Effects of small interfering RNA-mediated downregulation of the Krüppel-like factor 4 gene on collagen metabolism in human hepatic stellate cells.

The nuclear transcription factor Krüppel-like factor 4 (KLF4) has an important role in cellular biological processes. However, the influence of KLF4 on collagen metabolism remains to be elucidated. In the present study, the effects and underlying mechanism of action of KLF4 on collagen metabolism was investigated in human hepatic stellate cells (HSC), by downregulating KLF4 expression using small interfering RNA (siRNA). The effects of KLF4 silencing by three predesigned siRNAs (siRNA1‑3) were evaluated using both reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and western blotting in the human LX2 HSC line. The mRNA expression levels of KLF4 were decreased by ~34, 40, and 69% in the siRNA1, siRNA2, and siRNA3 groups, respectively, as compared with the control group. These results were concordant with the protein expression levels of KLF4, as determined by western blot analysis. In the siRNA3 group, the quantity of type Ⅰ and type III collagen, and the expression levels of collagen metabolism proteins including matrix metalloproteinase‑1 (MMP‑1) and tissue inhibitors of metalloproteinases‑1 (TIMP‑1), were determined using both RT‑qPCR and western blotting. Both the mRNA and protein expression levels of type I and type III collagen were significantly decreased in the siRNA3 group, as compared with the control group. The mRNA and protein expression levels of TIMP‑1 were also significantly reduced in the siRNA3‑treated cells, whereas the mRNA and protein expression levels of MMP‑1 were significantly upregulated. Furthermore, KLF4 gene silencing significantly decreased the expression levels of numerous cytokines, including transforming grow factor‑β1, tumor necrosis factor‑α, and interleukin‑1β. The results of the present study provide evidence of siRNA‑mediated silencing of KLF4 expression, which may promote extracellular matrix (ECM) degradation, and inhibition of ECM synthesis. Therefore, KLF4 may be a promising target for the development of novel antifibrotic therapies.