| Abstract: | Late passage fibroblasts show decreased cell-substrate adhesion. We provide evidence that the reduced adhesion is due to a defect in the adhesive glycoprotein fibronectin. Late passage cells become more adhesive in culture media that has been conditioned by the growth of early passage cells. Analysis of fibronectins purified from early and late passage cell conditioned media indicates that there are striking differences in their abilities to promote cell adhesion. Young cell fibronectin supports the maximal adhesion of both young and old cells. However, old cells require quantitatively more fibronectin. In contrast, old cell fibronectin is less effective in supporting the adhesion of either cell type. In addition, neither cell type achieves a normal morphology in the presence of old cell fibronectin. The results support the conclusion that the fibronectin released by late passage cells is defective and does not support normal cell-substrate interactions. |
