Engineering Bone Formation in Multi-Functional Nanocomposite Scaffolds

CBET-0756394 Jabba在骨再生的自然过程中，细胞外基质保护再生区免受软组织塌陷的影响，并向迁移细胞提供多种信号，引导迁移、基质降解和侵袭以及形态形成的级联过程。工程化支架应该模拟骨细胞外基质的复杂性，提供临时的结构支持，在细胞迁移的同时降解细胞，增加新基质形成的游离量，并为细胞黏附和增殖提供场所。人们假设，与具有多个共价连接活性结构域的功能化多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自然信号级联。考虑到这一假设，本项目的目标是确定具有多个生物活性结构域的多肽分别对临时结构支撑、基质降解伴随细胞迁移以及细胞黏附和增殖的影响。多结构域肽将水凝胶相与无机纳米磷灰石相共价连接，形成多功能复合支架。提出了三项任务来验证概念：首先，将使用分子模型来预测纳米复合材料的粘弹性响应，并找出磷灰石纳米颗粒、多功能磷灰石结合肽和基质金属蛋白酶可降解多肽交联剂的有效浓度范围。其次，复合支架调节细胞迁移到支架降解的能力将在体外与骨髓基质细胞(BMS)一起确定。第三，纳米复合基质对成骨/血管生成和矿化基质生成的影响将通过体外种植BMS细胞和体内植入大鼠颅骨缺损模型来确定。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、退行性间盘疾病的治疗、心脏瓣膜置换、靶向模拟肽药物输送系统，以及开发同时向多个谱系分化的祖细胞的底物。一个广泛的教育部分是这个项目的一部分，其中研究生和本科生将从整体研究方法中受益，该方法将材料科学与工程、生物化学、分子和细胞生物学以及整形外科结合在一起，为组织再生设计支架。作为推广计划的一部分，每年夏天都会挑选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.