The gut microbiome contributes to splenomegaly and tissue inflammation in a murine model of primary biliary cholangitis

Background: Splenomegaly is not just a consequence of numerous chronic and acute conditions but may also contribute to their severity, due to the interaction of the spleen with the gut microbiome. This study aimed to explore the effect of the gut microbiome on splenomegaly.

Methods: We used p40^-/-IL-2Rα^-/- mice as a murine model of primary biliary cholangitis (PBC) as per our previous study. Splenomegaly was evaluated by spleen weight. Severity of liver inflammation was evaluated by hepatic mononuclear cell (MNCs) number and pathological score. Changes of immune cells in the spleen and liver were detected by flow cytometry. The effects of the gut microbiome on splenomegaly and liver inflammation were observed by combined antibiotic treatment in p40^-/-IL-2Rα^-/- mice.

Results: A proportion of p40^-/-IL-2Rα^-/- mice developed splenomegaly. The results revealed that liver mononuclear cells infiltration, histological scores of hepatic inflammation, and bile duct damage were positively correlated with the degree of splenomegaly. Hepatic CD4⁺ and CD8⁺ T cells numbers were significantly higher in mice with splenomegaly, and this was particularly observed in activated effector memory CD4⁺ T and CD8⁺ T cells. A proportion of some other immune cells including granulocytes, B, natural killer (NK), and CD8⁺ T effector memory cells were also altered in the enlarged spleen. More importantly, administration of quadruple antibiotics to deplete gut microbiota relieved the splenomegaly of p40^-/-IL-2Rα^-/- mice, significantly alleviated liver inflammation, and caused a significant reduction of liver and spleen T cell accumulation and activation; however, single antibiotics did not induce these changes.

Conclusions: Splenomegaly was associated with more severe liver inflammation in our PBC murine model, and this effect was reversed by quadruple antibiotic treatment.