Improved Artificial Cartilage Regeneration Tissue by Using Fibroin Sponge

INTRODUCTION There have been many attempts to repair full-thickness articular cartilage defects using tissue-engineering techniques, focusing particularly on the regeneration of high-strength cartilage. Unfortunately, the strength is insufficient for fixation of the grafted part on large defect of joint surface. Current focus in our laboratory has been placed on the development of a novel silk fibroin sponge which, mechanically robust and can be designed to desired mechanical specifications including ultimate tensile strength, yield point and stiffness [1, 2]. The unique performance of these fibroin sponge are now being rediscovered and reconsidered as potentially useful biomaterials for a range of applications in clinical repairs and in vitro as scaffolds for tissue engineering. Chondrocytes knocked into the fibroin sponge proliferated and possessed its normal 3D phenotypic characteristics as we reported [1, 2]. However, according to its low-cell adhesive nature, seeding technique into the fibroin sponge is still a major problem encountered. Chondrocytes metabolism and homeostasis were known highly sensible and affected by the mechanical stimuli. In this study, a simple magnetic stirring system was developed to improve after-seeding tissue maturity. And fibroin sponge was used as a scaffold for in vitro cartilage regeneration system. Chondrocytes were harvested from 4-week-old Japanese white rabbits and inoculated in the fibroin sponge. Cultured in 37°C incubator for 3 days, transferred to magnetic stirring system and keep culturing until another 28 days. After 3 days of cultivation, the number of chondrocytes had increased and production of extracellular matrix was observed. Well-defined cartilage-like tissue was regenerated until 28 days of cultivation. Increase of better extracellular matrix (chondrotin sulfate) was also observed by using the system.