制备仿生微纳米结构的高强度硼锶生物玻璃支架修复负重骨缺损的实验研究

The repair of large bone defects in load-bearing limbs remains an unsolved clinical problem. Bone tissue engineering technique is the fundamental way to solve this problem. In the present study, we developed a novel borate/strontium bioactive glass after fully taking into account the needs of material science and biology. Our previous studies found that this material has good biocompatibility and osteoinductivity, as well as controllable degradation properties, thus meet all the necessary elements for bone tissue regeneration. In addition, we emulate nature’s design by three-dimensional printing borate/strontium glass and fabricate novel 3D biomimetic glass scaffolds with anisotropic characteristics. The prepared 3D porous scaffolds possess high mechanical strength owing to its well-controlled hierarchical pore structure consisting of parallel channels and the complete densification of the glass struts obtained after sintering, which can provide the required strength for load bearing application in desired direction. Therefore, systematic studies have been conducted by observation of rules variation of structure-strength-degradation and expression levels of key osteogenic gene related signaling molecules of hBMSCs via BMP-2/Smad signaling pathways after incubating with glass scaffolds in vitro, as well as application in an large animal model of segmental load-bearing femur defects. The bioactivity, degradability and molecular regulation mechanisms of promoting osteogenesis of borate/strontium glass scaffolds were comprehensively investigated and analysised. Our purpose is to develop a porous, high strength bone tissue engineering scaffolds for large load-bearing bone defect repair and provide theoretical and experimental basis for the development and clinical application of a new generation of bionic biological materials.

大段负重骨缺损的修复是骨科治疗的一大难题，骨组织工程技术是解决此问题的根本途径。本项目充分兼顾到材料学和生物学的需求，研制了一种具有良好生物相容性、骨诱导活性和可控的降解性能的硼锶生物玻璃，满足了骨组织再生的各种必需要素。采用三维打印技术制备出具有各向异性结构特征的微纳米尺寸的有序多孔支架，通过对其微米和纳米孔结构的精确控制，使其具有传统玻璃陶瓷支架所不具备的高强度，可以承载负重骨缺损修复所需的生理负荷。通过研究支架的结构-强度-降解性能之间的变化规律，以及其在BMP-2/Smad信号通路调控hBMSCs成骨分化和VEGF分泌的分子靶点及其作用途径，阐明其诱导成骨的分子调控机制，并通过大型动物负重骨缺损模型的应用研究，进一步验证支架在体内的诱导成骨能力、降解性能和力学表现，以期为临床大段负重骨缺损修复提供一种新型多孔高强度骨组织工程支架，为新一代仿生材料的研发和临床应用转化提供实验依据。

由于外伤、肿瘤、感染等原因造成的大段骨、皮肤肌肉缺损一直是临床一大治疗难题，传统治疗策略如自体或异体组织移植存在并发症诸多、来源有限等问题。组织工程技术为其重建开辟了一条新的途径，但传统生物材料和支架制备技术还不能完全满足临床治疗需求。本项目研发了一种新型功能性硼锶生物玻璃体系，为骨、皮肤肌肉组织再生提供了各种必需元素，结合3D打印技术，构建出具备结构可控的多孔高强度玻璃支架，并进行了如下研究：其组分、结构、强度和降解性能的内在联系；经BMP-2/Smad信号通路调控hBMSCs增殖分化及促进成骨/成血管相关基因蛋白表达分泌的作用规律；动物大段负重骨缺损、皮肤肌肉缺损模型的应用研究。结果显示该体系生物玻璃：1）相较于传统硅酸盐生物玻璃，可更有效地促进BMSCs增殖、成骨分化，上调成骨/成血管相关基因表达，诱导新生血管形成，促进再血管化和加速成骨进程。2）具备良好可控的打印性能，支架具有完全通孔、孔隙高度规则、强度高、可降解等优点，满足细胞长入的各项结构和力学参数要求，可有效修复大段负重骨缺损。3）通过负载金属Cu离子，进一步提高了成血管相关基因表达，促进层粘连蛋白和骨骼肌祖细胞形成，可有效修复皮肤、肌肉软组织缺损。本研究表明硼锶生物玻璃体系通过释放各种有效离子，为骨、皮肤、肌肉再生提供了一种正常的微环境，通过3D打印技术制备的高度规则的微纳米尺寸定向孔结构利于引导细胞长入、促成骨和血管发生，同时具备理想的各向异性的力学特征和可控的降解速率，可承担正常生理负荷，从而有效修复骨干负重骨缺损，以及皮肤肌肉软组织缺损。该生物玻璃体系和支架制备工艺的研发摒弃了传统技术需要负载细胞和生长因子等繁琐步骤，便于快速、大规模制备，为新一代仿生玻璃材料的研发提供实验依据。随着成果的临床应用转化，可大大提高骨缺损、骨不连等的治愈率，节省大量医疗成本，为解决临床疑难问题提供一种切实有效的治疗手段。