Final answer:
Mesenchymal stem cells grown on a very stiff substrate typically differentiate into muscle cells or osteoblasts, as the substrate's rigidity influences the cells' cytoskeleton organization and mechanical properties, affecting gene expression and cell function.
Step-by-step explanation:
When mesenchymal stem cells are grown on a very stiff substrate, they have been found to develop into cell types that reflect the mechanical properties of their environment. Research has shown that there is a mechanical coupling between the cell shape, the rigidity of the surroundings, and the organization of stress fiber in the cytoskeleton of stem cells. Specifically, for substrates around 10kPa in rigidity, stress-fiber polarization is maximized, which is conducive to the differentiation of stem cells into muscle cells.
This process is thought to influence gene expression relevant for muscle-like cells due to the contractile forces of the cells' cytoskeleton. Additionally, cells cultured on stiffer substrates become mechanically responsive in a different manner, as previous experiments have also shown the potential for mesenchymal stem cells to differentiate into osteoblasts, which are bone-forming cells. The overall substrate rigidity plays a critical role in determining what specialized cell types mesenchymal stem cells will become.