Single-cell transcription reveals hepatocyte-to-cholangiocyte reprogramming and biliary gene profile in biliary atresia

BACKGROUND: Ductular reaction (DR), characterized by the expansion of biliary epithelial cells in the portal area, is a typical hepatic pathology for biliary atresia (BA). The cellular source and function of DR remain poorly understood. Herein, we performed single-cell RNA sequencing (scRNA-seq) in BA to resolve the complexity of DR in BA. METHODS: A total of 4 BA and 3 normal control livers underwent scRNA-seq. The epithelial cells were extracted from all cells for further analysis. The cell types, functions, and differentiational trajectory of epithelial cells were determined. The biliary markers and transcription factors (TFs) were identified by combing public bulk and scRNA-seq data and validated by immunohistochemistry. RESULTS: ScRNA-seq identified the existence of biliary reprogramming in BA, and the reprogrammed cells expressed both hepatocyte and cholangiocyte markers. When compared with hepatocytes, genes of epithelial-mesenchymal transition, fibrosis, inflammation, and RNA metabolism were enriched in cholangiocytes and upregulated in BA. Pseudotime analysis depicted a differentiation trajectory from hepatocytes across reprogrammed cells to cholangiocytes in BA. Matrix metalloproteinase 7 (MMP7), VTCN1, and LAMC2 were identified as the biliary markers, and KLF5 and HNF1B were determined as the biliary TFs in BA. All the biliary markers and TFs were upregulated in BA when compared with controls. CONCLUSIONS: Dissecting the cellular source and function of cholangiocytes is essential to understand the pathological role of DR in BA. The identified specific biliary markers and TFs provide important insights into its potential diagnosis and mechanism exploration for BA in the future.