Transcriptional Regulation of Hepatic Stellate Cell Activation by siRNA for TGF-β1

Background : The cytokine-induced activation of hepatic stellate cells (HSC) plays a major role in liver fibrosis. Quiescent HSCs undergo phenotypic transformation called "transdifferentiation" in response to viral, chemical or immune insults to the liver. The cytokine TGF-beta 1 plays a key role in progressive liver fibrosis. Since small interfering RNA (siRNA) is a powerful tool for silencing gene expression post-transcriptionally, the present study aimed to determine whether synthetic TGF-beta 1 siRNA down-regulates the expression of the TGF-beta 1 gene in immortalized and activated rat HSCs (HSC-T6s). The study examined whether synthetic TGF-beta 1 siRNA prevents rat HSCs activation and extracellular matrix (ECM) production. Methods : TGF-beta 1 siRNA or a control (pU6) siRNA was added to HSC-T6 culture media. We then performed RT-PCR and western blot analyses for TGF-beta 1 and ECM components (fibronectin, type-I collagen, and TIMP-1). Results : TGF-beta 1 siRNA significantly down-regulated expression of TGF-beta 1 mRNA and protein and attenuated mRNA and protein expressions of type-I collagen, fibronectin, and TIMP-1, as compared to the control. Conclusions : TGF-beta 1 siRNA can effectively down-regulate the expression of TGF-beta 1 in rat HSC, resulting in significant inhibition of HSC activation and of ECM production. These data indicate that synthetic TGF-beta 1 siRNA can be a useful treatment modality to prevent liver fibrosis.