Palma C S, Tannous M A, Malta T M, Russo E M S, Covas D T, Picanço-Castro V
Instituto Nacional de Ciência e Tecnologia em Células-Tronco e Terapia Celular, Hemocentro de Ribeirão Preto, Ribeirão Preto, SP, Brasil.
Genet Mol Res. 2013 Apr 2;12(2):1054-60. doi: 10.4238/2013.April.2.22.
Genetic reprogramming of adult cells to generate induced pluripotent stem (iPS) cells is a new and important step in sidestepping some of the ethical issues and risks involved in the use of embryonic stem cells. iPS cells can be generated by introduction of transcription factors, such as OCT4, SOX2, KLF4, and CMYC. iPS cells resemble embryonic stem cells in their properties and differentiation potential. The mechanisms that lead to induced pluripotency and the effect of each transcription factor are not completely understood. We performed a critical evaluation of the effect of overexpressing OCT4 in mesenchymal stem cells and fibroblasts and found that OCT4 can activate the expression of other stemness genes, such as SOX2, NANOG, CMYC, FOXD3, KLF4, and βCATENIN, which are not normally or are very weakly expressed in mesenchymal stem cells. Transient expression of OCT4 was also performed to evaluate whether these genes are affected by its overexpression in the first 48 h. Transfected fibroblast cells expressed around 275-fold more OCT4 than non-transfected cells. In transient expression, in which cells were analyzed after 48 h, we detected only the up-regulation of FOXD3, SOX2, and KLF4 genes, suggesting that these genes are the earlier targets of OCT4 in this cellular type. We conclude that forced expression of OCT4 can alter cell status and activate the pluripotent network. Knowledge gained through study of these systems may help us to understand the kinetics and mechanism of cell reprogramming.
将成体细胞进行基因重编程以生成诱导多能干细胞（iPS细胞），是在规避使用胚胎干细胞所涉及的一些伦理问题和风险方面迈出的重要新步伐。通过导入转录因子，如OCT4、SOX2、KLF4和CMYC，可生成iPS细胞。iPS细胞在特性和分化潜能方面类似于胚胎干细胞。导致诱导多能性的机制以及每个转录因子的作用尚未完全明了。我们对在间充质干细胞和成纤维细胞中过表达OCT4的效果进行了批判性评估，发现OCT4可激活其他干性基因的表达，如SOX2、NANOG、CMYC、FOXD3、KLF4和β连环蛋白，这些基因在间充质干细胞中通常不表达或表达非常微弱。还进行了OCT4的瞬时表达，以评估这些基因在最初48小时内是否受其过表达的影响。转染的成纤维细胞表达的OCT4比未转染的细胞多约275倍。在48小时后对细胞进行分析的瞬时表达中，我们仅检测到FOXD3、SOX2和KLF4基因的上调，这表明这些基因是OCT4在这种细胞类型中的早期靶点。我们得出结论，OCT4的强制表达可改变细胞状态并激活多能网络。通过对这些系统的研究获得的知识可能有助于我们理解细胞重编程的动力学和机制。
