Objective:To establish the pulmonary metastasis model of osteosarcoma in rats.Methods:UMR106 cells(rat osteosarcoma strain) were cultured in RPMI1640 media and collected before transplantation and resuspended in serum-free media or collagen gel to a final concentration of 1×107 cells/ml.About 200μl cell suspensions were injected into the right proximal tibia of 3-week-old Sprague-Dawley rats.Twelve rats were used in every group sorted by resuspension fluid.All rats were treated by cyclosporin A and SMZ-TMP after transplantation.The dates of tumor appearance and rat death were noted

the size of tumor was measured once a week

the metastasis foci on the lung surface was counted and the limbs afflicted by tumor were observed by X-ray after death.Both the tumors in limb and lung were stained with hematoxylin and eosin

and analyzed by microscopy.Results:All rats developed local intratibial bone tumors that were radiographically and histologically similar to primary human osteosarcoma.The pulmonary metastasis foci were found in all rats at autopsy.The tumor formation time of serum-free media group was(10.0±1.65) days

shorter than that of collagen gel group

which was(17.8±0.87) days(P<0.0001).The metastasis foci in lung of serum-free media group were more than that of collagen gel group(155.25±36.63vs 91.5±29.56

P<0.0001).The rats of serum-free media group died earlier than collagen gel group(21.4days±6.67days vs 40.6days±9.52days

P<0.0001).Conclusions:The osteosarcoma model established by UMR106 cell strain orthotopic transplantation in SD rats

which is reliable

easily manipulated

tumor formation quickly and pulmonary metastasis in 100 percent

is a perfect model for study pulmonary metastasis of osteosarcoma.The model established by cells resuspened in serum-free media is better for the mechanism study

while the model established by collagen gel is better for pulmonary metastasis treatment study.