Research the origin of cells that contribute to the repair of osteochondral defect and application this for the acceleration of the tissue repair.

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We examined the possibility that cells circulating in peripheral blood participated in a natural repair process of the joint bone and cartilage injury by using green fluorescent protein transgenic transgenic(GFP) rat. In this study, we used the parabiosis model of GFP rat and wild one. Two weeks after parabiosis operation, vascular communication was confirmed by flow cytometry analysis. 1.5 mm diameter and 1.0 mm depth osteochondral defect was made in patella groove of femoral bone. Histrogical examination was done at 1, 2, 4, 24 weeks after surgery. In the early phase after the surgery, there were both GFP negative and positive cells in the defects of both rats of parabiosis. GFP positive chondrocytes was confirmed partly in the repair tissue of the wild rat of parabiosis. In the late phase after the surgery, the repaired defect was occupied by cells originated from the adjacent tissue not from the peripheral blood. The rate of cells originated from the peripheral blood was about 30-40% in the repair tissue at 1 week after surgery. While at 24 weeks after surgery that was about 0-7%. From these results, it is confirmed that cells circulating in peripheral blood contributed to repair of osteochondral defects in joint especially in early phase not only supplying the factors needed for repair but also supplying the repair cells.When injected granulocyte colony stimulating factor(G-CSF ; 150μg/kg pre day for 5 days) to rats, the nucleated cells in blood increased. After the cells increase, we made 1.5mm diameter and 1.0 mm depth osteochondral defect and observed up to 24 weeks. The repair of subchondral bone was accelerated although that of cartilage did not. To obtain better repair, we increased the nucleated cell more by injecting G-CSF for 14 days. After the cells increased more, we made defects and observed for 2 weeks. When we compared the repair of the preceding method with the new one, there were no significant differences between them.