骨髓源干细胞在脑组织的迁移和分化

Migration and differentiation of bone marrow-derived stem cells in the brain

骨髓源干细胞(BONE MARROW-DERIVED STEM CELLS,BMDSCS)能否迁移至脑组织并分化为神经胶质细胞和神经细胞是近年来成体干细胞研究的热点领域。有一些学者采用Y染色体和GFP基因作为骨髓源细胞标记物,通过血行输入受体动物后,在脑组织内发现了标记阳性细胞,并证实这些细胞有向神经胶质细胞和神经细胞分化的趋势;另有一些学者也采用GFP基因作为细胞标记物,但在受体动物脑组织并未发现标记阳性细胞。这些实验结果差异可能与观察时间长短、细胞标记方法和神经组织中标记基因沉默事件有关。就迁移到脑组织的BMDSCS 是否与宿主神经细胞整合的问题,有研究认为存在转分化(TRANSDIFFERENTIATION)机制,也有实验发现BMDSCS与小脑PURKINJE神经元之间有细胞融合现象。细胞转分化和细胞融合有可能是中胚层来源的BMDSCS向神经外胚层细胞变化的两种必要机制。讨论这些问题对阐明神经细胞的新老更替、损伤和修复机制是很有意义的。

Whether the bone marrow-derived stem cells （BMDSCs） might migrate into the brain and differentiate there into the neural cells is one of focus of current researches with regard to adult stem cells. There were some studies showing that a certain number of BMDSCs marked with Y chromosome and GFP gene and grafted through the vein of the host animals could be presented in their brain tissue and these migrated cells expressed the specific markers for glial and neuronal cells. There were other studies nevertheless reporting that none of those cells labeled with GFP gene were found in the brain after transplantation through the blood. The causes of such inconsistent results may be due to the times of observation, the methods for labeling the BMDSCs with GFP gene and the gene silence in the brain tissue. As for the integrity of the migrated BMDSCs in the host brain tissue, some experiments showed that they could be differentiated into the glia and neurons by an inducing mechanism from microenviroment in the host brain, while the other experiments proved that the cell fusion might occur between the migrated BMDSCs and the Purkinje cells. The differentiation and fusion of cells may be therefore the two essential ways for the BMDSCs to change their phenotypes from mesoderm to ectoderm. It therefore appears that further study of this matter is necessary to understand the cell replacement in the brain structure maintenance and repair.