Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5S 3G9, Canada.
Integr Biol (Camb). 2012 Nov;4(11):1367-76. doi: 10.1039/c2ib20098h.
Embryonic stem cells (ESC) and epiblast stem cells (EpiSC) are distinct pluripotent stem cell states that require different signaling pathways for their self-renewal. Forward transitions between ESC and EpiSC can be accomplished by changing culture conditions; however reverse transitions between EpiSC and ESC are rare events that require transgene insertion or culture on feeders. We demonstrate that transgene-free reversion of EpiSCs to ESCs can be enhanced by local microenvironmental control and the subsequent reactivation of dormant LIF-STAT3 signaling. Reactivation of LIF responsiveness occurs in regions of colony constraint (high local cell density) typical of culture on feeders, a condition that can be recapitulated using micropatterned (μP) colonies under defined conditions. This increased LIF responsiveness results in a subsequent increase in the frequency of EpiSC reversion. Importantly, the resulting revertant EpiSCs are functionally indistinguishable from naïve mESC. Our findings demonstrate that signaling pathway activation and repression create barriers to cell fate transitions that can be overcome by microenvironmental control.
胚胎干细胞（ESC）和上胚层干细胞（EpiSC）是两种不同的多能干细胞状态，它们的自我更新需要不同的信号通路。ESC 和 EpiSC 之间的正向转变可以通过改变培养条件来实现；然而，EpiSC 和 ESC 之间的反向转变是罕见的事件，需要转基因插入或饲养细胞培养。我们证明，通过局部微环境控制和随后重新激活休眠的 LIF-STAT3 信号，可以增强无转基因的 EpiSC 向 ESC 的逆转。在类似于饲养细胞培养的条件下（高局部细胞密度），在集落约束区域（高局部细胞密度）中会重新激活 LIF 反应性，这种条件可以使用微图案化（μP）集落在定义的条件下重现。这种增加的 LIF 反应性导致 EpiSC 逆转的频率随后增加。重要的是，由此产生的逆转 EpiSC 在功能上与幼稚 mESC 无法区分。我们的研究结果表明，信号通路的激活和抑制会在细胞命运转变中形成障碍，而微环境控制可以克服这些障碍。
