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Substrate elasticity dependent colony formation and cardiac differentiation of human induced pluripotent stem cells

Substrate elasticity regulates cell functions including cell aggregation and stem cell differentiation. The ability to manufacture substrates of desired elasticity over a broad range is therefore crucial for both fundamental research and advanced applications. In this work, we developed a method to fabricate dense elastomer pillars of different heights on a rigid substrate, providing an effective elasticity ranging from 3 to 168 kPa. Assisted with an elastomer stencil of honeycomb pattern for cell seeding, we obtained uniform colonies of human induced pluripotent stem cells (hiPSCs) and differentiated cardiomyocytes on the pillar substrates of different modulus. Our results showed that the elasticity of substrates significantly affected the cell colony formation via governing the colony edge propagation. More importantly, the results demonstrated that an intermediate substrate elasticity of about 9 kPa is preferable to reach an embryoid-like aggregation and optimal for cardiac differentiation of hiPSCs. Overall, this work sheds new insights on the importance of substrate modulus on cell aggregation and stem cell differentiation as well as the manufacturing of culture substrates with desired elasticity.