Biomimetic Scaffold Delivering Osteogenic Molecules for Alveolar Bone Engineering

描述（申请人提供）：牙周病和恶性肿瘤是毁灭性的并发症，往往导致切除下颌骨的大节段。各种基于骨诱导生长因子的治疗方法已经被开发出来，试图找到一种有效和更安全的骨再生方法。特别是，骨形态发生蛋白（BMPs）目前被批准用于脊柱融合、胫骨骨折修复、牙槽嵴或上颌窦增强。然而，bmp是高度多效性的分子，其超生理的高剂量要求导致不良副作用，如囊肿形成和骨形成效率低下。因此，有必要开发替代生长因子治疗策略，使用具有更特异性成骨作用的骨诱导因子。Nell-1 （nell -like protein-1）是一种新的成骨蛋白，最初在人类颅缝闭合患者的活性骨形成部位被发现，并且被认为是特异性靶向致力于成骨谱系的细胞。为了提供有效和更安全的骨再生修复大，复杂和结构缺陷，我们提出了一种新的计算机设计的仿生支架系统，用于控制局部递送Nell-1。该系统将由三维（3D）壳聚糖/海藻酸盐（Chi/Al）支架组成，在宏观和微观尺度上具有明确的几何形状，该支架由间接3D打印技术与仿生处理策略相结合创建，以赋予骨矿物模拟磷灰石微环境和成骨信号分子（Nell-1）。为了最大限度地实现骨再生，Nell-1还将与血小板衍生生长因子- bb （PDGF-BB）联合应用于临床治疗牙周骨缺损。本提议的具体假设是，计算机设计的仿生支架中有控制地递送Nell-1+PDGF可以增强牙槽骨缺损的修复。为了验证这一假设，我们提出了以下目标：1)开发具有结构可控和成骨分子（Nell-1+PDGF-BB）递送的仿生磷灰石包覆Chi/Al支架；2)通过植入Nell-1+PDGF-BB的仿生支架促进牙槽骨再生。Chi/Al支架结构将通过间接3D打印技术创建，以促进质量运输和容器的生长。在这个结构中，我们将创建一个仿生磷灰石涂层，并确定磷灰石层是否可以提高Nell-1和PDGF的传递效率。我们将在更大的下颌骨缺损模型中评估制备的仿生支架的成骨效果。此外，我们还将在支架中加入PDGF，并评估Nell-1+ PDGF联合使用对骨再生的影响，以最大限度地促进骨形成。这一建议的结果将对Nell-1介导的治疗方法的临床翻译至关重要，以增强牙槽骨再生，同时最大限度地减少当前骨诱导治疗的潜在不良影响。

DESCRIPTION (provided by applicant): Periodontal disease and malignant neoplasms are devastating complications often leading to the resection of large segments of the mandible. Various osteoinductive growth factor-based therapies have been developed in an attempt to find an effective and safer method of bone regeneration. In particular, bone morphogenetic proteins (BMPs) are currently approved for spinal fusion, tibial fracture repair, and alveolar ridge or maxillary sinus augmentation. However, BMPs are highly pleiotropic molecules and their supra-physiological high dose requirement leads to adverse side effects such as cyst formation, and inefficient bone formation. Thus, there is a need to develop alternative growth factor therapeutic strategies using osteoinductive factors with more specific osteogenic effects. Nell-1 (Nel-like protein-1) is a novel osteogenic protein originally identified in active bone forming sites of human craniosynostosis patients, and is believed to specifically target cells committed to the osteogenic lineage. To provide effective and safer bone regeneration for the repair of large, complex and structural defects, we propose a novel computer-designed, biomimetic scaffolding system for controlled local delivery of Nell-1. This system will consist of three-dimensional (3D) chitosan/alginate (Chi/Al) scaffolds with well-defined geometries on the macro- and micro-scales created from an indirect 3D printing technique in conjunction with biomimetic processing strategy to confer bone mineral-mimicking apatite microenvironment and osteogenic signaling molecules (Nell-1). To maximize bone regeneration, Nell-1 will be employed also in combination with platelet-derived growth factor-BB (PDGF-BB) in clinical use for the treatment of periodontal osseous defects. The specific hypothesis of this proposal is that controlled delivery of Nell-1+PDGF from computer-designed biomimetic scaffolds can enhance repair of alveolar bone defects. To investigate this hypothesis, we propose the following aims: 1) To develop biomimetic apatite-coated Chi/Al scaffolds with controlled architectures and delivery of osteogenic molecules (Nell-1+PDGF-BB); 2) To enhance alveolar bone regeneration by biomimetic scaffolds delivering Nell-1+PDGF-BB. Chi/Al scaffold architectures that facilitate mass transport and vessel ingrowth will be created from an indirect 3D printing technique. In this construct, we will create a biomimetic apatite coating and determine if apatite layer can increase Nell-1 and PDGF delivery efficiency. The bone formation efficacy of Nell-1 from the fabricated biomimetic scaffolds will be evaluated in a larger mandibular segmental defect model. In addition, we will also incorporate PDGF into the scaffolds and assess the effects of combined Nell-1+ PDGF on bone regeneration to maximize bone formation. The results from this proposal will be critical towards clinical translation of Nell-1 mediated therapeutics to augment alveolar bone regeneration while minimizing potential adverse effects of current osteoinductive therapeutics. PUBLIC HEALTH RELEVANCE: Loss of alveolar ridge due to periodontal disease, trauma, tooth loss or reconstructive surgery often leads to clinical situations exhibiting limited alveolar bone availability for dental implant placement. The proposed research provides effective and safer bone regeneration strategies combining a novel osteogenic protein with biomimetic scaffolding/delivery systems while minimizing potential adverse effects of current osteoinductive therapeutics.