Relationship between Adsorbed Fibronectin and Cell Adhesion on a Honeycomb-patterned Film

Abstract

Patterned surface topographies play vital roles in cellular response such as adhesion, proliferation, and differentiation. Here, we characterized adsorption of fibronectin (Fn) as a typical cell adhesion protein onto honeycomb-patterned porous films (“honeycomb film”) of poly (ε-caprolactone) (PCL) incubated in a Fn phosphate-buffered saline (PBS) solution by using atomic force microscopy (AFM) and confocal laser scanning microscopy (CLSM). In order to determine how cells respond to a honeycomb film, focal adhesion of porcine aortic endothelial cells (PAECs) cultured on the Fn coated honeycomb films in a serum free medium were characterized by using immunofluorescencet labeling of vinculin and focal adhesion kinase autophosphorylated at the tyrosine residue 397 (pY 397 FAK). Fn adsorbed around the pore periphery of a honeycomb film to form fibriller aggregates in a ring-shape structure. The sites of pY 397 FAK and vinculin were overlapped and agreed well with the adsorption site of Fn fibrils. This demonstrated that PAECs adhered onto the honeycomb films at focal contact points localized around pore periphery. The expression of pY397FAK determined by an immunoprecipitation method was 3 times higher than that on a PCL flat film as a reference. These results imply that the signaling mediated by a integrin receptor-Fn binding were activated on honeycomb films and this type of signaling was activated effectively on a honeycomb film compared with on a flat film. The cell response to honeycomb films (adhesion pattern and phosphorilation of FAK) was supposed to originate from the regularly arraigned adsorption pattern of Fn determined by the pore structure of the film.