抑制体细胞衰老促进诱导性多潜能干细胞(iPSC)生成的研究进展

Studies of Improved Efficiency of Induced Pluripotent Stem Cell Generation by Restraining Somatic Cell Senescence

诱导性多潜能干细胞(induced pluripotent stem cell,i PSC)是指对体细胞实施特定的诱导方法,将体细胞重编程获得的多潜能干细胞。最常用的诱导方法是利用基因导入技术,将与胚胎干细胞(embryonic stem cell,ESC)多潜能性相关基因的转录因子导入体细胞,激活内源多能性基因的表达,实现体细胞重编程。除转基因外,使用某些小分子物质或蛋白质等也可以实现体细胞重编程。i PSC与ESC在形态学、表观遗传学和分化能力上高度相似。由于i PSC来源于普通成体细胞,避免了胚胎干细胞面临的伦理道德和免疫排斥问题,使得这一技术在再生医学和畜牧生产上都具有广阔的应用前景。然而,i PSC的低生成率和高风险性逐渐成为制约该技术发展的主要障碍。生成效率和速率低,大大增加了获得i PSC的难度,工作量大且成本高;高风险性使i PSC无法安全应用于再生医学和生产转基因动物。这成为i PSC科研工作者亟待解决的两大问题。文章介绍了通过抑制体细胞衰老来促进i PSC生成的相关研究进展。该方法对体细胞重编程有显著效果,但同时也存在较大的安全性争议。控制细胞衰老凋亡的Ink4a/Arf位点,p53、p RB、p21等基因和蛋白因子可以及时清除体内损伤细胞,促进细胞衰老凋亡,抑制细胞癌变,组成了维护机体健康的重要调控通路。近年研究表明,抑制促细胞衰老凋亡基因的表达可显著提高i PSC生成的效率和速率,说明肿瘤发生和i PSC生成存在某些相同的调控通路。抑制体细胞衰老的方法主要有3类:改进培养液成分、使用新的转录因子和调节细胞培养环境。通过抑制体细胞衰老,最高可将小鼠i PSC生成效率提高到100%。这为高效获得i PSC,探索i PSC及肿瘤的生成机制提供了新思路。同时,此方法存在较大安全性问题。i PSC最初是由Oct4,Sox2,Klf4,c-Myc等4种转录因子诱导而来,这些因子本身都存在致癌风险。抑癌基因的失活使获得的i PSC致癌风险增大,成为制约该方法广泛应用的最主要障碍。文章概括了2008年以来通过抑制体细胞衰老促进i PSC生成的研究进展、存在问题和应用前景。

Induced pluripotent stem cell（i PSC） refers to reprogrammed somatic cells with some specific induction methods. The most common induction method is transmitting embryonic stem cell（ESC）-related transfactors into somatic cell, to activate endogenous pluripotent genes. Up to now, except transgene technology, some small molecular substances or proteins can also realize somatic reprogram. i PSC is remarkably similar to ESC in morphology, epigenetics and differentiation ability. Because the resources of i PSC are ordinary somatic cells, i PSC technology avoids the defects of ESC in morals and immunological rejection. As a result, i PSC has an expansive prospect both in regenerative medicine and animal production. However, the existing problems like low efficiency and high risk are key barriers which limit its development. Low-efficiency greatly increases the difficulty to achieve enough i PSC, it＇s time and cost-consuming. While the high-risk blocks its application in regenerative medicine and transgenic animal. These are two urgent problems in i PSC which need to be solved by researchers. A most efficient but also a high-risky method was described in this review-improving i PSC generation by restraining somatic cell senescence. This method can remarkably improve i PSC generation efficiency, while it＇s also high-risk. The locus, genes and protein factors such as Ink4a/Arf, p53, p RB and p21 in charge of eliminating injured cells in body, promote cell senescence and apoptosis to prevent cancerization, which compose the important regulatory pathways in organism. Recent studies showed that silence of these genes and pathways can improve the efficiency and speed of i PSC generation, which means the generation of i PSC and tumor may use some common regulatory pathways. There are three category methods to restrain somatic cell senescence, including ameliorating i PSC culture media, employing new transgenes and regulating culture environment. Mouse i PSC generation efficiency even can be improved to 100% by this way. These results provide a new method in efficiently obtaining i PSC and researching the generation mechanism of i PSC and tumor. At the same time, this method has to face the serious security problems. i PSC is firstly reprogrammed by four canon transgenes, Oct4, Sox2, Klf4 and c-Myc, these are oncogenic transfactors in some degrees. The silence of cancer suppressor genes will improve the cancer risk of i PSC, which becomes the most serious barrier for clinical replication of this method. This paper given an outline of studies on restraining cell senescence to improve i PSC generation efficiency, including the research progress, existing defects solutions and application prospect.