Oslo Sports Trauma Research Center

Description

Cartilage injuries may be localized to a small area (focal injury) or to larger areas as in osteoarthritis. Focal cartilage injuries may be caused by a traumatic event or a disease in the bone underlying the cartilage (osteochondritis dissecans). Surgical treatment of cartilage injuries is still controversial because we do not know if the results of treatment are better than the natural course. In addition we do not know whether any of the surgical treatment options are better than the others.

The four most common treatment options for cartilage repair are: Microfracture, mosaic plasty, periost transplantation and autologous chondrocyte transplantation. Most treated injuries are in the knee. In the microfracture technique several holes are made in the subchondral bone plate. The belief is that bone marrow cells migrates to the injury area and contributes to the formation of a fiber cartilage to replace the original cartilage. In mosaic plasty plugs consisting of cartilage and underlying bone are taken from less weight bearing areas of the joint and used to replace the injured cartilage. In periosteal transplantation the cartilage injury is covered by a periosteal flap. Periosteum contains mesenchymal stem cells that are thought to be the source of cartilage formation in this method. In autologous chondrocyte transplantation a small piece of cartilage is taken from a less weight bearing area of the joint, cultured and the number of cells are multiplied. After two or three weeks the Joint is opened, the defect is covered by periosteal flap, and the cells are injected under the flap.

There are few studies that compared the different methods, and we do not know if any of them are better than the others. A theoretical disadvantage of the use of chondrocytes is that these cells are mature cells that are past the stadium of cell differentiation and cell division. In autologous chondrocyte transplantation these mature cells are stimulated to cell division. mesenchymal stem cells are the "mother cell" of bone, cartilage, fat and muscle. Theoretically mesenchymal stem cells may be better than cartilage cells in forming cartilage be cause they still have a natural potential for cell differentiation and cell division. Some animal studies have been performed using mesenchymal stem cells with the same technique as in autologous chondrocyte transplantation. In deep defects into the subchondral bone, the use of mesenchymal stem cells induced bone formation in the areas lacking bone, and cartilage formation in the areas lacking cartilage.

We have established a model that studies cartilage injuries in the rabbit. In a comparative study, under standardized conditions, the cartilage injury is repaired using different established clinical methods for surgical treatment. We are planning a study of surgical treatment of cartilage injury in the rabbit patella comparing the use of autologous chondrocyte transplantation with the transplantation of mesenchymal stem cells. The cartilage cells and the stem cells will be harvested from 24 rabbits, and at the same time a four millimeter defect is created in the patella in both knees. The cells are cultured at the Institute of Immunology at the National Hospital. Two weeks later the rabbits will be operated with one of the methods in each knee. One half of the rabbits will be observed in 12 weeks, and the rest will be observed in 36 weeks. In this way we will obtain knowledge about the course of the cartilage formation and the long term results