促血管化的VEGF模拟肽修饰的丝素蛋白/磷酸八钙复合支架的构建与成骨机理研究

One of the major reasons of deficient healing of large bone defects in clinical practice is the insufficient blood supply after implantation of bone graft materials. Successful vascularization of bone grafts which possess decent osteogenic potential, therefore, is the key to repair large bone defects through bone tissue engineering approach. Octocalcium phosphate (OCP) has excellent biodegradability and osteoconductivity, yet lacks sufficient mechanical strength. Previously, we have found that silk fibrion (SF) can be used to improve the mechanical property, biodegradability and osteogenesis of OCP. In addition, while the vascular endothelial growth factor (VEGF) promotes angiogenesis, its bioactivity tends to deteriorate rapidly. In contrast, a VEGF-mimetic peptide (VMP), which has simple chemical structure and superior stability, appears to be a promising proangiogenesis factor. Therefore, in this project we aim to study the effect of vascularization, regulated by VMP modification, on the bone forming capability of SF/OCP composite scaffolds. The SF/OCP composite scaffolds will be prepared using co-precipitation technique and VMP will be consequently incorporated into them. The osteogenic mechanism and the potential synergy between vascularization and bone formation of the scaffold will be explored by in vitro experiments including scaffold degradation, VMP release behavior and osteogenesis and angiogenisis detections, and in vivo experiments including scaffold degradation, bone regeneration and angiogenesis using bone defect repair model. Together, findings from this study will likely improve the problem of insufficient blood supply in bone grafts for large bone defect repair, which will provide a solid foundation for the future development of bioactive materials for bone tissue engineering through an innovative approach.

骨修复材料体内移植后血供不足是临床上大段骨缺损长期不愈合的原因之一。因此，除材料的成骨性能外，其血管化是面向大段骨缺损修复的骨组织工程技术的关键。磷酸八钙(OCP)具有优良的生物降解和骨传导性能，但脆性高。我们的前期工作表明，丝素蛋白(SF)可改善OCP的力学、降解和成骨等性能。另一方面，可促血管生成的血管内皮生长因子(VEGF)易失活，而VEGF模拟肽(VMP)结构简单、性能稳定，是新型促血管化因子。为此，本项目拟探讨VMP修饰的SF/OCP复合支架中促血管化对骨再生的调控作用。将采用共沉淀法制备SF/OCP复合支架，并负载VMP，通过体外实验考察支架降解、VMP释放、成骨和血管生成潜能，进而考察在体内支架降解、骨再生和血管化程度，以此探寻材料的成骨机理及血管化与成骨的协同作用。本研究将有望改善大段骨缺损修复的骨移植物血供不足问题，并为新型高效组织工程骨修复材料研发提供理论基础和新思路。

骨修复材料体内移植后血供不足是临床上大段骨缺损长期不愈合的原因之一。提高骨植入材料的促管化功能是修复大段骨缺损的有效途径之一。为此，本研究目前已经顺利研制出两种负载促血管化药物的复合支架，用于大段骨缺损的修复，分别为负载二甲氧乙二酰甘氨酸(DMOG)的丝素蛋白/磷酸八钙（SF/OCP）复合支架和负载QK（VEGF模拟肽）的明胶/磷酸八钙复合水凝胶材料。其中，负载DMOG的SF/OCP复合支架是基于缺损处低氧的微环境，通过上调低氧诱导因子的表达，来促进血管化和成骨。而负载QK的明胶/磷酸八钙复合水凝胶材料中的QK可以直接发挥与VEGF类似的作用，促进血管化和成骨。基于与本项目相同的目的，即促骨再生/骨整合材料的研发，分别制备了具有较好的抗菌性能和骨整合性能的聚醚醚酮材料和具有良好生物相容性和力学性能的部分可降解聚丙烯酸酯骨水泥和全降解的丝素改性高强度磷酸钙骨水泥。以上研究，有望为新型高效组织工程骨修复材料研发提供理论基础和新思路。