Objective To investigate the expression of connective tissue growth factor (CTGF) and heat shock protein 47 (HSP47) in peritoneum fibrosis rats,and the mechanism of 1,25-dihydroxyvitamin D3 [1,25-(OH)2-VitD3] in inhibiting the peritoneum fibrosis.Methods Adult male Sprague-Dawley rats were randomly divided into 3 groups:control group (n=8),model group (n=8) and 1,25-dihydroxyvitamin D3 group (VitD3,n=8).The model of peritoneum fibrosis rats were induced by daily intraperitoneally injection of 15％ chlorhexidine gluconate (CHX) 0.2 ml/d with 0.1％ glucose for 4 weeks.Rats in VitD3 group were also treated with 1,25-(OH)2-VitD3 [i.p.6 ng· (100 g) 1 · d-1].Peritoneal transport function,renal function,peritoneum thickness and serum level of 25hydroxyvitamin D3 were detected.In vitro,primary cultured peritoneal mesothelial cells were divided into control group,high glucose group (HG,2.5％),CTGF siRNA intervention group (CTGF siRNA+HG),VitD3 intervention group (VitD3+HG) and combined intervention group (CTGF siRNA+VitD3+HG).Real-time PCR,Western blotting and immunofluorescence were applied to measure the expression of CTGF and HSP47,also ELISA was used to detect the protein level of FN in peritoneum and peritoneal mesothelial cells.Results Compared with control group,the peritoneal ultrafiltration in peritoneum fibrosis rats were significantly decreased (P ＜ 0.05),the absorbance level of peritoneal fibrosis,peritoneum thickness,the rate of dialysate urea nitrogen and blood urea nitrogen (DUN/BUN) and the expressions of CTGF and HSP47 were increased (all P＜0.05).After application of 1,25-dihydroxyvitamin D3,peritoneal fibrosis lesion was significantly improved,the peritoneum thickness,the expressions of CTGF and HSP47 were decreased (all P ＜ 0.05).In vitro,2.5％ high glucose induced-peritoneal mesothelial cells were respectively treated by CTGF siRNA,1,25-(OH)2-VitD3 and combined interventions,the expression of FN,CTGF and HSP47 was significantly lower than that in high glucose group (all P ＜ 0.05).Conclusions The expression of CTGF and HSP47 is significantly increased in peritoneal fibrosis rats.1,25-(OH)2-VitD3 may ameliorate the progression of peritoneal fibrosis via reducing the expression of CTGF,decreasing the expression of HSP47 and FN.