Using next-generation sequencing of microRNAs to identify host and/or pathogen nucleic acid signatures in samples from children with biliary atresia - a pilot study.

Biliary atresia (BA) is a progressive disease affecting infants resulting in inflammatory obliteration and fibrosis of the extra- and intra-hepatic biliary tree. BA may be grouped into type 1 isolated; type 2 syndromic, where other congenital malformations may be present; type 3 cystic BA, where there is cyst formation within an otherwise obliterated biliary tree; and cytomegalovirus-associated BA. The cause of BA is unclear, with immune dysregulation, inflammation and infection, particularly with cytomegalovirus (CMV), all implicated. In this study a total of 50/67 samples were tested for CMV DNA using quantitative real-time PCR. Ten liver tissue and 8 bile samples from 10 patients representing the range of BA types were also analysed by next-generation sequencing. CMV DNA was found in 8/50 (16 %) patients and a total of 265 differentially expressed microRNAs were identified. No statistically significant differences between the various types of BA were found. However, differences were identified in the expression patterns of 110 microRNAs in bile and liver tissue samples (<0.05). A small number of bacterial and viral sequences were found, although their relevance to BA remains to be determined. No direct evidence of viral causes of BA were found, although clear evidence of microRNAs associated with hepatocyte and cholangiocyte differentiation together with fibrosis and inflammation were identified. These include miR-30 and the miR-23 cluster (liver and bile duct development) and miR-29, miR-483, miR-181, miR-199 and miR-200 (inflammation and fibrosis).