Hepatic Stellate Cell-Specific Gene Silencing Induced by an Artificial MicroRNA for Antifibrosis In Vitro

We previously reported that the anti-transforming growth factor-beta1 (TGF-beta 1) ribozymes directed by T7 and CMV promoters could reverse the character of activated hepatic stellate cells (HSCs) in vitro and improve fibrotic pathology in vivo. However, nonspecific elimination of the effects of TGF-beta 1 without selectivity might have unfavorable consequences, such as overwhelming inflammation, tissue necrosis, etc. To establish an activated-HSC-specific gene silencing method and validate its feasibility for antifibrosis in vitro. An artificial intronic microRNA (miRNA) expression system was established, containing three parts: (1) a 1,074-bp SM-alpha actin promoter SMP8, which is a kind of RNA polymerase II promoter and has no activity in normal liver-derived cells but is switched on during the activation of HSCs, (2) intron1 modified by inserting an artificial pre-miRNA sequence against TGF-beta 1, and (3) report gene enhanced green fluorescent proteins (EGFP). The feasibility of this system for artificial microRNA expression was validated through microRNA detection by real-time polymerase chain reaction (PCR). Alteration of biological characteristics of HSCs with the anti-TGF-beta 1 miRNAs was preliminarily evaluated by measuring the expression levels of TGF-beta 1 and its downstream molecules, including collagen I, matrix metalloproteinase 2 (MMP2), tissue inhibitor of metalloproteinase 1 (TIMP-1), etc. The microRNA expression system could successfully produce mature anti-TGF-beta 1 miRNAs in an activated-HSC-specific manner. The microRNA-induced inhibition rate of TGF-beta 1 reached 70% and above. Accompanied by TGF-beta 1 suppression, its downstream targets such as collagen I, MMP2, TIMP-1, etc. were also significantly downregulated in vitro. Activated-HSC-cell-specific gene silencing could be induced well by the artificial intronic microRNA expression system to realize antifibrosis in vitro.