Krtolica Ana, Genbacev Olga, Escobedo Carmen, Zdravkovic Tamara, Nordstrom Adam, Vabuena Diana, Nath Aneel, Simon Carlos, Mostov Keith, Fisher Susan J
Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California 94143, USA.
Stem Cells. 2007 Sep;25(9):2215-23. doi: 10.1634/stemcells.2007-0230. Epub 2007 Jun 14.
During murine development, the formation of tight junctions and acquisition of polarity are associated with allocation of the blastomeres on the outer surface of the embryo to the trophoblast lineage, whereas the absence of polarization directs cells to the inner cell mass. Here, we report the results of ultrastructural analyses that suggest a similar link between polarization and cell fate in human embryos. In contrast, the five human embryonic stem cell (hESC) lines displayed apical-basal, epithelial-type polarity with electron-dense tight junctions, apical microvilli, and asymmetric distribution of organelles. Consistent with these findings, molecules that are components of tight junctions or play regulatory roles in polarization localized to the apical regions of the hESCs at sites of cell-cell contact. The tight junctions were functional, as shown by the ability of hESC colonies to exclude the pericellular passage of a biotin compound. Depolarization of hESCs produced multilayered aggregates of rapidly proliferating cells that continued to express transcription factors that are required for pluripotency at the same level as control cells. However, during embryoid body formation, depolarized cells differentiated predominantly along mesenchymal lineage and spontaneously produced hematoendothelial precursors more efficiently than control ESC. Our findings have numerous implications with regard to strategies for deriving, propagating, and differentiating hESC.
在小鼠发育过程中，紧密连接的形成和极性的获得与胚胎外表面的卵裂球向滋养层谱系的分配相关，而极性的缺失则引导细胞进入内细胞团。在此，我们报告了超微结构分析的结果，这些结果表明人类胚胎中极性与细胞命运之间存在类似的联系。相反，五条人类胚胎干细胞（hESC）系表现出顶-基、上皮型极性，具有电子致密的紧密连接、顶端微绒毛和细胞器的不对称分布。与这些发现一致，作为紧密连接成分或在极性中起调节作用的分子定位于细胞-细胞接触位点处hESC的顶端区域。紧密连接是有功能的，hESC集落能够排除生物素化合物的细胞周质通过即证明了这一点。hESC的去极化产生了快速增殖细胞的多层聚集体，这些细胞继续以与对照细胞相同的水平表达多能性所需的转录因子。然而，在胚状体形成过程中，去极化细胞主要沿间充质谱系分化，并且比对照ESC更有效地自发产生造血内皮前体。我们的发现对于hESC的衍生、增殖和分化策略具有诸多意义。
