The physical microenvironment regulates embryonic stem cells

The hypothesis is that physical properties of the microenvironment regulate mouse embryonic stem cells. Microtopographic features were fabricated by photolithography to create projections of varying heights and with different spacing on poly-dimethyl-silicone membranes. When stem cells were plated on the membranes, it was observed that proliferation of both embryonic stem cells and their cardiomyocyte progeny was attenuated when attached to the three dimensional projections. It was also observed that the projections needed to be a certain height to have this effect as lower projections did not blunt proliferation. Using pharmacological interventions, it was determined that stress fiber formation in the third dimension is responsible for the attenuation of proliferation as inhibiting stress fiber formation eliminated any decrease in proliferation caused by the projections. It was also determined that the projections did not induce differentiation of the embryonic stem cells away from their pluripotent phenotype. Furthermore, cardiomyocyte progeny derived from the stem cells showed a high degree of variation in beating rates compared to those cultured on flat membranes. Results suggest that microtopography affects both expansion and beating characteristics of mouse embryonic stem cells and their progeny.