Time-dependent changes in adhesive force between chondrocytes and silk fibroin substrate

In tissue engineering for cartilage repair using scaffold, initial chondrocyte–material interactions are significantly important for the following cell behaviors such as phenotypic expression and matrix synthesis. Silk fibroin scaffold is considered to be one of the useful materials in/on which chondrocytes can proliferate without dedifferentiating into fibroblast-like cells and can organize a hyaline-like tissue. For the purpose of seeking some useful aspects for designing scaffold, initial adhesive force of chondrocytes to the surface of fibroin substrate was measured by using a lab-made apparatus applying the cantilever beam method. It was found that the adhesive force per unit spreading area of chondrocytes on fibroin substrate had a clear peak between 6 and 12 h after seeding. From the results of immunofluorescence staining for actin and vinculin during this period, it could be thought that an immature formation of actin fibers which was uniquely observed at the periphery of cells attaching to fibroin substrate did not contribute to the increase of adhesive force. Results in this study suggested that surface of the fibroin substrate was gradually covered with some substances which inhibit the adhesion during this period. These cell–material interactions have a possibility to be useful information for designing the adhesive performance of scaffold surface in cartilage regeneration.