Abstract: Background/Aim: In hepatic stellate cells isolated from rat fibrotic livers, the amount of retinoid X receptor-alpha (RXR-α) mRNA is greatly reduced. However, the effectiveness of retinoids in the treatment of liver fibrosis is controversial. We hypothesized that increasing the expression levels of RXR-α in livers will improve the response of liver fibrosis to retinoids treatment.
Methods: pTracer-CMV2 vector harboring both green fluorescent protein and RXR-α genes was given to mice with carbon tetrachloride (CCl4)-induced liver fibrosis, by hydrodynamic-based in vivo transfection. Vitamin A was simultaneously administered to the mice. Sirius red staining and measurement of hydroxyproline content were performed to evaluate liver fibrosis. The incorporation of 5-bromo-2-deoxyribouridine (BrdU) was carried out to determine liver cell proliferation.
Results: Successful transfection and expression of exogenous RXR-α gene in the liver was determined by observance of green fluorescence under a confocal microscope, and detection of RXR-α protein by immunohistochemistry. Hepatic fibrosis, evaluated by both Sirius red staining with image analysis and quantity of hydroxyproline in livers of RXR-α-transfected group, tapered off remarkably. The hydroxyproline content and Sirius red-positive staining area on liver sections from RXR-α-transfected mice decreased by 34.3% and 54.63%, respectively, compared with the control group receiving empty vector. The labeling index of BrdU in non-parenchymal cells was much lower in livers from the RXR-α-transfected group than that of empty vector-transfected group.
Conclusions: Hydrodynamic-based in vivo transfection of the RXR-α gene can enhance the vitamin A-induced attenuation of liver fibrosis in mice. One of the possible mechanisms of action for this gene treatment is inhibition of non-parenchymal cell proliferation mainly composed of hepatic stellate cells in fibrotic livers.