Mikko Lammi

Adult cartilage has a limited intrinsic capacity to regenerate and heal after injury. Therefore, a range of repair techniques have been adopted in an attempt to restore function and prevent further degeneration and development of osteoarthritis. Tissue engineering (TE) of cartilage using biodegradable material as a scaffold for chondrocytes could help the restoration of functional tissue. In this thesis a novel biomaterial, recombinant human type II collagen (rhCII), was tested as a scaffold for chondrocytes. The rhCII was proven to be a safe material for chondrocytes, and it allowed cell growth and production of cartilage ECM constituents, type II collagen and proteoglycans (PGs). When rhCII was used as a scaffold to repair osteochondral defects in a rabbit model, the repair tissue contained typical articular cartilage ECM and the use of rhCII helped to achieve better filling of the cartilage defect. The rhCII-assisted repair tissue integrated well to the subchondral bone and the tissue showed mechanical durability especially in the deeper zones. However, the repair quality was not much improved when compared to the spontaneous healing process. In addition, the superficial layer of repair tissue showed fibrillation and type I collagen production. Furthermore, the integration into the adjacent cartilage was not completein either rhCII assistedor the spontaneous repair tissue. Therefore, before rhCII can be used in human patients, further studies concerning enhancing the integration, and preventing surface fibrillation of the repair tissue, are needed.