超顺磁性组织工程支架与外源磁场协同促进原位成骨的效应及机理研究

Large bone defects are a great challenge to reconstructive orthopaedic surgery, because the bone repair resulted from the conventional scaffold-induced bone regeneration in vivo is too slow to meet clinical demands. We consider that osteoblasts growing in the scaffolds implanted in defects are lack of constant and proper mechnical stimulation, which is one of the main reasons that lead to repair failures. Hence, it is crucial to make the scaffolds themselves have functions of giving cells mechanical stimulations. In this project, we will fabricate nanostructured composites with the integration of iron oxide magnetic nanoparticles. We hypothesized that the composite scaffolds generate small local vibration or deformation in response to extra applied magnetic fields due to their superparamagnetic properties. The small deformation and vibration apply stretch or twist force on cells growing in the scaffolds, which enhance scaffold-induced osteogenesis and lead rapid bone repair. We will investigate (1)the relationships between the scaffold chemistry, miscrostructures, strength and alternative frequency of extra magnetic fields and the superparamagnetic response behaviours, (2) interactions of scaffolds to the activation of mechanotransductive integrins, cytoskeletal linker proteins, integrin-associated signal cascades. (3) effects of scaffolds on the osteogenesis, and (4)interactions of the scaffolds to recruited macrophage cells (phenotypes and functions).Take above, to demonstrate mechanisms of the synergistic effect of superparamagentic scaffolds and magnetic fields and establish a new solution for scaffold-induced bone regeneration.

骨缺损处支架中的成骨细胞缺少持续和适度的力学刺激是导致其体内诱导成骨速度较慢和大块骨缺损难以修复的一个重要原因，如何使支架自身具有对细胞的力学刺激功能是加快新骨形成的关键问题。本项目拟构建含氧化铁磁性纳米颗粒的复合材料支架，利用超顺磁性纳米颗粒在外源磁场中，其磁矩由无序向与磁场同向转变的特性，使支架各处产生微振动和微形变，将磁场作用转化为支架对细胞的牵拉或者扭曲力。在静态或者交变磁场下，在多种细胞和动物骨缺损模型上，研究（1）支架的化学组成、微观结构、以及外源性磁场的强度和交变频率等因素与支架超顺磁响应能力之间的关系；（2）支架的超顺磁响应对成骨细胞表面的力传导分子（整合素）、细胞骨架结合蛋白及整合素相关信号通路的活化作用；（3）支架对成骨过程的促进作用；（4）支架环境中巨噬细胞功能的转变规律。阐明超顺磁性支架与外源性磁场促进骨组织再生的协同效应机制，建立支架引导成骨的新方法。

本项目重点开展了支架材料组成和微观结构与其超顺磁响应性及促成骨效应调控规律研究、超顺磁性支架与外源性磁场对创伤环境中巨噬细胞和成纤维细胞的作用研究、以及电传导性高模量水凝胶构建及其促进心肌样组织形成研究。. 系统比较了支架磁化性质的变化规律和促成骨分化的功能，阐释了支架的磁化性质与增强成骨功能的关联，并筛选出最佳组成和结构的支架，显著促进骨髓间充质干细胞的成骨分化和矿化；研究结果对于指导超顺磁性细胞支架的设计及其应用具有重要参考价值。. 从生物材料免疫学的角度研究了超顺磁响应性支架与外加磁场对巨噬细胞和成纤维细胞表型的调控规律与分子机制，阐明超顺磁性支架与磁场所产生的力学作用通过抑制TLR4/NF-κB、激活integins/FAK/ERK和VEGFR2（PI3K）/HIF-1α通路而调节成巨噬细胞和纤维细胞在创伤修复中的功能。为设计新型组织再生材料及实现其临床应用提供了新策略；同时，也为开展细胞生物学研究提供了新的平台技术。 . 开展了新型导电性水凝胶构建及其对心肌细胞成熟和心肌组织形成的探索研究，阐明该复合水凝胶通过激活α5β1整合素介导的力学信号转导通路和上调RhoA、HIF-1α的表达，显著增强了原代大鼠心肌细胞的体外成熟及其电生理功能，所形成的细胞/水凝胶复合体具有更为规律的自主搏动，其搏动频率对心脏毒性药物阿霉素具有长程响应，并能够快速有效地响应心率调节药物异丙肾上腺素的作用，有希望成为一种快速、成本相对较低的体外心脏药物的筛选及毒性评价平台。