Objective:To investigate the effect of celecoxib (CXB),a specific COX-2 inhibitor,on the proliferation of Han:SPRD-cy rats’ renal cyst,and to probe into the related mechanism.Methods: Totally 57 3-week-old male Han: SPRD heterozygous(cy/+) rats were randomly divided into 3 groups (n=19): control group (fed with normal forage),low dosage CXB group (3 mg·kg-1·d-1) and high dosage CXB (10 mg·kg-1·d-1) treatment groups.The animals and their bilateral kidneys were weighed; the 2-kidney weight/total body weight(2K/TBW)ratio was calculated.The renal cystic index(CI),fibrosis index, and inflammatory cell infiltration in interstitium were observed by pathologic renal tissue slices.The co-expression of PCNA and COX-2 was analyzed by double immunofluorescence labeling technique and laser scanning confocal microscopy.The expression of PCNA and COX-2 protein was examined by Western blotting analysis.Results: The 2K/TBW ratio of the low dosage group(\[1.10±0.009\]%) was significantly lower than that of the control group (\[1.33±0.02\]%) at the 16-week old,(P＜0.05).Compared with the control group,the inflammatory cell infiltration in other two groups was significantly decreased (\[2.6±0.26\],\[2.8±0.31\]vs \[3.7±0.33\]),P＜0.05).The fluorescence intensities of COX-2,PCNA in the low dosage CXB group was significantly lower than those of the control group (P<0.05).Compared with the control group,the other two groups had significantly decreased expression of COX-2(\[0.326±0.011\],\[0.409±0.008\] vs \[0.814±0.012\],P＜0.05) and PCNA (\[0.763±0.051\],\[0.925±0.042\] vs \[0.988±0.031\],P＜0.05).Conclusion: CXB at 3,10 mg·kg-1·d-1 can reduce inflammatory cell infiltration and inhibit the proliferation of Han:SPRD rat’s renal cyst,probably through inhibition of COX-2.