Fibroblast spreading and proliferation on hydrophilic and hydrophobic surfaces is related to tyrosine phosphorylation in focal contacts

Abstract

Fibroblasts adhesion, spreading, and proliferation was investigated in this study using glass and octadecyl glass (ODS) as models for hydrophobic substrata in the absence or presence of preadsorbed fibronectin (FN). To learn more about the underlying mechanism of the biocompatibility of materials, the organization of the β₁, integrin and the phosphorylation of tyrosine residues in focal contacts was investigated by immunofluorescence microscopy. The diminished adhesion and spreading of fibroblasts on hydrophobic ODS in comparison to clean glass was indicated by a diffuse presence of actin and by the absence of focal contacts and phosphotyrosine activity, In contrast, on hydrophilic glass, initial stress fibres and focal adhesions appeared accompanied by a moderate phosphotyrosine activity. The preadsorption of FN improved the interaction of fibroblast with both surfaces as indicated by the formation of prominent actin stress fibres and the clusterization of β₁ integrins in the focal contacts which was co-localized with an increased phosphotyrosine activity. The proliferation of fibroblasts measured after 72 h was inhibited on ODS in comparison to glass. Preadsorption of FN, however, increased the cell proliferation index on both surfaces, whch was higher than on pure glass. The improved cell adhesion, spreading, and proliferation of fibroblasts run in parallel with an increased total tyrosine phosphorylation activity measured by an enzyme immuno assay (EIA). It was concluded that the signalling via integrins might be a decisive event during the cell-biomaterial interaction.