BACKGROUND: Young age at portoenterostomy has been linked to improved outcome in biliary atresia, but pre-existing biological factors may influence the rate of disease progression. In this study, we aimed to determine whether molecular profiling of the liver identifies stages of disease at diagnosis. METHODS: We examined liver biopsies from 47 infants with biliary atresia enrolled in a prospective observational study. Biopsies were scored for inflammation and fibrosis, used for gene expression profiles, and tested for association with indicators of disease severity, response to surgery, and survival at 2 years. RESULTS: Fourteen of 47 livers displayed prominent features of inflammation (N=9) or fibrosis (N=5), with the remainder showing similar levels of both simultaneously. Differential profiling of gene expression of the 14 livers displayed a unique molecular signature containing 150 gene probes. Applying prediction analysis models, the probes classified 29 of the remaining 33 livers into inflammation or fibrosis. Molecular classification into the two groups was validated by the findings of increased hepatic population of lymphocyte subsets or tissue accumulation of matrix substrates. The groups had no association with traditional markers of liver injury or function, response to surgery, or complications of cirrhosis. However, infants with an inflammation signature were younger, while those with a fibrosis signature had decreased transplant-free survival. CONCLUSION: Molecular profiling at diagnosis of biliary atresia uncovers a signature of inflammation or fibrosis in most livers. This signature may relate to staging of disease at diagnosis and has implications to clinical outcomes.
Overall design
Clinical and laboratory data and liver biopies were obtained from 47 infants at diagnosis of biliary atresia and every 3-6 month intervals until 2 years of age as part of a prospective, observational study of the Biliary Atresia Research Consortium. Liver biopsies underwent histological scoring and those specimens classified as inflammation or fibrosis were used to generate a group-specific gene expression profile. The profile was used to assign a molecular stages of inflammation or fibrosis to the entire cohort. Molecular groups were tested for biological plausibility using immunostaining to quantify hepatic inflammatory cells, and quantitative PCR to reproduce the expression of gene groups and the expression of collagen genes. They were also tested for clinical relevance by testing of association with indicators of liver function, complications of disease, and clinical outcome.
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