Nature：从小鼠睾丸中获得多功能干细胞的新方法

生物谷

    美国科学家最近在制备干细胞方面取得了突破性进展，他们诱导小鼠睾丸中的一种精原干细胞SPC(spermatogonial  progenitor  cells)改变其精子发生的发育方向，形成了所谓的“多能成体精原干细胞”(multi-potent  adult  spermatogonial-derived  stem  cells，简称MASCs)。这一成果有望使科学家绕过颇受争议的胚胎干细胞，方便地获得充足的成体干细胞，以便用于组织修复和糖尿病、帕金森症等疾病的治疗。相关论文发表在9月20日的《自然》杂志上。

    在2006年3月，德国科学家在《自然》上报告称，他们能够在很短的数周内将成年鼠睾丸内的部分细胞转变成为“多能成体生殖干细胞”，而且它们十分类似于胚胎干细胞。而新的研究则是为了验证长期培养的高度增殖睾丸细胞能否形成类似的干细胞。

    领导最新研究的美国康奈尔大学Weill医学院的Shahin  Rafii表示，“最新研究真正新颖的地方在于，这些SPCs不需要进行基因操控，就能够形成具有多能性的成体干细胞。”之前的一些研究通过对一些结缔组织细胞进行基因操控，重组出具有干细胞潜能的成体细胞。不过，这种称为“诱导多能性”(induced  pluripotency)的基因重组方法在产生干细胞的同时，也会增加恶性细胞产生的风险。

     在新研究中，论文第一作者、美国霍华德休斯医学院的Marco  Seandel等人利用一个特殊的表达标记GPR125来区分出SPCs，这在此前的研究中是很少有的。同时，研究人员为这些细胞创造了完美的体外生物化学培养环境，包括特别的饲养细胞(feeder  cell)以及生长因子，为的就是让SPCs能够摆脱产生精子的发育方向，向多能性目标前进。

    进一步的研究表明，这些MASCs能够发展成为内皮细胞和组织(比如血管)、心脏细胞以及脑细胞等多种细胞类型。

    当然，该项研究成果要真正实现应用，还需要在人类身上进行类似的实验。Rafii表示，“对于男性而言，新的发现意味着，或许某一天这就是可方便获得的干细胞源。”此外，研究人员认为，他们的方法同样适用于雌性卵巢中的生殖细胞，尽管目前这只是理论上的推测。

    由于世界上其他的实验室尚未重复最新的实验，因此一些科学家仍对新的研究成果持怀疑态度。他们认为，新的成果要能站得住脚，仍需要更多的检验。(科学网  任霄鹏/编译)

原始出处：

Nature 449, 346-350 (20 September 2007) | doi:10.1038/nature06129; Received 1 June 2007; Accepted 27 July 2007

Generation of functional multipotent adult stem cells from GPR125+ germline progenitors

Marco Seandel1,3, Daylon James1, Sergey V. Shmelkov1, Ilaria Falciatori1, Jiyeon Kim1, Sai Chavala1, Douglas S. Scherr2, Fan Zhang1, Richard Torres5, Nicholas W. Gale5, George D. Yancopoulos5, Andrew Murphy5, David M. Valenzuela5, Robin M. Hobbs4,6, Pier Paolo Pandolfi4,6 & Shahin Rafii1

Howard Hughes Medical Institute, Department of Genetic Medicine, and,
Department of Urology, Weill Cornell Medical College, New York 10065, USA
Division of Medical Oncology, Department of Medicine, and,
Cancer Biology and Genetics Program, Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York 10065, USA
Regeneron Pharmaceuticals, Tarrytown, New York 10591, USA
Cancer Genetics Program, Beth Israel Deaconess Cancer Center, Harvard Medical School, Boston, Massachusetts 02115, USA

Correspondence to: Shahin Rafii1 Correspondence and requests for materials should be addressed to S.R. (Email: srafii@med.cornell.edu).

Adult mammalian testis is a source of pluripotent stem cells1. However, the lack of specific surface markers has hampered identification and tracking of the unrecognized subset of germ cells that gives rise to multipotent cells2. Although embryonic-like cells can be derived from adult testis cultures after only several weeks in vitro1, it is not known whether adult self-renewing spermatogonia in long-term culture can generate such stem cells as well. Here, we show that highly proliferative adult spermatogonial progenitor cells (SPCs) can be efficiently obtained by cultivation on mitotically inactivated testicular feeders containing CD34+ stromal cells. SPCs exhibit testicular repopulating activity in vivo and maintain the ability in long-term culture to give rise to multipotent adult spermatogonial-derived stem cells (MASCs). Furthermore, both SPCs and MASCs express GPR125, an orphan adhesion-type G-protein-coupled receptor. In knock-in mice bearing a GPR125– beta -galactosidase (LacZ) fusion protein under control of the native Gpr125 promoter (GPR125–LacZ), expression in the testis was detected exclusively in spermatogonia and not in differentiated germ cells. Primary GPR125–LacZ SPC lines retained GPR125 expression, underwent clonal expansion, maintained the phenotype of germline stem cells, and reconstituted spermatogenesis in busulphan-treated mice. Long-term cultures of GPR125+ SPCs (GSPCs) also converted into GPR125+ MASC colonies. GPR125+ MASCs generated derivatives of the three germ layers and contributed to chimaeric embryos, with concomitant downregulation of GPR125 during differentiation into GPR125- cells. MASCs also differentiated into contractile cardiac tissue in vitro and formed functional blood vessels in vivo. Molecular bookmarking by GPR125 in the adult mouse and, ultimately, in the human testis could enrich for a population of SPCs for derivation of GPR125+ MASCs, which may be employed for genetic manipulation, tissue regeneration and revascularization of ischaemic organs.