Functionalized Nanofibrous Scaffold for Endogenous Bone Regeneration

项目摘要 大面积骨缺损的修复仍然是一个重大的临床挑战。自体骨移植 仍然被认为是大多数应用的金标准，但它受到供体发病率的限制。 与从采集的骨制备解剖学形状的移植物相关的位点和挑战。 骨组织工程被认为是一种有前途的替代方案，其中两个研究最广泛的 生物材料介导的外源性干/祖细胞组织工程方法 移植（例如，骨髓间充质干细胞（BMSCs）和生长 因子/激素递送（例如，骨形态发生蛋白，BMP）。这些方法，BMP 特别是作为刺激剂潜在治疗用途而受到广泛关注 骨修复的过程FDA批准的BMP 2和BMP 7，成功用于治疗骨修复， 募集并诱导内源性干/祖细胞用于成骨分化。基于BMP 然而，由于几个关键障碍，治疗在临床实践中受到显著阻碍： 高剂量、高成本和严重副作用。因此，我们的目标是：（1）开发一种新的3D 纳米纤维（NF）支架，其可以调节内源性BMP和血管生成信号;以及 (2)在临界尺寸小鼠颅骨缺损模型中通过功能化支架促进骨修复。 我们的中心假设是，在不添加任何外源性细胞或生长因子的情况下， 仿生明胶NF支架可促进原位内源性骨再生。 骨形成的基本成分的功能化将通过以下方式实现：（1）BMP 用于选择性捕获和刺激来自骨的内源性BMP的结合肽（BBP）， 损伤部位诱导局部骨形成;和（2）去铁胺（DFO）用于模拟 暂时缺氧，从而触发血管生成/新血管形成/骨生成， 修复性细胞募集我们以前的工作表明，一个三维多孔，可生物降解的NF 支架有利于组织再生。另外的成骨信号（例如， 然而，骨形成蛋白/骨祖细胞）仍然是需要的，并且必须在NF支架中补充，以用于 骨再生在目标1中，我们将通过化学方法将BBP和DFO固定到NF支架上， 交联和纳米球掺入。修饰的生物活性功能 将通过测量BMP-2结合和BMP-2/VEGF表达来研究支架， 体外细胞培养模型。在目标2中，我们将研究固定化BBP和 DFO（单独和协同）对骨形成和血管生成的影响，使用临界大小的小鼠 颅骨缺损模型这项工作将推进知识和治疗翻译探索 BBP肽/DFO固定化生物材料用于挑战性骨修复的用途。

PROJECT SUMMARY Repair of large bone defects remains a significant clinical challenge. While autologous bone graft is still considered the gold standard for most applications, it is limited by morbidity at the donor site and challenges associated with preparing anatomically-shaped grafts from harvested bone. Bone tissue engineering is considered a promising alternative, with two of the most widely-studied tissue engineering approaches being biomaterials-mediated exogenous stem/progenitor cells transplantation (e.g., bone marrow mesenchymal stem cells, BMSCs) and growth factors/hormones delivery (e.g., bone morphogenetic protein, BMPs). These approaches, BMPs in particular, have received widespread attention for their potential therapeutic use as stimulators of bone repair. FDA-approved BMP2 and BMP7, used successfully in the treatment of bone repair, recruits and induces endogenous stem/progenitor cells for osteogenic differentiation. BMP-based therapy, however, has been significantly impeded in clinical practice due to several critical barriers: high dose, high costs, and serious side effects. Accordingly, we aim to: (1) develop a novel 3D nanofibrous (NF) scaffold that can modulate both endogenous BMP and angiogenic signals; and (2) promote bone repair by a functionalized scaffold in a critical-size mouse cranial defect model. Our central hypothesis is that, without the addition of any exogenous cells or growth factors, biomimetic gelatin NF scaffold can improve in situ endogenous bone regeneration. Functionalization of essential components for bone formation will be accomplished via: (1) BMP binding peptide (BBP) for selectively capturing and stimulating endogenous BMPs from osseous injury sites to induce local bone formation; and (2) desferrioxamine (DFO) for mimicking temporary hypoxia, thereby triggering angiogenesis/neovascularization/osteogenesis and reparative cell recruitment. Our previous work demonstrates that a 3D porous, biodegradable NF scaffold is advantageous in tissue regeneration. Additional osteogenic signals (e.g., BMPs/osteoprogenitors), however, are still required and must be supplemented in NF scaffold for bone regeneration. In Aim 1, we will immobilize BBP and DFO to NF scaffold by chemical crosslinking and nanosphere incorporation, respectively. The bioactive functions of modified scaffolds will be studied by measuring BMP-2 binding, and BMP-2/VEGF expression using an in vitro cell culture model. In Aim 2, we will investigate the contributions of immobilized BBP and DFO (alone and synergistically) to bone formation and angiogenesis, using a critical-size mouse cranial defect model. This work will advance knowledge and therapeutic translation by exploring the use of the BBP peptide/DFO immobilized biomaterials for challenged bone repair.