β-TCP/Mg-Zn多孔骨组织工程支架构建及其诱导成骨机制的研究

To repair and cure bone defect caused by trauma, infection, and tumors, there are many materials applied in orthopedics clinical works and related studies, including autograft, allograft and tissue engineering bone, in which tissue engineering bone research is a hotspot. As the core part of bone tissue engineering research, how to fabricate a scaffold with sufficient porosity, ideal mechanical properties, good osteogenic inductivity, and controlled biodegradation, is an intractable difficulty in current studies. Some studies showed that magnesium-based metal matrix material was expected to solve the above problem. Our previous study found its mechanical properties strengthened, osteogenic inductivity improved, and biodegradability optimized to match bone healing, by adding the appropriate proportion of zinc and β-TCP. However, its molecular osteogenesis mechanism and regulatory of mechanical properties need to be further studied, especially when it was made into a porous scaffold. So, our project intends to explore the following: 1) How to fabricate a porous β-TCP/Mg-Zn scaffold and regulate its performance, 2) The structure and formation mechanism of rhBMP-2 coated on porous-scaffold, controlled release, and slowing down biodegradation, 3) Osteogenic inductivity of the porous-scaffold, and 4) Molecular osteogenesis mechanism of Mg and/or Zn ion when focused on ERK/MAPK signaling pathway. Then, the study could provide a theoretical basis and technology prototype for the development of an ideal bone tissue engineering scaffold and its clinical applications.

用于创伤、感染、肿瘤等引起骨缺损的修复材料主要有自体骨、异体骨和组织工程骨，其中组织工程骨是研究的热点。而作为其核心的支架材料如何兼顾足够的孔隙率、理想的力学强度、良好的成骨性能及可控的降解速率，是目前研究的难点。国内外研究发现镁基材料可望解决上述问题，我们前期研究也发现镁基材料加入合适配比Zn与β-TCP，可改善力学性能并增强成骨能力，且其降解与骨质愈合匹配，但制作成多孔支架时其材料性能调控与诱导成骨机制尚待研究。为此，本项目拟从如下内容探索：1）多孔β-TCP/Mg-Zn支架的构建模式与性能调控规律；2）rhBMP-2在多孔支架表面的涂覆机理、缓释规律及延缓降解的行为；3）rhBMP-2缓释涂层多孔β-TCP/Mg-Zn支架诱导成骨能力；4）镁离子、锌离子于ERK/MAPK信号通路诱导成骨的分子生物学机制及其相互作用关系。以期为开发三维多孔骨组织工程支架及临床应用提供理论基础和技术原型

随着社会、经济的发展，各种原因导致的骨缺损病例快速上升。目前用于治疗骨缺损的修复材料或来源有限，或存在免疫排斥反应，或材料强度差，应用受到了限制。研究发现镁基材料具有与人体骨相似的弹性模量和密度、理想的力学强度、良好的细胞相容性和成骨性能。由于商用镁基材料降解速度快，高孔隙率时力学性能下降，致使在用作骨组织工程三维多孔支架修复承重部位的骨缺损方面鲜有报道，更未见其成骨机制研究。因此，本项目设计制备了带rhBMP-2缓释涂层的多孔β-TCP/Mg-Zn材料，研究其微观结构、力学性能、腐蚀性能、生物相容性及诱导成骨能力，并分析镁离子在ERK/MAPK信号通路诱导成骨的机制。研究表明，粉末冶金法制备的多孔Mg-3Zn-5TCP材料综合的力学、降解性能最优。随着孔隙率的增加。力学和腐蚀性能逐渐降低。我们在材料表面涂覆rhBMP-2明胶缓释微球，并证实了其良好的缓释性能。体外实验证实带rhBMP-2涂层的多孔Mg-3Zn-5TCP材料具备良好的生物相容性及诱导成骨能力，能促进骨髓间充质干细胞的增殖和成骨分化。在小动物体内实验中，带rhBMP-2涂层的多孔Mg-3Zn-5TCP材料在三个月内完全降解，完全修复了圆形骨缺损，对重要脏器未产生毒副反应。但在大动物体内实验中，材料快速降解并在短期内产生大量氢气，超出组织可吸收的范围，导致组织坏死、感染，暂无法满足大动物长骨骨段缺损的修复要求。Mg-Zn通过ERK/MAPK信号通路诱导成骨分化。