Evaluation of dynamic visco-elastic properties during cartilage regenerating process in vitro

The dynamic visco-elastic properties of regenerated cartilage tissue were measured to evaluate its mechanical function during cultivation. Harvested chondrocytes from 4-week-old Japanese white rabbits were inoculated into fibroin sponge at a cell concentration of about 5 x 10(7) cells/ml. Dynamic visco-elasticity measurements were performed under compressive loading to evaluate the load bearing function of the articular cartilage. The dynamic modulus and the dynamic loss of the regenerated cartilage increased and the peak value of tandelta, as well as the frequency at the peak, decreased with increasing cultivation time. The pores of the fibroin sponge became filled with newly formed tissue as cultivation time increased. These changes in the visco-elastic properties of the regenerated cartilage were compared with those of a model system, ethylene propylene diene monomer sponge with interstitial fluid, and appear to be a result of increased fluid flow resistance and internal loss. We conclude that the changes in the dynamic visco-elastic properties of the regenerated cartilage were caused because of narrowing of the fluid path by synthesized extracellular matrix.