Spleen deficiency enhances liver fibrosis in mice

Spleen is connected to liver through portal vein (PV). Although spleen is known as an immune regulatory organ, the role of spleen in the development of liver fibrosis is unknown. Here, we performed splenectomy before starting CCl₄ treatment, then investigated liver fibrosis. Methods: Male C57BL/6 mice were underwent splenectomy or sham surgery. 1 week later surgery, mice were treated with CCl₄ or vehicle twice weekly for 6 weeks. Splenic mRNA levels of pro-inflammatory cytokines including TNF-α, IL-6 and CCL2, anti-inflammatory cytokines including IL-10 and Arginase-1, and Lipocalin-2 were determined by qPCR. Liver fibrosis was evaluated by sirius red staining. Lipocalin-2 levels in PV were measured by ELISA. Results: Splenic pro- and anti-inflammatory cytokines mRNA expressions were not changed in both CCl₄ and vehicle treated sham mice. However, splenic Lipocalin-2 mRNA levels were increased 35 fold by CCl₄ treatment. Interestingly, sirius red positive area after CCL₄ treatment was significantly increased in splenectomized mice compared with sham mice (6.6±0.3% v.s 3.5±0.2%). Lipocalin-2 levels in PV following CCl₄ treatment were markedly decreased in splenectomized mice compared to sham mice (465.9±30.6ng/mL v.s. 327.5±35.0ng/mL). Conclusion: Enhanced liver fibrosis was found in spleen deficient mice. Lipocalin-2 is a secreted glycoprotein which induced macrophage deactivation in pneumonia mice model. The mechanism underlying exaggerated liver fibrosis most likely involves decreased Lipocalin-2 levels in PV. Spleen might have a protective role in liver fibrosis.