Aberrant TGF-β1 signaling contributes to the development of primary biliary cirrhosis in murine model

Abstract

To investigate whether transforming growth factor-β1 (TGF-β1) signaling pathway is involved in the pathogenesis of primary biliary cirrhosis (PBC). A murine model of PBC was developed by injection of polyinosinic polycytidylic acids (poly I: C) in C57BL/6 mice, and the liver expressions of TGF β1, TGF-β receptor I (TβRI), TGF-β receptor II (TβRII), p-Smad2/3, monoclonal α-smooth muscle actin antibody (α-SMA) and α1 (I) collagen in the mouse model and control mice were evaluated by immunohistochemistry, immunoblotting and real-time polymerase chain reaction (RT-PCR). Lymphocyte subsets in liver were analyzed using flow cytometry. The mouse model had several key phenotypic features of human PBC, including elevated levels of alkaline phosphatase, antimitochondrial antibodies, portal bile ducts inflammation, and progressive collagen deposition. Compared with control mice, protein and mRNA levels of TGF β1, TβRI, TβRII, p-Smad2/3, α-SMA and α1 (I) collagen in liver (1.7 ± 0.4 vs 8.9 ± 1.8, 0.8 ± 0.2 vs 5.1 ± 1.5, 0.6 ± 0.01 vs 5.1 ± 0.1, 0.6 ± 0.3 vs 2.0 ± 0.3, 0.9 ± 0.4 vs 3.4 ± 0.6, 0.8 ± 0.4 vs 1.7 ± 0.3, 1.1 ± 1.2 vs 11.8 ± 0.6, P < 0.05), and the total number and percentage of CD4⁺ CD25⁺ FOXP3⁺ and CD8⁺ lymphocytes (0.01 ± 0.001 vs 0.004 ± 0.00, 0.12 ± 0.04 vs 0.52 ± 0.23, P < 0.01) were higher in the mouse model. TGFβ1 might play a dual role in the development of PBC: it suppresses inflammatory response but operates to enhance fibrogenesis. The aberrant activity of TGF-β1 signaling contributes to the development of PBC.