Static and dynamic mechanical properties of extracellular matrix synthesized by cultured chondrocytes

Recently, an approach to restore cartilage defects, culturing autologous chondrocytes in vitro to create a three-dimensional tissue and then implanting the cultured tissue, has been developed. In this kind of approach, it is important to study whether the extracellular matrixes synthesized by cultured chondrocytes have appropriate mechanical property. In this study, we attempted to evaluate in detail mechanical properties of the extracellular matrix synthesized by chondrocytes in vitro. Therefore, we cultured bovine chondrocytes in agarose gel and assessed the changes in not only static but also dynamic mechanical properties during long-term culture. In addition, to assess the mechanical property of the extracellular matrix synthesized by chondrocytes only, we calculated the volume ratio of the extracellular matrix in agarose gel from the cross section and estimated the static Young's modulus of the extracellular matrix synthesized by cultured chondrocytes based on the Rule of Mixture. As a result, both the equilibrium aggregate modulus and dynamic Young's modulus of chondrocyte/agarose disks increased with time. The value of calculated modulus was larger than that of the pericellular matrix of cartilage explant. In conclusion, the biomechanical property of chondrocyte/agarose constructs and the matrix synthesized by chondrocytes were assessed in detail.