Abstract

Stem cell culture has been characterised using soluble signals on tissue culture plastic, providing a biochemical foundation for self-renewal and differentiation. Nonetheless, most previous stem cell research has overlooked the role of the extracellular matrix (ECM) and mechanical signalling, despite increasing evidence that they both mediate self-renewal and differentiation. To investigate the role of ECM and mechanical signalling, we have developed a novel hydrogel protocol that can be mechanically tuned, ranging from embryo stiffness to skeletal stiffness, while maintaining control of ECM density. We can now present any combination of ECM molecules to cells with independent control over matrix density and stiffness. With our hydrogels, we have explored mechanical and ECM signaling in pluripotent stem cells and oligodendrocyte progenitor cells (OPCs). We have shown, in both mouse and human, that we can maintain optimal naïve pluripotency using soft substrates with high ECM density, while stiff substrates with identical ECM density drives differences in the actuation of growth factor signaling pathways that drive heterogeneity and differentiation. We have also shown that we can reverse the loss of function associated with ageing and neurodegeneration in OPCs using soft substrates with high ECM density. We will present a number of functional studies and a quantitative analysis of RNA sequencing datasets to support the conclusion that mechanics is an essential regulator of stem cell identity. Ultimately, I will advance the hypothesis that mechanical sensing acts as a switch to modulate growth factor signaling to support either self-renewal or differentiation in stem cells.