, and provide sites for cell adhesion and proliferation. It is hypothesized that a composite scaffold crosslinked with a functionalized peptide that has multiple covalently-linked active domains can coordinate multiple regenerative functions, mimicking the natural signaling cascade leading to bone morphogenesis. With this hypothesis in mind, the objective of this project is to determine the effects of a peptide with multiple bioactive domains consisting of a domain that binds to apatite nanoparticles, a matrix metalloproteinase (MMP) degradable domain, and an integrin-binding RGD domain on temporary structural support, matrix degradation concurrent with cell migration, and cell adhesion and proliferation, respectively. The multi-domain peptide will covalently link the hydrogel phase to the inorganic nanoapatite phase to form a multi-functional composite scaffold. Three tasks are proposed to demonstrate the proof-of-concept: First, a molecular model will be used to predict the viscoelastic response of the nanocomposite and to find the effective range of concentrations of the apatite nanoparticles, multi-functional apatite-binding peptide, and the MMP degradable peptide crosslinker. Second, the ability of the composite scaffold to modulate cell migration to scaffold degradation will be determined in-vitro with bone marrow stromal (BMS) cells. Third, the effect of the nanocomposite matrix on osteogenesis/vasculogenesis and mineralized matrix production will be determined in-vitro by seeding with BMS cells and in-vivo by implantation in the rat calvarial defect model. The broader impact of this work lies in the application of these ideas to areas other than skeletal tissue regeneration, like dental restoration, osteoarthritis and cartilage regeneration, treatment of degenerative disk disease, replacement of heart valves, targeted peptidomimetic drug delivery systems, and in developing substrates for concurrent differentiation of progenitor cells to multiple lineages. A broad educational component is part of this project, wherein graduate and undergraduate students will benefit from the overall research approach, which integrates materials science and engineering, biochemistry, molecular and cell biology, and orthopedics to design scaffolds for tissue regeneration. As part of the outreach program, a high school student is selected each summer to participate in research related to tissue engineering.