Biodegradable Self-Inductive Scaffold for Cranial Regeneration

描述（由申请人提供）：本研究的长期目标是研究骨长入合成可生物降解的骨诱导支架，用于颅面缺损的重建。由于骨形态发生蛋白（BMPs）信号受到高度调控，移植物的负荷剂量必须比内源性高4-5个数量级（伴有不良副作用）。一个有吸引力的替代方案是使用基于bmp活性区域的肽来启动成骨级联。该策略涉及将骨诱导叠氮化物功能化的“BMP肽”（与重组人骨形态发生蛋白-2 （rhBMP-2）的氨基酸残基73-92相对应）共价连接到一种新型生物可吸收的聚（丙交酯-聚富马酸酯）（PLGF）支架上。PLGF中的短丙交酯-共乙醇酸链赋予了大分子的可降解性，而富马酸单元为结构支持提供了交联的位点。我们假设交联支架为再生区域提供结构支持，并通过迁移的骨髓基质（BMS）细胞与移植的BMP肽的相互作用诱导成骨。此外，支架会随着矿化基质的产生而降解，从而增加骨体积。本研究的目的是在体外和体内测定BMP肽移植PLGF支架的成骨能力和成骨程度。在Aim 1的第一部分，将确定PLGF组成和支架孔隙率对降解特性和机械强度的影响。Aim 1.1的结果是PLGF的最佳丙交酯：乙醇酸比和支架的最佳孔隙率。在Aim 1的第二部分，我们将在体外确定BMP肽移植PLGF对BMS细胞分化和矿化的影响。Aim 1.2的结果是BMP肽移植到PLGF支架上的最佳密度，由最高的矿物质含量来判断。在Aim 2中，我们将在体内确定BMP肽移植支架对临界尺寸大鼠颅骨缺损骨形成的影响。实验组包括BMP突变肽支架（阴性对照）、BMP肽支架（实验组）和BMP-2蛋白支架（阳性对照）。成功与否将根据新骨在支架上的连续桥接和骨矿物质密度来判断。

DESCRIPTION (provided by applicant): The long-term objective of this research is to study bone ingrowth into synthetic biodegradable osteoinductive scaffolds for reconstruction of craniofacial defects. Since bone morphogenetic proteins (BMPs) signaling is highly regulated, the graft has to be loaded with doses of 4-5 orders of magnitude (with adverse side effects) higher than the amount found endogenously. An attractive alternative is to use peptides, based on the active domains of BMPs to initiate the cascade of osteogenesis. The strategy involves covalent attachment of an osteoinductive azide-functionalized "BMP peptide", corresponding to amino acid residues 73-92 of the recombinant human bone morphogenetic protein-2 (rhBMP-2), to a novel bioresorbable poly(lactide-co-glycolide fumarate) (PLGF) scaffold. The short lactide-co-glycolide chains in PLGF impart degradability to the macromer while the fumarate units provide sites for crosslinking for structural support. We hypothesized that the crosslinked scaffold provides structural support to the regenerating region and induces osteogenesis by the interaction of migrating bone marrow stromal (BMS) cells with the grafted BMP peptide. Moreover, the scaffold will degrade concurrent with the production of mineralized matrix to increase bone volume. The aim of this proposal is to determine osteoinductivity and the extent of bone formation of BMP peptide grafted PLGF scaffold in-vitro and in-vivo. In the first part of Aim 1, the effect of PLGF composition and scaffold porosity on degradation characteristics and mechanical strength will be determined. The outcome of Aim 1.1 is the best lactide: glycolide ratio of PLGF and best porosity of the scaffold. In the second part of Aim 1, effect of BMP peptide grafted PLGF on differentiation and mineralization of BMS cells will be determined in-vitro. The outcome of Aim 1.2, is the best density of BMP peptide grafted to PLGF scaffold, as judged by the highest mineral content. In Aim 2, we will determine the effect of BMP peptide grafted scaffold on bone formation in critical-size rat cranial defect in-vivo. Experimental groups will include scaffolds grafted with mutant BMP peptide (negative control), BMP peptide (experimental group), and scaffolds with rhBMP-2 protein (positive control). Success will be judged by the continuous bridging of new bone across the scaffold and by bone mineral density. PUBLIC HEALTH RELEVANCE: Over twenty million people in USA are totally edentulous and about half a million children worldwide are born annually with congenital craniofacial deformities. Degradable biomaterials that are space occupying, osteoinductive, have the consistency to protect the defect from soft tissue collapse, and degrade concurrent with the formation of new extra-cellular matrix to increase bone volume have the potential for breakthroughs in the development of adaptable scaffolds to the changing craniofacial defect.