Shape-engineered fibroblasts: cell elasticity and actin cytoskeletal features characterized by fluorescence and...

The regulation of cell shape, which determines cell behaviors including adhesion, spreading, migration, and proliferation in an engineered artificial extracellular milieu, is an important task in tissue engineering and in development of functional biomaterials. To deepen the understandings of shape-dependent cell mechanics, the cell elasticity and structural features of the actin cytoskeleton (CSK) were characterized for shape-engineered fibroblasts; round and spindle-shaped cells cultured on photolithographically microprocessed surfaces, employing the cellular microindentation tests and fluorescence observation of actin CSK by the combination of atomic force microscopy (AFM) and fluorescence microscopy (FM). The relationships among cell elasticity, the structural features of actin CSK, and engineered cell shape were analyzed and compared with those of control cells that had been cultured on nonprocessed surfaces (termed naturally extended cells). Results showed that the spindle-shaped cells with sparse or no apical stress fibers (ASFs) exhibited similar stiffness to that of the naturally extended cells with dense ASFs. The elasticity of spindle-shaped cells was affected only slightly by the stress fiber (SF) density, which is in marked contrast to the significant correlation shown between cell elasticity and SF density in naturally extended cells. This result implies that the elasticity of regionally restricted adhesion-surface-induced shape-engineered cells, particularly of highly elongated cells, is affected predominantly by cell shape rather than by structural features of SFs.