中文摘要：

人表皮干细胞可以作为牙齿再生中上皮源性的种子细胞，但是其成釉分化的效率低下．本研究分离培养了人牙胚上皮细胞，利用E13．5的小鼠牙间充质与其重组，构建重组牙胚，对其成釉分化的潜能和机制进行研究．研究结果发现，体外培养的P1代人牙胚上皮细胞成釉率高达50％．随着传代次数的增加，成釉率明显下降．通过对牙上皮发育分化相关基因的表达检测和分析表明，重组牙胚成牙分化能力和成釉潜能的下降与牙上皮发育相关基因的表达状态密切相关．特别是FGF8表达水平的下调以及PITX2不同亚型在人牙胚细胞中表达量的不均衡，可能是导致人牙胚细胞成釉潜能下降并丧失的主要原因．本研究结果为理解牙齿再生过程中上皮源性的种子细胞的成釉机制提供了新的实验数据，对进一步提高表皮干细胞在牙齿再生过程中的成釉率有指导意义．

英文摘要：

Human keratinocyte stem cells （hKSCs） have been demonstrated as potential cell sources for the epithelial component in generation of bioengineered teeth. However, the efficiency of ameloblastic differentiation of hKSCs is rather low. In the study, we investigated the correlation of gene expression with ameloblastic differentiation capability using dental epithelial cells isolated from human embryonic tooth germs at the bell stage. We found that in vitro cultured human embryonic dental epithelial cells at passage 1, when recombined with El3.5 mouse dental mesenchyme, were able to undergo ameloblastic differentiation at 50% efficiency. However, the efficiency of ameloblastic differentiation of these ceils decreased as the cell culture passage increased. Gene expression analysis revealed down-regulation of several critical genes in the cultured human embryonic dental epithelial cells with reduced ameloblastic differentiation capability, especially the down-regulation of FGF8 and altered expression pattern of PITX2 isoforms. Our results reveal a correlation of the expression levels of several critical genes with the ameloblastic differentiation capability of epithelial ceils, and provide insight into future generation of bioengineered teeth for tooth replacement therapy.