Force-induced fibronectin fibrillogenesis in vitro

Polymerization of fibronectin (FN) and its assembly into fibers, in vitro, is a two-step self-assembly process, initiated by the formation of a stable FN sheet made of globular particles at the air-liquid interface, and followed by shear-force driven fibrillogenesis along a superhydrophobic surface made of elastic micropillars. The initially-formed fibrils, displaying rough'' surfaces with globular subdomains, can be further stretched into smooth'' fibers with a characteristic diameter of 14 nm. Using high-resolution scanning electron microscopy, we demonstrated that the fibers formed in vitro are highly similar to an FN matrix produced by cultured fibroblasts. Furthermore, we showed that the stretched FN fibrils can support cell adhesion, and display antigenic epitopes which appear to be sequestered in the relaxed molecules. These findings suggest that cells are able to mechanically fine-tune the biological activity of the underlying matrix by modulating its structure, surface properties and organization.