Schenke-Layland Katja, Angelis Ekaterini, Rhodes Katrin E, Heydarkhan-Hagvall Sepideh, Mikkola Hanna K, Maclellan W Robb
Cardiovascular Research Laboratory, UCLA School of Medicine, 675 C.E. Young Dr., MRL 3-645, Los Angeles, California 90095-1760, USA.
Stem Cells. 2007 Jun;25(6):1529-38. doi: 10.1634/stemcells.2006-0729. Epub 2007 Mar 15.
The earliest segregation of lineages in the developing embryo is the commitment of cells to the inner cell mass or the trophoectoderm in preimplantation blastocysts. The exogenous signals that control commitment to a particular cell lineage are poorly understood; however, it has been suggested that extracellular "niche" and extracellular matrix, in particular, play an important role in determining the developmental fate of stem cells. Collagen IV (ColIV) has been reported to direct embryonic stem (ES) cell differentiation to mesodermal lineages in both mouse and human ES cells. To define the effects of ColIV on ES cell differentiation and to identify the resulting heterogeneous cell types, we performed microarray analyses and determined global gene expression. We observed that ColIV induced the expression of mesodermal genes specific to hematopoietic, endothelial, and smooth muscle cells and, surprisingly, also a panel of trophoectoderm-restricted markers. This effect was specific to collagen IV, as no trophoblast differentiation was seen on collagen I, laminin, or fibronectin. Stimulation with basic fibroblast growth factor (FGF) or FGF4 increased the number of trophoectodermal cells. These cells were isolated under clonal conditions and successfully differentiated into a variety of trophoblast derivatives. Interestingly, differentiation of ES cells to trophoblastic lineages was only seen in ES cell lines maintained on embryonic feeder layers and was caudal-type homeobox protein 2 (Cdx2)-dependent, consistent with Cdx2's postulated role in trophoectoderm commitment. Our data suggest that, given the appropriate extracellular stimuli, mouse embryonic stem cells can differentiate into trophoectoderm. Disclosure of potential conflicts of interest is found at the end of this article.
发育胚胎中细胞谱系的最早分离是在植入前囊胚期细胞向内细胞团或滋养外胚层的定向分化。目前对控制细胞向特定细胞谱系定向分化的外源性信号了解甚少；然而，有人提出细胞外“生态位”和细胞外基质在决定干细胞的发育命运中尤其发挥着重要作用。据报道，IV型胶原蛋白（ColIV）可引导小鼠和人类胚胎干细胞（ES细胞）分化为中胚层谱系。为了确定ColIV对ES细胞分化的影响并鉴定由此产生的异质性细胞类型，我们进行了微阵列分析并测定了整体基因表达。我们观察到ColIV诱导了造血、内皮和平滑肌细胞特异性的中胚层基因的表达，令人惊讶的是，还诱导了一组滋养外胚层特异性标志物的表达。这种作用是IV型胶原蛋白特有的，因为在I型胶原蛋白、层粘连蛋白或纤连蛋白上未观察到滋养层分化。用碱性成纤维细胞生长因子（FGF）或FGF4刺激可增加滋养外胚层细胞的数量。这些细胞在克隆条件下分离出来，并成功分化为多种滋养层衍生物。有趣的是，ES细胞向滋养层谱系的分化仅在维持于胚胎饲养层上的ES细胞系中可见，并且依赖于尾型同源盒蛋白2（Cdx2），这与Cdx2在滋养外胚层定向分化中假定的作用一致。我们的数据表明，在适当的细胞外刺激下，小鼠胚胎干细胞可以分化为滋养外胚层。潜在利益冲突的披露见本文末尾。
