TNFR1-mediated signaling is important to induce the improvement of liver fibrosis by bone marrow cell infusion

The importance of TNF-alpha signals mediated by tumor necrosis factor receptor type 1 (TNFR1) in inflammation and fibrosis induced by carbon tetrachloride (CCl(4)), and in post-injury liver regeneration including a GFP/CCl(4) model developed as a liver repair model by bone marrow cell (BMC) infusion, was investigated. In mice in which TNFR1 was suppressed by antagonist administration or by knockout, liver fibrosis induced by CCl(4) was significantly decreased. In these mice, intrahepatic macrophage infiltration and TGF-beta 1 expression were reduced and stellate cell activity was decreased; however, expression of MMP-9 was also decreased. With GFP-positive BMC (TNFR1 wildtype, WT) infusion in these mice, fibrosis proliferation, including host endogenous intrahepatic macrophage infiltration, TGF-beta 1 expression and stellate cell activity, increased significantly. There was no significant increase of MMP-9 expression. In this study, TNFR1 in hosts had a promoting effect on CCl(4)-induced hepatotoxicity and fibrosis, whereas BMC infusion in TNFR1 knockout mice enhanced host-derived intrahepatic inflammation and fibrosis proliferation. These findings differed from those in WT recipient mice, in which improvement in inflammation and fibrosis with BMC infusion had previously been reported. TNFR1-mediated signaling might be important to induce the improvement of liver fibrosis by bone marrow cell infusion.