生物材料仿生支架促进间充质干细胞向成骨细胞分化的机制研究

Mesenchymal stem cells (MSCs) have the capacity to differentiate into a variety of cell lineages under suitable environmental stimuli. In recent years, there has been increasing interests in nanostructure-stimulated differentiation of MSCs by biomimetic scaffolds. In our previous work, we have developed two types of scaffold materials which can stimulate the differentiation of MSCs into osteoblasts in the absence of chemical or cytokine treatment: (1) Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) nanofibrous scaffolds loaded with hydroxyapatite nanoparticles were fabricated using electrospinning technique; (2)By taking self-assembled colloidal crystal films as templates, inverse opal nanostructured polymeric scaffolds and the stretched nanostructured scaffolds were fabricated . Compared to the nonstructured flat films, results indicated that above two types of scaffolds significantly promote the osteogenic differentiation of MSCs. In this project, we will focus on the mechanistic study of spontaneous osteogenic differentiation of MSCs on above developed biomimetic scaffolds. The results will facillitate the committed differentiation of MSCs into osteoblasts at high efficiency, which is essentially useful for the further application in bone tissue engineering and regeneration.

干细胞定向分化是近年来生物医学研究的热点，具有重要的科学意义，应用价值与应用前景。随着组织工程的发展和干细胞研究的深入,人们发现材料的表面化学和微纳米结构可以调控间充质干细胞的分化。在前期的工作中我们已经获得两类仿生支架，可以实现大鼠骨髓间充质干细胞自主向成骨细胞分化：（1）采用静电纺丝技术制备的负载羟基磷灰石（HA）纳米颗粒的聚3-羟基丁酸戊酸共聚酯（PHBV）纳米纤维支架，(2)采用自组装胶体粒子模板法制备的具有反蛋白石结构的纳米多孔支架以及不同程度静态拉伸支架。 在本申请中，我们将研究以上两类仿生支架促进间充质干细胞自主向成骨细胞分化的分子机制，理解这些调控机制有利于实现骨髓间充质干细胞在仿生支架上向成骨细胞高效定向分化的目的，对未来临床植入和组织修复将具有重要意义。

随着组织工程的发展和干细胞研究的深入,人们越来越多地认识到干细胞生长的微环境直接影响到干细胞的定向分化,利用具有合适的材料表面化学特性和微纳米结构的仿生支架可以人为调控间充质干细胞的定向分化。我们分别采用自组装胶体粒子模板法制备了具有反蛋白石结构的纳米多孔支架及其静态拉伸支架,以及采用静电纺丝法制备了PHBV和纳米羟基磷灰石（HA）复合纳米纤维支架。在这两类仿生支架表面培养大鼠骨髓间充质干细胞，在不加入任何诱导剂的情况下,研究其自主向成骨细胞分化的状况。我们在细胞培养不同时期分别检测了干细胞形态和细胞骨架的变化，以及成骨细胞标志物和成骨相关基因的表达,表明可以较好地向成骨细胞分化。进一步我们检测了调控成骨细胞分化的几个重要信号通路的活性变化，包括Wnt-beta-catenin, BMP-SMAD以及MAPK信号通路，初步阐明了两类仿生支架促进间充质干细胞向成骨细胞分化的调控机制，并且优化出两种具有优异成骨特性的仿生支架，对未来临床植入和骨组织修复具有重要意义。