Effect of topological cues on material-driven fibronectin fibrillogenesis and cell differentiation

Fibronectin (FN) assembles into fibrillar networks by cells through an integrin-dependent mechanism. We have recently shown that simple FN adsorption onto poly(ethyl acrylate) surfaces (PEA), but not control polymer (poly(methyl acrylate), PMA), also triggered FN organization into a physiological fibrillar network. FN fibrils exhibited enhanced biological activities in terms of myogenic differentiation compared to individual FN molecules. In the present study, we investigate the influence of topological cues on the material-driven FN assembly and the myogenic differentiation process. Aligned and random electrospun fibers were prepared. While FN fibrils assembled on the PEA fibers as they do on the smooth surface, the characteristic distribution of globular FN molecules observed on flat PMA transformed into non-connected FN fibrils on electrospun PMA, which significantly enhanced cell differentiation. The direct relationship between the fibrillar organization of FN at the material interface and the myogenic process was further assessed by preparing FN gradients on smooth PEA and PMA films. Isolated FN molecules observed at one edge of the substrate gradually interconnected with each other, eventually forming a fully developed network of FN fibrils on PEA. In contrast, FN adopted a globular-like conformation along the entire length of the PMA surface, and the FN gradient consisted only of increased density of adsorbed FN. Correspondingly, the percentage of differentiated cells increased monotonically along the FN gradient on PEA but not on PMA. This work demonstrates an interplay between material chemistry and topology in modulating material-driven FN fibrillogenesis and cell differentiation.