Nano-scale control of cellular environment to drive embryonic stem cells selfrenewal and fate.

Embryonic stem cells (ESC) are pluripotent cells capable to give rise to any embryonic cell lineage. In culture, these cells form colonies creating their own niche. Depending upon the molecular and physico-chemical environment, the pluripotent cells oscillate between two metastable states of pluripotency either reminiscent of the inner cell mass of the embryo or the epiblast, a stage of development which give rise to the three embryonic layers, ectoderm, endoderm and mesoderm. Herein, we used PLL/HA nanofilms cross-linked to various degrees to modulate the nanoenvironment of ESCs. Adhesion of ESC on nanofilms increased from native films to highly cross-linked films. The adhesion process was associated with cell proliferation. Expression of genes markers of the ICM decreased with adhesion of cells to cross-linked films. In parallel, genes more reminiscent of the epiblast, were turned on. ESC differentiation within embryoid bodies further revealed that cell pluripotency was better retained when cells did not adhere on native films. We further report that both the stiffness and the chemistry of nanofilms play a key role in modulating the niche of ESC and in turn govern their selfrenewal and fate. (c) 2009 Elsevier Ltd. All rights reserved.