Immune-Metabolic Regulation of Biliary Atresia

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Biliary atresia (BA) is a cholestatic liver disease of infancy and is the leading cause of pediatric liver transplantation. Current evidence supports the principle that BA arises from an aberrant immune response to an environmental trigger. However, the exact mechanism of disease remains unknown. While macrophages (M) have been implicated in both human and murine BA, M are heterogeneous by nature and the metabolic networks responsible for pro-restorative vs pro- inflammatory M polarization have not been defined. Our central premise is that identifying macrophage-specific immune-metabolic signatures associated with patient outcome will lead to novel prognostic biomarkers and cell-subset specific therapies to prolong transplant-free survival. We have been the first to identify a prognostic metabolite signature in BA infants at the time of diagnosis. We have shown that distinct changes in serum arginine metabolites, particularly increased polyamines, in BA infants at the time of diagnosis was associated with increased survival with native liver (SNL) at the age of 2 years despite no baseline differences in clinical characteristics. Polyamines are known to reprogram M to an anti-inflammatory phenotype, in part through efferocytosis (i.e. apoptotic cell uptake). Our preliminary data found that BA patients with a polyamine-high metabolic signature had increased hepatic numbers of previously characterized monocyte-like M (MLM, increased expression for genes associated with monocytes) and serum GM-CSF. We thereby hypothesize that recruited MLM promote hepatic adaptation to biliary obstruction; thus, metabolic and epigenetic reprogramming of MLM towards and anti-inflammatory phenotype will be associated with SNL at 2 years of age. To investigate this hypothesis, we will: 1) define the prognostic role for serum arginine metabolites, and 2) identify cell subset specific transcriptional phenotypes associated with SNL.