Objective　　　 To establish a rabbit model of superparamagnetic iron oxide (SPIO)-labeled chondrocytes magnetic targeting in the treatment of cartilage defects.　　　 Methods　　　 Eight rabbits were used to create osteochondral defect of 5.0 mm in diameter

6.0 mm in depth in the left knee joint

and then all animals were divided into 2 groups randomly

that is

experimental group and control. A powerful magnet of neodymium iron boron (NdFeB) was placed into the defect in the experimental group

while the bone cement in the control. Rabbit chondrocytes were labeled with BrdU and SPIO

and then injected into the knee joint cavity of rabbit models. Animals were sacrificed in 1 week after the injection. The distal femurs containing the defects were resected

fixed

decalcified

and then performed by HE

Prussian blue and anti-BrdU staining.　　　 Results　　　 All animals were alive at the end of the experiment. Histological and immunohistochemical staining showed that a large of double-labeled chondrocytes were deposited around the osteochondral defect area

and the double-labeling indicated these cells were exogenous and in a shape like chondrocytes. But in the control group

fibrotic proliferation was observed in the defect

with a great deal of inflammatory cells and some scattered double-labeled cells (a few deposited in the middle of defect). Significant difference was found in the number of double positive cells in the defect between the 2 groups (t=6.343

P=0.001).　　　 Conclusion　　　 This animal model displayed that BrdU and SPIO-labeled chondrocytes can be targeted to the bone defect of rabbit knee joint through magnetic targeting transplantation

indicating magnetic targeting improves transplanted cells’ alive and growth in the target place. It can be applied for the research of magnet targeting in the repair of osteochondral defect in rabbits.