Activation of primary hepatic stellate cells and liver fibrosis induced by targeting TGF-β1/Smads signaling in Schistosomiasis of mice

Abstract

Background: In mice, liver fibrosis is the most serious pathologic change during Schistosoma japonicum (S. japonicum) infection. Schistosomiasis is mainly characterized by schistosome egg-induced granulomatous fibrosis. Hepatic stellate cells (HSCs) are mainly responsible for the net accumulation of collagens and fibrosis formation in the liver. Activated HSCs regulated by transforming growth factor-β1 (TGF-β1)/Smad signaling have emerged as the critical regulatory pathway in hepatitis virus or carbon tetrachloride-induced liver fibrosis. However, the detailed mechanism of HSCs activation in schistosome-induced liver fibrosis remains not well-elucidated. Methods: S. japonicum-induced murine models and control group were generated by abdominal infecting with 15 (±1) cercariae. The purity of cultured primary HSCs was evaluated by immunocytochemistry. The histopathological changes of the liver in infected mice were estimated by hematoxylin-eosin and Masson staining. Dynamic expression of pro-fibrotic molecules and microRNAs were detected by quantitative Real-time PCR (RT-qPCR). Mainly members involved in TGF-β1/Smad signaling pathway were examined via RT-qPCR and Western blot.Results: The egg-induced granulomatous inflammation formed at 4 weeks post-infection (wpi) and kept a progressive development. Alpha-smooth muscle actin (α-SMA), Collagen Ⅰ, Collagen Ⅲ, TGF-β1, Smad2, Smad3, and Smad4 showed a significant increase in mRNA and protein expression compared with the control group at 7 weeks and 9 wpi, while observed an opposite effect on Smad7. In addition, the mRNA expression of microRNA-21 (miRNA-21) was significantly increased at 7 wpi, and the mRNA expression of miRNA-454 was decreased starting from 4 wpi.Conclusion: Our present findings uncovered that HSCs regulated by TGF-β1/Smad signaling pathway play an important role in liver fibrosis of S. japonicum-infected mice, which may provide proof-of-concept for liver fibrosis in Schistosomiasis.