Promotion of liver regeneration and anti-fibrotic effects of the TGF-β receptor kinase inhibitor galunisertib in CCl4-treated mice

The cytokine transforming growth factor-beta (TGF-beta) serves a key role in hepatic fibrosis and has cytostatic effects on hepatocytes. The present study investigated the anti-fibrogenic and regenerative effects of the TGF-beta receptor type I kinase inhibitor galunisertib (LY2157299) in mice with carbon tetrachloride (CCl4)-induced liver cirrhosis and in vitro. Mice were intraperitoneally treated with CCl4 for 8 weeks. At week 5, the mice were divided randomly into four treatment groups: Vehicle-treated; and treated with low-; middle-; and high-dose galunisertib, which was administered from weeks 5-8. The mice were sacrificed after 8 weeks of CCl4 treatment. Liver fibrosis, as evaluated by histology and determination of hydroxyproline content, progressed during week 4-8 of CCl4 treatment in the vehicle-treated mice. Galunisertib treatment dose-dependently prevented liver fibrosis, as demonstrated by the direct inhibition of alpha-smooth muscle actin-positive activated hepatic stellate cells (HSCs) after 8 weeks of CCl4 treatment. The levels of active matrix metalloproteinase (MMP)-9 in galunisertib-treated livers were significantly increased compared with the vehicle-treated livers. In the high-dose group, the number of PCNA-positive hepatocytes and endothelial cells markedly increased compared with the vehicle group. Reverse transcription-quantitative PCR analysis verified that interleukin-6 and epiregulin expression levels were significantly increased in livers from the group treated with high-dose galunisertib compared with the vehicle-treated group. Galunisertib inhibited the proliferation of activated HSCs and collagen synthesis in addition to restoring MMP activity. Moreover, galunisertib promoted liver remodeling by proliferating hepatocytes and vascular endothelial cells, while significantly increasing liver weight. These results are consistent with the cytostatic action of TGF-beta that negatively regulates liver regeneration, and demonstrated that galunisertib inhibited TGF-beta signaling, halted liver fibrosis progression and promoted hepatic regeneration. The results of the present study suggest that galunisertib may be an effective treatment for liver cirrhosis.