Extracellular Matrix Proteins are Necessary for Mouse Embryonic Stem Cell Differentiation and May Guide Stem Cell Fate

Abstract

While in vitro differentiation protocols often rely exclusively on soluble growth factors to direct mouse embryonic stem cell (mESC) fate, the ESC niche contains both soluble factors and fibrillar extracellular matrix (ECM) proteins, including fibronectin (FN). Moreover, some of the soluble factors used to guide differentiation (e.g. Activin A) are known to increase the expression of ECM proteins, though the functional importance of this change is not well understood. We examined whether ECM proteins were necessary for promoting and directing mESC differentiation. mESCs, grown as embryoid bodies under differentiating conditions in the absence of FN, maintained expression of the pluripotency marker, Nanog. The embryoid bodies also showed a spatiotemporal correlation between expression of FN and GATA4, a marker for differentiation. When differentiated on a gelatin substrate, mESCs create a fibrillar ECM containing fibronectin and laminin components, while the presence of leukemia inhibitory factor (LIF), a maintainer of mESC pluripotency, inhibits the production of this fibrillar matrix. Ongoing work is investigating how the composition of this cell-derived ECM changes when soluble growth factors are used to guide ESC fate and whether these changes are necessary to efficiently direct differentiation. Together these data imply that FN is necessary for mESC differentiation and that the extracellular matrix may be an important director of stem cell fate.