MORPHOLOGICAL EVIDENCE FOR A DIFFERENT FIBRONECTIN RECEPTOR ORGANIZATION AND FUNCTION DURING FIBROBLAST ADHESION ON HYDROPHILIC AND HYDROPHOBIC GLASS SUBSTRATA

A polyclonal antibody against the beta 1 subunit of the fibronectin (F N) receptor was used to mimic the early events of integrin receptor fu nctioning to study the initial cellular processes during the organizat ion of FN matrix on biomaterials. Hydrophilic glass and hydrophobic oc tadecylsilane (ODS) surfaces have been applied as models for different biocompatible materials. By immunofluorescence we could demonstrate t hat FN receptors organize on the: dorsal cell surface of adhering fibr oblasts in a specific linear pattern along with actin filaments, but o nly if the cells were attached to hydrophilic glass. In contrast, FN r eceptors were not reorganized on hydrophobic octadecylsilane (ODS). In parallel experiments, FN matrix formation after 72 h of incubation on the same substrata has been analyzed microscopically, and quantified by cell ELISA, in order to be further correlated with the integrin rec eptor functioning in contact with the biomaterials. II was found that FN structuring and the amount of FN matrix have been significantly dim inished on ODS that was related to the observed changes in integrin re ceptor functioning. To learn more about the mechanism of this phenomen on, desorption of I-125-FN from these substrata was studied and found to be significantly decreased on hydrophobic ODS. As a consequence, FN receptor (function) might be arrested on the ventral cell surface, th us the important role of beta 1 integrins in the positional organizati on of the FN matrix may be disturbed. In light of these facts, antibod y-induced clustering of FN receptor can be considered as a useful mode l for studying the early steps of FN matrix formation on biomaterials.