Combination leflunomide and methotrexate impedes the recovery of liver fibrosis, partly through inhibition of myeloid cell admittance

The process of liver fibrosis is reversible and involves a recovery phase. In the present study, the potential side effects of combination leflunomide and methotrexate (LEF+MTX), a conventional rheumatoid arthritis therapy used in the resolution of liver fibrosis, was investigated. In a carbon tetrachloride-induced liver fibrosis model, the results of hepatic pathology demonstrated that the LEF+MTX combination delayed the recovery of fibrosis, although the activation of hepatic stellate cells in vitro was inhibited. A total of four liver fibrosis-associated indicators, hyaluronic acid, laminin, procollagen type III and collagen IV, maintained high levels in the serum of LEF+MTX-treated mice, while detection of bone marrow-driven monocytes in the blood by flow cytometry indicated that they were significantly decreased. Notably, the results of immunofluorescence staining of hepatic myeloid cells and detection of vascular growth factor A (VEGF-A) in blood and liver suggested that the reduced degeneration of collagen in liver sinusoids was associated with decreased myeloid cell adhesion and the downregulation of VEGF-A in the liver. The present results suggested that in certain cases, treatment with LEF+MTX may impede the recovery of hepatic fibrosis-associated diseases in mice.