Choudhary Meenakshi, Zhang Xin, Stojkovic Petra, Hyslop Louise, Anyfantis George, Herbert Mary, Murdoch Alison P, Stojkovic Miodrag, Lako Majlinda
North East Institute for Stem Cell Research and Institute of Human Genetics, University of Newcastle, International Centre for Life, Newcastle, United Kingdom.
Stem Cells. 2007 Dec;25(12):3045-57. doi: 10.1634/stemcells.2007-0296. Epub 2007 Sep 13.
Human embryonic stem cells (hESC) promise tremendous potential as a developmental and cell therapeutic tool. The combined effort of stimulatory and inhibitory signals regulating gene expression, which drives the tissue differentiation and morphogenetic processes during early embryogenesis, is still very poorly understood. With the scarcity of availability of human embryos for research, hESC can be used as an alternative source to study the early human embryogenesis. Hyaluronan (HA), a simple hydrating sugar, is present abundantly in the female reproductive tract during fertilization, embryo growth, and implantation and plays an important role in early development of the mammalian embryo. HA and its binding protein RHAMM regulate various cellular and hydrodynamic processes from cell migration, proliferation, and signaling to regulation of gene expression, cell differentiation, morphogenesis, and metastasis via both extracellular and intracellular pathways. In this study, we show for the first time that HA synthase gene HAS2 and its binding receptor RHAMM are differentially expressed during all stages of preimplantation human embryos and hESC. RHAMM expression is significantly downregulated during differentiation of hESC, in contrast to HAS2, which is significantly upregulated. Most importantly, RHAMM knockdown results in downregulation of several pluripotency markers in hESC, induction of early extraembryonic lineages, loss of cell viability, and changes in hESC cycle. These data therefore highlight an important role for RHAMM in maintenance of hESC pluripotency, viability, and cell cycle control. Interestingly, HAS2 knockdown results in suppression of hESC differentiation without affecting hESC pluripotency. This suggests an intrinsic role for HAS2 in hESC differentiation process. In accordance with this, addition of exogenous HA to the differentiation medium enhances hESC differentiation to mesodermal and cardiac lineages. Disclosure of potential conflicts of interest is found at the end of this article.
人类胚胎干细胞（hESC）作为一种发育和细胞治疗工具具有巨大潜力。在早期胚胎发育过程中，调节基因表达的刺激信号和抑制信号共同作用驱动组织分化和形态发生过程，但目前对此仍知之甚少。由于用于研究的人类胚胎数量稀少，hESC可作为研究早期人类胚胎发育的替代来源。透明质酸（HA）是一种简单的保湿糖，在受精、胚胎生长和着床期间大量存在于女性生殖道中，在哺乳动物胚胎的早期发育中发挥重要作用。HA及其结合蛋白RHAMM通过细胞外和细胞内途径调节从细胞迁移、增殖、信号传导到基因表达调控、细胞分化、形态发生和转移等各种细胞和流体动力学过程。在本研究中，我们首次表明，HA合酶基因HAS2及其结合受体RHAMM在植入前人类胚胎和hESC的所有阶段均有差异表达。与显著上调的HAS2相反，在hESC分化过程中，RHAMM表达显著下调。最重要的是，敲低RHAMM会导致hESC中几种多能性标志物的下调、早期胚外谱系的诱导、细胞活力的丧失以及hESC周期的改变。因此，这些数据突出了RHAMM在维持hESC多能性、活力和细胞周期控制中的重要作用。有趣的是，敲低HAS2会抑制hESC分化，而不影响hESC的多能性。这表明HAS2在hESC分化过程中具有内在作用。与此一致的是，在分化培养基中添加外源性HA可增强hESC向中胚层和心脏谱系的分化。潜在利益冲突披露见本文末尾。
