Nature子刊两项iPS技术突破或成iPS转折点

　　

2007年，美国和日本科学家发现，应用人和鼠的正常皮肤细胞，导入KLF4、OCT4、SOX2和C-MYC四种基因，即可由正常体细胞转化成多能干细胞。这种基因诱导而产生的多能干细胞称为诱导多能干细胞(iPs).除了皮肤细胞，其他体细胞也可以产生iPS。

 

可以说多能干细胞研究和应用将会成为21世纪最伟大的医学生物学成就之一。然而，iPS从研究理论走向临床应用还有很艰难的路要走。现阶段，iPS临床应用所遭遇的瓶颈是：1.诱导转化成iPS的效率过低。2. C-MYC 和KLF4两基因具有致癌性。iPS所面临的这两个问题是制约iPS临床应用的最大问题。

 

近期在Nature Biotechnology上两篇文章，一一破解两个阻碍iPS走向临床应用的问题。成为iPS技术成功走向临床应用的基石。

 

诱导效率提高100倍

详细报道请参见：Nature子刊：iPS重大突破 诱导效率提升100倍

 

iPS技术最初的诱导效率只有1/1000，这个最大的弱点为制备大量的iPS细胞带来困难。

 

来自西班牙的研究者从一根头发上分离人类角质化细胞，再通过慢病毒载体将4个转录银子基因，即Oct4、Sox2，c-Myc和Klf4导入角质化细胞中。经过基因重排，将角质化细胞转化成具有多能性的干细胞样细胞（iPS）。所生产的角质化细胞源的iPS细胞称为KiPS，这些KiPS细胞与人类胚胎干细胞没有明显的差异，具有典型的干细胞样特征。

 

研究者对小鼠的成纤维细胞、干细胞和肠细胞，以及人类的角质化细胞进行iPS生产实验，研究发现人类角质化细胞生产iPS的效率明显高于其他类型的细胞生产的效率（高100倍），至今角质化细胞诱导效率如此高的机理仍旧不明。

 

Efficient and rapid generation of induced pluripotent stem cells from human keratinocytes

 

【Abstract】

The utility of induced pluripotent stem (iPS) cells for investigating the molecular logic of pluripotency and for eventual clinical application is limited by the low efficiency of current methods for reprogramming. Here we show that reprogramming of juvenile human primary keratinocytes by retroviral transduction with OCT4, SOX2, KLF4 and c-MYC is at least 100-fold more efficient and twofold faster compared with reprogramming of human fibroblasts. Keratinocyte-derived iPS (KiPS) cells appear indistinguishable from human embryonic stem cells in colony morphology, growth properties, expression of pluripotency-associated transcription factors and surface markers, global gene expression profiles and differentiation potential in vitro and in vivo. To underscore the efficiency and practicability of this technology, we generated KiPS cells from single adult human hairs. Our findings provide an experimental model for investigating the bases of cellular reprogramming and highlight potential advantages of using keratinocytes to generate patient-specific iPS cells.

 

 

突破致癌障碍

详细报道请参见：Nature子刊： iPS革新技术突破致癌障碍 安全iPS指日可待

 

哈佛大学干细胞研究所的科学家们使用一种化学因子丙戊酸（valproic acid ，VPA）取代KLF4和C-MYC基因，VPA是一种组蛋白脱乙酰基酶的抑制剂，用VPA联合OCT4和SOX2基因可促进人类初级成纤维细胞基因重排，进而转化成具有胚胎干细胞样特征的多能干细胞。

 

研究者称，使用该化学方法可制备安全的iPS，为临床应用打下坚实的基础。

 

Induction of pluripotent stem cells from primary human fibroblasts with only Oct4 and Sox2

【Abstract】

Ectopic expression of defined sets of genetic factors can reprogram somatic cells to induced pluripotent stem (iPS) cells that closely resemble embryonic stem (ES) cells. The low efficiency with which iPS cells are derived hinders studies on the molecular mechanism of reprogramming, and integration of viral transgenes, in particular the oncogenes c-Myc and Klf4, may handicap this method for human therapeutic applications. Here we report that valproic acid (VPA), a histone deacetylase inhibitor, enables reprogramming of primary human fibroblasts with only two factors, Oct4 and Sox2, without the need for the oncogenes c-Myc or Klf4. The two factor–induced human iPS cells resemble human ES cells in pluripotency, global gene expression profiles and epigenetic states. These results support the possibility of reprogramming through purely chemical means, which would make therapeutic use of reprogrammed cells safer and more practical.