Genetic Labeling Does Not Detect Epithelial-to-Mesenchymal Transition of Cholangiocytes in Liver Fibrosis in Mice

• Published in: Gastroenterology (New York, N.Y. 1943) Vol. 139; no. 3; pp. 987 - 998
• Main Authors: Scholten, David, Österreicher, Christoph H, Scholten, Anjali, Iwaisako, Keiko, Gu, Guoqiang, Brenner, David A, Kisseleva, Tatiana
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-09-2010
• Subjects: Animals; Bile Ducts - surgery; Biomarkers - metabolism; Calcium-Binding Proteins - genetics; Carbon Tetrachloride; Cell Lineage; Cell Transdifferentiation - genetics; Chemical and Drug Induced Liver Injury - genetics; Chemical and Drug Induced Liver Injury - metabolism; Chemical and Drug Induced Liver Injury - pathology; Collagen Type II - genetics; Crosses, Genetic; Disease Models, Animal; EMT; Epithelial Cells - metabolism; Epithelial Cells - pathology; Fibroblasts - metabolism; Fibroblasts - pathology; Gastroenterology and Hepatology; Genes, Reporter; Glial Fibrillary Acidic Protein - genetics; Hepatic Stellate Cells - pathology; Immunohistochemistry; Keratin-19 - genetics; Ligation; Liver - metabolism; Liver - pathology; Liver Cirrhosis - genetics; Liver Cirrhosis - metabolism; Liver Cirrhosis - pathology; Liver Regeneration - genetics; Luminescent Proteins - biosynthesis; Luminescent Proteins - genetics; Mesenchymal-to-Epithelial Transition; MET; Mice; Mice, Transgenic; Promoter Regions, Genetic; Proteins - genetics; RNA, Untranslated; S100 Calcium-Binding Protein A4; S100 Proteins; Ab; α-smooth muscle actin; FSP-1; BDL; fibroblast-specific protein-1; GFP; α-SMA; bile duct ligation; RT-PCR; yellow fluorescent protein; HSC; hepatic stellate cell; collagen α2(I); Col2(I); YFP; antibody; cytokeratin-19; Mesenchymal-to-Epithelial Transition; EMT; green fluorescent protein; ECM; epithelial-to-mesenchymal transition; GFAP; K19; Pan-CK; pancytokeratin; reverse transcription polymerase chain reaction; MET; glial fibrillary acidic protein; extracellular matrix
• ISSN: 0016-5085; 1528-0012
• DOI: 10.1053/j.gastro.2010.05.005

Background & Aims Chronic injury changes the fate of certain cellular populations, inducing epithelial cells to generate fibroblasts by epithelial-to-mesenchymal transition (EMT) and mesenchymal cells to generate epithelial cells by mesenchymal-to-epithelial transition (MET). Although contribution of EMT/MET to embryogenesis, renal fibrosis, and lung fibrosis is well documented, role of EMT/MET in liver fibrosis is unclear. We determined whether cytokeratin-19 positive (K19+ ) cholangiocytes give rise to myofibroblasts (EMT) and/or whether glial fibrillary acidic protein positive (GFAP+ ) hepatic stellate cells (HSCs) can express epithelial markers (MET) in response to experimental liver injury. Methods EMT was studied with Cre-loxP system to map cell fate of K19+ cholangiocytes in K19YFP or fibroblast-specific protein-1 (FSP-1)YFP mice, generated by crossing tamoxifen-inducible K19CreERT mice or FSP-1Cre mice with Rosa26f/f-YFP mice. MET of GFAP+ HSCs was studied in GFAPGFP mice. Mice were subjected to bile duct ligation or CCl4 -liver injury, and livers were analyzed for expression of mesodermal and epithelial markers. Results On Cre-loxP recombination, >40% of genetically labeled K19+ cholangiocytes expressed yellow fluorescent protein (YFP). All mice developed liver fibrosis. However, specific immunostaining of K19YFP cholangiocytes showed no expression of EMT markers α-smooth muscle actin, desmin, or FSP-1. Moreover, cells genetically labeled by FSP-1YFP expression did not coexpress cholangiocyte markers K19 or E-cadherin. Genetically labeled GFAPGFP HSCs did not express epithelial or liver progenitor markers in response to liver injury. Conclusion EMT of cholangiocytes identified by genetic labeling does not contribute to hepatic fibrosis in mice. Likewise, GFAPCre -labeled HSCs showed no coexpression of epithelial markers, providing no evidence for MET in HSCs in response to fibrogenic liver injury.