Objective To investigate the relationship between the expression of Wnt induced secreted protein-1 (WISP-1) and the fibrosis of renal biopsy tissue in IgA nephropathy (IgAN) patients.Methods Fifty-three patients firstly diagnosed as IgA nephropathy by renal biopsy were included and classified according to Oxford and Lee's classification.Sixteen patients with MCD entered the fibrosis negative control group,and fourteen healthy adults entered the normal control group.The expression of WISP-1 in renal tissues and serum of all subjects were detected by immunohistochemistry and ELISA respectively.Results Immunohistochemistry results showed that WISP-1 was not expressed in MCD patients and normal human kidney tissues,which was abundantly deposited in renal tissue of patients with focal proliferative IgAN with renal interstitial fibrosis.The serum level of WISP-1 in IgAN patients was significantly higher than that in normal subjects (P=0.015) and MCD patients (P=0.030).In the subgroup analysis of IgAN renal fibrosis,the serum concentration of WISP-1 of fibrosis grade between 0-10％ (F1 group) and fibrosis ＞ 25％ (F3 group) were significantly higher than that in the normal group and the MCD group (all P ＜ 0.05).There was no significant difference between F2 group (10％ ＜ fibrosis≤25％) and normal group or MCD group (P ＞ 0.05).Conclusions The expression of WISP-1 in serum and renal tissue of renal interstitial fibrosis IgAN patients is higher than that of normal and MCD patients without renal fibrosis,and the IgAN patients' serum level of WISP-1 is significantly increased in fibrosis lower score group.The expressions of WISP-1 in serum and renal tissue are related to the occurrence of IgAN renal interstitial fibrosis,in which WISP-1 may play an important role as an early precursor factor in the pathogenesis of IgAN renal interstitial fibrosis.