Activated Hepatic Stellate Cells and Portal Fibroblasts contribute to cholestatic liver fibrosis in MDR2 knockout mice.

Abstract

BACKGROUND AND AIMS\nChronic liver injury often results in activation of hepatic myofibroblasts and development of liver fibrosis. Hepatic myofibroblasts may originate from three major sources; Hepatic Stellate Cells (HSCs), Portal Fibroblasts (PFs), or fibrocytes. Their contribution to liver fibrosis varies dependent on the etiology of liver injury. Here we assessed the composition of hepatic myofibroblasts in multidrug resistance gene 2 knockout (Mdr2-/-) mice, a genetic model that resembles primary sclerosing cholangitis in patients.\n\n\nMETHODS\nMdr2-/- mice expressing a collagen-GFP reporter were analyzed at different ages. Hepatic nonparenchymal cells isolated from collagen-GFP Mdr2-/- mice were sorted based on collagen-GFP and vitamin A. A nicotinamide adenine dinucleotide phosphate oxidase (NOX) 1/4 inhibitor was administrated to Mdr2-/- mice during ages 12- to 16-weeks-old to assess the therapeutic approach targeting oxidative stress in cholestatic injury.\n\n\nRESULTS\nThy1+ activated PFs (aPFs) accounted for 26%, 51%, and 54% of collagen-GFP+ myofibroblasts in Mdr2-/- mice at 4 weeks, 8 weeks, and 16 weeks of age, respectively. The remaining collagen-GFP+ myofibroblasts were composed of activated HSCs (aHSCs), suggesting that PFs and HSCs are both activated in Mdr2-/- mice. BM-derived fibrocytes minimally contributed to liver fibrosis in Mdr2-/- mice. Development of cholestatic liver fibrosis in Mdr2-/- mice was associated with early recruitment of Gr1+ myeloid cells and upregulation of pro-inflammatory cytokines (4 weeks). Administration of a NOX inhibitor to 12-week-old Mdr2-/- mice suppressed activation of myofibroblasts and attenuated development of cholestatic fibrosis.\n\n\nCONCLUSIONS\naPFs and aHSCs contribute to cholestatic fibrosis in Mdr2-/- mice, and serve as targets for anti-fibrotic therapy.\n\n\nLAY SUMMARY\nActivated Portal Fibroblasts and Hepatic Stellate Cells, but not fibrocytes, contributed to the production of the fibrous scar in livers of Mdr2-/- mice, and these cells can serve as targets for anti-fibrotic therapy in cholestatic injury. Therapeutic inhibition of the enzyme nicotinamide adenine dinucleotide phosphate oxidase (NOX) in Mdr2-/- mice reversed cholestatic fibrosis, suggesting that targeting of NOXs can provide a novel strategy for treatment of cholestatic fibrosis.