：由精原干细胞培养得到的类胚胎干细胞系
（图片来源：上海交大冯立新教授）
精原干细胞(SSCs)是干细胞临床应用的理想材料，通过研究发现，精原干细胞在体外培养过程中会有一部分细胞自主变成类似胚胎干细胞的一种细胞。但是自主转化的时间周期较长，通常需要几个月时间，而且转化率非常低，通过病毒载体转染后虽然增加了转化效率但是引入外源基因会造成临床应用潜在危险。伊利诺伊大学研究人员最近研究发现精原干细胞可通过诱导直接转化成各种终端细胞，转化过程中不需要添加外源基因。
在最新研究中，研究人员巧妙运用上皮组织细胞和细胞间质诱导精原干细胞成为各种终端细胞。上皮组织中存在很多腺体，可分泌大量酶和激素及其他细胞生长因子。20世纪50年代科学家就已经发现上皮组织对其所在器官的细胞生长分化起到巨大作用，上皮细胞通过分泌行为可诱导细胞分化成不同形态和功能的终端细胞。
伊利诺伊大学研究人员将精原干细胞与前列腺上皮组织细胞混合移植到小鼠体内时，精原干细胞转化为前列腺细胞；当精原干细胞与皮肤上皮组织细胞混合移植到小鼠体内时，精原干细胞转化为皮肤细胞；将精原干细胞与子宫上皮细胞混合移植到小鼠体内时，精原干细胞也转化成子宫细胞。通过用荧光蛋白标记表明转化为各种终端细胞的的确为精原干细胞。
研究人员表示这项技术有望代替胚胎干细胞广泛应用于临床及再生医学领域，避免了胚胎干细胞来源和伦理问题及iPS细胞的安全性问题。（生物谷Bioon.com）
生物谷推荐原始出处：
Stem Cells Vol. 27 No. 7 July 2009, pp. 1666 -1675 doi:10.1002/stem.93
Direct Transdifferentiation of Stem/Progenitor Spermatogonia Into Reproductive and Nonreproductive Tissues of All Germ Layers
Liz Simona, Gail C. Ekmana, Natalia Kosterevaa, Zhen Zhanga, Rex A. Hessa, Marie-Claude Hofmanna,b, Paul S. Cookea,c
aDepartment of Veterinary Biosciences,University of Illinois, Urbana, Illinois, USA
bInstitute for Genomic Biology, and University of Illinois, Urbana, Illinois, USA
cDivision of Nutritional Sciences, University of Illinois, Urbana, Illinois, USA
Pluripotent stem cells have great clinical potential for tissue regeneration/repair in humans. The use of embryonic stem (ES) cells is ethically controversial, leading to searches for other sources of pluripotent stem cells. Testicular spermatogonial stem cells (SSCs) produce the spermatogenic lineage. Under in vitro conditions, SSCs have the ability to give rise to pluripotent ES-like cells. We hypothesized that stem/progenitor spermatogonia could directly transdifferentiate into different tissue types if they were recombined with inductive mesenchymes from fetal/neonatal organs using a tissue separation/recombination methodology and grown in vivo. Green fluorescent protein transgenic mice were used to track cell lineages. Our results indicate that stem/progenitor spermatogonia recombined with the appropriate mesenchyme can directly transdifferentiate in vivo into tissues of all germ layers, including prostatic, uterine, and skin epithelium. In addition, transdifferentiated tissue expressed molecular, histological, and functional markers of the appropriate epithelium. The ability of stem/progenitor spermatogonia to directly generate various epithelia emphasizes their clinical potential, and if human SSCs have similar properties, this may have applications in human regenerative medicine.
