The etiology and pathogenesis of bile duct obstruction in children with biliary atresia are largely unknown. We have previously reported that, despite phenotypic heterogeneity, genomic signatures of livers from patients display a proinflammatory phenotype. Here, we address the hypothesis that production of IFN-γ is a key pathogenic mechanism of disease using a mouse model of rotavirus-induced biliary atresia. We found that rotavirus infection of neonatal mice has a unique tropism to bile duct cells, and it triggers a hepatobiliary inflammation by IFN-γ-producing CD4 + and CD8 + lymphocytes. The inflammation is tissue specific, resulting in progressive jaundice, growth failure, and greater than 90% mortality due to obstruction of extrahepatic bile ducts. In this model, the genetic loss of IFN-γ did not alter the onset of jaundice, but it remarkably suppressed the tissue-specific targeting of T lymphocytes and completely prevented the inflammatory and fibrosing obstruction of extrahepatic bile ducts. As a consequence, jaundice resolved, and long-term survival improved to greater than 80%. Notably, administration of recombinant IFN-γ led to recurrence of bile duct obstruction following rotavirus infection of IFN-γ-deficient mice. Thus, IFN-γ-driven obstruction of bile ducts is a key pathogenic mechanism of disease and may constitute a therapeutic target to block disease progression in patients with biliary atresia.

Biliary atresia is a severe cholangiopathy of early infancy that destroys extrahepatic bile ducts and disrupts bile flow. With a poorly defined disease pathogenesis, treatment consists of the surgical removal of duct remnants followed by hepatoportoenterostomy. Although this approach can improve the short-term outcome, the liver disease progresses to end-stage cirrhosis in most children. Further improvement in outcome will require a greater understanding of the mechanisms of biliary injury and fibrosis. Here, we review progress in the field, which has been fuelled by collaborative studies in larger patient cohorts and the development of cell culture and animal model systems to directly test hypotheses. Advances include the identification of phenotypic subgroups and stages of disease based on clinical, pathological and molecular features. Stronger evidence exists for viruses, toxins and gene sequence variations in the aetiology of biliary atresia, triggering a proinflammatory response that injures the duct epithelium and produces a rapidly progressive cholangiopathy. The immune response also activates the expression of type 2 cytokines that promote epithelial cell proliferation and extracellular matrix production by nonparenchymal cells. These advances provide insight into phenotype variability and might be relevant to the design of personalized trials to block progression of liver disease.

Deficiency for mdr2, a canalicular phospholipid floppase, leads to excretion of low phospholipid “toxic” bile causing progressive cholestasis. We hypothesize that pharmacological inhibition of the ileal apical sodium-dependent bile acid transporter (ASBT) blocks progression of sclerosing cholangitis in mdr2−/− mice. 30-day-old, female mdr2−/− mice were fed high-fat chow containing 0.006% SC-435, a minimally absorbed, potent inhibitor of ASBT, providing on average 11 mg/kg/day of compound. Bile acids (BA) and phospholipids were measured by mass spectrometry. Compared with untreated mdr2−/− mice, SC-435 treatment for 14 days increased fecal BA excretion by 8-fold, lowered total BA concentration in liver by 65%, reduced total BA and individual hydrophobic BA concentrations in serum by >98%, and decreased plasma ALT, total bilirubin, and serum alkaline phosphatase levels by 86, 93 and 55%, respectively. Liver histology of sclerosing cholangitis improved, and extent of fibrosis decreased concomitant with reduction of hepatic profibrogenic gene expression. Biliary BA concentrations significantly decreased and phospholipids remained low and unchanged with treatment. The phosphatidylcholine/BA ratio in treated mice corrected towards a ratio of 0.28 found in wild type mice, indicating decreased bile toxicity. Hepatic RNAseq studies revealed upregulation of putative anti-inflammatory and antifibrogenic genes, including Ppara and Igf1 and downregulation of several pro-inflammatory genes, including Ccl2 and Lcn2, implicated in leukocyte recruitment. Flow cytometric analysis revealed significant reduction of frequencies of hepatic CD11b+F4/80+ Kupffer cells and CD11b+Gr1+ neutrophils, accompanied by expansion of anti-inflammatory Ly6C− monocytes in treated mdr2−/− mice. Conclusion Inhibition of ASBT reduces BA pool size and retention of hydrophobic BA, favorably alters the biliary PC/BA ratio, profoundly changes the hepatic transcriptome, attenuates recruitment of leukocytes, and abrogates progression of murine sclerosing cholangitis.

Objectives To examine the medical status of children with biliary atresia (BA) with their native livers after hepatic portoenterostomy (HPE) surgery. Study design The Childhood Liver Disease Research and Education Network (ChiLDREN) database was utilized to examine subjects with BA living with their native livers 5 or more years after HPE and to describe the prevalence of subjects with BA with an “ideal” outcome, defined as no clinical evidence of chronic liver disease, normal liver biochemical indices (aspartate aminotransferase, alanine aminotransferase, gamma glutamyl transpeptidase, platelet count, total bilirubin, International Normalized Ratio, and albumin) and normal Health-Related Quality of Life (HRQOL) 5 or more years after HPE. Results Children with BA (n=219; 43% male) with median age 9.7 years were studied. Median age at HPE was 56 (range 7-125) days. Median age- and sex-adjusted height and weight Z-scores at 5 year follow-up were 0.487 (interquartile range [IQR]: -0.27 to 1.02) and 0.00 (IQR: -0.74 to 0.70), respectively. During the 12 preceding months, cholangitis and bone fractures occurred in 17% and 5.5%, respectively. HRQOL was reported normal by 53% of patients. However, only 1.8% met the study definition of “ideal” outcome. Individual tests of liver synthetic function (TB, Alb, and INR) were normal in 75%, 85% and 73% of the study cohort. Conclusion Cholangitis and fractures in long-term survivors underscore the importance of ongoing medical surveillance. Over 98% of this North American cohort of subjects with BA living with native livers 5 or more years after HPE have clinical or biochemical evidence of chronic liver disease.