Fibronectin anchorage to polymer substrates controls the initial phase of endothelial cell adhesion

Early stages of the adhesion of human endothelial cells onto a set of smooth polymer films were analyzed to reveal the modulation of cell-matrix interactions by the physicochemical constraints of predeposited fibronectin (FN). Hydrophobic and hydrophilic polymer substrates, consisting of poly(octadecene-alt-maleic anhydride) and poly(propene-alt-maleic anhydride) films, were coated with similar amounts of FN at conditions of either covalent or noncovalent immobilization. The well-defined substrates permit variation of the anchorage of FN at invariant topography, pliability, and molecular composition. Although all of the compared FN coatings were effective in stimulating attachment of endothelial cells, the initial formation of cell-matrix adhesions was found to be controlled by the type of interaction between predeposited FN and the underlying substrate. Covalent linkage and hydrophobic interactions of the predeposited FN with the polymer films interfered with the rapid generation of focal and fibrillar adhesions. It was demonstrated that this was caused by the fact that only weakly bound FN could become readily reorganized by the adherent cells. Upon prolonged culture periods at standard cell culture conditions, secretion and deposition of organized extracellular matrix by the attached cells was found to balance out the differences of the substrates.