PDGF-BB修饰对骨髓间充质干细胞归巢效率及骨折修复效果的影响及其机理研究

Tissue regeneration by cell homing is considered as an alternative to local cell transplantation. Currently, cell homing-based bone regeneration is still relying on the spontaneous migration of stem/progenitor cells, which are insufficient for repairing critical-sized bone defects. In order to understand the mechanism of cell homing to bone defects and solve the bottleneck problem of cell source in translating this novel regeneration strategy into clinical applications, we intend to work on the aspects as follows. 1) enhancement of the sensitivity of MSC to PDGF-BB gradient by conjugating PDGFR onto the surface of MSCs; 2) optimization of PDGF-BB concentration profiles in bone defect sites via light-sensitive mesoporous nano-particles; 3) investigation of the efficiency of MSC migration into bone defect and the effects of anchored MSCs on bone defect repair in a Rat tibia defect model. This comprehensive study would answer following two questions: 1) why is the number of cells migrated into bone defect so low; 2) how to recruit more MSCs into bone defects for enhanced bone regeneration. This project would elucidate ways for directed migration of transplanted MSCs into bone defects, thus enhancing the efficiency of cell-homing based bone regeneration.

当前基于细胞归巢的的骨修复依赖自发的MSC迁移，MSC数量低造成难以修复大面积的骨缺损。为了主动地诱导更多的MSC在骨折处聚集，本项目拟通过在MSC表面修饰PDGF-BB的受体PDGFR，增强MSC对PDGF-BB的敏感性；制备负载具有高效趋化功能的生长因子PDGF-BB的光敏感介孔纳米颗粒，在骨折处创建优化的PDGF-BB浓度模式（局部浓度大小及动态变化）。另外，利用大鼠胫骨骨折模型探讨MSC向骨折处定向迁移的效率以及迁移的MSC参与骨折修复的效果。对输注MSC在体内定向迁移的研究将回答“为什么输注的MSC向骨折处迁移的效率不高”这一科学问题和“怎样诱导更多的MSC向骨折处迁移”这一技术问题，使当前以细胞归巢为基础的骨组织工程研究更近一步，为大面积骨缺损这一临床难题的解决做出贡献。

正畸治疗常常需要健康的牙周基础，从而保证正畸的效果，成人正畸往往伴随牙周问题，而牙周疾病的传统治疗手段无法实现组织再生。近年来，分子生物学、细胞学技术和组织工程学飞速发展，牙周组织工程技术应运而生，成为牙病治疗研究的热点。课题组利用琼脂糖低黏附水凝进行hPDLSCs的三维培养，获得一批能在扩增同时保持良好干性的细胞，从而为牙周组织工程提供更加稳定的种子细胞来源。在培养细胞过程中，发现高代数细胞经过三维培养后形态有恢复趋势；课题组利用流式细胞术分析发现三维培养细胞的CD146阳性率较高；同时结合Q-PCR检测不同维度培养下细胞的干性基因以及成纤维相关基因表达，发现Nanog、Oct-4、Sox-2等干性基因表达增高；经过成骨诱导后，利用茜素红染色协同Q-PCR检测发现三维培养下细胞成骨基因表达及钙离子沉淀明显多于二维贴壁培养。在实验进行过程中发现。三维培养后基因SCT-1均显著表达，并初步探索其与干细胞经三维培养后生物学特性的改变关系。该研究为有望为牙周组织修复提供更优质的种子细胞，并为牙周组织再生工程学提供科学依据，同时也打开了解决成人正畸过程中出现的骨缺损等牙周问题的新思路。