Engineering integrin signaling for promoting embryonic stem cell self-renewal in a precisely defined niche

We present development and use of a 3D synthetic extracellular matrix (ECM) analog with integrin-specific adhesion ligands to characterize the microenvironmental influences in embryonic stem cell (ESC) self-renewal. Transcriptional analysis of 24 integrin subunits followed by confirmation at the translational and functional levels suggested that integrins α₅β₁, α_vβ₅, α₆β₁ and α₉β₁ play important roles in maintenance of stemness in undifferentiated mouse ESCs. Using the well-defined matrix as a tool to activate integrins α₅β₁ plus α_vβ₅, α₆β₁ and α₉β₁, individually and in combination, differential integrin activation was demonstrated to exert exquisite control over ESC fate decisions. Simultaneous ligation of these four integrin heterodimers promoted self-renewal, as evidence by prolonged SSEA-1, Oct4 and Nanog expression, and induced Akt1 kinase signaling along with translational regulation of other stemness-related genes. The biofunctional network we have designed based on this knowledge may be useful as a defined niche for regulating ESC pluripotency through selective cell-matrix interactions, and the method we present may be more generally useful for probing matrix interactions in stem cell self-renewal and differentiation.