| While cells attach, spread, migrate, proliferate, and differentiate in three-dimensional (3-D) micromechanical environments, the mechanical factors of these environments influence the shapes, sizes, and adhesion forces of the cells. The mechanical factors may include the stress of the substrate, the shape and size of the substrate, and the curvature of the substrate, etc. The effects of substrate stiffness on cell behaviors have been extensively studied; however, the effects of substrate curvature are not well-documented. In the 3-D micromechanical environments, the surface curvature is a fundamental parameter to describe the geometry of the substrate on which a cell is growing. The curvature of the surface to which cells adhere can have profound effects on cell behaviors. To reveal these cell mechanobiological responses to substrate curvatures, It is introduced a novel, simple, and flexible class of substrates, polyacrylamide gels embedded with micro glass balls ranging in diameter from 5 pm to 6 mm, to culture cells. The surfaces of the micro glass balls are fundamental geometric features in 3-D micromechanical environments.;NIH-3T3 fibroblasts and adipose-derived human mesenchymal stem cells (hMSCs) were cultured on these glass ball embedded gels. Morphologies of cells growing on glass balls were analyzed by using an optical microscope and a 3-D confocal laser scanning microscope. Differentiations of stem cells growing on the glass balls were analyzed by using real time quantitative polymerase chain reaction (RT-qPCR).;The curvature of the surface to which a cell adhere has profound effects on cell attachment and morphology. Cell spreading behavior responded to the local stiffness effect induced by the embedded glass balls in the gels. Experiments showed that the cells did not spread on a st gel but wrapped over the small glass balls, and the cells spread on a soft gel by attaching to the two small separate glass balls. It was observed that the fibroblasts and hMSCs were sensitive to the curvatures of the glass balls. Significant differences in cell attachment rates, migration speeds, morphologies, and differentiations were noted depending on the diameters of the micro glass balls. To the best of our knowledge, this is the first experimental attempt to study cell responses to spherically-shaped substrates. These cell culture experiments imply that this class of substrates, micro glass ball embedded gels, can be useful tools to study cell mechanobiological responses to substrate curvatures and its applications in 3-D cellular bioengineering and mechanobiology. |
