To investigate the relationship between Snail and renal tubular epithelial-mesenchymal transition (EMT) or tubulointerstitial fibrosis (TIF) at tissue and cellular levels and to observe the changes of miRNA profile after transfecting Snail gene into human renal tubular epithelial cells (HK-2),to further elucidate the importance of miRNA in the pathogenesis of renal fibrosis.Methods The expression of Snail and EMT-related proteins vimentin,SMA,E-cadherin was detected by immunohistochemistry in renal tissues of 40 patients with IgA nephropathy.The expression of Snail,E-cadherin and SMA in normal control group,empty transfection group and Snail gene transfection group was detected by Western blot and RT-PCR.Furthermore,differentially expressed miRNAs were screened by gene chip.Results By immunohistochemistry,Snail expression was positively correlated with vimentin and SMA,negatively correlated with E-cadherin in IgA nephropathy.The higher degree of the TIF,the stronger the expression of Snail.Compared with the control group,the expression of Snail,vimentin and SMA in the snail transfected group increased.However,E-cadherin decreased at gene and protein level by the RT-PCR and Western blot (P ＜ 0.05).The difference was statistically significant.Five distinctly different miRNAs were screened by gene chip after Snail gene was transfected into HK-2 cells,and then 5 026 potential target genes were predicted.Conclusion Snail expression is closely related with renal tubular epithelial mesenchymal transition and tubulointerstitial fibrosis,and it may be used as a new target in EMT prevention.Differentially expressed miRNAs may be involved in the development of EMT and TIF.