Inhibitory effect of specific small interference RNA targeted against transforming growth factor β1 in mice with hepatic fibrosis infected with Schistosoma japonicum

Objective To investigate the inhibitory effect of small interference RNA (siRNA) targeted against transforming growth factor β1 (TGFβ1) in mice with hepatic fibrosis infected with Schistosoma japonicum. Methods Three short hairpin RNAs (shRNA) targeting different positions of TGFβ1 and one unrelated control sequence (HK) were designed and cloned to a plasmid pGenesil-1 respectively to obtain four recombinant expression vectors. Thirty male BALB/c mice were randomly divided into six groups, including normal group, model group, control group (pGenesil-HK) and three treatment groups (pGenesil-TGFβ1-m1, pGenesil-TGFβ1-m2 and pGenesil-TGFβ1-m3) and each group had five mice. The hepatic fibrosis animal models infected with Schistosoma japonicum were constructed. The levels of hydroxyproline (HYP) in liver tissue were examined by biochemistry. Liver histopathology was examined by hematoxylin-eosin and Masson staining. The mRNA expression and protein expression levels of TGFβ1, mothers against decapentaplegic homolog (Smad) 3, Smad 7 and α-smooth muscle actin (α-SMA) in the livers were detected by quantitative real time polymerase chain reaction (RT-qPCR) and Western blot. Two independent samples t test was used to compare the measurement data between groups. Results The liver fibrogenesis was obviously improved in all treatment groups compared with model group.The levels of HYP of liver tissue in all treatment groups were significantly lower than that in model group (t=14.870, 7.097 and 10.741, respectively, all P<0.01). The mRNA expression levels of TGFβ1, Smad 3 and α-SMA(model group vs pGenesil-TGFβ1-m1 group, t=3.235, 5.141 and 10.026, respectively; model group vs pGenesil-TGFβ1-m2 group, t=3.396, 5.145 and 4.951, respectively; model group vs pGenesil-TGFβ1-m3 group, t=3.511, 5.429 and 6.485, respectively)and protein (model group vs pGenesil-TGFβ1-m1 group, t=8.847, 8.044 and 10.746, respectively; model group vs pGenesil-TGFβ1-m2 group, t=9.709, 7.484 and 10.847, respectively; model group vs pGenesil-TGFβ1-m3 group, t=9.672, 8.766 and 11.508, respectively) were significantly decreased in all treatment groups compared with model group (all P< 0.01), while the levels of Smad 7 mRNA and protein were significantly increased in all treatment groups compared with model group(t=11.742 and 11.211, respectively in pGenesil-TGFβ1-m1 group; t=14.446 and 13.736, respectively in pGenesil-TGFβ1-m2 group; t=10.892 and 10.908, respectively in pGenesil-TGFβ1-m3 group, all P< 0.01). Conclusions Specific siRNA targeting TGFβ1 could significantly inhibit the liver fibrogenesis in mice infected with Schistosoma japonicum. The anti-fibrosis mechanisms of the siRNA maybe associated with the down-regulation of TGFβ1, Smad 3 and α-SMA expressions and up-regulation of Smad 7 expression in liver tissue, which results in suppressing the activation of hepatic stellate cells. Key words: Transforming growth factor beta 1; RNA, small interfering; Schistosoma japonicum; Hepatic fibrosis