Visco-elastic properties of cartilage tissue regenerated with fibroin sponge.

The mechanical properties of regenerated cartilage tissue were measured to evaluate changes in their visco-elastic properties during cultivation. An indentation test and dynamic visco-elasticity measurements were carried out on cartilage tissue cultured with rabbit chondrocytes that had been inoculated into the fibroin sponge. A 1.5-mm-diameter porous indentor was used for the indentation test, in which time-dependent strain curves were derived from measurements taken under several loading conditions. Dynamic visco-elasticity measurements were performed under compressive loading to evaluate the load-bearing function of the articular cartilage. Although the amount of permanent deformation was not influenced by the duration of cartilage regeneration, the amount of creep deformation increased with longer cultivation. The E' value of the regenerated cartilage increased and the peak value of tan delta and the frequency at the peak became lower with longer cultivation. It is suggested that the changes in the time-dependent strain curves and dynamic visco-elastic properties of the regenerated cartilage were caused by maturation of the cultured cartilage tissue.