Although WNT proteins are predominantly associated with embryogenesis, they are also important in disease progression. Previous studies described regulation of WNT-5A by the fibrogenic growth factor TGFβ. This interaction warrants further studies into the role of WNT-5A in liver fibrosis. Although gene-array studies identified increased WNT5 in fibrotic livers, the functional role of WNT-5A in this liver disease is not described yet. Therefore, our aim was to elucidate its role in liver
fibrosis. We studied the expression of WNT-5A in mouse and human livers in more detail and examined the relation between WNT-5A and various fibrosis-associated growth factors, cytokines and extracellular matrix proteins. WNT-5A and collagen I expression in normal and fibrotic mouse and human livers were analyzed with RT-PCR, ubiquitin-Proteasome pathway Western blot, and immuno-histochemistry.
The effects of cytokines/growth factors on WNT-5A and collagen I expression in LX2 cells were analyzed with RT-PCR and Western blot. The effects of WNT-5A on the expression of matrix proteins were determined after incubation of LX2 cells with WNT-5A siRNA in the absence and presence of TGFβ. WNT-5A gene and protein expression was significantly higher in fibrotic mouse and human livers compared to normal. Immunohistochemical analysis showed PD0325901 that WNT-5A expression was found in fibrotic collagen-rich areas of mouse and human livers. WNT-5A staining co-localized with desmin staining in these areas. In vitro studies with myofibroblasts showed that WNT-5A expression was significantly increased after incubation with TGF-β while PDGF-BB and pro-inflammatory cytokines (IL1β and TNFα) did not change WNT-5A expression. After silencing
of WNT-5A in myofibroblasts, using WNT-5A siRNA, reduced levels of collagen I, vimentin, and fibronectin in TGF-β-stimulated LX2 cells were found as compared to transfection controls. Interestingly, the antifibrotic cytokine IFNγ suppressed WNT-5A and collagen type I expressions in vitro. In addition, hepatic WNT-5A and collagen Ievels were significantly Urocanase reduced in CCL4 exposed (8 weeks) mice treated with (targeted) IFNγ as compared to untreated fibrotic mice. In conclusion, WNT-5A is significantly upregulated in fibrotic livers in particular in myofibroblasts in fibrotic bands. WNT-5A expression in myofibroblasts is induced by TGFβ and is involved in the regulation of various fibrotic matrix proteins. Targeted IFNγ therapy reduces hepatic WNT-5A expression and ameliorates liver fibrosis. These results identify WNT-5A as a potential new antifibrotic drug target.