Engineering structural bone allografts for enhanced repair and reconstruction

项目摘要 在美国，每年有超过500，000例骨移植手术， 用于33%的骨移植手术的组织。虽然尸体上的同种异体骨 并且供体已被广泛用于修复骨缺损，骨同种异体移植物还没有 与自体骨移植相比，达到了相似的疗效水平。此外，骨 用于治疗临界大小骨缺损的同种异体移植物显示出极慢的植入和坏死， 60%的长期失败率是由于纤维化不愈合、血管化不良、 骨整合、感染和微裂纹扩展。为了改善愈合， 整合，已经开发了策略来修饰骨同种异体移植物，以增强其 成骨和血管生成特性。这些策略包括用聚合物涂覆， 不掺入不同的药物，用腺相关病毒包被-骨 形态发生蛋白2（AAV-BMP 2）载体，用含有骨髓的水凝胶包被 干细胞（BMSCs），用BMSCs接种的生物膜包裹。但这些 策略与许多问题相关，包括i）纤维化组织形成，ii） 活细胞的参与，iii）不均匀的愈伤组织形成，和iv）病毒载体的安全性。因此，我们认为， 迫切需要设计现成的骨同种异体移植物以提高它们的功效， 关键尺寸骨缺损的修复性能。本研究的主要目的是 具有能够释放抗纤维化剂和骨的新型涂层的工程化骨同种异体移植物 以同时或顺序的方式施用生长调节因子以改善愈合， 骨整合为了验证假设并实现主要目标，我们的策略 包括：i）建立BMP-2诱导的同种异体骨工程化方法 肽和TGF-β信号传导抑制剂;和ii）评估抗纤维化功效， 小鼠股骨中工程化同种异体骨的新骨形成和骨整合 缺陷模型;和3）检查在骨缺损期间TGF-β和BMP-2信号传导之间的拮抗作用。 同种异体骨移植修复我们希望确定抗纤维化药物和骨生长的作用 表面工程骨修复严重骨缺损的调控因素 同种异体移植所提出的策略还可以用于各种应用， 促进组织再生。

PROJECT SUMMARY Bone grafting procedures number over 500,000 annually in the United States, with allograft tissues used for 33% of the bone grafting operations. Although bone allografts from cadavers and donors have been utilized extensively to repair bone defects, bone allografts have not achieved the similar level of efficacy as compared with bone autografts. Furthermore, bone allografts for treatment of critical-sized bone defects show extremely slow engraftment and ≈ 60% long-term failure rates due to fibrotic nonunions, poor vascularization, poor osteointegration, infections, and microcrack propagation. To improve the healing and integration, strategies have been developed to modify bone allografts to enhance their osteogenic and angiogenic properties. These strategies include coating with polymers with and without incorporation of different drugs, coating with adeno-associated virus – bone morphogenetic protein 2 (AAV-BMP2) vectors, coating with hydrogels containing bone marrow stem cells (BMSCs), wrapping with BMSCs-seeded nanofiber membranes. However, these strategies are associated with many problems including i) fibrosis tissue formation, ii) involvement of living cells, iii) uneven callus formation, and iv) safety of virus vectors. Therefore, there is an urgent need to engineer off-the-shelf bone allografts to improve their efficacy and performance in repair of the critical-sized bone defects. The primary objective of this study is to engineer bone allografts with a novel coating capable of releasing anti-fibrotic agents and bone growth regulating factors in either simultaneous or sequential fashion to improve the healing and osteointegration. To test the hypothesis and accomplish the primary objective, our strategy includes: i) Establish a method of engineering bone allograft with incorporation of BMP-2 peptides and a TGF-β signaling inhibitor to the coatings; and ii) Assess the anti-fibrotic efficacy, new bone formation, and osseointegration of engineered bone allografts in a murine femoral defect model; and 3) Examine the antagonism between TGF-β and BMP-2 signaling during bone allograft repair. We expect to identify the role of anti-fibrotic agents and bone growth regulatory factors on the healing of a critical bone defect through surface engineered bone allografts. The proposed strategy could also be useful in various applications aimed at promoting tissue regeneration.